Applied Industrial Ergonomics 4.3_tcm1038-133720

Disclaimer The information contained in this manual is based on current, accurate, and reliable sources relating to ergonomics and other fields of study in human performance. No warranty, guarantee, or representation is made by Humantech, Inc. as to the absolute correctness or sufficiency of any representation contained in this manual. Humantech, Inc. assumes no liability for the use of the information in this manual. In no event shall Humantech, Inc. be liable for lost profits, special, incidental, direct, indirect, exemplary, punitive, or consequential damages.

Copyright © 2008 by Humantech, Inc. All rights reserved, including the right of reproduction in whole or in part in any form.

Humantech® is a registered trademark of Humantech, Inc.

Applied Industrial Ergonomics – Version 4.3 ISBN 978-0-9821894-2-9

Notice Humantech encourages readers to copy and use the forms in this manual for personal use. Please note that these forms are copyrighted by Humantech, Inc. and can only be used under the following circumstances:

Readers may copy forms with the understanding that such copies shall be used solely for the personal use of the individual in connection with his/her application of Applied Industrial Ergonomics principles to his/her employment.

The rights granted by this limited license are not transferable to any other individual or person without Humantech’s express written permission.

No forms may be modified without the express written consent of Humantech, and proper copyright and trademark notices must be kept on all copies of the forms.

Except for the rights granted above, Humantech reserves any and all copyright rights, trademark rights, trade secret rights, and all other rights protected under any doctrine of intellectual property. By way of example, but not limitation, Humantech retains the exclusive right to

A. sell or distribute copies of any portion of the Applied Industrial Ergonomics manual to any third party,

B. create alterations or derivative works based on the Applied Industrial Ergonomics manual, and

C. utilize any copy of the Applied Industrial Ergonomics manual for purposes of consulting, delivering services, or otherwise assisting any third party.

Visit Humantech online at www.humantech.com for more information.

i

Contents

Applied Industrial Ergonomics

Chapter 1 Introduction to Occupational Ergonomics...................... 1 Welcome....................................................................................................2 About This Manual.....................................................................................2 Course Objectives .....................................................................................3 Ergonomics is a Process, Not a Program .................................................4 What is Occupational Ergonomics? ..........................................................5 Why Ergonomics? .....................................................................................5 Designing for the 30-Inch View™..............................................................6 Ergonomics as a Business Agenda.........................................................10 Applying Human Performance Ergonomics – The Tools ........................16 How This Manual is Organized ...............................................................29 References ..............................................................................................30

Chapter 2 Work-Related Musculoskeletal Disorders..................... 33 About This Chapter..................................................................................34 "Work Doesn’t Need to be a Pain!"®........................................................35 Would You Do it This Way?.....................................................................36 Posture, Force, and Frequency...............................................................37 What are Work-Related Musculoskeletal Disorders?..............................38 WMSDs in Industry..................................................................................40 How Do WMSDs Occur? .........................................................................41 Types of WMSDs.....................................................................................45 References ..............................................................................................54

Chapter 3 Recognizing Ergonomic Issues..................................... 57 About This Chapter..................................................................................58 Introduction to the Ergonomics Hit List™................................................59 The Hit List – "Find It"..............................................................................60 The Hit List – "Fix It" ................................................................................71 Ask the Operator .....................................................................................76 Continuous Improvement Process ..........................................................77 The Ergonomics Action Form™ ..............................................................79 Completing the Ergonomics Action Form................................................81 Avoiding Potential Pitfalls With the Ergonomics Action Form .................88

App l i ed I ndus t r i a l E rgonomics

ii

© 2008 Humantech

Chapter 4 Evaluating Ergonomic Risk Factors.............................. 91 About This Chapter..................................................................................92 Ergonomic Risk Factors Defined.............................................................93 Ergonomic Risk Factor Surveys ..............................................................94 The BRIEF™ Survey ...............................................................................95 Applying the BRIEF Survey.....................................................................97 Physical Stressors and the BRIEF Survey............................................111 Scoring the BRIEF Survey.....................................................................113 Completing the BRIEF Survey ..............................................................114 Measuring Risk Reduction.....................................................................118 Avoiding Potential Pitfalls With the BRIEF Survey................................120 References ............................................................................................120

Chapter 5 Prioritizing Ergonomic Risks ...................................... 125 About This Chapter................................................................................126 Introduction to Ergonomic Risk Prioritization.........................................127 Risk Prioritization Tools .........................................................................128 The BEST™ ..........................................................................................128 Completing the BEST Form...................................................................131 Avoiding Potential Pitfalls With the BEST .............................................138 The EASY™ ..........................................................................................139 Completing the EASY Form ..................................................................147 Avoiding Potential Pitfalls With the EASY .............................................156 Identifying High Priority Job/Tasks ........................................................156

Chapter 6 Manual Material Handling Analysis ............................. 159 About This Chapter................................................................................160 Introduction to Manual Material Handling..............................................161 Risk Factors for the Back ......................................................................162 The Revised NIOSH Lifting Equation ....................................................162 The NIOSH Composite Lifting Index .....................................................178 Uses for the Revised NIOSH Lifting Equation.......................................179 Avoiding Potential Pitfalls With the Revised NIOSH Lifting Equation ...180 Psychophysical Analysis: Push, Pull, and Carry ...................................181 Manual Material Handling Example.......................................................192 Manual Material Handling Analysis Flowchart.......................................196 References ............................................................................................197

iii

Contents

Chapter 7 Ergonomic Design Guidelines..................................... 199 About This Chapter................................................................................200 Ergonomics in Workstation Design .......................................................201 Design and Build Guidelines .................................................................204 Avoiding Potential Pitfalls With the Design and Build Guidelines .........218 Static Anthropometric Data....................................................................218 References ............................................................................................233

Chapter 8 Cost Justifying Ergonomic Improvements ................. 237 About This Chapter................................................................................238 Introduction to Cost Justification ...........................................................239 Ergonomics and Value-Added Analysis ................................................241 Ergonomics and Motion Time Analysis – The STEP™.........................242 Estimating Ergonomic Improvement Benefits, Cost Recovery..............244 The Cost Justification Worksheet..........................................................246 Avoiding Potential Pitfalls When Cost Justifying With STEP ................253 References ............................................................................................253

Chapter 9 The Job Improvement Process.................................... 255 About This Chapter................................................................................256 Introduction to the Job Improvement Process.......................................257 Identify Feasible and Effective Improvements.......................................257 Implement Improvements ......................................................................266

Chapter 10 Performing an Ergonomics Review............................. 271 About This Chapter................................................................................272 What is an Ergonomics Review?...........................................................273 Step 1: Select a Job to Review ............................................................274 Step 2: Gather Data..............................................................................275 Step 3: Analyze the Data......................................................................298 Step 4: Complete the Job Improvement Process.................................299

Chapter 11 Surviving the First 90 Days ......................................... 305 About This Chapter................................................................................306 The First 90 Days ..................................................................................306 Structuring the Ergonomics Process (Plan) ..........................................308 Initiating Job Improvement, Demonstrating Success (Do) ....................313 Adding Strength and Longevity to the Ergonomics Process.................319


iv

© 2008 Humantech

Appendices ....................................................................................... 323 Appendix A: Basis for the BRIEF ..........................................................324 Appendix B: Basis for the Design and Build Guidelines........................328

Index.................................................................................................. 335

1

1 hapter 1 Introduction to Occupational Ergonomics

Welcome....................................................................................................2 About This Manual.....................................................................................2 Course Objectives .....................................................................................3 Ergonomics is a Process, Not a Program .................................................4 What is Occupational Ergonomics? ..........................................................5 Why Ergonomics? .....................................................................................5 Designing for the 30-Inch View™..............................................................6 Ergonomics as a Business Agenda.........................................................10 Applying Human Performance Ergonomics – The Tools ........................16 How This Manual is Organized ...............................................................29 References ..............................................................................................30


2

© 2008 Humantech

Welcome Welcome to the Applied Industrial Ergonomics training class. You will learn, and more importantly, practice many valuable skills used to improve problem jobs in a manufacturing/industrial setting. Since this is your class, we want you to get the most out of it. To ensure that this is a meaningful educational experience, we recommend that you participate with enthusiasm.

Some ways in which you can positively influence this training include:

If you have a question, ask it!

If you need clarification, get it!

If you have a concern, voice it!

This educational material and the corresponding sessions have been shaped and refined over the years by participants like you. We hope that at the end of the training you will formally record your evaluation of this course so that we may continue to improve.

About This Manual This manual provides the skills and tools that will allow you to effectively improve the ergonomics of problem jobs in a manufacturing/industrial setting. It is intended for individuals responsible for finding and improving problem jobs in industrial environments, typically ergonomics committee members, site-based engineers, and health and safety staff.

The accompanying Applied Industrial Ergonomics Toolbox CD-ROM contains a wealth of information to help you improve problem jobs, including the following:

Blank forms you can print and use

Software and spreadsheets

Time Savings and Cost Justification Microsoft Excel® spreadsheet for evaluating productivity impact of job improvements and calculating payback periods

Manual Material Handling Guidelines Microsoft Excel® spreadsheet for determining safe limits for lifting, lowering, pushing, pulling, and carrying tasks

Humantech overview with articles, past newsletters, case studies, and other useful information if you'd like to learn more about ergonomics

3

Chapter 1: Introduction to Occupational Ergonomics

Course Objectives After completing this course, you will be able to:

Describe why ergonomics is important to companies

Identify common work-related musculoskeletal disorders (WMSDs) and their signs and symptoms

Quickly and easily identify ergonomic issues and solutions using the Ergonomics Hit List™

Identify ergonomic risk factors using the Baseline Risk Identification of Ergonomic Factors (BRIEF™) Survey

Prioritize jobs based on ergonomic risk factors and other data

Analyze manual material handling tasks with advanced ergonomics assessment tools including:

Psychophysical analysis guidelines for push, pull, and carry NIOSH Lifting Equation

Specify basic working heights, reach distances, and force limits using design guidelines

Cost justify improvements using the Standard Time Efficiency Process (STEP™) methodology

Perform an ergonomics job review using the appropriate methods

Structure the ergonomics process for success in the critical first 90 days

For more information about using this manual, see How This Manual is Organized on page 29.


4

© 2008 Humantech

Ergonomics is a Process, Not a Program Ergonomics is a board-accredited profession that has developed significantly over the past three quarters of a century. The early efforts of human factors research and human engineering, led by the military, have progressed to a broad application of ergonomics within industry and culture. More and more companies are recognizing the benefits of the common sense approach utilized by ergonomics.

Ergonomics represents a journey of continuous improvement for the workplace. Figure 1.1 illustrates the ergonomic improvement process. One of the most significant features of this process is that a basic awareness of ergonomics is needed to begin. However, once the process has begun, the cycle repeats itself continually.

Too often, businesses fail to sustain ergonomics efforts because they focus only on large-scale improvements in the very short term. Participants think they have to hit a "home run" every time at the plate or else they have failed. This is a mistake! "Base-hit" improvements, which represent small job enhancements, are the key to winning with ergonomics. Problems in jobs may have taken 15, 20, or 25 years to develop. It may take 15, 20, or even 25 months to counteract their effect.

Figure 1.1 Ergonomic Improvement Process

5


What is Occupational Ergonomics? Occupational ergonomics is the science of improving employee performance and well-being in relation to job tasks, equipment, and environment. It is a relentless pursuit and continuous effort to design the workplace for what people do well, and design against what people do not do well, thereby fitting the job to the person to enhance human performance.

The desire to improve tools and working conditions is an innate human trait. The conceptual basis of ergonomics has existed for over 500 years. As a result of a surge in activities associated with increasing industrialization, the discipline began to formalize during the twentieth century. The word ergonomics was created in 1949 to define a growing area of research and engineering interest involving the interaction of people with industrial and military technology and demanding physical environments.

The combination of the Greek words ergon, meaning work, and nomos, meaning laws, resulted in the term we use today. Fundamentally, ergonomics was a simple and straightforward discipline. Criteria were developed that defined the limits of human capacity. Descriptive statistics outlined visual and auditory perception, mental workload limits were roughly defined, human reach and strength limits were cataloged, and initial work on physiological capacity defined cardio-pulmonary limits for exertion. Taken together, these laws of work defined the limits to human capability much like the specifications for a machine define its limits.

Why Ergonomics? People are the sole source of productivity in your company. A clever person could say they are also the soul source of productivity.

Shiny buildings, machines, cute slogans, and fancy boardroom tables won’t make money for your corporation—it’s your people, and their brains and muscles, working to meet your bottom line. Big-picture strategies do not focus on the real problems facing the U.S.; on the contrary, they blind us to them. Whenever someone announces, “Let’s look at this from 30,000 feet,” ask them if they have been on a plane lately. At 30,000 feet, you can’t see anything; your head, literally and metaphorically, is in the clouds.

Rather, the key to success is at 30 inches. That’s where the power of people resides. At 30 inches, you can see people’s faces. At 30 inches, people converse, reach for tools, and sit at computers. At 30 inches, issues are not abstractions; they must be dealt with conclusively, discretely, and with the tools at hand.

At 30 inches, ergonomics provides the framework for designing workstation characteristics (workstation heights, force requirements, etc.) to match human performance capabilities. Through simple, cost-effective job improvements that support both task needs and human performance capabilities, the discipline of ergonomics seeks to eliminate WMSDs, maximize productivity, and enhance process stability and product quality.


6

© 2008 Humantech

Designing for the 30-Inch View™ The rationale for applying ergonomics at the 30-inch level is straightforward and can be explained through a simple comparison. The reasons for operating a machine within a specified set of limits are self-evident:

If we operate a machine within the limits of its design, we will achieve optimal productivity.

If we consistently operate a machine outside of its limits (as a tachometer indicates when an engine operates outside its limits), the machine will be unreliable and eventually break down.

Figure 1.2 A Tachometer Indicates Exceeded Limits

We can apply a similar logic to people. Because the ergonomics discipline provides us with formal definitions of the cognitive, physiological, and biomechanical capacities of the human, we can apply the information to optimize productivity while avoiding injury through workplace design:

If task demands and the work environment are designed to accommodate our biological capacity, the human will achieve optimal human productivity and minimum error.

If task demands require a person to operate continuously outside of his or her capacity, the human will perform the work unreliably and may eventually break down.

Using the model of implementation derived for machines, the contribution of ergonomics is clear. The knowledge derived from ergonomics allows industry to design workplace characteristics to match human performance capabilities.

The 30-Inch view of Ergonomics is a way to optimize human performance by ensuring that the workplace supports both task needs and employee capabilities. It seeks to maximize productivity and reliability while eliminating WMSDs through simple, cost-effective job improvements.

7


To combine the principles of ergonomics, design for what people do well and against what they do not do well. Use the following accepted management tools to ensure breakthrough improvements in health and safety and in productivity that drive sustainable bottom-line savings:

Risk management – a clear understanding of the problem ensures that improvement efforts are directed at the highest priority concerns.

Continuous improvement – simple and effective problem solving methods lead to low cost/high impact job improvements.

Engineering design – clear specifications ensure that workplace modifications are optimized.

Cost justification – easy to use methods capture the savings from proposed ergonomic job improvements to ensure project funding.

The 30-Inch View builds on conventional ergonomics activities to achieve new levels of health and safety excellence, and provides previously unattainable improvements in productivity. Humantech’s proprietary methodologies combine simple problem solving methods with cost-effective workplace solutions and innovative cost justification techniques. Three elements of successful ergonomics include:

A practical approach to workplace assessment and improvement

Innovative techniques to demonstrate business value

Sustainable systems to ensure long-term success

Practical Approach Simple and effective problem solving methods have been demonstrated through decades of success in the workplace. Conventional ergonomics approaches tend to stall as a result of too much analysis, or fail due to a lack of data to drive the process. Ergonomics at 30 inches employs innovative methodologies to derive the correct data and to maximize the contribution of ergonomics to your health and safety and business performance.

This approach quantifies ergonomic risk and identifies opportunities to improve productivity in one assessment method. Ergonomics must be fully integrated with improvement initiatives such as Six Sigma and Lean Manufacturing. Humantech analysis and solutions fit into these approaches to ensure that health and safety goals are met while driving on-time, on-cost, and on-quality performance.


8

© 2008 Humantech

Demonstrating Business Value Cost justification techniques based on standard accounting practices drive breakthrough improvements in health and safety performance, workers’ compensation costs, and productivity. Every workplace improvement project generates a return on investment (ROI) statement that assures the dollars spent on workplace modifications are dollars that will contribute to your bottom line.

The business case for conventional ergonomics approaches is based primarily on measuring the financial benefit of reduced workers' compensation costs related to WMSDs. These costs are simple to measure with the accurate recordkeeping systems that industry has developed over the past few decades. They are an excellent macro-indicator of progress. However, workers' compensation costs typically cannot be tracked to specific tasks or workstations, and are rarely useful in cost justifying improvements.

Ergonomics brings a significant amount of visibility to the business value proposition by quantifying the savings associated with removing barriers to production. If the design of the workplace is a barrier to the amount of time employees spend on value-added tasks, there is an opportunity to improve the performance of your people through ergonomic improvements.

Sustainable Systems Sustainable improvement begins with a practical approach that delivers a clear value to the business. Ergonomics builds on these fundamentals by integrating ergonomics into existing management structures, which may vary from ISO 14001-type environmental management systems to Six Sigma initiatives to Lean production systems—and transferring skills to ensure long-term success.

Far too often, ergonomic improvements are implemented one by one, with no focus on addressing system-wide problems. Ergonomics drives workplace enhancements that organizations can easily replicate across similar problems, further leveraging company efforts.

9


The Industrial Athlete One way to think about ergonomics is to look closely at athletic performance. Athletes are wonderful models for human performance because they push every element of human capability to the maximum. For instance, a sprinter must have explosive acceleration, the motivation to practice day after day, someone to help him perfect his form, and the right equipment to make it to the winner’s circle. In short, there are four elements an athlete needs to be successful:

Skill

Will (motivation)

Good coaching

Great equipment

But great equipment is critical. Imagine a world-class sprinter who must compete in soccer cleats. Racing against a non-athlete (in poor condition with poor form) in sprinter’s shoes, the sprinter would likely win the event even with the wrong shoes for the sport. However, if the race were repeated over and over, many times a day, day after day, the athlete’s performance would begin to suffer. At first, the soccer cleats would be a hassle, but the athlete would fight through and win. Then the race would become painful, but our athlete is motivated and would continue to win. Over time, the pain would become chronic (hurting even when the race is over), and the athlete would lose his edge and perhaps suffer permanent disability, allowing the non-athlete to beat him at his own sport. Thus, the importance of having the right equipment for successful human performance is obvious.

Think of the workplace as the running shoes for an industrial worker. To be successful, our workers need the right equipment for their sport. If the running shoes (workplace) are a hassle, the industrial athlete will fight through and get the job done. Even when work becomes painful, our industrial athlete will continue to be successful. It’s usually only after the pain becomes chronic and unbearable that the industrial athlete reports the condition.

Figure 1.3 The Ergonomics Continuum

At this point, the industrial athlete may have already developed a WMSD, a disorder of the muscles, nerves, tendons, ligaments, joints, cartilage, or spinal discs that is the result of exposure to ergonomic risk factors (force, frequency, posture) over time.


10

© 2008 Humantech

With the right equipment and solid work processes, the workplace can enable industrial athletes to achieve new heights in productivity and quality. However, when the workplace is a burden, the industrial athlete often lags behind in his production measures and can find himself on the bench with an injury.

Ergonomics as a Business Agenda Optimizing employee performance to improve productivity while decreasing injuries makes good business sense. By deploying an effective ergonomics initiative, companies can achieve sustained improvements in health and safety performance metrics, workers’ compensation costs, and productivity.

There are three business drivers that make a compelling argument for companies to deploy an ergonomics initiative:

Health and safety

Regulatory requirements

Production efficiency

Health and Safety Reducing work-related musculoskeletal disorders is a common reason that organizations improve workplace ergonomics. The financial benefit of reduced workers’ compensation costs resulting from WMSDs is a business driver for many ergonomics programs. These losses are common measures determined from health and safety record keeping systems that industry has developed over the past few decades.

The following facts illustrate the importance of ergonomic considerations in the workplace to ensure injury-free employees:

WMSDs account for 34% of all lost-workday injuries and illnesses, according to the Bureau of Labor Statistics (BLS).

Each year, WMSDs account for more than $15 to $20 billion in workers’ compensation costs in the United States.

WMSDs account for $1 of every $3 spent for workers’ compensation costs.

11


Costs of specific WMSD incidents vary considerably, particularly by location; workers’ compensation systems vary greatly between countries and even by state in the U.S. The graph below illustrates approximate averages for three types of WMSDs as reported by various data sources in the U.S.

��

��

��

��

��

��

��

��

�!

��

�"��

Figure 1.4 Approximate Average Costs of WMSDs

Average Cost of Work-Related Strains and Sprains in the U.S. Strains and sprains are typically defined as occupational injuries that result from damage to the muscles or ligaments from overexertion or external events such as tripping.

$8,759 (National Council on Compensation Insurance)

$13,935 (Texas Workers’ Compensation Research Center)

$15,757 (Injury Facts, National Safety Council)

Average Cost of Work-Related Cumulative Trauma Disorders (CTDs) in the U.S. Cumulative trauma disorders are typically defined as occupational illnesses that result from repeated exposure to microtrauma.


$10,000 (Liberty Mutual Group)


$21,812 (Texas Workers' Compensation Research Center)


12

© 2008 Humantech

Average Cost of Work-Related Low Back Injuries in the U.S. Low back disorders often result from repeated trauma from overexertion or poor working postures, but have been typically defined as occupational injuries.



$33,829 (Texas Workers' Compensation Research Center)

Ergonomics = Fewer WMSDs and Lower Workers’ Compensation Costs It is widely accepted that effective ergonomics programs can help companies limit WMSDs and reduce their workers' compensation costs. A General Accounting Office (GAO) report published in 1997 studied five businesses that experienced reductions in workers' compensation costs directly related to ergonomic improvements. The reductions ranged from 35% to 91% after they implemented an ergonomics program, resulting in workers' compensation savings of over $3.5 million dollars per year for the five companies combined.

Figure 1.5 Percentage Reduction in Workers' Compensation Costs for WMSDs

13


Regulatory Requirements Regulations specific to WMSDs and ergonomics are becoming more widespread and vary considerably by country and state. For instance, the European Union has established Council Directives related to WMSDs, and each country has established regulations to comply with the directives.

In the U.S., the Occupational Safety and Health Administration (OSHA) uses the General Duty Clause as an enforcement mechanism to ensure that companies have WMSD prevention programs where appropriate. The General Duty Clause is contained in the OSH Act of 1971 and states that each employer shall furnish each employee with a place that is free from recognized hazards likely to cause death or serious physical harm.

In addition to the Federal OSHA activities, California has enacted the California State Repetitive Motion Injury (RMI) Standard. This mandatory rule applies to all jobs with more than one work-related repetitive motion injury. An ergonomics program must be implemented for all jobs with more than one RMI. The ergonomics program must include worksite evaluation, controlling exposures that have caused RMIs, and employee training.

Production Efficiency The design of workplaces, including elements such as tool selection and workstation setups, represents performance-shaping factors that determine an individual’s ability to accomplish job tasks in a reliable and efficient manner. Barriers to performance include fatiguing forces, extended reaches, and excessive motions. If these barriers are present in jobs, injury rates will increase, and quality and production will suffer.

A "value-added" analysis illustrates the link between ergonomics and productivity. The formulas used to quantify the impact of improved ergonomics differ depending on the type of activity—repetitive versus non-repetitive.


14

© 2008 Humantech

Calculating Added Value in Repetitive Activities Repetitive activities occur in manufacturing plants, distribution centers, call centers, and many other environments. People are assigned to tasks that they perform in a predefined manner at a predefined rate. Incremental improvements to the ergonomics of their workplace designs are magnified hundreds or thousands of times a day as people repeat the activities.

For example, modifying the reach distance to a parts bin on an assembly line (addressing an ergonomic risk) can decrease the time spent reaching, a non-value-added task, by 0.6 seconds per piece. The time saved becomes significant when you multiply the 0.6 seconds by 200,000 (number of units produced per year) and $18 per hour (fully burdened labor rate), to calculate a $600 savings each year from improving process effectiveness while reducing the risk of WMSDs.

Measuring savings from incremental ergonomic improvements is important because the savings add up fast and can be tied to specific improvements. Reduction in cycle time ranging from 25% to 40% is common when workstations and job/tasks are redesigned to improve ergonomics.

Calculating Added Value in Non-Repetitive Activities Non-repetitive activities occur in the office, process industry, laboratories, and most professional positions. People are responsible for completing activities, but their output is not measured on a micro basis. Here, the important measure of value-added is "time on task" or the amount of time people spend on their core job activities.

Improved ergonomics in the workplace can influence time on task because people spend more time on those activities that do not cause them discomfort. A lab technician who reviews hundreds of samples per day at a poorly arranged microscope workstation will have less time on task than someone who is working with comfortably designed equipment.

The time on task model is valuable because of the potential savings in human capital through improved ergonomics. A 2% increase in productivity—just 10 more minutes per day on core job activities—can contribute $900 per year in added human capital per person (36 hours per year x $50,000 fully burdened salary). While 2% makes a significant contribution, studies have shown that a 20% improvement in productivity is a reasonable expectation with improved office workstations.

15


Case Study Examples Numerous examples demonstrate how improved ergonomics positively affects the bottom line. Humantech's Web site (www.humantech.com) provides numerous case studies that quantify the impact of ergonomics on various performance measures. Three of these are summarized below:

Hamilton Sundstrand used the combined the efforts of training cross-functional teams and involvement of line employees to improve morale and workstation conditions. The company's recordable injury rate decreased from 3.63 (1999) to 0.6 (2006). At the same time, it reduced its lost workday rate by 84%.

Corning (Goose Creek, SC) improved the manual handling process of its lens blanks by implementing a transport system to improve safety, quality, delivery, and cost, which translated into a 75% reduction in defect rate. Total cost avoidance was $3.6 million per year.

Dow Corning (Hemlock, MI) redesigned its silicone process operation to reduce manual material handling by 80%. With the improved work area, productivity has increased by 375%, while labor cost savings were estimated to be around 300, 000 per year. Additional financial benefits included increased sales and reduced workers’ compensation costs.

The following table summarizes the types of improvements these companies experienced.

Table 1.1 Measurable Benefits from Improved Ergonomics

Company Workers' Comp. Productivity Quality Absenteeism

Hamilton Sundstrand

Corning

Dow Corning


16

© 2008 Humantech

Applying Human Performance Ergonomics – The Tools The past two decades have taught us that using the right tool for the job is critical to a successful ergonomics process. Using good, proven tools, but for the wrong purpose, will lead to inefficiencies and a poorly performing ergonomics process.

You can use the tools you will learn about in this course to answer these basic questions:

Table 1.2 Using Tools to Solve Your Ergonomics Challenges

Question Tools

Do I have a problem? Ergonomics Hit List™ Ergonomics Action Form™

How bad is it? BRIEF™ Survey NIOSH Lifting Equation Psychophysical Analysis

Where should I start? BEST Assessment™ EASY™

What should I do about it? Design and Build Guidelines

Does the solution solve the problem? BRIEF Survey™ NIOSH Lifting Equation Psychophysical Analysis

How do I pay for it? STEP™

What are the steps to make it happen? Chapter 9, The Job Improvement Process

The sections that follow offer a preview of these tools.

17


Ergonomics Hit List The Ergonomics Hit List is an observation tool that helps you identify ergonomic issues and resolve them. It answers the question "Do I have a problem?"

The Hit List uses a Find It – Fix It – Check for Success process to apply simple solutions to obvious challenges. The Hit List is described in Chapter 3, Recognizing Ergonomic Issues.

Figure 1.6 The Ergonomics Hit List


18

© 2008 Humantech

Ergonomics Action Form The Ergonomics Action Form is used in conjunction with the Ergonomics Hit List to ensure a participative approach to problem solving. It answers the question "Do I have a problem?"

The Ergonomics Action Form functions as a tracking form to document ergonomic improvements. It is described in Chapter 3, Recognizing Ergonomic Issues.

Figure 1.7 The Ergonomics Action Form

19


BRIEF Survey The BRIEF (Baseline Risk Identification of Ergonomic Factors) Survey is an initial screening tool that uses a structured and formalized rating system to determine ergonomic acceptability. It answers the questions "How bad is the problem?" and "Does the solution solve the problem?"

The BRIEF examines nine body areas for ergonomic risk factors as well as five physical stressors. The BRIEF Survey is described in Chapter 4, Evaluating Ergonomic Risk Factors.

Figure 1.8 The BRIEF


20

© 2008 Humantech

BEST Assessment The BEST (BRIEF Exposure Scoring Technique) assessment is a ranking tool for determining the ergonomic priority of job/tasks based on BRIEF Survey results. It adjusts for different time exposures to ergonomic risk to determine a job hazard score, and takes into account any physical stressors present while performing the job. It answers the question "Where should I start?" This tool is described in Chapter 5, Prioritizing Ergonomic Risks.

Figure 1.9 The BEST Assessment

21


EASY The EASY (Ergonomic Assessment SurveY) is a ranking tool for determining the ergonomic priority of job/tasks based on BRIEF Survey results as well as employee discomfort data and job injury/illness history. It answers the question "Where should I start?" The EASY is described in Chapter 5, Prioritizing Ergonomic Risks.

Figure 1.10 The EASY


22

© 2008 Humantech

Design and Build Guidelines Design and build guidelines are provided for workstations, tools, and equipment to minimize design incompatibility and to optimize human performance. They answer the question "What should I do about the problem?"

The design and build guidelines are described in Chapter 7, Ergonomic Design Guidelines.

Work Reach Guidelines

Criteria Dimension Description

A. Horizontal Reach – Precision Tasks

Max. 11" (279 mm)

B. Horizontal Reach – High-Frequency (≥ 2/min.) or High-Force (≥ 10 lb or 4.5 kg) Tasks

Max. 16" (406 mm)

C. Horizontal Reach – Large Product Assembly Tasks

Max. 22" (559 mm)

Horizontal reach distance from front edge of workstation to hand grasping point

D. Vertical Reach – High-Frequency (≥ 2/min.) or High-Force (≥ 10 lb or 4.5 kg) Tasks

Max. 62" (1.58 m)

E. Vertical Reach – Infrequent or Low-Force Tasks

Max. 74" (1.88 m)

Vertical reach distance from standing surface to hand grasping point

Figure 1.11 Design and Build Guidelines Example

23


NIOSH Lifting Equation The National Institute for Occupational Safety and Health (NIOSH) published the "Revised NIOSH Equation for the Design and Evaluation of Manual Lifting Tasks." This model can be used to determine safe lifting and lowering limits based on task factors including geometry of the lift, frequency of lifting, and load weight. It answers the questions "How bad is the problem?" and "Does the solution solve the problem?"

The NIOSH Lifting Calculation is described in Chapter 6, Manual Material Handling Analysis.

Figure 1.12 Manual Material Handling Guidelines Spreadsheet – NIOSH Lifting Guidelines Sheet


24

© 2008 Humantech

Psychophysical Analysis Guidelines for pushing, pulling, and carrying tasks are used to determine safe limits based on person and task characteristics. They answer the questions "How bad is the problem?" and "Does the solution solve the problem?"

Psychophysical analysis guidelines are described in Chapter 6, Manual Material Handling Analysis.

Figure 1.13 Manual Material Handling Guidelines Spreadsheet – Push Guidelines Sheet

25


STEP The STEP (Standard Time Efficiency Process) Analysis is a way to estimate time savings resulting from ergonomic improvements. It relates reductions in reaching and walking distances to standard time data. The time savings can then be used to cost justify investments in ergonomic improvements. The STEP answers the question "How do I pay for the improvement?"

The STEP Analysis is described in Chapter 8, Cost Justifying Ergonomic Improvements.

Figure 1.14 Cost Justification Worksheet


26

© 2008 Humantech

Using the Right Tool for the Job Too often, people practicing ergonomics become bogged down with complicated formulas and assessment methodologies and equipment. They suffer "paralysis by analysis" and have trouble making gains or improvements. The skilled person is the one who can identify and efficiently use the right tool for the job. Figures 1.15, 1.16, and 1.17 show how you can determine when to use the tools for identifying, prioritizing, and resolving ergonomic issues.

Figure 1.15 Using the Right Tool for the Job

27


Job ImprovementProcess

Clearly Identify the Challenges - NIOSH Lifting Equation (lifting tasks) - MMH Guidelines (push, pull, carry) - Design and Build Guidelines

Brainstorm Controls - Engineering - Administrative - Work Practices

Evaluate Impact of Controls - BESTTM Assessment (WMSD risk) - STEPTM (productivity) - NIOSH Lifting Equation (lifting tasks) - MMH Guidelines (push, pull, carry) - Design and Build Guidelines

Prioritize Controls

Financial Approval - Cost Justification Worksheet

ImplementErgonomic JobImprovements

Key: BEST Assessment - Prioritizes job/tasks based on exposure to WMSD risk factors STEP Analysis - Projects impact of job improvements on productivity NIOSH Lifting Equation - Determines limits for lifting and lowering tasks MMH Guidelines - Determine limits for push, pull, carry tasks Design and Build Guidelines - Provides criteria for dimensions and force Cost Justification Worksheet - Calculates payback period for improvements

Figure 1.16 The Job Improvement Process


28

© 2008 Humantech

Figure 1.17 The Implementation Process

29


How This Manual is Organized Ergonomics follows the principles of effective ergonomic risk management. This approach has been proven successful in hundreds of companies and is consistent with ergonomics standards and guidelines.

Recognize workplace risk factors that contribute to WMSDs, those tasks that require forceful exertions, high rates of repetition, and awkward postures.

Evaluate employee exposure to workplace hazards by comparing job activities to quantitative guidelines for human performance.

Control workplace hazards found to result in significant risk exposure.

This manual focuses on improving problem jobs. The chapters are organized according to the principles of ergonomic risk management.

��

��

��

��

��

�� !�"��

��#�� $!�"��

��

�� %��

��&� ��%�

��'��'��(��)��

��

��*��%+��'��%��

��&� ��!��

Figure 1.18 How This Manual is Organized


30

© 2008 Humantech

References Bureau of Labor Statistics, Lost-Worktime Injuries and Illnesses: Characteristics

and Resulting Time Away From Work, USDL 02-196, Washington, D.C., 2002.

European Agency for Safety and Health at Work, Repetitive Strain Injuries in the Member States of the European Union, 2002.

General Accounting Office, Worker Protection: Private Sector Ergonomics Yield Positive Results, 1997.

Health and Safety Statistics, Part 2: Occupational Ill-health Statistics, Health and Safety Executive, 2001.

National Academy of Sciences, Musculoskeletal Disorders and the Workplace: Low Back and Upper Extremities, National Academy Press, 2001.

National Safety Council, Injury Facts, 2001 edition.

Occupational Safety and Health Administration, National News Release: USDL 99-3331999, Washington, D.C., 1999.

Preventing Pain Sitting at Your Desk, www.chw.healthinkonline.com/ dohealth/member/vitWellness.asp?wellID=472

31


Notes


32

© 2008 Humantech

Notes

33

2 hapter 2 Work-Related Musculoskeletal Disorders

About This Chapter..................................................................................34 "Work Doesn’t Need to be a Pain!"®........................................................35 Would You Do it This Way?.....................................................................36 Posture, Force, and Frequency...............................................................37 What are Work-Related Musculoskeletal Disorders?..............................38 WMSDs in Industry..................................................................................40 How Do WMSDs Occur? .........................................................................41 Types of WMSDs.....................................................................................45 References ..............................................................................................54


34

© 2008 Humantech

About This Chapter Chapter 2 is part of the Recognition phase of ergonomic risk management.

��

� ��!��"��

��

��

��

�� !�"��

��#�� $!�"��

#��

�� %��

��&� ��%�

��'��'��(��)��

$�%��

��*��%+��'��%��

��&� ��!��

Figure 2.1 Where We Are Now

This chapter describes the different types of work-related musculoskeletal disorders (WMSDs) and how they occur. You'll find answers to these questions:

Why should I recognize WMSDs?

What are WMSDs?

How do I identify common WMSDs and their signs and symptoms?

35

Chapter 2: Work-Related Musculoskeletal Disorders

"Work Doesn’t Need to be a Pain!"® The exertion associated with "putting in a good day’s work" is a familiar experience for all of us. In general, we feel pride at having done a good job, and, although we may be tired, we can still go home and spend an active evening with our family and friends. A fair effort for a good day’s work is acceptable.

Dragging ourselves home, with barely enough energy to make it to the couch, suffering muscle cramps, numbness, and pain, and not being able to get out of bed in the morning because of pain, is not acceptable. Putting in a good day’s work is one thing; punishing our bodies is another. Pain is an early warning sign that we are doing something wrong.

For example, when we drive a car we are careful to keep the car within an RPM band that is "safe" for the engine. If we don’t, we know that the increased wear and tear will shorten the life of the engine, and we will be faced with costly repairs.

Just like cars, people have certain limits. If we work outside those limits, we will accelerate fatigue in body components, shortening their functional life. This applies to the heart of a person just as it does to the engine of a car, to our muscles as it does to the drive train, and to our nervous system as it does to the electrical system and controls.

If we exceed the capacity of the human for the better part of each day, the components will decay, become unreliable, and may eventually fail. Just as we must run machines within their limits, we must also keep people within limits.

Figure 2.2 Human Performance Gap

Pain is an early warning sign that something is potentially wrong with the job or the way we are performing it. Remember: "Work doesn’t need to be a pain!"


36

© 2008 Humantech

Would You Do it This Way? Ergonomics is a common-sense way of looking at the workplace. Keep in mind that people, not machines, are the sole source of producing products, fixing equipment, and ensuring product quality.

Every time we look at a job we must remember that people do the job. We must ask ourselves a fundamental question: Would I do it this way? We must look for improvements until we can honestly say "we would do it this way".

Figure 2.3 "Would you do it this way?"

By thoughtfully reviewing a workstation layout or the design of a hand tool, we are often able to intuitively identify what is wrong with the design and begin to develop solutions.

Ergonomics is an attitude, a way of looking at the workplace.

After reviewing a job, can we honestly answer that this is the most

functional,

comfortable,

safe, and

logical way to do the job?

Or do certain tasks or pieces of hardware stand out as awkward, difficult, or even painful to use? It is this awkwardness, difficulty, and pain that can lead to musculoskeletal disorders, or MSDs.

37


Posture, Force, and Frequency Ergonomic issues in the workplace can be summarized as awkward postures, excessive forces, and extreme frequencies of movement. These are the primary risk factors for the development of WMSDs (described on the following page). Just like the fire triangle, in which three components—fuel, source of ignition, and oxygen—create fire, postures, forces, and frequencies can work together to turn small ergonomic issues into big problems and create an Ergonomics Fire Triangle.

Figure 2.4 The Ergonomics Fire Triangle

Posture ► Awkward postures (non-neutral joint positions) Force ► Excessive force (pressure, weight, or grip) Frequency ► Extreme frequency and/or duration of movement

The same risk factors that contribute to WMSDs are also barriers to industrial performance. Repeatability of manufacturing operations is compromised when extreme postures are required, and recovery times from high force applications increase the non-value-added content of job tasks. At a microelement level, the same motions that contribute to ergonomic risk are the motions that rob operations of efficiency.

The Ergonomics Fire Triangle reminds us to focus job improvement efforts on the most critical ergonomic issues.


38

© 2008 Humantech

What are Work-Related Musculoskeletal Disorders? Without the four elements of skill, will, good coaching, and great equipment, our industrial athlete cannot be successful. Not only will the industrial athlete be unsuccessful, he or she may develop a special type of disorder that affects connective tissues, a work-related musculoskeletal disorder or WMSD.

WMSDs are disorders of the muscles, nerves, tendons, ligaments, joints, cartilage, or spinal discs that are the result of exposure to ergonomic risk factors over time. They are not a diagnosis, but a class of disorders with similar characteristics. The disorders occur as a result of months and years of overuse of human joints and connective tissues such that they become sore and sometimes unusable. WMSDs are not the result of an instantaneous or acute event such as a trip, slip, or fall.

Work-related indicates that they occur in relation to certain activities performed routinely on the job. The National Institute of Occupational Safety and Health (NIOSH) defines the link between WMSDs and workplace ergonomic risk exposures as one of the following:

Musculoskeletal disorders to which the work environment and the performance of work contribute significantly

or

Musculoskeletal disorders that are made worse or longer lasting by working conditions (NIOSH, 1997)

Other terms commonly used to refer to these types of disorders include cumulative trauma disorders, repetitive motion disorders, repetitive strain injuries, and overuse syndrome.

39


The "Trauma Bucket" An easy way to visualize WMSDs is to think of your body as a bucket. Microtrauma from your job and from non-job activities drips into your body’s "trauma bucket." Fortunately, the body can heal with time and safely absorb a certain amount of trauma (like a healing valve at the bottom of the bucket). But, if we place more trauma into the bucket than the natural healing process can absorb, the result is impaired movement, or in the worst cases, a disabling injury.

Figure 2.5 The Trauma Bucket

Every one of us has a trauma bucket of a different size. Just as individuals respond differently to low-dose exposures to toxins, with some becoming ill very quickly and others never being affected, people respond differently to microtrauma from ergonomics hazards. This explains why only some people at a challenging job develop WMSDs while the rest fight through the hassles and pain without a recordable injury or illness.


40

© 2008 Humantech

WMSDs in Industry WMSDs are not isolated to any one industrial sector; in fact, we can find thousands of reported injuries/illness across all sectors. The Bureau of Labor Statistics (BLS) publishes detailed characteristics for WMSD cases that resulted in at least one lost day from work. Figure 2.6 below compares the Cumulative Trauma Incidence Rate for major manufacturing sectors as reported by the BLS.

Incidence rate refers to the number of injuries per 100 full-time employees. According to the BLS, repetitive motion incidents make up approximately 8% of all lost workday WMSDs.

Figure 2.6 Repetitive Motion Incidence Rates by Industry Sector (BLS, 2001)

Based on this data, four manufacturing sectors appear to have substantially different repetitive motion incidence rates:

Food and kindred products

Apparel and textiles

Furniture and fixtures

Rubber and plastics products

These sectors represent industries that rely on high volume, manual work that is known to be challenging.

41


How Do WMSDs Occur? As the "Trauma Bucket" (Figure 2.5) helps illustrate, WMSDs are based on a dose and response relationship. Similar to hearing loss, they occur gradually over a long period of exposure to a low-level harmful agent. A brief exposure to these agents would not cause harm, but prolonged exposure results in reduced ability to function.

To control WMSDs, we first must understand the factors that contribute to their development. Ergonomic risk factors are "conditions of a job, process, or operation that contribute to the risk of developing Cumulative Trauma Disorders" (OSHA, 1990). The presence of risk factors does not necessarily predict that an individual will suffer a health problem as a result of exposure to the risk factor. Rather, a risk factor is a condition of the workplace that increases one’s chance of developing a WMSD, and to which exposure should be limited, or totally avoided, in pursuit of a 100% healthy and safe working environment.

A substantial body of credible epidemiological research provides strong evidence that three physical work-related risk factors contribute to the development of WMSDs (NIOSH, 1997; NAS 2001): awkward postures, excessive forces, and extreme frequencies of movement.

Posture There are certain postures in which the joints can absorb force more easily than in others. Phrased another way, there are certain postures in which the body is more susceptible to injury. Typically, the closer to the extremes of a joint’s range of movement, the less capable the joint is. An extreme posture by itself may stress joint components and reduce or occlude blood flow. Consequently, we attempt to maintain a neutral joint posture while performing our work.

Figure 2.7 illustrates the results of a study that compared the effect of two different types of pliers: traditional straight handled pliers and bent handled pliers. Bent handled pliers were provided to one group of trainees to enable a straight wrist posture. According to the study, approximately 65% of the trainees that used the traditional straight pliers experienced tenosynovitis, epicondylitis, and carpal tunnel irritation, as opposed to 10% of the trainees that used the bent handled tool (Tichauer, 1978).


42

© 2008 Humantech

Figure 2.7 Improved Posture Reduced WMSDs

Force Gripping, pinching, pushing, pulling, and lifting objects place additional force on the body's joint structures. Increasing these forces requires additional muscle exertion, and places greater loads on joints and connective tissues. Prolonged or repeated exertions of this type can cause a feeling of fatigue, and may contribute to musculoskeletal problems when there is inadequate time for rest or recovery.

Frequency An aluminum soda can is a good example of how low forces can damage the underlying structure when applied repeatedly. Lightly squeezing an aluminum can will cause the sides to bend inward, but the can will regain its shape. The force applied was not strong enough to immediately cause damage. However, if we repeatedly apply this same force, say 100 or 200 times, the can develops a fatigue debt and a break can occur in the aluminum sides.

It is the same for the human body, but instead of 100 or 200 repetitions, the frequency is measured in the thousands and tens of thousands of repetitions. The repeated application of a force that is not strong enough to cause immediate damage can, over time, induce fatigue in our connective tissues and wear them out.

Frequency exists on a continuum. At one extreme of the continuum exists high frequency, or repetition. At the other extreme is the lack of frequency, or duration. Both high frequency movements and sustained postures can contribute to fatigue debt. The longer the period of continuous work, the longer the required recovery or rest time. Tendons and muscles can often recover from the fatigue debt if sufficient time passes between exertions. Fatigue and muscle-tendon strain can accumulate if motions are frequently repeated. Effects of repetitive motions from performing the same work activities increase when awkward postures and forceful exertions are involved.

43


Combination of Risk Factors As individual risk factors, posture, force, and frequency are all significant. But when combined, these risk factors become much more important and contribute to wear and tear injuries at a greater rate than would be intuitive.

One study examined the effects of hand repetition and grasping force on WMSDs (Silverstein, 1985). The combination of risk factors greatly increases the odds of developing a WMSD; exposure to either high force or highly repetitive tasks alone increased the risk of a WMSD by about three times, while exposure to both high force and highly repetitive tasks increased the risk of WMSDs by 17 times.

Figure 2.8 Odds Ratios for Force, Frequency, and Combined Risk Factors


44

© 2008 Humantech

Physical Stressors Certain physical stressors can accelerate the onset of WMSDs by reducing blood flow to tissues. The most common physical stressors in the workplace include:

Vibration – contact with vibrating objects such as grinding tools (segmental vibration) or while operating heavy equipment (whole-body vibration). Segmental vibration can lead to reduced blood flow to the exposed body part, which causes stiffness and numbness in the affected area. Exposure to whole-body vibration for extended periods of time, as in driving a truck cross-country, can result in digestive and back disorders.

Low temperatures – regular exposure (more than two hours per day) to temperatures below 66°F. The body responds to prolonged exposure to low temperatures by limiting blood flow to the extremities. A reduction in blood flow to the fingers and hands can cause numbness and reduces grip strength.

Soft tissue compression – static force applied to the body for prolonged periods, for example, resting the elbows on a hard surface while sitting. The reduction in blood flow is a result of pressure on the body tissues. This is a concern particularly when blood vessels are located near the surface of the skin, such as on the back of the hand.

Impact stress – a dynamic force applied to the body, for example, using the hand as a hammer. The body responds to impact stress by limiting blood flow to the exposed body part.

Glove issues – working with gloves that fit poorly or increase the force needed to grasp objects. Gloves that are too tight restrict blood flow to the fingers and cause numbness in the fingers. Gloves that are too large not only limit dexterity, but also result in higher force gripping. Gloves that decrease the coefficient of friction between the object being handled and the gloves also increase the amount of force that the operator must exert in order to handle the object.

45


Types of WMSDs Three basic types of WMSDs for the upper extremities are tendon disorders, nerve disorders, and neurovascular disorders. WMSDs also include back disorders. This section discusses some of the more common WMSDs and their symptoms and risk factors.

Tendon Disorders Tendons connect muscles to bones. When we contract muscles in our forearm (the movers), the tendons (cables) pull on the bones (levers) in our hand and create movement. These movement mechanics apply to other areas of the body as well.

Figure 2.9 Lever System of the Hand and Arm

Tendon disorders typically occur at or near the joints where the tendons rub nearby ligaments and bones. Exposure to non-neutral postures with high force or high repetition may cause the tendons or tendon sheaths to become inflamed or irritated. The affected body area may become inflamed as a result of this contact. Common symptoms are a dull aching sensation over the tendon, discomfort with specific movements, and tenderness to touch.


46

© 2008 Humantech

The following table provides a summary of tendon disorders. The sections that follow describe them in more detail.

Table 2.1 Risk Factors for Tendon Disorders

Tendon Disorder Description Occupational Risk Factors

Tendinitis Swelling of the tendons Repetitive and forceful manual exertions

Tenosynovitis Swelling of the tendons and the tendon sheath wall

Extremely repetitive motions

DeQuervain's disease

Swelling of the tendon and tendon sheath at the base of the thumb

Hand twisting with forceful gripping

Ganglion Cyst Accumulation of fluid within the tendon sheath

Repetitive and forceful hand exertions

Epicondylitis Irritation of the forearm tendon near the elbows

Using the arm for impact or jerky throwing motions, repeated or forceful forearm rotation while bending the wrist

Tendinitis All force from muscles is transmitted through the tendon cables. If we continually stress the cables, they can become irritated, sore, and swollen, resulting in tendinitis. Tendinitis is common in the wrist, elbow, and shoulder.

Figure 2.10 Tendinitis – Swollen Tendon

47


Tenosynovitis Tenosynovitis, often the result of extremely repetitive motions, is swelling of the tendons and tendon sheath wall. Tissue builds up on the tendon sheath wall, causing bumps on the sheath.

Figure 2.11 Tenosynovitis – Swollen Synovial Sheath

DeQuervain’s Disease DeQuervain’s disease is a common type of stenosing tenosynovitis (a combination of tendinitis and tenosynovitis) in which the tendon and tendon sheath swell at the base of the thumb. It results from excessive hand twisting with forceful gripping. This disorder is named after the French doctor who first described it.

Figure 2.12 DeQuervain's Disease


48

© 2008 Humantech

Ganglion Cyst This bump under the skin is caused by the accumulation of fluid within the tendon sheaths. The fluid accumulates as the result of repetitive and forceful hand exertions. Balancing heavy trays on a fully extended wrist as restaurant wait staff often do can lead to ganglion cysts.

Figure 2.13 Ganglion Cyst

Epicondylitis Tennis elbow, or lateral epicondylitis, is one of the more common WMSDs. Lateral epicondylitis is irritation of the muscle and tendons that attach to the end of the humerus (upper arm bone) on the outside of the elbow.

Golfer’s elbow, or medial epicondylitis, also a common WMSD, is an irritation of the muscle and tendons that attach to the end of the humerus (upper arm bone) on the inside of the elbow.

Figure 2.14 The Elbow Joint

49


Nerve Disorders Nerve disorders commonly occur as a result of nerve entrapment or pressure on the nerve. The entrapment or pressure may be a result of (1) repetitive cumulative trauma to a muscle over a long period, the resulting muscle swelling causing pressure on the nerve, or (2) mechanical irritation of the nerve by surrounding tendons or muscles. The entrapment or pressure on the nerve will impede blood flow, oxygenation, and nerve signal transmission. Symptoms may include loss of sensory and motor function.

The following table provides a summary of nerve disorders.

Table 2.2 Risk Factors for Nerve Disorders

Nerve Disorder Description Occupational Risk Factors

Carpal Tunnel Syndrome

Compression of the median nerve from swelling of the finger flexor tendons in the wrist

Repetitive high force gripping, gripping with non-neutral wrist postures

Cubital Tunnel Syndrome

Compression of the ulnar nerve from mechanical stress near the elbow

Repeated or sustained pressure on the elbow from hard or sharp edges


50

© 2008 Humantech

Carpal Tunnel Syndrome Tendons leading from the forearm to the fingers, the median nerve, and blood vessels pass through the carpal tunnel at the wrist. If the tendons and tendon sheaths running through the carpal tunnel become irritated and begin to swell, the median nerve may be impinged. Chronic swelling of the finger flexor tendons can lead to carpal tunnel syndrome.

Carpal tunnel syndrome has become well known due to media exposure. However, it is a relatively rare disease; less than 5% of all WMSD incidents resulting in at least one day away from work were reported as carpal tunnel syndrome by the Bureau of Labor Statistics (BLS, 2001).

Figure 2.15 The Carpal Tunnel

Cubital Tunnel Syndrome Many people rest their elbows on their work surfaces, sometimes to support the weight of their head, other times to relieve stress on their back. The ulnar nerve, which runs near the elbow, can become pressured when the elbow is exposed to hard surfaces such as unpadded tabletops. This can lead to cubital tunnel syndrome.

Figure 2.16 The Cubital Tunnel

51


Neurovascular Disorders Neurovascular disorders affect both nerves and nearby blood vessels. They occur as a result of pressure on these tissues or result from exposure to vibration. The affected area of the body may experience reduced circulation, resulting in less oxygen and nutrients to the muscles. Typical symptoms are pain, numbness, tingling, cold sensitivity, prickly sensations, or skin color change.

The following table provides a summary of common neurovascular disorders.

Table 2.3 Risk Factors for Neurovascular Disorders

Neurovascular Disorder

Description

Occupational Risk Factors

Thoracic Outlet Syndrome

Compression of the nerves and blood vessels between the neck and shoulders

Carrying loads over the shoulder, frequent reaching above shoulder level

Hand-Arm Vibration Syndrome

Reduced blood supply to the fingers caused by closure of the digital arteries

Forceful gripping and prolonged use of vibrating tools, including both hand-held and stationary tools

Thoracic Outlet Syndrome Thoracic outlet syndrome is the general term used to describe compression of the nerves and blood vessels between the neck and shoulders. It can occur during activities such as frequent reaching above shoulder level or carrying heavy objects.

Figure 2.17 The Shoulder Girdle Figure 2.18 Neck Anatomy


52

© 2008 Humantech

Hand-Arm Vibration Syndrome Also known as "white finger syndrome" and "Raynaud’s Phenomenon of Occupational Origin," hand-arm vibration syndrome affects the fingers causing intermittent numbness or tingling, and often the skin turns pale or cold. Other symptoms are a reduction in grip strength and finger dexterity. It is caused by forceful gripping and prolonged use of vibrating tools (e.g., pneumatic hammers, chain saws, power grinders) and is accelerated by exposure to cold temperatures.

Back Disorders Back disorders are also classified as work-related musculoskeletal disorders. The most common areas for injury are related to tendon/ligament, muscle, and nerves. To understand these types of injuries we should understand the anatomy and mechanics of the back.

Anatomy of the Back The figure below illustrates that the back is a flexible, curved column composed of a series of bones (vertebrae) separated by shock absorbing discs. The structure is held in compression by a large number of muscles and ligaments. By acting together, they give the spine the ability to bend and twist. The spine also protects the spinal cord and acts as a distribution center for the nerves that run between the brain and the other parts of the body.

Figure 2.19 The Spine

Anatomically, the spine is an unstable structure. We create the illusion of its stability by using muscle groups in the trunk to keep the back stable.

53


Mechanics of the Back The back can be modeled as a simple lever system that supports the weight of the upper body as well as any loads supported by the upper body. Since the muscles that act to balance the upper body are very close to the fulcrum of this lever system (the base of the spine), the back is at a significant mechanical disadvantage whenever the load is extended outward.

Types of Back Disorders Back disorders may include the following:

One-time exertion injuries, those that occur as the result of one incident, may include both sprains and strains. A sprain is generally caused by a one-time exertion that tears a ligament, whereas a strain is generally caused by a one-time exertion that tears a tendon.

Deterioration of the shock-absorbing discs in the lower back results in degenerative disc diseases. Due to the human anatomical structure, this weakening typically occurs on the face of the shock absorber near the nerve roots that feed into and out of the spinal cord. As the shock absorber bulges, direct contact with the nerve roots can occur.

Figure 2.20 A Leaky Disc Can Put Pressure on Nerves

Herniated/ruptured/bulging discs are caused by degenerative disc disease or injury to the spine. Disc disease may result from tiny tears or cracks in the outer shell (capsule) of the disc. The jelly like material inside the disc may be forced out through the tears or cracks in the capsule, causing the disk to bulge, break open (rupture), or break into fragments. The herniated disc itself generally does not cause pain; the pain usually occurs when the disc presses against a nerve, and the nerve becomes inflamed and swollen.

Sciatica is a symptom frequently associated with a lumbar herniated disc. Pressure on one or several nerves that contribute to the sciatic nerve can cause pain, burning, tingling, and numbness that extends from the buttock into the leg and sometimes into the foot.


54

© 2008 Humantech

References Bureau of Labor Statistics, 2001, http://www.bls.gov/iif.

National Academy of Sciences, Musculoskeletal Disorders and the Workplace: Low Back and Upper Extremities, National Academy Press, 2001.

National Institute of Occupational Safety and Health (NIOSH), Musculoskeletal Disorders (MSDs) and Workplace Factors, 1997, http://www.cdc.gov/niosh/ergoosci1.html.

Occupational Safety and Health Administration (OSHA), 3123: Ergonomics Program Management Guidelines for Meatpacking plants, Washington, D.C., 1990.

Silverstein, B.A., The Prevalence of Upper Extremity Disorders in Industry, Ann Arbor, Center for Ergonomics, University of Michigan, 1985.

Tichauer, E.R., The Biomechanical Basis of Ergonomics, Wiley Interscience, New York, 1978.

55


Notes


56

© 2008 Humantech

Notes

57

3 hapter 3 Recognizing Ergonomic Issues

About This Chapter..................................................................................58 Introduction to the Ergonomics Hit List™................................................59 The Hit List – "Find It"..............................................................................60 The Hit List – "Fix It" ................................................................................71 Ask the Operator .....................................................................................76 Continuous Improvement Process ..........................................................77 The Ergonomics Action Form™ ..............................................................79 Completing the Ergonomics Action Form................................................81 Avoiding Potential Pitfalls With the Ergonomics Action Form .................88


58

© 2008 Humantech

About This Chapter Chapter 3 is part of the Recognition phase of ergonomic risk management.

��

� ��!��"��

��

��

��

�� !�"��

��#�� $!�"��

#��

�� %��

��&� ��%�

��'��'��(��)��

$�%��

��*��%+��'��%��

��&� ��!��


This chapter introduces the Ergonomics Hit List and Ergonomics Action Form, tools you can use to identify ergonomic issues through observation, generate job improvement ideas, and turn your ideas into an action plan. You'll find answers to these questions:

Why should I recognize ergonomic issues?

What are ergonomic issues?

How can I identify ergonomic issues and job improvements?

59

Chapter 3: Recognizing Ergonomic Issues

Introduction to the Ergonomics Hit List™ The Ergonomics Hit List is a simple tool that will help you identify ergonomic issues and job improvements.

Figure 3.2 The Ergonomics Hit List Card (Front)

When to Use the Hit List Observation is the most basic form of workplace assessment. The Ergonomics Hit List is a fundamental observation tool that helps you identify obvious ergonomic issues in all work situations. Because the Ergonomics Hit List is a qualitative approach, apply it when the level of necessary detail about the job is low and when off-the-shelf solutions are readily available.

Limitations of the Hit List The Ergonomics Hit List does not provide measurable (quantifiable) risk evaluation, nor does it prioritize jobs for ergonomic intervention. When a high level of detail about a job is necessary and when off-the-shelf solutions are not readily available, use other assessment tools such as the BRIEF Survey (Chapter 4, Evaluating Ergonomic Risk Factors), or the BEST or EASY (Chapter 5, Prioritizing Ergonomic Risks).


60

© 2008 Humantech

The Hit List – "Find It" Identifying ergonomic issues is the first step in the ergonomic improvement process. The Ergonomics Hit List defines ten Find It items, and the Ergonomics Action Form (see page 79) provides a format for describing them for resolution.


The sections that follow describe each Find It item in detail. Included are common work-related activities in which the issues are often identified, and potential ergonomic improvements that can reduce or eliminate the issues.

Find It: Ten easy-to- remember ergonomic issues you can identify through direct observation.

61


Wash Rag WMSDs can occur without a substantial force component being involved. Several studies have demonstrated that even the combination of a bent wrist posture and relatively moderate task frequencies can cause damage.

The Hit List item Wash Rag is the condition of extreme wrist bending, so named after any posture that we would use to squeeze out a rag. The wrist postures involved have very exact names describing their movements, including radial and ulnar deviation, and flexion and extension. Wash Rag provides a simple, easy to remember way to visualize these postures, all of which we should avoid. A straight wrist posture is always best.

Figure 3.4 Wash Rag

Common Wash Rag Activities Potential Improvements

Retrieving parts from bins Angled and/or low height bins

Screwdriver use Powered tools Wrong tool for the job Pistol grip tools for vertical work activity, in-

line tools for horizontal work activity

Part installation Angled worktable, possibly using a jig or fixture

Keyboarding Proper keyboard height and angle


62

© 2008 Humantech

Elbows Out The body knows that working with a bent wrist can cause harm. When confronted with a poor working condition that would require wrist bending, or Wash Rag, we subconsciously transfer the stress to the elbow by "winging" it out to the side. The Hit List item Elbows Out reflects this posture.

Elbows Out is an attempt to keep the wrist straight. This is a common defense mechanism our body uses to avoid ergonomic issues involving the wrists. For example, Elbows Out is often the result of using screwdrivers to manually drive screws; employees often "wing out" the elbow during the continuous forearm rotation involved in the task.

Elbows Out postures can result in the compression of nerves between the muscles of the forearm and/or inflammation of the tendons at the elbow. For this reason, elbow soreness or injury often occurs before wrist injury.

Look for the Elbows Out and remember they are associated with poor ergonomic conditions.

Figure 3.5 Elbows Out

Common Elbows Out Activities Potential Improvements

Hand starting/threading a bolt or fastener

Powered tools

Wrong tool for the job Pistol grip tools for vertical work activity, in-line tools for horizontal work activity

Using pliers Angled handle pliers

Opening pressure valves Motorized valves Screwdriver use Battery powered tools, different fastener

63


Shoulder Too High/Too Low Shoulder Too High/Too Low reminds us that if the shoulder is too high, the job is too high, and if the shoulder is too low, the job is too low. Our body is very flexible and we accommodate to the work environment. Yet bending over and reaching up are high-risk postures that can contribute to WMSDs.

Every working height, reach distance, and placement of tools, equipment, and controls in the work environment must be designed with every employee in mind, from the largest to the smallest, and all sizes in between. Simply considering an average worker’s size is not sufficient. For example, consider shoe size. If one employee requires a size seven shoe, and another employee requires a size eleven, we would not choose an average shoe size of nine to accommodate them both—size nine would fit neither. Similarly, we must match workstation and equipment sizes to the sizes of the operators, or ergonomic issues may result.

Figure 3.6 Shoulder Too High/Too Low

Common Shoulder Too High/Too Low Activities

Potential Improvements

High storage of materials Lower the storage height below shoulder level, provide rolling stepstools with casters that lock with applied weight

Low/high work height Adjustable height tables Seated computer work Adjustable height chairs and stools with

footrests for smaller employees

Low/high placement of switches, levers, buttons

Place switches near elbow height

Retrieving parts from totes Lower bin heights and arrange in a semi-circle


64

© 2008 Humantech

Hungry Head Most work activities require the employee to see, for example, when assembling a product, inspecting a completed unit for defects, or looking upstream at an assembly line to gauge production levels. Hungry Head refers to the search for visual information. If sight lines are not clear, or areas are poorly lit, the body will naturally position the eyes to be in the best position to see what they need to see.

Hungry Head conditions lead primarily to muscular pain in the neck and upper back/shoulder. Over time, this posture may compress the nerves and restrict blood flow.

Figure 3.7 Hungry Head

Common Hungry Head Activities


Looking into a microscope or at a computer monitor

Height-adjustable platforms under microscopes and monitors, height adjustable work table

Bent neck doing precision work (e.g., small part assembly)

Self-supporting magnifying glasses with task lighting, angled work area using a jig or fixture

Inspection Provide task lighting

Reading dials or displays Proper height and size of dials and displays General assembly work Raise and angle work surface

65


Butts Up The back is constructed to provide a substantial amount of mobility. However, in return for this mobility, we must accept some shortcomings associated with an unstable and curved column of support. Loads are unequally distributed in a curved spine, and high muscle forces are required to stabilize it. Consequently, the lower back (lumbar area) can be at risk for injury.

Butts Up is a condition of bending over, thus extending the upper body over the floor. To keep the body from falling over, the spine is transformed into a rigid cantilever by muscular action. This action can generate extremely high compressive forces in the lower back muscles and the spinal discs located between the vertebrae.

What do you observe on the shop floor? If you see a lot of "butts" instead of a lot of faces, it is because people must bend over to retrieve, handle, or place materials.

Figure 3.8 Butts Up

Common Butts Up Activities Potential Improvements

Lifting bins off floor Load levelers or lift tables to maintain consistent retrieval heights

Retrieving boxes of finished parts off the floor

Raise boxes on tables

Reaching into wire storage crates Lift and tilt tables


66

© 2008 Humantech

Twist and Shout Parts, tools, and work activities not positioned directly in front of the employee may introduce body twisting into the operation. Twisting while working generates shear and compressive forces into the cervical (neck) and lumbar (lower back) regions of the spinal discs, escalating the chance of injury.

Twist and Shout is the condition of twisting at the neck or back while performing work activities. This posture may be the result of the physical work arrangement. For example, the parts necessary to complete an assembly activity may be located to the side rather than directly in front of the employee. Twist and Shout may also be the result of poor work practices, such as twisting the body to place items on a pallet rather than taking a step to assume a more neutral position before placing the items.

One way to identify Twist and Shout postures is to observe the location of the shoulders in relation to the hips. If you see that the shoulders are not in the same line as the hips, you have Twist and Shout postures.

Figure 3.9 Twist and Shout

Common Twist and Shout Activities


Poor placement of shared tools

Individualized work areas to limit cross-reaching for commonly used items, proper placement of instruments (e.g., if used by right hand, place on right side)

Reaching across the body to retrieve parts

Place part bins on the side of retrieval

Retrieval from bins Tilting or gravity feed bins

Excessive reaching to parts

Reduce reach to parts, deliver parts on a gravity slide closer to the employee

67


Horizontal Distance Observe how far employees must reach to retrieve tools, gather parts, activate buttons, flip switches, and lift totes. The farther the reach, the larger the amount of force required to counterbalance upper body weight.

This force is magnified when lifting is part of the activity. Small loads, held at a distance, can increase the amount of force on the lower back by as much as 15 times. For example, a 10-pound (4.5 kg) weight held away from the body with the arms outstretched and the back bent forward generates about 150 pounds (68 kg) of force on the lower back.

Horizontal Distance is the condition of working far away from the body, either in front or to the side. If a work activity requires a far reach, the potential for ergonomic risk to the shoulders and back increases. Horizontal Distance also increases the time necessary to complete an activity. Reaching may be necessary, but excessive reaching is wasteful and inefficient. By eliminating or reducing far reaches, work activities can become faster and easier to perform.

Figure 3.10 Horizontal Distance

Common Horizontal Distance Activities


Reaching into equipment Reduce excessive guarding and/or equipment components to minimize reach distance, install a tray that loads into equipment for processing

Excessive reaching to part bins

Bring part bins closer, deliver parts on a gravity slide, tilt bins

Lack of toe clearance Provide a toe cutout

Retrieving/placing boxes on pallets

Swivel top table


68

© 2008 Humantech

Sit vs. Stand To ensure that people can perform a job task consistently time after time while also minimizing potential ergonomic risk, choose the appropriate working position—Sit vs. Stand—for the particular task.

Operations involving high visual attention (critical inspection tasks), fine finger motion (small parts assembly), and long processing times (all day long) are good candidates for sitting. For sitting tasks, provide a proper chair with good lumbar (lower back) support and height adjustability, foot support, and adequate leg clearance with no leg obstructions.

Standing is a good choice for operations that require operator mobility (taking a step or two to retrieve parts) or moderate application forces (inserting fasteners with a powered tool), or where work activity varies from one product to another (operator works many machines at the same time). Anti-fatigue matting and foot rails are recommended for stationary workstations.

Sit vs. Stand also helps us to spot poor sitting and standing conditions like the one pictured below.

Figure 3.11 Sit vs. Stand

Common Sit vs. Stand Activities


Prolonged standing Provide anti-fatigue matting, foot rail

Thick conveyors (inadequate knee clearance)

Low profile (thin) conveyors to increase leg clearance

Knee obstructions Provide knee clearance, remove excess guarding

Sitting or standing all day Sit-stand seating

Sitting all day Good ergonomic seating with lumbar support

69


Bad Vibes Exposure to vibration from hand tools can permanently damage the small blood vessels and nerves in the fingers. Vibration also induces muscle fatigue because the gripping force required to hold, control, and use the tool is increased. Although newer tools provide better vibration dampening, regular maintenance is necessary to ensure that they are operating within their design specifications. Whole-body vibration has also been shown to increase employee discomfort, disorientation, and joint degeneration in the feet and knees.

Bad Vibes is a condition in which the employee is exposed to vibration. Although it is sometimes difficult to observe or precisely measure, ask the employee if the tool/equipment is causing noticeable vibration.

Figure 3.12 Bad Vibes

Common Bad Vibes Activities


Tool vibration (e.g., grinders, sanders)

Vibration-absorbing grips for tools, routine tool maintenance and bit replacement, provide tools with built-in vibration dampening

Vibration from large machining equipment

Separation of floor standing equipment and adjacent platforms, install anti-vibration pads under equipment or between equipment and work platform

Vibratory parts feeders Isolate parts feeder on separate table


70

© 2008 Humantech

Contact Contact stress is another name for soft tissue compression. Contact occurs when a hard or sharp piece of equipment or tool edge places pressure on soft body tissue such as the legs, abdomen, forearms, or palms of the hands. This contact increases the force component of the job while reducing blood flow to the affected body area. In addition, contact may lead to skin irritation. Continued contact may cause blood vessels to compress and the skin to harden.

Operators may sit differently at workstations to avoid contact stress to the legs, hold tools in awkward positions to avoid a sharp or hard edge, or even reach farther than normal at a workstation to avoid a pointed workstation corner or fixture.

Look for, and ask employees about Contact conditions, which often require only minor adjustments to result in significant improvements to working conditions.

Figure 3.13 Contact

Common Contact Activities Potential Improvements

Leaning elbows against a hard table edge

Radius (round) table edge, pad table edge, add table edge protector

Holding sharp, pointy tool handles

Rounded tool handle, pad tool handle, replace tool

Leg interference under the work table while seated

Remove obstruction, standing workstation

Hand/arm contact with pointed jigs/fixtures

Round jig/fixture edges

Small tool handles Larger tool handles, rounded end on tool handles

71


The Hit List – "Fix It" The three Hit List Fix It items represent solution strategies for resolving ergonomic issues. These solution strategies, combined with the perspective of "Would you do it this way?," can be used to pinpoint practical job improvements that affect operator comfort, health, and performance.


Fix It: Three solution strategies to identify low-cost/high-impact job improvements.


72

© 2008 Humantech

Tool/Target Ergonomic issues are the result of a mismatch between the workstation and the employee and/or the tool used in the work activity. Changing either the tool that is used or the target location can improve all ergonomic issues; when an employee does not use a specific tool, the tool is the employee’s hand. It is important to note that ergonomic improvements often occur by changing both the tool and the target.

Change the Tool Tools are designed for specific applications in a specified direction. If an employee uses the wrong tool to complete a task, he or she may resort to non-neutral postures such as wrist deviations and shoulder raising, which increase the chance of injury. It is important to select and use a tool that is appropriate for the specific work activity to promote more neutral body postures. Here are general guidelines for tool selection and design:

Use pistol grip tools when applying force horizontally, on a vertical surface

Use in-line tools when applying force vertically, on a horizontal surface

Lengthen or shorten handles and tool bits to bring the reach to the tool into the operator’s Comfort Zone (see the next section)

Provide a secondary tool handle for better control and improved postures

Balance tools and orient them in the direction of use

Change the Target If the proper tool cannot be used, change the target orientation to fit with the tool and promote neutral body postures. Ways to modify the target include:

Provide a jig or fixture to orient the part for easy access

Provide adjustable height tables

Establish a Standard Operating Procedure (SOP) to ensure that people use the equipment the way it was designed to be used

Figure 3.15 Change the Tool or Change the Target

73


Comfort Zone Working near the limits of a joint’s range of motion is difficult and increases exposure to ergonomic risk. Everyone performs best when working in an area directly in front of the torso called the Comfort Zone. This area is where we are the strongest, possess and execute the most control, and have the best visual acuity. In addition, working inside the Comfort Zone may also reduce the time necessary to perform a work activity because unnecessary movements are reduced or eliminated.

The Comfort Zone is made up of the natural, semi-circular movements or motions of the human body. A combination of both horizontal and vertical movements, the Comfort Zone extends from the knee (24" or 610 mm) to the shoulder (62" or 1.58 m), and no more than 20° to either side of the body.

This zone is further optimized for body postures and motion in a region, called the Optimal Comfort Zone. This region is located a few inches below (38" or 965 mm) and above (49" or 1.25 m) the elbow, and directly in front of the body. Whenever possible, parts, work activities, critical buttons, and visual displays should be located within the Optimal Comfort Zone.

Maximum Optimal

��

��

��

��

Figure 3.16 Maximum and Optimal Comfort Zones


74

© 2008 Humantech

The Comfort Zone and Motion Motion is any movement a person makes, such as reaching for parts and bending over to place boxes on a pallet. These motions may be necessary to complete the work activity, but generally do not add value to the product. Often termed "non-value-added" or "wasteful" motions, they are the result of arranging equipment, parts, tools, and supplies without consideration for ergonomic concerns or specifications. Not only can wasteful motions increase exposure to ergonomic risk, they can also increase the time necessary to perform the work activity, and can affect your ability to meet your customers’ needs.

When tools and workstations are arranged within the Optimal Comfort Zone, operators and materials have a shorter distance to travel. Eye movements, hand movements, and body movements are reduced, resulting in less ergonomic risk and improved efficiency.

Opportunities to eliminate motion can be identified and addressed in everyday tasks. Consider these guidelines:

Keep enough parts in part bins for only an hour or two of production to minimize the bin sizes, allowing more opportunity to get work items into the Comfort Zone.

Move materials, controls, and displays closer to their point of use.

Motions can also be combined to result in reduced motions. The motion of picking up several tools repeatedly can be reduced by combining multiple tools into one tool. When one tool can do multiple tasks, it can be picked up once and used for many functions while still in the operator’s hand. In addition, a single tool is easier to accommodate in the Comfort Zone than multiple tools.

Use vertical space in the Comfort Zone as well as horizontal table space. Placing tools on balancers can position them closer when needed.

Remove unnecessary steps or activities in the job sequence.

Store items at heights that do not increase bending or overhead reaching.

Position workstation surfaces at heights that promote neutral postures.

75


Don’t Give Me Static Blood flow is critical to maintaining operator performance, connective tissue, and nerve health. Soft tissue compression, from prolonged static force application (gripping, carrying, bending over), exposure to vibration (Bad Vibes), or contact with hard or sharp edges can impede blood flow to the muscles, connective tissues, and nerves.

Don’t Give Me Static is a way to remember that our bodies rely on good blood flow. Some things we can do to improve operator comfort and productivity include the following:

Pad hard surfaces and sharp edges that operators may come into contact with.

Review tasks that require operators to exert force in one position for more than ten seconds to see if movement or microbreaks can be introduced.

Look for ways to isolate vibrating tools or add vibration tool wrap.

Use positioning devices to reduce force requirements when objects must be held for prolonged periods. Figure 3.17 illustrates a tool positioner that reduces requirements for holding the tool in place.

Ensure that handles have:

Appropriate diameter: 1.2" – 1.7" (30 – 43 mm) diameter round handles for power grips, 0.3" – 0.6" (8 – 15 mm) diameter for precision grips

Appropriate length: 3.8" – 6.0" (95 – 152 mm) Padding (should not add to the diameter beyond guidelines) Flanges, if force is exerted along the axis of the handle

Figure 3.17 Don’t Give Me Static


76

© 2008 Humantech

Ask the Operator Engaging operators in conversation about ergonomic issues is vital to uncovering the root cause of Find It items and identifying practical Fix It items. The person doing the job knows more about job tasks and what may work (or not work) than anyone else. The Ergonomics Hit List can be a means for establishing a common dialogue in ergonomics. A little education goes a long way in getting operators involved and contributing to the ergonomic improvement process.

The Ergonomics Action Form (page 79) is a formal mechanism for documenting ergonomic issues and capturing improvement ideas. Operators often identify easy, cost-effective job improvements resulting simply from job experience.

The real expert in any operation is the person who does it every day. Ask the operator to identify ergonomic problems that you might otherwise miss.

In addition, consider asking operators the following questions to gain greater insight into the operation:

What is the least desirable or most difficult part of this operation?

While performing this operation, do you experience any pain or discomfort?

Have there been any ergonomic injuries associated with this operation?

What suggestions do you have for improving this work area?

Are there any quality or production issues associated with this operation?


Ask the Operator: The most important data source for identifying and resolving ergonomic issues is the operator.

77


Continuous Improvement Process Finding and fixing ergonomic issues is an important step in the ergonomics process. To ensure that all good improvement ideas are put into place, and improvement doesn’t stop at the first idea, a continuous improvement process is needed. The back of the Ergonomics Hit List includes key elements to help you understand how to get the most out of the Find It and Fix It approach.

Figure 3.19 The Ergonomics Hit List Card (Back)

Check for Success: Confirm that Fix It improvements resolve Find It issues (and don’t create additional concerns).

FORM: A reminder to share successful improvements with other areas that have similar challenges.

The 30-Inch View: Where people, work, and the environment intersect.


78

© 2008 Humantech

The 30-Inch View Within an arm’s length of every employee are the obstacles to and opportunities for workplace improvement. A fresh perspective here—where people, work, and the environment intersect—can have dramatic and far-reaching effects on the entire business.

Find It – Fix It – Check for Success Continuous improvement has become the mantra of business. Finding low cost ways to incrementally improve processes has been proven to pay off in the short term and long run. One key learning from the Kaizen/continuous improvement community is the need to routinely check for success.

The Find It – Fix It approach is a simple and straightforward way to identify and resolve ergonomic issues. But even the most well thought-out improvements can come up short or contribute to other challenges that weren’t anticipated. Checking for success is a critical step to ensuring that Fix It improvements resolve the issues and do not create additional concerns.

Fix Once, Repeat Many (FORM) Companies are discovering that many ergonomic challenges are similar across different departments, locations, or business units. By taking the time to share improvements, whether via company conferences, internal web sites, or just plain networking, they are able to accelerate the ergonomics initiative, and spend more time implementing improvements and less time assessing challenges. This technique is known as FORM, or Fix Once, Repeat Many.

Sharing best practices is routine, particularly in global companies. When a best practices approach is applied to ergonomics, the benefit of workplace improve-ments becomes clear. Raising an assembly line 8" (203 mm) works just as well in Los Angeles as it does in Buffalo, Budapest, and New Delhi. In contrast, instituting job rotation schedules or stretching exercise programs is difficult to replicate due to the nuances of administering these programs.

The FORM approach to ergonomics problem solving is most effective when supported by common analysis techniques and centralized access to solutions. This is why companies are finding that enterprise-wide ergonomics initiatives can achieve sustained success with an emphasis on sharing solutions.

79


The Ergonomics Action Form™ Documentation is an important part of an ergonomics process. The Ergonomics Action Form is a structured worksheet that allows you to capture the presence of ergonomic issues in an operation along with improvement ideas. The Hit List "Find It" items are located on the front (Figure 3.20), while the back combines the "Fix It" items with the Hit List elements of a continuous improvement process (Figure 3.21).

Figure 3.20 The Ergonomics Action Form (Front)


80

© 2008 Humantech

Figure 3.21 The Ergonomics Action Form (Back)

When to Use the Ergonomics Action Form The Ergonomics Action Form is best used as a first step in participative problem solving. Because the form is observation-based, multiple operators trained in the Ergonomics Hit List can provide insight into ergonomic issues and job improvements without requiring detailed analysis. The Ergonomics Action Form is an appropriate tool for integration with continuous improvement (Kaizen) and behavior-observation safety initiatives.

Limitations of the Ergonomics Action Form The Ergonomics Action Form does not quantify risk factors, and therefore does not support data-driven prioritizing of problem jobs. For more information about prioritizing jobs based on ergonomic risk, see Chapter 5, Prioritizing Ergonomic Risks.

In addition, since issues identified on the Ergonomics Action Form do not have threshold limits, this tool is difficult to use to specify risk factor reduction goals for job improvements. For more information about quantitative risk analysis, see Chapter 4, Evaluating Ergonomic Risk Factors.

81


Completing the Ergonomics Action Form The Ergonomics Action Form formalizes the observations from the Ergonomics Hit List. It does not generate a risk score, but rather captures observations of ergonomic issues and improvement ideas and turns them into an action plan.

To complete the Ergonomics Action Form, you’ll follow these steps:

Step 1 Complete job information.

2 List all major tasks observed.

3 Indicate Hit List items observed.

4 Record comments or notes.

5 Transfer Hit List items observed (from front).

6 Brainstorm and record potential improvements.

7 List the top three improvements.

8 Sign off and follow up.

Step 1: Complete Job Information First, identify the job the Ergonomics Action Form pertains to by indicating the following items in the Complete Job Information area of the form. Also record the current date.

Job name

Site

Department

Station

Shift

Product


82

© 2008 Humantech

Step 2: List All Major Tasks Observed Major tasks are those activities that you observe in a job or operation. Breaking jobs into tasks is a fairly subjective exercise; a rule of thumb is that there should be three to ten major tasks in a job. For example, the major tasks for the "Band Saw" operation are shown below:

Figure 3.22 Major Job Tasks

83


Step 3: Indicate Hit List Items Observed Check the box next to each ergonomic issue observed. In the example below, six Hit List items were present in the job:

Wash Rag

Shoulder Too High/Too Low

Butts Up

Twist and Shout

Horizontal Distance

Contact

Figure 3.23 Hit List Items Observed


84

© 2008 Humantech

Step 4: Record Comments or Notes Record comments or notes from your observations and interactions with operators. Typical comments include:

Reports of job-related discomfort

Operator comments on job challenges and potential improvements

Information about forces and loads

Varying conditions, such as product fit challenges related to component quality

Figure 3.24 Comments or Notes

Step 5: Transfer Hit List Items Observed Transfer the Hit List items observed (marked in Step 3) from the front of the form.

Figure 3.25 Hit List Items Transferred from Front

85


Step 6: Brainstorm and Record Potential Improvements Engage operators and others to identify potential ergonomic improvements using the Fix It items from the Ergonomics Hit List to spur ideas. For each potential improvement, mark the ergonomic issues that will be addressed by the improvement. Finally, for those items that have approval for moving forward, write your initials in the box and the date of approval.

Figure 3.26 Record Potential Improvements

Step 7: List the Top Three Improvements List the top three improvement ideas based on your brainstorming exercise. This information can be used to communicate effective improvements to other areas with similar challenges.

Figure 3.27 Top Three Improvements


86

© 2008 Humantech

Step 8: Sign Off and Follow Up Write the name of the person to whom this form will be submitted for approval. Include a date for following up to confirm that the improvements have been implemented, and to ensure that no new challenges have been created as a result of the improvements.

Figure 3.28 The Final Step

The Completed Ergonomics Action Form The completed Ergonomics Action Form for the Band Saw operation is shown below.

Figure 3.29 Completed Ergonomics Action Form for Band Saw Operation (Front)

87


Figure 3.30 Completed Ergonomics Action Form for Band Saw Operation (Back)


88

© 2008 Humantech

Avoiding Potential Pitfalls With the Ergonomics Action Form The following table lists potential pitfalls you may encounter when using the Ergonomics Action Form and a recommended approach for each.

Table 3.1 Potential Ergonomics Action Form Pitfalls

Potential Pitfall Recommended Approach

The ergonomic issues need to be quantified.

We want the ergonomic assessment tools in our process to be objective.

The Ergonomics Action Form focuses on postures, yet the job under review has other ergonomic issues.

Our company has addressed all the "low-hanging fruit" and the Ergonomics Action Form seems too simple and ineffective.

Use quantifiable approaches like the BRIEF, BEST, EASY, and NIOSH Lifting Equation.

89


Notes


90

© 2008 Humantech

Notes

91

4 hapter 4 Evaluating Ergonomic Risk Factors

About This Chapter..................................................................................92 Ergonomic Risk Factors Defined.............................................................93 Ergonomic Risk Factor Surveys ..............................................................94 The BRIEF™ Survey ...............................................................................95 Applying the BRIEF Survey.....................................................................97 Physical Stressors and the BRIEF Survey............................................111 Scoring the BRIEF Survey.....................................................................113 Completing the BRIEF Survey ..............................................................114 Measuring Risk Reduction.....................................................................118 Avoiding Potential Pitfalls With the BRIEF Survey................................120 References ............................................................................................120


92

© 2008 Humantech

About This Chapter Chapter 4 is part of the Evaluation phase of ergonomic risk management.

��

� ��!��"��

��

��

��

�� !�"��

��#�� $!�"��

#��

�� %��

��&� ��%�

��'��'��(��)��

$�%��

��*��%+��'��%��

��&� ��!��


This chapter explains how to use the BRIEF Survey, a tool for identifying ergonomic risk factors in job/tasks. We'll address these questions:

Why should I evaluate ergonomic risk?

What is ergonomic risk?

How do I evaluate ergonomic risk?

93

Chapter 4: Evaluating Ergonomic Risk Factors

Ergonomic Risk Factors Defined OSHA defines ergonomic risk factors as "conditions of a job, process, or operation that contribute to the risk of developing Cumulative Trauma Disorders" (OSHA 3123, 1990). Ergonomic risk factors should be interpreted as one would consider any other risk factor. The presence of a risk factor does not necessarily predict that an individual will suffer a health problem as a result of exposure to the risk factor. Rather, a risk factor is a condition of the workplace that increases one’s chance of developing a WMSD and to which exposure should be limited, or totally avoided, in pursuit of a goal of a 100% healthy and safe working environment.

Everybody knows of an Aunt Betty or Uncle Jim who smoked for decades yet lived to be 90. Being a smoker does not automatically mean you will get lung cancer, but it has been shown that smoking increases the likelihood of getting lung cancer. Therefore, smoking is a risk factor.

Similarly, performing a job that requires high force pinch grips and wrist deviations will not automatically lead to a WMSD, but the likelihood of being afflicted increases.

Remember that:

Risk factors do not indicate that injury is certain to occur.

The presence of a risk factor does not necessarily mean that an operator will experience discomfort from a certain task.

Improvements can be made in a job by reducing risk factors.


94

© 2008 Humantech

Ergonomic Risk Factor Surveys There are many ways to analyze jobs for ergonomic risk factors or ergonomic stressors (Keyserling et al., 1991; Ulin et al., 1992). Job analyses generally take one of three forms:

Checklist – the simplest to conduct, but is not flexible and may not ask appropriate questions for a particular job. Checklists have been known to be misused if the user has not been adequately trained.

Interactive form-based – takes considerable time and effort to develop and sometimes has the same challenges as a checklist.

Narrative (open-ended) method – thorough, straightforward, easy to learn and use, and is generally known as an acceptable method of measuring ergonomic risk in a job.

Conducting a narrative job analysis requires the following steps:

Recognize ► 1. Collect background job information (preferably via videotape) 2. Break the job into its essential functions

Evaluate ► 3. Identify risk factors for each task 4. Identify root causes for each risk factor

Control ► 5. Generate and implement solutions 6. Follow up after solutions have been implemented

This chapter discusses Step 3 in this process, identifying risk factors.

Ergonomic Job Analysis Ergonomic job analysis is a general term describing a variety of techniques by which you can identify potential ergonomic issues and job improvements. While some of these techniques are very involved and can require specialized training, three techniques are common in industry:

Systematic observation – requires repeated observation of operator activities to identify issues and solutions. The Ergonomics Hit List™ (Chapter 3) is an adequate tool for systematic observations.

Discomfort survey – formalized survey to identify the types of job-related discomfort in the working population as well as operator-generated ideas for improving their jobs. A discomfort survey form is provided in Chapter 5, Prioritizing Ergonomic Risks.

Risk factor survey – formalized observation tool that identifies specific risk factors associated with job/tasks and their root causes. The BRIEF Survey is an example of a risk factor survey.

95


The BRIEF™ Survey BRIEF (Baseline Risk Identification of Ergonomic Factors) is an initial screening tool that uses a structured and formalized rating system to identify ergonomic acceptability on a task-by-task basis.

Figure 4.2 The BRIEF Survey


96

© 2008 Humantech

The BRIEF examines nine body areas for WMSD risk factors:

Left hand/wrist

Right hand/wrist

Left elbow

Right elbow

Left shoulder

Right shoulder

Neck

Back

Legs

The BRIEF also takes into consideration physical stressors that tend to accelerate WMSDs:

Vibration

Low temperatures

Soft tissue compression

Impact stress

Glove issues

When to Use the BRIEF Survey Because the BRIEF is a quantifiable method of measuring the amount of ergonomic risk in a job, apply the BRIEF when a high level of detail is necessary and/or when readily available off-the-shelf solutions are not feasible. In contrast, apply the Hit List when the level of necessary detail about the job is low and when off-the-shelf solutions are readily available. (For more information about the Hit List, see Chapter 3, Recognizing Ergonomic Issues.)

Limitations of the BRIEF Survey The BRIEF is designed to analyze a job with specific tasks that are repeated throughout the cycle. The BRIEF Survey works best in environments where operators routinely perform job/tasks using repeatable methods or procedures.

97


Applying the BRIEF Survey The BRIEF is a posture- and force-based risk assessment. Posture and force risk factors are significant by themselves, while duration and frequency risk factors generally amplify the hazard presented by the posture and force risk factors.

Because posture and force risk factors are primary to the BRIEF, always start by identifying postures and forces. While watching a videotape of a task, focus on the postures and forces of the large body parts first because they are easier to identify. A good order to follow is to look at the neck, back, and legs, the elbows and shoulders, and finally the hands and wrists. Many times, the postures and forces of the hands and wrists are subtle and are best captured by watching the video in slow motion and occasionally pausing the video.

Only after reviewing the posture and force risk factors, evaluate the frequency and duration components. These apply to the frequency and duration of risk factor exertions (a movement that contains a posture risk factor, force risk factor, or both).

Frequency – defined as the frequency of risk factor exertions. Frequency is an additive measure of various posture and force risk factors. However, a single exertion that contains both posture and force risk factors is counted only once. For example, score frequency for the back if you observed back twisting once and back bending greater than 20° once in the same minute. However, if you observed back twisting while exerting more than 25 pounds (11.3 kg) once in a minute, do not score frequency for the back.

Duration is defined as the duration of risk factor exertions. For example, grasping a handle with both hands using a power grip with more than 10 pounds (4.5 kg) of force for more than 10 seconds would score duration for the both hands and wrists. Once the exertion ends, start counting over again. For example, suppose you observed the left arm raised more than 45° for periods of eight seconds, three times in a minute. Since no single exertion broke the ten-second mark, do not score duration for the left shoulder.

Each major joint in the human body has particular strengths and weaknesses. Knowing that combinations of posture, force, frequency, and duration contribute to WMSD risk will guide you in the early identification of potentially damaging job designs.

The following pages detail the risk factors for each of these body areas:

Hands/wrists Elbows Shoulders Neck Back Legs

Note: Refer to Appendix A: Basis for the BRIEF for a scientific basis for the BRIEF Survey.


98

© 2008 Humantech

Tendon Mechanics We use our hands and wrists for virtually every activity in our daily lives. It is important to remember that they are strongest when they are straight, or in a "neutral posture". Working outside of this neutral posture while applying a force, repeating a non-neutral posture, or maintaining a non-neutral posture for a period of time can lead to WMSDs. Let’s take a closer look at the hand and wrist to determine why non-neutral postures coupled with high forces, frequency, and/or duration can be detrimental to the wrist.

There are many anatomical features of the hand/wrist, including muscles, tendons, ligaments, bones, and nerves.

Figure 4.3 Muscle, Tendons, and Bones

Figure 4.4 Nerve and Ligament

99


When the wrist bends into non-neutral postures, the median nerve and the tendons rub over the hard edge of the bones in the wrist which increases the potential for developing WMSDs such as tendinitis, tenosynovitis, and carpal tunnel syndrome (described in Chapter 2, Work-Related Musculoskeletal Disorders).

Figure 4.5 Non-neutral Wrist Postures

As the wrist leaves the straight, or neutral posture, we also lose grip strength. Figure 4.6 shows that grip strength can decrease by up to 45% (Eastman Kodak, 1986).

Figure 4.6 Grip Strength and Posture

Because of these limitations of the wrist, it is important to remember to:

Keep it straight.


100

© 2008 Humantech

Risk Factors for the Hands and Wrists

Posture Risk Factors

Flexed > 45° Measured with respect to the bend across the top of the wrist.

Extended > 45° Measured with respect to the bend across the top of the wrist.

Ulnar Deviation Any noticeable deviation opposite the thumb.

Radial Deviation Any noticeable deviation toward the thumb.

101


Force

Pinch Grip > 2 lb (0.9 kg)

An application of force by the fingers around an object without the thumb touching the forefinger.

When the measured force exerted is 2 lb or greater. If there are no measurements, a guideline is the force required to write with a pencil.

Finger Press > 2 lb (0.9 kg)

An application of pressure by one or more fingers to one face of an object.

When the measured force exerted is 2 lb or greater.

Power Grip > 10 lb (4.5 kg)

Thumb overlapping or touching the forefinger while exerting > 10 lb.

Duration > 10 seconds - Any one force or posture risk factor sustained for 10 seconds or longer.

Frequency > 30/minute - A cumulative measure of any combination of force and posture risk factors occurring thirty times per minute or more.

For example, if an operation requires 5 pinch grips, 3 ulnar deviations, 20 flexions, and 2 extensions, all within a minute’s time, mark Frequency as a risk factor for the operation.


102

© 2008 Humantech

Risk Factors for the Elbow


Rotated Forearm

Neutral forearm position is 15° from pronation (palm down). Rotated forearm is then defined as rotation + 45° from neutral position.

Fully Extended The angle created at the elbow joint by the forearm and the upper arm. When that angle meets or exceeds 135°, mark Fully Extended as a risk factor for the operation.

Force > 10 lb (4.5 kg) - A force exerted on or by the arm. This could occur when picking up an object weighing 10 lb or greater or applying a force of 10 lb or greater.

Examples:

Picking up a 12 lb (5.4 kg) briefcase off the ground

Using a hammer to drive a nail

Using a screwdriver when the rotational force exceeds 10 lb (4.5 kg)

Note: When exerting force with two arms, the limit is > 15 lb (6.8 kg).


Frequency > 2/minute - A cumulative measure of any combination of force and posture risk factors occurring twice per minute or more.

103


Risk Factors for the Shoulder


Arm Behind Body

Marked by the elbow noticeably crossing the plane created by the back.

Arm Raised > 45°

The angle of the arm raised 45° or more with respect to the torso.

Shoulders Shrugged

Marked by any noticeable deviation of the shoulder joint raised upward toward the ear.

Force > 10 lb (4.5 kg) - A force exerted on or by the shoulder. This could occur when picking up an object weighing 10 lb or greater or applying a force of 10 lb or greater.

Examples:

Sitting in an office chair with arm rests positioned too high

Reaching overhead, with full extension, to retrieve material on a top shelf

Lifting a heavy (50-lb) box onto a conveyor that is too high

Lifting a heavy suitcase into the trunk of a car

Note: When exerting force with two arms, the limit is > 15 lb (6.8 kg).




104

© 2008 Humantech

Risk Factors for the Neck


Flexed > 30° Neck bent > 30° from the torso.

Extended Any noticeable backward deviation.

Sideways Any noticeable sideways deviation.

Twisted > 20° Neck twisting > 20°.

105


Force > 2 lb (0.9 kg) - A force exerted on or by the neck. This could occur from wearing personal protective equipment that weighs 2 lb or greater.




106

© 2008 Humantech

Back Biomechanics The back is an inherently unstable structure. Figure 4.7 gives the illusion that the back is a nice straight column. We know from architecture that columns offer support. Support is one of two main functions of the back. Flexibility is the other. Figure 4.8 shows that the back is actually made up of an "S" curve, which provides the necessary flexibility. The human back is the best design to handle the different demands of support (strength) and flexibility (mobility).

Figure 4.7 Spinal Column – Back View Figure 4.8 Spinal Column – Side View

A closer look at the spinal column reveals that between each spinal bone (vertebra) is an intervertebral disc.

Figure 4.9 Vertebrae and Discs

The purpose of these discs is threefold: to act as shock absorbers, to prevent bone-to-bone contact, and to prevent bone to nerve contact. The shock absorption quality allows us to bend and twist without injury. But like a car shock absorber, our discs can also wear out with overuse. Replacement of these parts isn’t as easy as taking our back to the garage.

107


Forces on the back, in combination with poor postures, can cause severe damage to the back. To understand how back injures occur we must understand how the back functions. The back can be modeled as a simple lever system that supports the weight of the upper body as well as any loads supported by the upper body. Since the muscles that act to balance the upper body are very close to the fulcrum of this lever system (the base of the spine), the back is at a significant mechanical disadvantage whenever the load is extended outward. The length of the lever arm for the back muscles is about 2" (51 mm), while the length of the lever arm for the load can approach 30" (762 mm). The back muscles must generate forces 10 to 20 times the load being lifted when the torso is bent forward.

Figure 4.10 The Mechanical Disadvantage of the Back

These forces on the back and, in turn, the discs, can result in bulged, ruptured, herniated, and slipped discs.

Figure 4.11 Bulged Disc


108

© 2008 Humantech

Risk Factors for the Back


Flexed > 20° The angle the back is bent forward from vertical.

Sideways Any noticeable sideways deviation.

Extended Any noticeable backward bending.

Twisted Any noticeable back twisting.

Unsupported No or insufficient lumbar support while seated.

109


Force > 25 lb (11.3 kg) - Refers to the weight of an object being handled.




110

© 2008 Humantech

Risk Factors for the Legs


Squat A bend created at the knee of 45° or less from horizontal.

Kneel One or both knees touching the ground.

Unsupported No foot support while seated.

Force Foot Pedal > 10 lb (4.5 kg) - A force of 10 lb or greater exerted by the ankle to activate a foot pedal.

Duration > 30% of Day - A cumulative measure of any combination of force and posture risk factors occurring for a total of 30% of the day or more.


111


Physical Stressors and the BRIEF Survey A physical stressor increases the force component of the job while reducing blood flow to the affected body area.

Vibration Vibration can be characterized as either segmental or whole-body. The body responds to segmental vibration by limiting blood flow to the exposed body part, which causes stiffness and numbness in the affected body area. To grip an object that is constantly in motion, such as a small power tool, and to counteract the loss of feeling, increased grip force is often required.

Exposure to whole-body vibration for extended periods of time, as in driving a truck cross-country or operating a fork-truck, can result in digestive and back disorders. More intense whole-body vibration over a shorter period of time, as in operating a jack hammer, results in segmental vibration to the hands and wrists, and may even limit visual acuity.

On the BRIEF Survey, check the Vibration box in the Identify Physical Stressors section of the form (Step 4) whenever you observe vibration in the operation or the operator reports it. Write the letter "V" on the body area(s) exposed to the vibration. For whole-body exposure, circle the figure and write the letter "V" next to the circle.

Low Temperatures The body responds to prolonged exposure to low temperatures (below 66°F) by limiting blood flow to the extremities. A reduction in blood flow to the fingers and hands reduces grip strength and can cause numbness. Working at a shipping dock or inside a meat packing facility are two examples of operations that may involve low temperatures.

On the BRIEF Survey, check the Low Temperatures box in the Identify Physical Stressors section of the form (Step 4) whenever the operator is exposed to temperatures below 66°F for more than two hours per day. For whole-body exposure, circle the figure and write the letter "L" next to the circle.

Soft Tissue Compression Soft tissue compression is the restriction of blood flow caused by static force applied to the body for prolonged periods of time, for example, resting the elbows on a hard surface while sitting, leaning the forearms on a table edge, or gripping a sharp handled tool. The reduction in blood flow is a result of pressure on body tissues. This is a concern particularly when blood vessels are located near the surface of the skin, as on the back of the hand.

On the BRIEF Survey, check the Soft Tissue Compression box in the Identify Physical Stressors section of the form (Step 4) whenever you observe it in the operation or the operator reports it. Write the letter "S" on the body area(s) exposed to the soft tissue compression.


112

© 2008 Humantech

Impact Stress Impact stress, as in using the hand as a hammer or the torque reaction from using a tool, is a dynamic force applied to the body. The body responds to impact stress by limiting blood flow to the exposed body part. Repeated exposure to impact stress can cause trauma to the tissues, such as bruising. Repeated exposure to impact stress may cause stiffness and numbness in the affected body area.

On the BRIEF Survey, check the Impact Stress box in the Identify Physical Stressors section of the form (Step 4) whenever you observe it in the operation or the operator reports it. Write the letter "I" on the body area(s) exposed to the impact stress.

Glove Issues Glove issues include working with gloves that fit poorly or increase the force needed to grasp objects. Gloves that are too tight restrict blood flow to the fingers and cause numbness in the fingers. Gloves that are too large not only limit dexterity, but they also result in higher force gripping. Gloves that decrease the coefficient of friction between the object being handled and the gloves also increase the amount of force that the operator must exert in order to handle the object.

Examples of glove issues include wearing oversized gloves for tasks that involve fine finger movements, or wearing plain cotton gloves to lift smooth cardboard boxes.

On the BRIEF Survey, check the Gloves Issues box in the Identify Physical Stressors section of the form (Step 4) whenever you observe it in the operation, or the operator reports that the gloves do not fit properly or make the task more difficult to perform. Write the letter "G" on the hand(s) exposed to the glove issues.

113


Scoring the BRIEF Survey After all risk factors have been identified on the BRIEF, you can determine a score for each body area by adding the number of checked boxes for each body area. For example, a task was observed to have two posture risk factors for the neck (flexed 30° and twisted 20°) as well as the frequency risk factor (two per minute) for the neck. Score both posture and frequency for the neck, resulting in a score of 2. The job is considered medium risk for the neck.

��

��

��

��

��

��

��

��

��

� !"#$%& ' �"'( (�&! �&%)

Figure 4.12 Scoring the BRIEF

The highest possible score for each body area is 4. Scores of 2 or more for any body area indicate increased risk and should be evaluated further.


114

© 2008 Humantech

Completing the BRIEF Survey To complete the BRIEF Survey, you’ll follow these steps:

Step 1 Complete job information

2 Identify risks

3 Determine risk rating

4 Identify physical stressors

The following sections step through this process using the "Pallet Loading" operation as an example.

Note: This example addresses only the Hands & Wrists portion of the BRIEF Survey for demonstration purposes. When completing a BRIEF, address all body areas.

Step 1: Complete Job Information First, identify the job the BRIEF pertains to by indicating the following in the Complete Job Information box. Also record the current date.

Job name

Site

Station

Department

Shift

Product

115


Step 2: Identify Risks Mark the Posture and Force boxes when risk factors are observed for each body area. (You may also circle the postures observed.) For those body areas with Posture or Force risk factors, mark Duration and Frequency boxes when limits are exceeded.

Figure 4.13 Step 2 – Identify Risks

For the Pallet Loading operation, these risk factors were observed:

Both the right and left hands and wrists were exposed to non-neutral postures.

The left hand and wrist used a pinch grip of greater than or equal to 2 lb (0.9 kg).

The right hand and wrist held the risk postures (those circled) for 10 seconds or longer.

The left hand and wrist was observed using a combination of risk postures (those circled) for 30 times per minute or more.


116

© 2008 Humantech

Step 3: Determine Risk Rating In the Score box, write the number of risk factor categories (0 to 4) checked for each body part. Using the table, circle the corresponding Risk Rating for each body part (H, M, L).

Figure 4.14 Step 3 – Determine Risk Rating

For the Pallet Loading operation:

The left hand/wrist had posture, force and frequency boxes checked, resulting in a score of 3, high risk.

The right hand/wrist had posture and duration boxes checked, resulting in a score of 2, medium risk.

117


Step 4: Identify Physical Stressors Check the boxes for physical stressors observed and use the corresponding letters to indicate on the body diagram where these stressors occur.

Figure 4.15 Step 4 – Identify Physical Stressors

For the Pallet Loading operation:

There was soft tissue compression to the upper legs from leaning against the pallet.

The operator was exposed to temperatures lower than 66°F because the shipping department is located in the warehouse facility, which is not climate controlled.


118

© 2008 Humantech

Measuring Risk Reduction A primary advantage of using the BRIEF to evaluate a job is that it provides you with the ability to quantify improvements. The following example shows how the BRIEF can be used to measure the effect of an improvement to a workstation.

Example The completed BRIEF Survey form for the Pallet Loading operation is shown below. The greatest ergonomic concerns at this workstation were the left hand/wrist, right elbow, and right shoulder.

Figure 4.16 Completed BRIEF Survey for Pallet Loading

To improve the Pallet Loading workstation, a pallet lift with a swivel top was installed to minimize reaching across pallets while loading boxes. Figure 4.17 shows the BRIEF completed after the improvements were implemented.

119


Figure 4.17 BRIEF Completed After Ergonomic Improvements

Comparing the scores from the first BRIEF to the second clearly shows an improvement:

Implementation of a combination pallet lift and swivel surface reduced the BRIEF scores for the right elbow and right shoulder from a high risk rating to a medium risk rating.

The BRIEF scores for the neck and back were reduced from a medium risk rating to a low risk rating.

Soft tissue compression to the legs from leaning against the pallet was eliminated for the pallet loading operation.

Hands & Wrists Elbows Shoulders

Left Right Left Right Left Right Neck Back Legs

Original 3 2 2 4 2 4 2 2 1 Intervention 3 2 2 2 2 2 1 1 1 Difference 0 0 0 2 0 2 1 1 0


120

© 2008 Humantech

Avoiding Potential Pitfalls With the BRIEF Survey The following table lists potential pitfalls you may encounter when using the BRIEF, and a recommended approach for each.

Table 4.1 Potential BRIEF Survey Pitfalls


The operation has a very long cycle time or no cycle time.

List all tasks involved in the operation. Determine the tasks of highest concern, based on operator comments and injury history. Complete the BRIEF on those high concern tasks.

There are multiple operators at the same job.

Find the most experienced operator and complete the BRIEF on his/her workstation. For comparison, complete the BRIEF for another operator and compare the results.

Multiple operators rotate through the same workstation.

Find the most experienced operator to use as the subject. For comparison, complete the BRIEF on an operator that does the job differently. Complete the BRIEF based on the entire shift length rather than the single operator exposure length.

The job cannot be videotaped (for security reasons).

Complete the BRIEF in "real time", as you are watching the operator work. This is less reliable, but with a cooperative employee, it is possible.

No experienced operators could be located to videotape a job/task.

Do not complete the BRIEF using an inexperienced operator. Return to the job/task after the operators have accumulated 30 days experience.

References Armstrong, T.J. et al., Ergonomics Considerations in hand and Wrist Tendinitis, J

Hand Surg, 5, 830-837, 1987.

Armstrong, T. J. et al., Investigation of cumulative trauma disorders in a poultry processing plant, American Industrial Hygiene Assoc. Journal, 43, 103-115, 1982.

Armstrong, T. J., and Chaffin, D.B., Carpal tunnel syndrome and selected personal attributes, Journal of Occupational Medicine, 21, 481-486, 1979.

Barnhart, S. et al., Carpal Tunnel Syndrome Among Ski Manufacturing Workers, Scand J Work Environ Health, 17, 46-52, 1991.

Bernard, B.P., Musculoskeletal Disorders (MSDs) and Workplace Factors, Washington, DC: National Technical Information Service, 1997.

121


Buckle, P. W., et al., Musculoskeletal disorders (and discomfort) and associated work factors, In N. Corlett, J. Wilson, and I. Manenica, (Eds.), The Ergonomics of Working Posture, London: Taylor & Francis, 1986.

Burdorf, A. and Sorock, G., Positive and Negative Evidence of Risk Factors for Back Disorders, Scand J Work Environ Health, 23, 243-256, 1997.

Chaffin, D. B., et al., Occupational Biomechanics, New York: Wiley, 1999.

Chiang, H-C, et al., Prevalence of Shoulder and Upper-Limb Disorders Among Workers in the Fish-Processing Industry, Scand J Work Environ Health, 19, 126-131, 1993.

Dartiques, J.F. et al., Prevalence and Risk Factors of Recurrent Cervical Pain Syndrome in a Working Population, Neuroepidemiology, 7, 99-105, 1988.

Eastman Kodak Company, Ergonomic Design for People at Work Volume 2, New York: Van Nostrand Reinhold, 1986.

Feldman, R.G. et al., Peripheral Nerve Entrapment Syndromes and Ergonomic Factors, American Journal of Industrial Medicine, 4, 661-681, 1983.

Genaidy, A.M. et al., Ergonomic Risk Assessment: Preliminary Guidelines for Analysis of Repetition, Force, and Posture, J Hum Ergol (Tokyo), 1, 45-55, 1993.

Grandjean, E. and Hunting, W., Ergonomics of Posture – Review of Various Problems of Standing and Sitting Posture, Applied Ergonomics, 8.3, 135-140, 1977.

Hales, T.R. and Bernard, B.P., Epidemiology of Work-Related Musculoskeletal Disorders, Orthop Clin North Am, 4, 679-709, 1996.

Keyserling, W.M., Workplace Risk Factors and Occupational Musculoskeletal Disorders, Part 2: A Review of Biomechanical and Psychophysical Research on Risk Factors Associated with Upper Extremity Disorders, Am Ind Hyg Assoc J, 61, 231-243, 2000.

Keyserling, W.M., Armstrong, T.J., and Punnett, L., Ergonomic job analysis: A structured approach for identifying risk factors associated with overexertion injuries and disorders, Appl. Occup. Environ. Hyg., 6(5):353-363, 1991.

Keyserling, W.M., Postural Analysis of the Trunk and Shoulders in Real Time, Ergonomics, 29, 569-583, 1986.

Kuorinka, I. and Forcier, L., Work Related Musculoskeletal Disorders (WMSDs): A Reference Book for Prevention, Bristol PA: Taylor & Francis, 1995.

Macfarlane, G.J. et al., Employment and Physical Work Activities as Predictors of Future Low Back Pain, Spine, 10, 1143-1149, 1997.

Moore, J.S. and Garg, A., Upper Extremity Disorders in a Pork Processing Plant: Relationships Between Job Risk Factors and Morbidity, Am Ind Hyg Assoc J, 8, 703-715, 1994.


122

© 2008 Humantech

Muggleton, J.M. et al., Hand and Arm Injuries Associated with Repetitive Manual Work in Industry: A Review of Disorders, Risk Factors and Preventative Measures, Ergonomics, 5, 714-739, 1999.

OSHA, Ergonomics Program Management Guidelines for Meatpacking Plants, Washington: Occupational Safety and Health Administration (OSHA 3123), 1990.

Putz-Anderson, V., Cumulative trauma disorders: A manual for musculoskeletal diseases of the upper limbs, London: Taylor & Francis, 1988.

National Research Council and the Institute of Medicine, Musculoskeletal Disorders and the Workplace, Washington, DC: National Academy Press, 2001.

Nicholson, A.S. et al., A Guide to Manual Materials Handling, London: Taylor & Francis, 1997.

Ohlsson, et al., Repetitive Industrial Work and Neck and Upper Limb Disorders in Females, Am J Ind Med, 27, 731-747, 1995.

Punnett, L. and Keyserling, W.M., Exposure to Ergonomics Stressors in the Garment Industry: Application and Critique of Job-Site Analysis Methods, Ergonomics, 7, 1099-1016, 1987.

Punnett, L. et al., Back Disorders and Non-Neutral Trunk Postures of Automobile Assembly Workers, Scand J Work Environ Health, 5, 337-346, 1991.

Roquelaure, Y. et al., Occupational and Personal Risk Factors for Carpal Tunnel Syndrome in Industrial Workers, Scand J Work Environ Health, 5, 364-369, 1997.

Silverstein, B.A., The Prevalence of Upper Extremity Cumulative Trauma Disorders in Industry, Doctoral Dissertation, The University of Michigan, Ann Arbor, MI, 1985.

Sommerich, C.M. et al., Occupational Risk Factors Associated with Soft Tissue Disorders of the Shoulder: A Review of Recent Investigations in the Literature, Ergonomics, 6, 697-717, 1993.

Stetson, D.S. et al., Median Sensory Distal Amplitude and Latency: Comparisons Between Non-exposed Managerial/Professional Employees and Industrial Workers, Am J Ind Med, 24, 175-189, 1993.

Ulin, S. and Armstrong, T.J., A strategy for evaluating occupational risk factors of musculoskeletal disorders, Journal of Occupational Rehabilitation, 2(1), 1992.

Van Cott, H.P., and Kinkade, R. G., Human Engineering Guide to Equipment Design, Washington, D.C.: U.S. Government Printing Office, 1972.

Viikari-Jantara, E.R.A. The Scientific Basis for Making Guidelines and Standards to Prevent Work-Related Musculoskeletal Disorders, Ergonomics, 10, 1097-1117, 1997.

123


Notes


124

© 2008 Humantech

Notes

125

5 hapter 5 Prioritizing Ergonomic Risks

About This Chapter................................................................................126 Introduction to Ergonomic Risk Prioritization.........................................127 Risk Prioritization Tools .........................................................................128 The BEST™ ..........................................................................................128 Completing the BEST Form...................................................................131 Avoiding Potential Pitfalls With the BEST .............................................138 The EASY™ ..........................................................................................139 Completing the EASY Form ..................................................................147 Avoiding Potential Pitfalls With the EASY .............................................156 Identifying High Priority Job/Tasks ........................................................156


126

© 2008 Humantech


��

� ��!��"��

��

��

��

�� !�"��

��#�� $!�"��

#��

�� %��

��&� ��%�

��'��'��(��)��

$�%��

��*��%+��'��%��

��&� ��!��


This chapter describes two tools for prioritizing jobs based on ergonomic risk— the BEST assessment and the EASY. We'll address these questions:

Why should I prioritize ergonomic risk?

What is the function of ergonomic risk prioritization?

How do I prioritize jobs based on ergonomic risk?

127

Chapter 5: Prioritizing Ergonomic Risks

Introduction to Ergonomic Risk Prioritization Risk prioritization is a proven strategy for ensuring that resources are directed at the jobs and/or tasks that will benefit the most from ergonomic improvements. Without risk prioritization, ergonomics initiatives tend to become bogged down in reactionary activities and progress stalls.

Risk or Hazard? "Risk" and "hazard" are not synonymous:

A hazard is a situation, behavior, physical agent, or substance that can cause harm. If your workplace is free of hazards, it is by definition a safe and healthy workplace. If your workplace is not free of hazards, the potential for harm exists, and it is therefore unsafe. The number of hazards present, the potential harm those hazards can cause, and the number of people exposed to the hazards all combine to define the level of risk.

Risk is defined with three components: the frequency of an event, the harm or consequence of exposure to the event, and the number of people exposed per unit of time.

To differentiate between the two, a hazard addresses the presence or absence of a harmful agent, whereas risk is influenced by multiple factors and is conditional upon the hazard level. Therefore, to have an effective risk assessment system, it must combine consequence (symptoms, injury, or illness) with consideration for exposure.

Principles of Risk Management Prioritizing ergonomic risks allows you to manage them. There are three principles of ergonomic risk management:

Ergonomic risks are prioritized and there is a clear identification of high-risk job/tasks. Often, a chart is used to graphically identify those job/tasks with high, moderate, and low risk exposure.

Ergonomic job improvements are focused on those job/tasks with the highest risk exposures, not just those with recent injuries.

Once job improvements are implemented and proven successful, they are replicated to similar jobs with similar risks.


128

© 2008 Humantech

Risk Prioritization Tools There are two tools for prioritizing ergonomic risk. Both tools use information from a completed BRIEF Survey, however, the tools are suited for different types of work environments. This chapter explains, in detail, how to use both tools.

The BRIEF Exposure Scoring Technique, or BEST, applies to all operations in all work environments. It combines the BRIEF scores for body areas with physical stressor information, and adjusts for different amounts of work exposure time to determine priorities in work environments. For more information, see When to Use the BEST on page 130.

For special situations, in which injury/illness data is attributed to specific operations and where discomfort information is available from experienced operators, use the Ergonomic Assessment SurveY, or EASY. The EASY combines BRIEF Survey scores with injury/illness data and employee feedback to determine priorities in work environments. For more information, see When to Use the EASY on page 141.

The BEST™ The BRIEF Exposure Scoring Technique, or BEST builds on the BRIEF Survey to determine a job hazard score. It adjusts for different time exposures to ergonomic risk, and takes into account any physical stressors present while performing the job.

Figure 5.2 The BEST Risk Prioritization Process

129


The BEST form builds on BRIEF Survey analysis to determine a job hazard score. A BRIEF Survey must be completed for a job prior to completing the BEST form.

Figure 5.3 The BEST


130

© 2008 Humantech

When to Use the BEST Use the BEST to prioritize operations with any of the following characteristics:

Repetitive and/or varied

Frequent and/or infrequent

Varying and/or similar work time exposures

Performed for any number of hours per week

Regular job rotation

Exposure to physical stressors

Limitations of the BEST The BEST is limited to the ergonomic risk factors addressed in the BRIEF Survey. It does not address additional body areas, for example the foot, which could be important in some jobs. It also does not address additional threshold limits to the BRIEF risk factors, which may be important when distinguishing ergonomic risk between similar job/tasks or when calculating incremental improvement when risk factors are reduced, but not reduced to the level of the BRIEF threshold limits. For example, if you reduce back bending from 60° to 30°, the risk factor is reduced but the reduction does not affect the BEST score for the job.

The BEST Scoring System The BEST generates a score from 0 to 125, with a higher score representing a higher priority level. A job hazard score is generated based on:

BRIEF Survey scores

Physical stressors (vibration, low temperatures, soft tissue compression, impact stress, and glove issues)

Task exposure times

BEST scores are classified as Low, Medium, High, or Very High priority for ergonomic improvement/intervention as shown in the table below.

Table 5.1 BEST Priority Ranges

Priority

Low Medium High Very High

0 – 9 10 – 29 30 – 49 50 – 125

131


Completing the BEST Form To complete the BEST form, you’ll follow these steps:


2 Transfer BRIEF scores for each body area.

3 Determine conversion factors for each body area.

4 Add conversion factors together.

5 Summarize physical stressor scores.

6 Add physical stressor scores together.

7 Calculate job risk factor score.

8 Determine time exposure multiplier.

9 Calculate job hazard score.

The sections that follow step through this process using the "Pin Press" job as an example.

Step 1: Complete Job Information First, identify the job the BEST pertains to by indicating the following items in the Complete Job Information area of the form. Also record the current date.

Job name Site Station Department Shift Product


132

© 2008 Humantech

Step 2: Transfer BRIEF Scores for Each Body Area The following is a completed BRIEF Survey for the "Pin Press" job. In this job, the operator uses a press to insert a pin into a small hinge. The operator uses several bent wrist postures while applying pinch grips. The operator sits sideways at a conveyor with parts located in a bin across the conveyor.

Figure 5.4 Completed BRIEF Survey for Pin Press

Transfer BRIEF Survey scores for each of the nine body areas. The figure below shows the transferred BRIEF scores for the Pin Press job.

Figure 5.5 Transferred BRIEF Scores

133


Step 3: Determine Conversion Factors for Each Body Area Determine the appropriate Conversion Factor, or risk weighting, for each BRIEF score based on the following criteria:

BRIEF Survey Score

BEST Conversion Factor

4 10

3 5

2 3

1 1

0 0

Next, for each body area, fill in the conversion factor on the BEST form as shown.

Figure 5.6 Completed Conversion Factors

Step 4: Add Conversion Factors Together Add together the conversion factors for the nine body areas determined in Step 3 and record the result in the Add Conversion Factors box.

Figure 5.7 Summed Conversion Factors


134

© 2008 Humantech

Step 5: Summarize Physical Stressor Scores Indicate where physical stressors (vibration, low temperatures, soft tissue compression, impact stress, and glove issues) were recorded on the BRIEF Survey, and score each occurrence with 2 points. In our example, only Soft Tissue Compression was recorded.

Figure 5.8 2 Points for Each BRIEF Physical Stressor

Step 6: Add Physical Stressor Scores Together Add the physical stressor scores to determine the value for Step 6.

Figure 5.9 Summed Physical Stressor Scores

135


Step 7: Calculate Job Risk Factor Score Add the Conversion Factor total from Step 4 (31) to the Physical Stressor score total from Step 6 (2) to determine the Job Risk Factor Score (33).

Figure 5.10 Conversion Factors + Physical Stressors = Job Risk Factor Score

Step 8: Determine Time Exposure Multiplier The total exposure to this job is 3 hours per day, 5 days per week (15 hours per week). Determine the appropriate multiplier and record it in the box.

Figure 5.11 Time Exposure Multiplier


136

© 2008 Humantech

Step 9: Calculate Job Hazard Score To determine the Job Hazard Score, multiply the Job Risk Factor Score from Step 7 (33) by the Time Exposure Multiplier from Step 8 (0.8). The result is a Job Hazard Score of 26.4, making this a medium priority job.

Figure 5.12 Calculated Job Hazard Score

137


The Completed BEST Form The completed BEST form for the Pin Press job is shown below.

Figure 5.13 Completed BEST Form for Pin Press

Remember that the BEST generates a job hazard score, adjusting for different time exposures. Like the EASY, the BEST is most useful when viewed in comparison with other jobs’ scores. For example, if the "Insert Clip" job had a job hazard score of 52, the job would be considered a Very High risk, versus the Pin Press job with a job hazard score of 26.4 (Medium).


138

© 2008 Humantech

Avoiding Potential Pitfalls With the BEST The following table lists potential pitfalls you may encounter when using the BEST and a recommended approach for each.

Table 5.2 Potential BEST Pitfalls


The job time varies on a daily basis.

Use an average job time (use typical days, ignore abnormal days).

The daily job time is unknown. Talk with two or more experienced operators to estimate job time per day.

The job is performed several times throughout the day.

Use the total time that the job is performed during the course of a typical day.

The job is not performed every day.

Use the time that the job is performed during the course of a typical day.

139


The EASY™ The Ergonomic Assessment SurveY (EASY) allows you to identify and rank job/tasks by degree (frequency and priority) of ergonomic factors.

The EASY combines information from multiple data sources—an ergonomic risk summary for the job (BRIEF), injury/illness data (Medical Data form), and employee discomfort data (Employee Survey)—and results in an overall score for each job. The EASY score will allow you to prioritize job/tasks so that you can focus your ergonomic improvement efforts on the highest risk jobs first. This prioritization process is illustrated below:

Figure 5.14 The EASY Risk Prioritization Process


140

© 2008 Humantech

The EASY form provides a way to record the presence of risk indicators and tally an overall EASY score for a job.

Figure 5.15 The EASY Form

141


When to Use the EASY Use the EASY to prioritize operations with any of the following characteristics:

Repetitive and frequent

Similar work exposure times

Performed for a minimum of 20 hours per week

Medical records attribute injuries/illnesses to the specific operation

More than one operator is available to interview regarding physical discomfort

Note that the EASY is not recommended as a valid prioritization tool for operations with the following characteristics:

Varied and infrequent

Varying work exposure times

Performed for less than 20 or more than 40 hours per week

Medical records attribute injuries/illnesses to a department or job classifications

Regular job rotation

Only one operator is available to interview regarding physical discomfort

Limitations of the EASY The EASY relies on operator input and medical data in addition to information collected in the BRIEF Survey. Consequently, the quality of the EASY scores is based on the quality of operator interviews and medical tracking systems. If WMSDs are not properly diagnosed, or are poorly tracked to jobs and body areas, the EASY scores will not provide reliable data. In addition, the EASY does not prioritize well where there is great variation in the content of job/tasks, as in material handling tasks in warehouses.


142

© 2008 Humantech

The EASY Scoring System The EASY generates a two-part Job EASY Score for each job, for example, 6 – 2.

The first part of the score ranges from 0 (lowest priority) to 7 (highest priority). This value is determined from individual scores for each of nine body areas (left and right hand/wrist, elbow, shoulder, neck, back, and legs) in terms of

ergonomic risk (BRIEF Survey),

injury/illness data (Medical Data form), and

employee discomfort data (Employee Survey).

It reflects the highest score out of all nine body areas.

Figure 5.16 illustrates how the scores of the three data sets combine to result in this part of the EASY score:

4 points for BRIEF Survey 2 points for Medical Data Form 1 point for Employee Survey

7 points total

Figure 5.16 The EASY 7-Point Scale

143


The first part of the Job EASY Score allows you to classify the job as Low, Medium, or High priority for ergonomic improvement/intervention as described in Table 5.3.

Table 5.3 EASY Priority Ranges and Criteria

Priority

EASY Score

Criteria

Low 0 or 1 All body areas receive an EASY score of 0 or 1. Priority scores in this range generally indicate that there was no history of injury/illness for this area, there may be indications of operator pain or discomfort, and the BRIEF Survey noted a low risk rating.

Medium 2 - 4 One or more body areas receive an EASY score of 2, 3, or 4 (no body areas have a score of 5 or greater). This indicates that either the BRIEF Survey noted a medium or high risk rating or there are employee reports of pain or discomfort, history of injury/illness, or both for a body area.

High > 5 One or more body areas receive an EASY score of 5 or more. Priority scores in this range indicate that the BRIEF Survey noted a medium or high risk rating and there are employee reports of pain or discomfort, history of injury/illness, or both for a body area.

The second part of the Job EASY Score ranges from 1 to 9. It indicates the number of body areas with the highest score. This part of the score allows you to further prioritize jobs with similar scores.

For example, suppose you have the following EASY results for the Spring Install, Bracket Install, and Test Lights jobs. The jobs would rank as shown in the Priority Rank column. Therefore, the Bracket Install job would be your first priority for ergonomic intervention.

Table 5.4 EASY Priority Ranking

Job EASY Score Priority Rank

Spring Install 6 - 2 2

Bracket Install 6 - 4 1

Test Lights 4 - 4 3


144

© 2008 Humantech

EASY Input Sources The EASY combines information from the BRIEF, Medical Data form, and Employee Survey to calculate an overall risk score for each job.

The BRIEF Survey A key source of input into the EASY is the BRIEF (Baseline Risk Identification of Ergonomic Factors). The BRIEF risk factor survey examines nine body areas for ergonomic risk factors. This survey represents the most in-depth ergonomic review of the three EASY data sets and is therefore given the highest scoring weight—4 points—in the EASY scoring system.

A BRIEF score of 2 or more (medium or high risk) for a body area will trigger circling that body area on the EASY.

Figure 5.17 The BRIEF Survey Form

145


Medical Data Form Injury/illness data is assumed to be accurate and verifiable with appropriate medical management protocols. It represents a robust data point, but one that is primarily historical. It is therefore given a scoring weight of 2 points in the EASY scoring system.

The presence of a recordable WMSD on the OSHA 300 Log in the past three years that can be tracked to the job/task under review will trigger circling the associated body area on the EASY.

Figure 5.18 The Medical Data Form

Also note the following when completing a Medical Data form:

Record only ergonomic-related injuries (tendonitis, carpal tunnel syndrome, strains, sprains, etc.) on the Medical Data form. Do not record acute injuries (slips, trips, burns, cuts, etc.).

If data on an OSHA 300 Log is incomplete, for example, carpal tunnel syndrome is recorded, but right or left wrist is not indicated, record both wrists as being affected.


146

© 2008 Humantech

Employee Survey The Employee Survey is an important input source into the EASY, and is administered on a one-on-one basis to avoid group bias. However, employee discomfort information is typically the most subjective of the three data sets and is therefore given a scoring weight of 1 point in the EASY scoring system.

Any indication of pain or discomfort reported by experienced operators (more than 30 days at that position) for the job/task under review will trigger circling the associated body area on the EASY.

Figure 5.19 The Employee Survey Form

147


Completing the EASY Form To complete the EASY, you’ll follow these steps:


2 Complete the EASY Scoring Matrix (transfer BRIEF, Medical Data form, and Employee Survey data to EASY form) and calculate an EASY score for each body area.

3 Determine the Job EASY Score.

The following sections step through this process using the "Spring Install" job as an example.

Step 1: Complete Job Information First, identify the job the EASY pertains to by indicating the following in the Complete Job Information box. Also record the current date.

Job name Site Station Department Shift Product


148

© 2008 Humantech

Step 2: Complete the EASY Scoring Matrix, Calculate Body Area EASY Scores In Step 2, you'll transfer information from the BRIEF Survey, Medical Data form, and Employee Survey to the EASY form, which then allows you to calculate the EASY Score for each of the nine body areas.

Transfer BRIEF Scores The following is a completed BRIEF Survey for the Spring Install job. In this job, the operator installs a small spring into the body of a desktop printer. The operator uses several bent wrist postures while applying pinch grips. The operator must lean and reach to a bin across the workstation to retrieve the springs.

Figure 5.20 Completed BRIEF Survey for Spring Install

149


A BRIEF score of 2 or more (medium or high risk) triggers circling the body area on the EASY form. The Spring Install job had several medium or high-risk body areas:

Left hand/wrist

Left shoulder

Right hand/wrist

Right shoulder

Back

Complete the BRIEF portion of the EASY Scoring Matrix as shown:

Figure 5.21 Completed BRIEF Information


150

© 2008 Humantech

Transfer Injury/Illness Data The OSHA 300 Log was reviewed for the Spring Install workstation and it was found that one operator received medical treatment for thoracic outlet syndrome in the left shoulder. Another operator was also treated for tendinitis in the right wrist.

Figure 5.22 Completed Medical Data Form

Spring Install

Left Shoulder Right Wrist

Thoracic Outlet Syndrome 6/6/08 2 2 Tendinitis 8/4/08 0 3

Assembly 9/15/08 SL L.

R

91270

151


The presence of a recordable WMSD on the OSHA 300 Log in the past three years that can be tracked to the job/task under review will trigger circling the body area on the EASY form. The Spring Install job had two WMSDs for the following body areas:

Left shoulder

Right hand/wrist

Complete the Medical portion of the EASY Scoring Matrix as shown:

Figure 5.23 Completed Medical Information


152

© 2008 Humantech

Transfer Employee Discomfort Data The figure below is the filled in Employee Survey for the "Spring Install" job. The operator experienced pain in the left elbow, right shoulder, back, and the legs.

Figure 5.24 Completed Employee Survey

Spring Install 9/15/08 SL

#2 10:34 – 20:45

8 hours 200 Springs per shift None

8 hours

8 2

Grasping small springs Continually reaching to bins

Move bins closer

Assembly

91270

153


Any indication of pain or discomfort given by experienced operators (more than 30 days in that job) of the job/task under review will trigger circling the body area on the EASY form. The Spring Install operator reported pain in the following body areas:

Left Elbow

Right Shoulder

Back

Legs

Complete the Employee portion of the EASY Scoring Matrix as shown:

Figure 5.25 Completed Employee Information


154

© 2008 Humantech

Calculate EASY Score for Each Body Area

Calculate the EASY Score for each body area by adding up the circled items (for each area) and recording the result in the EASY Score box.

Figure 5.26 Completed EASY Scores

Step 3: Determine Job EASY Score The Job EASY score is comprised of two elements:

Highest EASY Score

Number of body areas with that score

For the Spring Install job, the highest EASY score is 6 (left shoulder and right hand/wrist), indicating that this job is a high priority (see The EASY Scoring System on page 142 for scoring ranges). Record this number in the Highest EASY Score box.

Two body areas had an EASY score of 6, so record a 2 in the Number With This Score box. This part of the EASY score allows you to further prioritize jobs with similar scores.

Figure 5.27 Completed Job EASY Score

155


The Completed EASY The completed EASY form for the Spring Install job is shown below. The job is a high priority because the Job EASY Score is 6 – 2.

Figure 5.28 Completed EASY for Spring Install

Remember that the EASY is a method that identifies and ranks operations by degree of ergonomic factors. The EASY score is most useful when viewed in comparison with other jobs’ EASY scores. For example, if the "Test Lights" job had an EASY score of 4 – 4, it would be considered medium priority, versus the Spring Install job with an EASY score of 6 – 2, a high priority job.


156

© 2008 Humantech

Avoiding Potential Pitfalls With the EASY The following table lists potential pitfalls you may encounter when using the EASY, and a recommended approach for each.

Table 5.5 Potential EASY Pitfalls


Medical data is difficult to track from the OSHA 300 Log to specific job/tasks.

Perform incident investigations to track recordable incidents to job/tasks.

There are multiple operators at some job/tasks but not others.

Complete an EASY for each job/task regardless of the number of operators. Interview all operators if possible, and indicate pain or discomfort on the Employee Survey even if only one operator reports it.

Job rotation makes it difficult to track recordable incidents to job/tasks.

One approach is to indicate incidents for all job/tasks through which an injured operator rotates. Another approach is to use the BEST rather than the EASY to prioritize risks.

Job/tasks have been modified (through ergonomic improvements or otherwise).

If ergonomic risk factors have been eliminated (according to the BRIEF Survey), historical injury/illness data for affected body areas no longer applies.

Could not locate experienced operators to interview at a job/task.

Do not interview inexperienced operators. Return to the job/task after the operators have accumulated at least 30 days of experience.

Identifying High Priority Job/Tasks The BEST and EASY methodologies are used for different circumstances and are based on different scoring systems. The table below summarizes the scoring levels for high priority job/tasks.

Table 5.6 What Determines BEST and EASY High Priority Jobs?

Prioritization Method Scoring System High Priority Jobs

BEST Indicates a job hazard score from 0 to 125.

A job hazard score of 30 or more.

EASY Indicates a score from 1 to 7 for nine body areas.

One or more body areas receive an EASY score of 5 or more.

157


Notes


158

© 2008 Humantech

Notes

159

6 hapter 6 Manual Material Handling Analysis

About This Chapter................................................................................160 Introduction to Manual Material Handling..............................................161 Risk Factors for the Back ......................................................................162 The Revised NIOSH Lifting Equation ....................................................162 The NIOSH Composite Lifting Index .....................................................178 Uses for the Revised NIOSH Lifting Equation.......................................179 Avoiding Potential Pitfalls With the Revised NIOSH Lifting Equation ...180 Psychophysical Analysis: Push, Pull, and Carry ...................................181 Manual Material Handling Example.......................................................192 Manual Material Handling Analysis Flowchart.......................................196 References ............................................................................................197


160

© 2008 Humantech


��

� ��!��"��

��

��

��

�� !�"��

��#�� $!�"��

#��

�� %��

��&� ��%�

��'��'��(��)��

$�%��

��*��%+��'��%��

��&� ��!��


This chapter discusses the NIOSH lifting model and push/pull/carry guidelines, tools that help you evaluate manual material handling tasks. We'll address these questions:

Why should I analyze manual material handling tasks?

What is the function of manual material handling analysis?

How do I analyze manual material handling tasks?

161

Chapter 6: Manual Material Handling Analysis

Introduction to Manual Material Handling Manual material handling activities, by nature, involve forces or loads. For example, lifting and carrying involve manipulating a load, while pushing and pulling involve applying a force to move an object.

Researchers have developed a number of methods to determine safe loads for operators including application of biomechanical, psychophysical, and physiological models.

��#� ��$

%$ �#��# $��$��*("!# �&�&+%

%# $��&

Figure 6.2 Force Limits

Force limits are derived from these three fields of scientific study:

Biomechanics. Chaffin (1999) cites a definition of biomechanics: it uses laws of physics and engineering concepts to describe motion undergone by the various body segments and the forces acting on them during normal daily activities. Biomechanics integrates physical and engineering sciences with biological and behavioral sciences to determine forces acting on the human body.

Psychophysics. Psychophysical methods utilize people's perception of maximum allowable loads or forces for a given task. Experiments were performed giving the subject control of either the weight or force variables, while all other task variables such as frequency, size, height, distance, etc., were controlled by the experimenter. According to Snook (1991), there is a direct relationship between an operator’s perception of the muscular effort required and the amount of force. Exceeding the perceived amount of force could lead to back and shoulder injuries.

Physiology. Physiological methods use whole-body fatigue as the basis for the amount of weight to be transported over a period of time. Scientists have determined the acceptable energy expenditure for an 8-hour workday to be 3.1 Kcal/min (Waters et al, 1993). Acceptable weights for lifting/lowering, carrying, and pushing/pulling tasks are derived by comparing the energy expenditure of the task to the acceptable energy expenditure.


162

© 2008 Humantech

Risk Factors for the Back The primary risk factors for the back, like those for the other areas of the body, are force, frequency, and posture. Increasing the weight of an object, increasing the frequency at which it must be handled, and forcing an operator into end ranges of motion to handle the object increase the likelihood of a back injury. In many cases, manual material handling is unavoidable, which raises these questions:

How much risk currently exists?

How can that risk be reduced?

The concepts introduced in this chapter will help provide guidelines for answering these questions.

The Revised NIOSH Lifting Equation The Revised NIOSH (National Institute for Occupational Safety and Health) Lifting Equation is a tool for assessing the physical stress of two-handed manual lifting and lowering tasks. The equation is designed for evaluating single-task and multiple-task lifting and lowering scenarios based on research that combines biomechanical, psychophysical, and physiological criteria in the development of a low back injury.

Note: For additional information about the Revised NIOSH Lifting Equation, see the Applications Manual for the Revised NIOSH Lifting Equation. Humantech's Web site at www.humantech.com includes a direct link to the manual.

163


When to Use the Revised NIOSH Lifting Equation How can you determine whether the NIOSH Lifting Equation is applicable for the job or task in question? If lifting/lowering occurs along with any of the conditions listed below, the NIOSH Lifting Equation is not applicable.

with one hand

for over 8 hours

while seated or kneeling

in a restricted work space

with unstable objects

while carrying, pushing, or pulling

with high speed motion

with wheelbarrows or shovels

with unreasonable foot/floor coupling

in an unfavorable environment

If the equation is applicable, you must determine if the job should be analyzed as a single-task or multi-task manual lifting job, and if significant control (i.e., requiring precision placement of the load) is required at the destination of the lift.

A single-task lifting job is one in which

the task variables (e.g., horizontal location, load weight, etc.) do not significantly vary from task to task, or

only one task is of interest (e.g., worst case scenario).

Multi-task lifting jobs have variables that vary. Thus, each task must be analyzed separately to calculate individual LI's, and these LI's are then combined to determine the cumulative effect of the lifting on the risk of a lower back disorder.

Note: Refer to The NIOSH Composite Lifting Index on page 178 for information about assessing a multi-task lifting job.

Measurements should be taken at both the origin and destination of the lift if significant control is required at the destination. This is usually the case when one or more of the following is true:

the worker must re-grasp the load at the destination of the lift

the worker must momentarily hold the object at the destination

the worker must carefully position or guide the load at the destination


164

© 2008 Humantech

Recommended Weight Limit (RWL) The Revised NIOSH Lifting Equation uses six task variables and a load constant of 51 pounds (23.2 kg) to establish a safe lifting limit called the Recommended Weight Limit (RWL). The six variables account for exposure to force, frequency, and posture (recall the Ergonomics Fire Triangle in Chapter 2). The RWL is a "not to exceed" number for the particular task being analyzed. As lifts are performed toward the task variable limits, the load constant is reduced.

The RWL is defined for a specific set of task conditions as the weight of the load that 90% of healthy workers could perform over a substantial period of time.

The RWL is defined by the following equation:

RWL = LC x HM x VM x DM x AM x FM x CM

In this equation, LC (Load Constant) = 51 pounds (23.2 kg), and each M is a multiplier. Refer to the next section, The NIOSH Lifting Variables, for information about the variables H, V, D, A, F, and C.

Note: For additional information about the multipliers, see the Applications Manual for the Revised NIOSH Lifting Equation.

165


The NIOSH Lifting Variables The sections that follow describe the NIOSH lifting task variables and how to obtain measurements for each.

H = Horizontal location

V = Vertical location

D = Travel distance

A = Angle of asymmetry

F = Lifting frequency/duration

C = Coupling classification

'

(

)

*

Figure 6.3 NIOSH Lifting Variables


166

© 2008 Humantech

Horizontal Location (H) Horizontal location (H) is measured at the start of the lift. It is the distance from the midpoint of the line joining the inner ankle bones to a point projected on the floor directly below the midpoint of the hand grasps (i.e., load center), as defined by the large middle knuckle of the hand.

)+,��*�'

-�.��'�%/�.�

(�,*)+�

(��*.�+

))+,��*��/�*��/.

'

'/,�0/.�*��/�*��/.

%/�.��/-�%,/1+��/.2�(!%/�.��+�3++.�..+,�*.4�+��/.+�

'/,�0/.�*�

��*,�%/�.�

,�- .��

%/�.��/-%,/�+��/.

'/,�0/.�*�

�*�+,*�

'/,�0/.�*��/�*��/.

2�(!%/�.��+�3++.�..+,�*.4�+��/.+�

Figure 6.4 Graphic Representation of Horizontal Location (As Taken From NIOSH)

Ideally, the horizontal distance is 10" (254 mm) or less. Although objects may be held closer than 10", a notable increase in risk does not exist until the object reaches a horizontal location of 10". The maximum value of H is 25" (635 mm).

If H is less than 10", use H = 10" as your measurement.

If H is greater than 25", the RWL is equal to 0. Objects at a distance of more than 25" from the ankle midpoint generally cannot be lifted vertically without a loss of balance.

167


Vertical Location (V) Vertical location (V) is measured vertically from the floor to the midpoint between the hand grasps, as defined by the large middle knuckle. The minimum vertical location is 0" (0 mm), or floor surface, and the maximum is 70" (1.78 m).

If V is less than 0", the RWL is equal to 0.

If V is greater than 70", the RWL is equal to 0.

Ideally, the vertical location is 30" (762 mm); this is considered knuckle height for a 50th percentile employee.

Travel Distance (D) Travel distance (D) is the measure of vertical displacement during a lift. For instance, if you pick up a box at 27" (686 mm) and place it on a shelf at 37" (940 mm), the vertical travel distance is 10" (254 mm).

Ideally, the vertical travel distance is 10" or less. The minimum vertical travel distance is 10", and the maximum is 70" (1.78 m). If D is less than 10", use D = 10" as your measurement.


168

© 2008 Humantech

Angle of Asymmetry (A) The angle of asymmetry (A) refers to the amount of back twisting at the beginning or end of a lift from the sagittal plane (center of the Comfort Zone). The minimum is 0° and the maximum is 135°. Ideally, the angle of asymmetry is 0°.

�*5��*��.+

*�622+�,6��.+

%/�.��/-%,/1+��/.

-,/.�*�%�*.+

*

*

'

*�622+�,��*.5�+

�*5��*�%�*.+

%/�.��/-%,/1+��/.

�*5��*�

-,/.�*�

,�- .��2�(!%/�.�

�+�3++.��..+,*.4�+��/.+�

Figure 6.5 Graphic Representation of Angle of Asymmetry (As Taken From NIOSH)

In many cases of asymmetric lifting, the worker will pivot or use a step turn to complete the lift. Because this may vary significantly between workers and between lifts, assume that no pivoting or stepping occurs. This provides the greatest protection for the worker.

To identify asymmetric lifting, look for workplace conditions where:

The origin and destination of the lift are oriented at an angle to one another

The lifting motion is across the body (e.g., swinging bags or boxes)

The lifting is done to maintain body balance in obstructed workplaces, on rough terrain, or on littered floors

Operators are under time pressure to perform lifting tasks

169


Lifting Frequency / Duration (F) Frequency (F) refers to the average number of lifts made per minute, as measured over a 15-minute period. The minimum frequency is 0.2 lifts per minute (one lift every 5 minutes), and the maximum is 15 lifts per minute. Ideally, the frequency of lifting is once every five minutes or less.

For lifts less than 0.2 lifts per minute, use F = 0.2.

For anything greater than 15 lifts per minute, the RWL is equal to 0.

If the worker does not lift continuously during the 15-minute sampling period, use the following method to determine the correct frequency:

Calculate the total number of lifts performed over the 15-minute period (i.e., lift rate x work time). For example: 8 min. of lifting (10 lifts/min.) followed by 7 min. of light work

Divide the total number of lifts by 15. Frequency rate = (10 x 8)/15 = 5.33 lifts/min.

Use the resulting value as the frequency (F) to determine the frequency multiplier.

If the worker lifts continuously for the 15-minute period, the lifting frequency would be the actual 10 lifts/minute.


170

© 2008 Humantech

Duration is based on the patterns of continuous work-time and recovery-time periods. A continuous work-time period is defined as a period of uninterrupted work. Recovery-time is defined as the duration of light-work activity (e.g., sitting at a desk or table, monitoring operations, light assembly work, etc.) following a period of continuous lifting.

Duration can be classified into one of three categories: short, moderate, or long.

Short Duration. Lifting tasks that have a work duration of one hour or less, followed by a recovery time equal to 1.2 times the work time fall into this category. For example, a 45-minute lifting job must be followed by a 54-minute recovery period before beginning a subsequent lifting session. If the recovery time is not met, and a subsequent lifting session is required, the total lifting time must be combined to correctly determine the duration category. In addition, if the recovery period does not meet the time requirement, add the work time and the recovery time together to determine the total duration.

As another example, assume a worker lifts continuously for 30 minutes, performs a light work task for 10 minutes, and then lifts for an additional 45 minutes. In this case, the recovery time (10 minutes) is less than 1.2 times the initial 30-minute work time (36 minutes). Thus, the two work times (30 and 45 minutes) must be added together to determine the duration. Because the total work time exceeds one hour, the job is classified as moderate duration. On the other hand, if the recovery period between lifting sessions were increased to 36 minutes, the short duration category would apply, even though total lifting was greater than one hour.

Moderate Duration. Lifting tasks that have a duration of more than one hour, but not more than two hours, followed by a recovery period of at least 0.3 times the work time fall into this category. For example, if a worker continuously lifts for two hours, a recovery period of at least 36 minutes is required before beginning a subsequent lifting session. If the recovery time requirement is not met, and a subsequent lifting session begins, the total work time must be added together.

Long Duration. Lifting tasks that have a duration between two and eight hours, with standard industrial rest allowances (e.g., morning, lunch and afternoon rest breaks) fall into this category.

171


Coupling (C) Coupling is the definition of hand-to-object contact when lifting/lowering. Loads equipped with proper handles or cutouts not only facilitate lifting, but also reduce the likelihood that the load will be dropped.

Following are some general guidelines to follow with regard to coupling:

An optimal handle design has a .75 – 1.5" (19 – 38 mm) diameter, > 4.5" (114 mm) length, 2" (51 mm) clearance, cylindrical shape, and a smooth, non-slip surface.

An optimal handhold cutout has these approximate characteristics: > 3" (76 mm) height, 4.5" (114 mm) length, semi-oval shape, > 2" (51 mm) clearance, smooth non-slip surface, and > .43" (11 mm) container thickness (e.g., double thickness cardboard).

An optimal container design has < 16" (406 mm) width, < 12" (305 mm) height, and a smooth, non-slip surface.

A worker should be able to clamp the fingers at nearly 90° under the container, such as is required when lifting a box from the floor.

A container is considered less than optimal if it has a width >16" (406 mm), height >12" (305 mm), rough or slippery surfaces, sharp edges, asymmetric center of mass, unstable contents, or requires the use of gloves. A loose object is considered bulky if the load cannot easily be balanced between the hand grasps.

A worker should be able to comfortably wrap the hand around the object without excessive wrist deviations or awkward postures. The grip should not require excessive force.

Coupling is classified as good, fair, or poor, as described in the following table.

Table 6.1 Hand-to-Object Coupling Classification

Good Fair Poor

For containers (boxes, crates, etc.) of optimal design, "good" coupling includes handles or handhold cutouts of optimal design.

For containers of optimal design, "fair" coupling includes handles or handhold cutouts of less than optimal design.

Containers of less than optimal design, or loose parts or irregular objects that are bulky, hard to handle, or have sharp edges.

For loose parts or irregular objects not usually containerized (castings, stock, supply materials), "good" coupling is a comfortable grip in which the hand can easily wrap around the object.

For containers of optimal design with no handles or handhold cutouts, or for loose parts or irregular objects, "fair" coupling is a grip in which the hand can flex about 90°.

Lifting non-rigid bags (i.e., bags that sag in the middle).


172

© 2008 Humantech

Obtaining Your Variable Measurements Sometimes it is difficult to take measurements of the variables when an operator is busy working. A recommended approach is to use masking tape to tape lines on the floor representing the variables that must be measured.

Apply a straight line of tape on the floor connecting the locations of the operator's two ankles.

Apply a straight line of tape on the floor to indicate the locations of the operator's middle knuckles of both hands where the object is being lifted.

Apply a straight line of tape connecting the centers of the first two lines of tape.

These lines of tape can then be used to accurately measure the horizontal distance and angle of asymmetry if twisting occurs during the lift.

Lifting Index (LI) The RWL can be compared to the actual weight of the load being lifted to establish a Lifting Index (LI). The LI is an index of relative physical stress associated with a particular manual lifting task. To calculate the LI, use the following equation:

LI = Load Weight / RWL

�� 7��8��$��$��$

�� 7 �#��$��$�� $�8��8��$�9

� :�� :�� 7 �#��$$��$�� #��;� &��$�9

,�8

6��

5��

Figure 6.6 Three Categories of Lifting Index

As the magnitude of the LI increases, the level of the risk for a given employee increases, and a greater percentage of the workforce is likely to be at risk for developing lifting-related low back pain and potential low back disorders.

173


Interpreting Lifting Equation Results The RWL is the "not to exceed" number for the particular task being analyzed. In other words, it is the highest weight at which the working population can safely perform the lifting task.

For example, if you calculate an RWL of 9 lb (4 kg) for a task, the weight of the object being picked up should not exceed 9 lb (4 kg). If the weight being handled exceeds the RWL, target the task for ergonomic improvement to reduce low back injury risk.

Uses for the RWL include the following:

Use the RWL to set size and weight limits of a product or packaging at a particular workstation. If a box being handled weighs 20 lb (9 kg), and the RWL is 18 lb (8.2 kg), a possible solution is to package the box with fewer items inside to reduce the overall weight.

If the size or weight of an object cannot be changed, try changing other factors in the lifting equation to increase the RWL. For instance, increase the vertical distance in a lift from ground level to 32" (813 mm) (by installing a lift table) to increase the RWL, thereby allowing the operator to lift more weight safely. The horizontal distance has the greatest impact on reducing the RWL and should be minimized whenever possible.

Calculate the RWL for lifting tasks still on the drawing board. Evaluate the effectiveness of countermeasures before they are implemented.


174

© 2008 Humantech

Applying the NIOSH Lifting Equation The NIOSH Lifting Equation is provided via CD-ROM in a computer spreadsheet application as part of Humantech's Manual Material Handling Guidelines Microsoft® Excel (for both Macintosh and Windows operating systems) spreadsheet.

You can use the NIOSH Lifting Guidelines sheet to calculate the RWL and LI for a lifting task. Simply enter the variables for the task, and the spreadsheet determines the results for you.

Figure 6.7 Manual Material Handling Guidelines Spreadsheet – NIOSH Lifting Guidelines Sheet

175


The NIOSH Lifting Guidelines sheet consists of five sections:

Job Title. This information does not affect the calculation of the RWL and Lifting Index, but is useful for documenting the job analysis.

Figure 6.8 NIOSH Lifting Guidelines Sheet – Job Title

Model Inputs. There are eight input boxes for entering the task variables analyzed by the NIOSH Lifting Equation. Each of these variables is key to the calculation of the RWL and LI.

Figure 6.9 NIOSH Lifting Guidelines Sheet – Model Inputs


176

© 2008 Humantech

Multipliers. This section displays the multipliers calculated from the model inputs. These multipliers can help you identify opportunities for ergonomic intervention because they show the relative gains that can be realized by addressing each task variable. The closer the multiplier is to 1, the higher the RWL and the lower the LI.

Figure 6.10 NIOSH Lifting Guidelines Sheet – Multipliers

177


Model Output. This section displays the two main outputs of the NIOSH Lifting Equation, the RWL and LI, as well as two outputs (FIRWL and FILI) used for evaluating infrequent lifting tasks (see below).

Figure 6.11 NIOSH Lifting Guidelines Sheet – Model Outputs

RWL = (for a specific set of task conditions) the weight of the load that 90% of healthy workers could perform over a substantial period of time.

LI = ratio of the load weight to the RWL. It allows different lifting tasks to be ranked for relative physical stress.

FIRWL, the Frequency Independent Recommended Weight Limit, and FILI, Frequency Independent Lifting Index, are used to calculate the RWL and LI for a single (non-repetitive) lift. The FIRWL and FILI for each task reflect the compressive force and muscle strength demand for a single repetition of that task (the Frequency multiplier, or FM, equals 1.0).


178

© 2008 Humantech

Recommendations. This section displays a recommendation based on the LI calculated for the task.

For tasks with an LI of 1.0 or lower, the message "Nominal Risk" displays, indicating that 90% of healthy workers could perform this lift.

For tasks with an LI above 1.0, the message "Engineering or Administrative Controls should be implemented" displays, indicating an increased level of risk of low back injury.

Figure 6.12 NIOSH Lifting Guidelines Sheet – Recommendations

The NIOSH Composite Lifting Index The NIOSH Composite Lifting Index (CLI) is used to assess the risk of an operation in which multiple lifts take place, or in which each lift has variables that vary significantly from one another. This analysis is based on the following assumptions:

Performing multiple lifting tasks will increase the physical or metabolic load, and this increased load should be reflected in a reduced recommended weight limit (RWL) and increased lifting index (LI).

An increase in the LI depends upon the characteristics of the additional lifting tasks.

An increase in the LI due to the addition of one or more tasks is independent of the LI of any of the preceding tasks.

The Manual Material Handling Guidelines spreadsheet includes a tab for calculating the CLI for jobs with up to 10 lifting tasks. This analysis requires the same data inputs as the NIOSH Lifting Equation, but the model inputs must be determined for each of the lifting tasks.

Note: For detailed information about how to apply the CLI, see the Applications Manual for the Revised NIOSH Lifting Equation.

179


Uses for the Revised NIOSH Lifting Equation The NIOSH Lifting Equation has several valuable uses:

Evaluate lifting tasks for acceptable risk. Existing lifting conditions can be assessed and the load weight compared to the Recommended Weight Limit (RWL).

Prioritize hazardous jobs for ergonomic intervention. Existing lifting conditions that are not acceptable can be rank-ordered by degree of risk based on the Lifting Index (LI).

Evaluate proposed lifting conditions for acceptable risks. Workstations and processes can be evaluated and corrected at the design stage, before employees are placed at risk of injury.

Highlight opportunities for reducing lifting hazards. Multipliers reflect the relative impact of changing the task variables.


180

© 2008 Humantech

Avoiding Potential Pitfalls With the Revised NIOSH Lifting Equation

The following table lists potential pitfalls you may encounter when using the NIOSH Lifting Equation, and a recommended approach for each.

Table 6.2 Potential NIOSH Lifting Equation Pitfalls


The employee performs a one-handed lift or lower.

Use the BRIEF; NIOSH does not apply to one-handed lifting and lowering.

The employee performs a variety of different lifting activities throughout the workday.

Use the Manual Material Handling Guidelines spreadsheet (NIOSH CLI Guidelines sheet) to calculate a CLI for up to ten tasks.

The employee loads an entire pallet and there is not enough time to assess every object location.

Conduct either a worst-case or best-case lifting scenario: Worst-case – Identify the largest Horizontal

Location with the largest Vertical Location away from the 30" (762 mm) optimum location. If the worst position has an acceptable RWL, the other object locations are acceptable for the RWL.

Best-case – Identify the closest Horizontal Location with the smallest Vertical Location away from the 30" (762 mm) optimum location. If the best position has an unacceptable RWL, the other object locations are also unacceptable for the RWL.

The employee performs only a single lift once per hour.

Use the spreadsheet (NIOSH Lifting Guidelines sheet) to calculate a frequency-independent RWL and LI (FIRWL and FILI).

Assumption: The RWL and LI are acceptable for this lifting activity. Therefore this job is free from ergonomic risk.

Although the calculated RWL and LI may be acceptable, the lifting task may still contain ergonomic risk factors that could lead to a WMSD.

The task is a lowering task for which I'd like to calculate the RWL.

Measure all the task variables at the beginning of the lower and enter them into the equation. The travel distance is the change in vertical height from the origin to the destination of the lower.

In order to both lift and set down the object, the employee must use significant control.

Measure the variables for the initiation and completion of the lift and calculate two RWLs. Use the lower of the two values.

181


Table 6.2 Potential NIOSH Lifting Equation Pitfalls (Cont.)


The employee lifts an object over a lip or obstruction and then lowers the object behind it (e.g., lifting into a deep bin).

Use two equations: Evaluate the lift to the top of the lip or

obstruction before lowering begins. Evaluate the lower from the top of the lip or

obstruction to the bottom of the bin.

The employee lifts and then carries an object.

Use where the operator holds the object before carrying it as the destination of the lift to collect your measurement (i.e., vertical travel distance).

Psychophysical Analysis: Push, Pull, and Carry Psychophysical analysis, a method that measures the load an individual perceives he/she can handle to define human capabilities and limitations, is a proven method of quantifying manual handling task specifications.

The best-known results of psychophysical analysis are the Design of Manual Handling Tasks: Tables of Maximum Acceptable Weights and Forces (Snook, Ciriello, 1991). Snook gathered data on people's perceptions of what they thought their performance capabilities would be, given a variety of parameters for pushing, pulling, and carrying tasks. The tables have led to the development of guidelines for designing and evaluating these types of tasks. The purpose of the guidelines is to encourage the control of industrial low back pain by reducing the number of instances, the duration of injuries, and the duplication of injuries.

Guidelines based on the Snook tables for push/pull and carry tasks reside in the same Humantech spreadsheet—Manual Material Handling Guidelines—that contains the NIOSH Lifting Equation. A separate sheet is provided for each of the three categories (Push, Pull, and Carry).


182

© 2008 Humantech

For example, the Pull Guidelines sheet looks like this:

Figure 6.13 Pull Guidelines Sheet – Manual Material Handling Guidelines Spreadsheet

Each sheet lists the maximum acceptable forces, for the specified task and gender, by the percentage of the industrial population capable of performing the task. The maximum acceptable forces also take into consideration the approximate hand height, frequency, and horizontal travel distance of the push, pull, or carry.

When selecting a value that represents what the majority of the work population should be capable of performing with minimal risk of injury, Snook (1991) found that a worker is three times more susceptible to low back injury if performing a manual handling task that is acceptable to less than 75% of the working population. Snook also determined that designing the job to fit 75% of the work force can reduce up to one-third of industrial back injuries. Therefore, Humantech recommends using the 75% female capability value as a design goal to minimize the risk of injury to the majority of the work population.

Use caution when evaluating a multiple-component task. The Snook (1991) analysis provides maximum acceptable weights and forces for individual manual handling tasks or components (pushing, pulling, carrying). Frequently, industrial tasks involve combinations of more than one component. Snook (1991) found that in a multiple-component task, the weight or force of the component with the lowest percent of population is the best estimate of the maximum acceptable weight or force for the entire task. Therefore, each component of a combined task should be analyzed separately using the frequency of the combined task.

183


Applying the Guidelines for Pushing, Pulling Tasks The following two tables serve as starting points in the design process of pushing and pulling tasks. Limits are provided for several scenarios, referencing the maximum acceptable force corresponding to 75% of the female population. Refer to your Applied Industrial Ergonomics Toolbox CD for the complete set of push/pull guidelines.

Table 6.3 Pushing Limits

Approx. Hand Location

Push Distance

Frequency (push/min.)

Initial Force

Sustained Force

Chest 7' (2.1 m) 1/5 min. 53 lb (24 kg) 35 lb (16 kg)

Forearm 7' (2.1 m) 1/5 min. 53 lb (24 kg) 33 lb (15 kg)

Thigh 7' (2.1 m) 1/5 min. 42 lb (19 kg) 29 lb (13 kg)




Table 6.4 Pulling Limits

Approx. Hand Location

Pull Distance

Frequency (pull/min.)

Initial Force

Sustained Force








184

© 2008 Humantech

Push/Pull Guidelines in the Spreadsheet The Humantech Manual Material Handling Guidelines spreadsheet includes a sheet for pushing tasks, and a similar sheet for pulling tasks. For example, the Push Guidelines sheet looks like this:

Figure 6.14 Push Guidelines Sheet – Manual Material Handling Guidelines Spreadsheet

185


Push/Pull Guidelines Sheet Input To use the Push and Pull Guidelines sheets and generate safe pushing and pulling limits, the following task information must be known or measured:

Gender. Gender of the individual who will be performing the activity.

Height. Location of the hands when pushing or pulling. Choose the closest, but worst-case hand position to be conservative. For pushing tasks, the optimum hand position is at forearm height. For pulling tasks, the optimum hand position is at thigh height.

Percent (%). Percent of the capable population that should be able to perform this activity. The recommended goal is to design for 75% of the female population.

Distance (feet/meters). Typical travel (pushing or pulling) distance of the object. If the travel distance is not available in the drop-down list, choose the closest, but longer distance to be conservative. The optimum distance is the shortest.

Frequency (pushes or pulls per minute). Average number of times per minute the individual pushes or pulls the object. (Some frequencies do not apply based on the distance pushed, e.g., physically impossible to push 200 feet (61 m) once every six seconds.) If the frequency is not available in the drop-down list, choose the closer but higher frequency to be conservative.

Figure 6.15 Push/Pull Guidelines Sheets – Input Options


186

© 2008 Humantech

Push/Pull Guidelines Sheet Output For pushing and pulling tasks, the Manual Material Handling Guidelines spreadsheet produces a result for both acceptable initial force and acceptable sustained force.

Initial Force (lb/kg). Force required to transform an object at rest into motion. The force required to stop an object is directly related to the starting force. Initial force values are achieved when objects must go up/down ramps, around corners, and must travel on poor flooring.

Sustained Force (lb/kg). Force required to keep an object in motion. The sustained force is lower than the Initial Force.

Figure 6.16 Push/Pull Guidelines Sheets – Output Values

Applying the Guidelines for Carrying Tasks The following table serves as a starting point in the design process of carrying tasks. Limits are provided for several scenarios, referencing the maximum acceptable force corresponding to 75% of the female population. Refer to your Applied Industrial Ergonomics Toolbox CD for the complete set of carry guidelines.

Table 6.5 Carrying Limits

Approx. Carrying Height

Carrying Distance

Frequency (carry/min.)

Max Acceptable Weight of Carry

Elbow 7' (2.1 m) 1 carry/5 min. 35 lb (16 kg) Hand 7' (2.1 m) 1 carry/5 min. 42 lb (19 kg) Elbow 7' (2.1 m) 1 carry/30 min. 35 lb (16 kg) Hand 7' (2.1 m) 1 carry/30 min. 42 lb (19 kg) Elbow 14' (4.3 m) 1 carry/5 min. 35 lb (16 kg) Hand 14' (4.3 m) 1 carry/5 min. 37 lb (17 kg) Elbow 14' (4.3 m) 1 carry/30 min. 35 lb (16 kg) Hand 14' (4.3 m) 1 carry/30 min. 37 lb (17 kg)

187


Carry Guidelines in the Spreadsheet The Humantech Manual Material Handling Guidelines spreadsheet includes a sheet for carrying tasks:

Figure 6.17 Carry Guidelines Sheet – Manual Material Handling Guidelines Spreadsheet


188

© 2008 Humantech

Carry Guidelines Sheet Input To use the Carry Guidelines sheet and generate safe carrying limits, the following task information must be known or measured:

Gender. Gender of the individual performing the activity.

Height. Location of the hands when carrying. Choose the closest, but worst-case hand position to be conservative. The optimum hand position is at hand height.

Percent (%). Percent of the capable population that should be able to perform this activity. The recommended goal is to design for 75% of the female population.

Distance (feet/meters). Typical travel (carrying) distance of the object. If the travel distance is not available from the drop-down list, choose the closest, but longer distance to be conservative. The optimum distance is the shortest.

Frequency (carries per minute). Average number of times per minute the individual carries the object. If the frequency is not available in the drop-down list, choose the closest, but higher frequency to be conservative.

Figure 6.18 Carry Guidelines Sheet – Input Options

Note: The maximum acceptable weight values should be reduced by approximately 15% when handling boxes without handles, and by approximately 50% when handling objects requiring extended horizontal reaching.

189


Carry Guidelines Sheet Output For carrying tasks, the Manual Material Handling Guidelines spreadsheet produces a Maximum Acceptable Weight (lb/kg), the maximum safe carrying weight based on the specified inputs.

Figure 6.19 Carry Guidelines Sheet – Output Value

Example Carry Calculation Using Carry Guidelines Determine the maximum acceptable carrying weight for a female who carries a 30-pound (13.6 kg) tote of automotive parts at elbow height about 12 feet (3.7 m) every 30 minutes throughout an eight-hour workday.

Step 1: Define the Variables The variables for this scenario are as follows:

Gender = female

Carrying height = 40" (1.02 m)

Carrying distance = 12' (3.7 m)

Frequency = 1 carry every 30 minutes

Object weight = 30 lb (13.6 kg)

Step 2: Enter Data Into Spreadsheet and Determine Result Use the Manual Material Handling Guidelines spreadsheet (Carry Guidelines sheet) to enter the data:

Select Female gender.

Select Elbow Height, the closest value to the carrying height of 40 inches (1.02 m)

Select Percent. The recommended goal is to design for 75% the female population.

Select Distance. There is no 12' (3.7 m) value, so select the next closest, conservative value, 14' (4.3 m).

Select Frequency (1 carry every 30 minutes)


190

© 2008 Humantech

Figure 6.20 Result: Maximum Acceptable Weight of Carry = 35 Pounds (16 kg)

Step 3: Determine Course of Action The object weight (30 pounds or 13.6 kg) does not exceed the Maximum Acceptable Weight Limit (35 pounds or 15.9 kg). Therefore, no intervention is necessary at this time.

Measuring Improvement Using Push/Pull/Carry Guidelines Ergonomic improvements based on push/pull/carry guidelines will minimize the likelihood of injury due to pushing, pulling, and carrying tasks.

Potential improvements to increase the percentage of employees capable of performing the pushing, pulling, or carrying activity include:

Increasing the percent of employees capable of performing the pushing, pulling, or carrying activity.

Improving the hand position of the activity.

Reducing the travel distance necessary to move the object.

Limiting the frequency of the material handling activity.

191


Guidelines Limitations The derivation of the push/pull/carry guidelines involved psychophysical analysis to measure perceived human limitations and capabilities. Gathering this data relies on individuals to report when they felt that they were at their pushing, pulling, and carrying limits. Some of the data points do not follow conventional logic. For instance, men can generally push more than women, yet there are few data points that suggest otherwise due to the self-reported information.

Avoiding Potential Pitfalls With Push/Pull/Carry Guidelines The following table lists potential pitfalls you may encounter when using the push/pull/carry guidelines, and a recommended approach for each.

Table 6.6 Potential Push/Pull/Carry Guidelines Pitfalls


The employee lifts or lowers an object.

Use the NIOSH Lifting Equation to calculate a RWL and LI.

Assumption: The forces and weights are acceptable for this manual handling activity. Therefore this job is free from ergonomic risk.

Although the guidelines may be acceptable, the lifting task may still contain ergonomic risk factors that could lead to a WMSD.

Two employees perform this activity.

The guidelines are valid only for single-employee activities.

The employee pushes an object on a worktable a distance of less than one foot.

Use the minimum push distance of 7 feet (2.1 m). It may overestimate the value, but still provides good information about what is acceptable to the population.


192

© 2008 Humantech

Manual Material Handling Example An operator performs the following tasks (as shown in Figure 6.21) for an entire eight-hour shift:

Lift 6 boxes from the ground.

Carry them to a cart located 10' (3.0 m) away.

When the cart is full, push it to a packing station located 24' (7.3 m) away.

��

��

��

�

��

��

��

��

��

��

Figure 6.21 Lifting, Carrying, and Pushing

To find out if these tasks are within the recommended guidelines, we need the following information:

Weight of boxes (lb) = 30 (13.6 kg)

Initial force to push cart (lb) = 35 (15.9 kg)

Sustained force to push cart (lb) = 22 (10.0 kg)

Time to load 6 boxes on cart = 20 minutes

Number of times pushing operation is performed in an 8-hour day = 21

Boxes have optimally designed cutouts

There is no twisting involved in the lift

We can divide the operation into three components:

Lifting

Carrying

Pushing

193


Lifting H = 15" (381 mm)

V (origin) = 7" (178 mm)

V (destination) = 43" (1.09 m)

D = 43 - 7 = 36" (914 mm)

F = 6 boxes x 21 times = 126 boxes per shift

An operator works 8 hours from which 30 minutes are usually reserved for a meal, and there are two breaks of 15 minutes each. Therefore, total working time is 7 hours.

F = 126 boxes/(7 hours x 60 minutes/hour) = 0.3 lifts/minute

A = 0 (no twisting)

Coupling = good

The task variables do not differ significantly from lift to lift, therefore the NIOSH Lifting equation for single lifts applies. Entering the variables into the Manual Material Handling Guidelines spreadsheet results in a RWL of 20.8 lb (9.4 kg).

Figure 6.22 NIOSH Lifting Guidelines Example


194

© 2008 Humantech

Carrying Carry guidelines are obtained from the spreadsheet:

Figure 6.23 Carry Guidelines Example

195


Pushing Current push forces: 35 lb (15.9 kg) initial

22 lb (10.0 kg) sustained

Push guidelines are obtained from the spreadsheet:

Figure 6.24 Push Guidelines Example

Interpretation of Results The following table compares current weights and forces with recommended weights and forces, and indicates whether each task is acceptable (within recommended guidelines).

Table 6.7 Interpretation of Results

Task Current Guideline Acceptable?

Lifting 30 lb (13.6 kg) 20.8 lb (9.4 kg) No

Carrying 30 lb (13.6 kg) 33 lb (15 kg) Yes

Pushing Initial: 35 lb (15.9 kg) Sustained: 22 lb (10.0 kg)

Initial: 51 lb (23 kg) Sustained: 29 lb (13 kg)

Yes


196

© 2008 Humantech

Material Handling Guidelines Refer to Chapter 7, Ergonomic Design Guidelines, for guidelines that provide design and selection criteria for manual material handling.

Manual Material Handling Analysis Flowchart Refer to the flowchart below to help you determine if the NIOSH Lifting Equation is applicable to a task, which variables to collect, and the appropriate type of manual material handling analysis to perform.

,-��""��$��.��/+��0��+��1��+��%��+��%��"��+��$��$2��

,,#��%��$��%��%3��%��4�553��+��6

7*��%��+��"��3��$2��3��"��

-�

8�� 8�� 8��

8��

8��

-� -�

-�

-�

��"��-!9�(��"��

:��!��;

��%��<,,

!��2�$.��%

��$��''(��"��

��$��$��"��-!9�(�:��

=��$��4>�''(��"��6

��

��=��<7

:��<

��.��.��)��

:��3"��3�"��3��<

?�! ��

!��-!9�(�""��$��<,

&�� &��'��(��)&&'*!��+��,��-%��

?�! ��

+��3�"��3��"��+��"��+��$��+��$��.��"��+��$��

Figure 6.25 Manual Material Handling Analysis Flowchart

197


References Chaffin, D. B., et al., Occupational Biomechanics, New York: Wiley, 1999.

Snook, S. H. and Ciriello, V. M., Design of Manual Handling Tasks: Revised Tables of Maximum Acceptable Weights and Forces, Ergonomics, 30(9), 1991.

Waters, T.R., Putz-Anderson, V., Garg, A., and Fine, L.J., Revised NIOSH Equation for the Design and Evaluation of Manual Lifting Tasks, Ergonomics, 36(7), 1993.


198

© 2008 Humantech

Notes

199

7 hapter 7 Ergonomic Design Guidelines

About This Chapter................................................................................200 Ergonomics in Workstation Design .......................................................201 Design and Build Guidelines .................................................................204 Avoiding Potential Pitfalls With the Design and Build Guidelines .........218 Static Anthropometric Data....................................................................218 References ............................................................................................233


200

© 2008 Humantech

About This Chapter Chapter 7 is part of the Control phase of ergonomic risk management.

��

� ��!��"��

��

��

��

�� !�"��

��#�� $!�"��

#��

�� %��

��&� ��%�

��'��'��(��)��

$�%��

��*��%+��'��%��

��&� ��!��


This chapter describes the Design and Build Guidelines. These guidelines specify ergonomics criteria for workstations, tools, and equipment, thereby providing a reference point from which to make your workplace design and purchasing decisions. We'll address these questions:

Why should I apply ergonomic design guidelines?

What is the function of ergonomic design guidelines?

How do I apply ergonomic design guidelines?

201

Chapter 7: Ergonomic Design Guidelines

Ergonomics in Workstation Design The goal of ergonomic design is to optimize the performance of an individual operation within the context of the overall manufacturing or distribution system in which it exists. Good ergonomic design of workstations, tools, and equipment ensures that human performance is part of this optimization.

Workplaces must be designed to meet process requirements while remaining within human capabilities.

Note: Information in this chapter is simplified for ease of use. The publications referenced at the end of this chapter, along with Humantech’s The Handbook of Ergonomic Design Guidelines, can provide more in-depth information about ergonomic design guidelines.

Ergonomic design guidelines translate human performance considerations into purchasing specifications.

The ergonomic design criteria in this chapter are organized into a series of Design and Build Checklists on the Applied Industrial Ergonomics Toolbox CD. You can use the checklists to

evaluate existing workstation designs, tools, and equipment, and thereby identify root causes of current ergonomic issues, and

evaluate potential ergonomic job improvements to workstations, including tool and equipment purchases, to confirm that the solution will resolve the problem.


202

© 2008 Humantech

Design Basis for Human Performance Ergonomic design guidelines are based on studies of population capabilities. The intent is to set criteria that will optimize performance for most, if not all, of the working population. The design criteria are based on anthropometry studies of healthy, working-age adults.

Anthropometry is defined as the science of studying human body dimensions. The word can be divided into two components:

Anthro = people

metry = the measurement of

There are two basic types of anthropometry:

Functional anthropometry considers human capabilities to perform a function, such as reaching across a work surface to grasp an object. Refer to Design and Build Guidelines beginning on page 204. Information is provided for the North American population.

Static anthropometry considers the fundamental dimensions of the human body, for example, the length of a person’s forearm. Refer to Static Anthropometric Data on page 218. Information is provided for the North American, European, Asian, and Latin American populations.

Goals of applying Anthropometry:

Minimize design incompatibility

Optimize human performance

Strength guidelines are calculated from studies of maximum exertion capabilities for a population. In order to accommodate most healthy, working-age adults, the 5th percentile female data is referenced. These figures are then reduced by 80% to reflect repetitive activity. The strength guidelines often match the criteria for the BRIEF Survey but occasionally result in different limits due to the different approach to setting the limits (figures in the BRIEF Survey reflect the threshold levels that have been shown in scientific research to increase the likelihood of WMSD).

203


Design for Adjustability Whenever possible, a range of adjustability should be provided that can meet the needs of a large group of people. It is often not cost-effective to design for everyone, so adjustable equipment and workstations are frequently based on the requirements of 90% of the population. However, this means that the extremely tall and short individuals will not be accommodated.

Figure 7.2 illustrates the range of people sizes (static anthropometry). Refer to Static Anthropometric Data beginning on page 218 for data that applies to other populations.

Figure 7.2 North American Height Dimensions (Data Includes Wearing Safety Shoes with 1" Soles)

Design for Extremes In certain situations, design should be based on the extremes. For example, doors should be high enough for the tallest and largest since everyone else would then be able to walk through. Similarly, ladder rungs should be strong enough to hold the largest person. On the other hand, frequently used reference material should be placed within the reach of the shortest operators, since taller individuals will be able to reach them.

Do Not Design for the Average Often, "when you design for the average, you limit the most." Most design dimensions must accommodate reaches (design for the smallest) or clearances (design for the largest). Designing for the average typically leaves out the vast majority of users. For example, imagine if shoes were made only in size 7; while a small percentage of the population would be accommodated, most of us would find the solution unacceptable.


204

© 2008 Humantech

Design and Build Guidelines In this section, you'll find functional design criteria derived from scientific research in the form of design and build guidelines for the following:

Work reaches

Standing workstations

Seated workstations

Material handling

Force

Standing arm strength

Tools

The Design and Build Checklists on the Applied Industrial Ergonomics Toolbox CD were designed to provide an easy way to apply the functional design criteria to new or existing tools, equipment, and workstations. The checklists consolidate many different design criteria into an easy-to-apply format. One checklist is provided for each area listed above.

An example of a Design and Build Checklist for tool design and selection is shown on the following page. It includes areas for documenting the job, the current measures of the job, whether the job is currently acceptable, and improvements for enhancing those measures that are not currently acceptable.

When to Use Design and Build Guidelines If you've identified existing ergonomic risks, what should you do about them? Addressing the physical aspects of the work environment (seating, work surface height, reaching, exerted forces, etc.) using the design and build guidelines may reduce one or more of the ergonomic risk factors. The guidelines formalize the limits of human capabilities into a format you can easily apply when improving existing work environments, and when developing purchasing criteria for new equipment.

Limitations of Design and Build Guidelines The design and build guidelines are generic and may not adapt easily to your unique work environment.

205


Figure 7.3 Design and Build Checklist Example

Design Criteria: Human performance design considerations

Job Information: Identifies workstation location and product variations

Illustration: Quick reference to each of the design criteria


206

© 2008 Humantech

Work Reaches The guidelines below provide criteria for work surface reach dimensions. This information is useful for laying out work and material storage locations.

Table 7.1 Work Reach Guidelines



Max. 11" (279 mm)


Max. 16" (406 mm)


Max. 22" (559 mm)

Horizontal reach distance from front edge of workstation to hand grasping point


Max. 62" (1.58 m)


Max. 74" (1.88 m)

Vertical reach distance from standing surface to hand grasping point

Figure 7.4 Work Reach Guidelines

207


Standing Workstations The guidelines below provide design criteria for workstations in which the operator is intended to be standing. They are useful for designing work surface locations and features.

Table 7.2 Standing Workstation Guidelines


A. Hand Working Height

Optimal Zone Adj. 38" – 47" (0.97 – 1.19 m) Fixed: 42" (1.07 m)

Acceptable Zone Adj. 30" – 57" (0.76 – 1.45 m) Fixed: 42" (1.07 m)

Precision or Visually Demanding Tasks

Adj. 40" – 51" (1.02 – 1.30 m) Fixed: 45" (1.14 m)

Vertical distance from standing surface to hand working height

B. Display Height Adj: 58" – 71" (1.47 – 1.80 m) Fixed: 66" (1.68 m)

Vertical distance from standing surface to top of viewable portion of display screen

C. Optimal Viewing Distance

Adj: 18" – 30" (457 – 762 mm) Fixed: 23" (584 mm)

Horizontal distance from eye to display screen surface

D. Knee Space Depth Min. 6" (152 mm) Beneath the work surface, horizontal distance from front of table to back of the workstation

E. Foot Rail Height 6" (152 mm) Vertical distance from standing surface to top of foot rail

Knee Space Width Min. 30" (762 mm) Beneath the work surface, horizontal width across front or work surface

Figure 7.5 Standing Workstation Guidelines


208

© 2008 Humantech

Seated Workstations The following guidelines provide criteria for workstations in which the operator is intended to be seated. They are useful for designing work surface locations and features.

Table 7.3 Seated Workstation Guidelines


A. Hand Working Height – Precision or Visually Demanding Tasks

Adj. 27" – 36" (686 – 914 mm) Fixed: 36" (914 mm)


B. Display Height Adj. 35" – 46" (0.99 – 1.17 m) Fixed: 46" (1.17 m)

Vertical distance from standing surface to top of viewable portion of display screen


Adj: 18" – 30" (457 – 762 mm) Fixed: 23" (584 mm)

Horizontal distance from eye to display screen surface

D. Work Surface Thickness

Max. 2" (51 mm) Thickness from bottom of work surface to top of work surface at its largest dimension anywhere the knees may contact

E. Knee Space Depth Min. 18" (457 mm) Beneath the work surface, horizontal distance from front of table edge to back of the workstation

Knee Well Width 30" (762 mm) Beneath the work surface, horizontal width across front of work surface

Figure 7.6 Seated Workstation Guidelines

209


Material Handling The guidelines below provide criteria for lifting and lowering dimensions. This information is useful for designing load sizes and locations.

Table 7.4 Material Handling Guidelines


A. Hand Working Height – Comfort Zone Bottom

Min. 24" (610 mm)

B. Hand Working Height – Comfort Zone Top

Max. 62" (1.58 m)

C. Hand Working Height – Optimal Comfort Zone Bottom

Min. 38" (965 mm)

D. Hand Working Height – Optimal Comfort Zone Top

Max. 49" (1.25 m)


Figure 7.7 Material Handling Guidelines


210

© 2008 Humantech

Force Force guidelines are provided to accommodate a full range of healthy, working-age adults. Guidelines include both frequent (≥ 2 force applications per minute) and infrequent (< 2 force applications per minute) situations.

Two types of guidelines are provided:

Recommended: to optimize human performance Acceptable: not-to-exceed

Table 7.5 Finger Push Force Guidelines

Frequent (≥ 2/min) Infrequent (< 2/min) Force Exertions: Finger Push Recommended Acceptable Recommended Acceptable

1 index finger 3.4 lb (1.5 kg)

5 lb (2.3 kg)

8.6 lb (3.9 kg)

11.2 lb (5.1 kg)

2 fingers on same hand

5.0 lb (2.3 kg)

7.5 lb (3.4 kg)

12.5 lb (5.7 kg)

16.3 lb (7.4 kg)

2 fingers on different hands

11.0 lb (5.0 kg)

16.5 lb (7.5 kg)

27.5 lb (12.5 kg)

35.8 lb (16.3 kg)

Figure 7.8 Finger Push

211


Table 7.6 Finger Pull Force Guidelines

Frequent (≥ 2/min) Infrequent (< 2/min) Force Exertions: Finger Pull Recommended Acceptable Recommended Acceptable

1 finger 3.9 lb (1.8 kg)

6.0 lb (2.7 kg)

9.6 lb (4.3 kg)

12.5 lb (5.7 kg)


8.4 lb (3.8 kg)

12.5 lb (5.7 kg)

20.9 lb (9.5 kg)

27.1 lb (12.3 kg)

Figure 7.9 Finger Pull

Table 7.7 Thumb Push Force Guidelines

Frequent (≥ 2/min) Infrequent (< 2/min) Force Exertions: Thumb Push Recommended Acceptable Recommended Acceptable

1 thumb 5.3 lb (2.4 kg)

8.0 lb (3.6 kg)

13.3 lb (6.0 kg)

17.3 lb (7.8 kg)

2 thumbs 10.0 lb (4.5 kg)

15.0 lb (6.8 kg)

25.0 lb (11.3 kg)

32.5 lb (14.7 kg)

Figure 7.10 Thumb Push


212

© 2008 Humantech

Table 7.8 One-Handed Pinch-Grip Force Guidelines

Frequent (≥ 2/min) Infrequent (< 2/min) Force Exertions: Pinch Grip Recommended Acceptable Recommended Acceptable

Chuck pinch grip (with wrist deviation)

2.0 lb (0.9 kg)

2.4 lb (1.1 kg)

4.0 lb (1.8 kg)

5.1 lb (2.3 kg)

Chuck pinch grip (no wrist deviation)

3.2 lb (1.4 kg)

4.7 lb (2.1 kg)

7.9 lb (3.6 kg)

10.3 lb (4.7 kg)

Key pinch grip (with wrist deviation)

2.0 lb (0.9 kg)

2.9 lb (1.3 kg)

4.8 lb (2.2 kg)

6.3 lb (2.9 kg)

Key pinch grip (no wrist deviation)

3.9 lb (1.8 kg)

6.0 lb (2.6 kg)

9.7 lb (4.4 kg)

12.6 lb (5.7 kg)

Chuck pinch grip: thumb opposing the pads of the index and middle fingers Wrist deviation: noticeable flexion, extension, ulnar, radial Key pinch grip: thumb opposing the side of the index finger

Figure 7.11 One-Handed Pinch Grip

213


Table 7.9 Power-Grip Force Guidelines

Frequent (≥ 2/min) Infrequent (< 2/min) Force Exertions: Power Grip Recommended Acceptable Recommended Acceptable

1 hand (with wrist deviation)

6.4 lb (2.9 kg)

9.5 lb (4.3 kg)

15.9 lb (7.2 kg)

20.7 lb (9.4 kg)

1 hand (no wrist deviation)

12.7 lb (5.8 kg)

19.1 lb (8.7 kg)

31.8 lb (14.4 kg)

41.3 lb (18.7 kg)

2 hands (with wrist deviation)

9.0 lb (4.1 kg)

13.5 lb (6.1 kg)

22.6 lb (10.2 kg)

29.3 lb (13.2 kg)

2 hands (no wrist deviation)

18.0 lb (8.2 kg)

27.1 lb (12.3 kg)

45.1 lb (20.5 kg)

58.6 lb (26.7 kg)

Wrist deviation: noticeable flexion, extension, ulnar, radial

Figure 7.12 Power Grip


214

© 2008 Humantech

Table 7.10 Push/Pull with Grip Force Guidelines

Frequent (≥ 2/min) Infrequent (< 2/min) Force Exertions: Push/Pull Recommended Acceptable Recommended Acceptable

With 1-handed grip on plastic surface

6.7 lb (3.1 kg)

10.1 lb (4.6 kg)

16.9 lb (7.7 kg)

21.9 lb (10.0 kg)

With 1-handed grip on rubber surface

8.0 lb (3.6 kg)

12.0 lb (5.4 kg)

20.0 lb (9.1 kg)

25.9 lb (11.8 kg)

Figure 7.13 Push/Pull with Grip

215


Standing Arm Strength Standing strength guidelines provide criteria for arm exertions while standing.

Table 7.11 Standing Arm Strength Guidelines

Frequent (≥ 2/min) Infrequent (< 2/min) Force Exertions Recommended Acceptable Recommended Acceptable

A. Push out at shoulder height – 1 hand

6.8 lb (3.1 kg)

10.2 lb (4.6 kg)

17.0 lb (7.7 kg)

22.1 lb (10.1 kg)

B. Push out at elbow height – 1 hand

7.4 lb (3.4 kg)

11.1 lb (5.1 kg)

18.5 lb (8.4 kg)

24.1 lb (11.0 kg)

C. Push out at elbow height – 2 hands

11.8 lb (5.4 kg)

17.7 lb (8.0 kg)

29.5 lb (13.4 kg)

38.3 lb (17.4 kg)

D. Pull in at shoulder height – 1 hand

7.0 lb (3.2 kg)

10.5 lb (4.8 kg)

17.6 lb (8.0 kg)

22.8 lb (10.3 kg)

E. Pull in at elbow height – 1 hand

7.5 lb (3.4 kg)

11.2 lb (5.1 kg)

18.7 lb (8.5 kg)

24.3 lb (11.1 kg)

F. Pull in at elbow height – 2 hands

13.1 lb (5.9 kg)

19.6 lb (8.9 kg)

32.7 lb (14.8 kg)

42.4 lb (19.2 kg)

A B C

D E F

Figure 7.14 Standing Arm Strength


216

© 2008 Humantech

Table 7.11 Standing Arm Strength Guidelines (Cont.)

Frequent (≥ 2/min) Infrequent (< 2/min)

Force Exertions Recommended Acceptable Recommended Acceptable

G. Pull down from overhead – 2 hands

17.9 lb (8.1 kg)

26.8 lb (12.2 kg)

44.7 lb (20.3 kg)

58.1 lb (26.4 kg)

H. Pull up from knee height – 1 hand

6.3 lb (2.9 kg)

9.5 lb (4.3 kg)

15.8 lb (7.2 kg)

20.5 lb (9.3 kg)

I. Pull across body (lateral) at waist height – 1 hand, elbow fully extended

2.5 lb (1.1 kg)

3.8 lb (1.7 kg)

6.3 lb (2.9 kg)

8.2 lb (3.7 kg)

J. Pull across body (lateral) at waist height – 1 hand, elbow at 90º

3.3 lb (1.5 kg)

5.0 lb (2.3 kg)

8.4 lb (3.8 kg)

10.9 lb (4.9 kg)

K. Lift up at shoulder height – 2 hands

4.7 lb (2.1 kg)

7.0 lb (3.2 kg)

11.7 lb (5.3 kg)

15.3 lb (6.9 kg)

L. Lift up at elbow height – 2 hands

7.7 lb (3.5 kg)

11.5 lb (5.2 kg)

19.1 lb (8.7 kg)

24.9 lb (11.3 kg)

M. Press down at elbow height – 1 hand

12.8 lb (5.8 kg)

19.2 lb (8.7 kg)

30.0 lb (13.6 kg)

41.6 lb (18.9 kg)

G H I J

I/J K L M

Figure 7.15 Standing Arm Strength (Cont.)

217


Tools The following guidelines provide criteria for tool design and selection.

Table 7.12 Tool Guidelines


A. Handle Length 3.8" – 6.0" (95 – 152 mm)

Distance from base to top of handle

B. Power Grip

Handle Diameter 1.2" – 1.7" (30 – 43 mm)

Diameter throughout entire grasping area

Tool Weight Max. 4 lb (1.8 kg) Maximum tool weight

C. Precision Grip


Diameter throughout entire grasping area

Tool Weight Max. 1 lb (0.5 kg) Maximum tool weight

D. Handle Span Fully Closed Min. 2" (51 mm)

E. Handle Span Fully Open Max. 3.5" (89 mm)

Distance between the two outer grasping surfaces of the tool

Figure 7.16 Tool Guidelines


218

© 2008 Humantech

Avoiding Potential Pitfalls With the Design and Build Guidelines The following table lists potential pitfalls you may encounter when using the Design and Build Guidelines and a recommended approach for each.

Table 7.13 Potential Design and Build Guidelines Pitfalls


The plant population includes very large or very small individuals.

Measure the capabilities of individuals representative of the extremes.

Reach distances, work heights, or force requirements vary from day to day.

Design for the worst-case scenarios. Be sure to check the effect on other scenarios so you don’t create a new ergonomic challenge.

Product sizes vary, affecting working heights.

Investigate multiple working heights using either height adjustable work surfaces or dedicated work areas. Investigate raising and lowering the operator using personal platforms.

There is no work surface front edge from which to measure reach distances.

Use the Design and Build diagram to approximate where to measure from, typically 1” (25 mm) to 5” (127 mm) from the front of the body).

Static Anthropometric Data The following sections contain anthropometric data relevant to workplace design for several geographic populations. As a general rule, when applying anthropometric data:

1. Determine the body dimension and type of measurement (static or dynamic) important to design (for example, elbow height is important in determining standing work height).

2. Determine the "principle" that should apply (for example, design for the extremes, average, or an adjustable range).

3. Locate the appropriate data. Note that a one-inch allowance for shoes is included in the anthropometric data.

For some of the following information, the appropriate decision for application has been suggested or has been incorporated in the data set.

In using the following data, the largest refers to the 95th percentile male, and the smallest refers to the 5th percentile female.

The information in this section was derived from Body Space – Anthropometry, Ergonomics, and the Design of Work (Pheasant, 1996).

219


Sitting Height

Figure 7.17 Sitting Height

Definition Vertical distance from the sitting surface to the top of the head, measured with the person sitting erect, looking straight ahead, knees at right angles.

Application This measure is useful in determining head clearance in confined seated spaces or privacy panels.

Percentile Selection Because this is a clearance measure, accommodate the largest.

Small Female Large Male

North American 31.5" (800 mm) 38.4" (975 mm)

European 31.3" (795 mm) 38.0" (965 mm)

Asian 30.7" (780 mm) 37.6" (955 mm)

Latin American 30.5" (775 mm) 37.2" (945 mm)


220

© 2008 Humantech

Sitting Minimum Leg Clearance

Figure 7.18 Sitting Minimum Leg Clearance

Definition Vertical distance from the sitting surface to the top of the thigh at its maximum vertical height, measured with the person sitting erect with knees at right angles.

Application This data is necessary to establish the dimensions below the work surface so that adequate sitting clearance will be allowed between the top of the thigh and the bottom of the work surface. It also assists in determining seat heights.




European 4.9" (125 mm) 7.3" (185 mm)

Asian 4.1" (104 mm) 6.3" (160 mm)


221


Sitting Knee Height

Figure 7.19 Sitting Knee Height

Definition Vertical distance from the floor to the uppermost point on the knee, measured with the subject sitting erect, knees at right angles.

Application This measure is useful in determining the clearance necessary between the knees and the underside of the work surface when seated.




European 17.9" (455 mm) 23.4" (594 mm)

Asian 16.1" (409 mm) 21.3" (541 mm)



222

© 2008 Humantech

Sitting Popliteal Height

Figure 7.20 Sitting Popliteal Height

Definition Vertical distance from the floor to the underside of the thigh, measured with the person sitting erect, knees at right angles, feet on the floor.

Application This measure is useful in determining work surface heights and seat height range of adjustability.

Percentile Selection Adjustability to accommodate the range of percentiles is desirable.



European 14.0" (356 mm) 19.3" (490 mm)

Asian 12.8" (325 mm) 17.5" (445 mm)


223


Sitting Buttock-Calf Length

Figure 7.21 Sitting Buttock-Calf Length

Definition Horizontal distance from the plane of the back point of the buttocks to the back of the leg at the knee, measured with the subject sitting erect with knees at right angles.

Application This data is useful in determining seat pan length. The angle of the seat and the slope of the front edge of the seat should be considered.

Percentile Selection Accommodate the smallest.



European 17.1" (434 mm) 21.7" (551 mm)

Asian 15.2" (386 mm) 19.5" (495 mm)



224

© 2008 Humantech

Sitting Elbow Rest Height

Figure 7.22 Sitting Elbow Rest Height

Definition Vertical distance from the sitting surface to the bottom of the right elbow, measured with the subject sitting erect with the upper right arm vertical at the side, and the forearm at a right angle to the upper arm.

Application This data together with other data and proper considerations are helpful in determining heights of armrests, work surfaces, tables, and consoles for seated operators.




European 7.3" (185 mm) 11.6" (295 mm)

Asian 6.5" (165 mm) 11.4" (290 mm)


225


Sitting Eye Height

Figure 7.23 Sitting Eye Height

Definition Vertical distance from the sitting surface to the inner corner of the eye, measured with the subject sitting erect.

Application The value of this measurement is in determining sight lines and optimum fields of vision for the seated operator.




European 27.0" (686 mm) 33.3" (846 mm)

Asian 26.0" (660 mm) 33.1" (841 mm)



226

© 2008 Humantech

Sitting Shoulder Height

Figure 7.24 Sitting Shoulder Height

Definition Vertical distance from the sitting surface to the uppermost point on the lateral edge of the shoulder, measured with the subject sitting erect.

Application This is important for shelf height.

Percentile Selection Because reach is the operative factor, accommodate the smallest.



European 19.9" (505 mm) 25.4" (645 mm)

Asian 20.1" (511 mm) 25.8" (655 mm)


227


Standing Height

Figure 7.25 Standing Height

Definition Distance from the standing surface to the top of the head, measured with the individual standing erect. Remember to compensate for operator’s standing on tip-toes, reaching up, raising during walking, or standing on objects (such as a pallet) on top of the standing surface.

Application Overhead clearance for fixtures.



North American 60.8" (1.54 m) 74.6" (1.89 m)

European 60.3" (1.53 m) 74.0" (1.88 m)

Asian 58.3" (1.48 m) 70.9" (1.80 m)

Latin American 58.4" (1.48 m) 70.4" (1.79 m)


228

© 2008 Humantech

Standing Eye Height

Figure 7.26 Standing Eye Height

Definition Distance from the standing surface to the eyes, measured with the individual standing erect.

Application Standing display heights and sight access over obstructions.




European 56.3" (1.43 m) 69.7" (1.77 m)

Asian 53.4" (1.36 m) 65.6" (1.67 m)


229


Standing Shoulder Height

Figure 7.27 Standing Shoulder Height

Definition Distance from the standing surface to the top of the shoulders, measured with the individual standing erect. Standing shoulder height defines the top of the Comfort Zone (bottom is knee height).

Application Manual material handling below shoulder level will reduce the likelihood of WMSDs.




European 48.8" (1.24 m) 61.4" (1.56 m)

Asian 44.3" (1.13 m) 57.3" (1.46 m)



230

© 2008 Humantech

Standing Elbow Height

Figure 7.28 Standing Elbow Height

Definition Distance from the standing surface to the bottom of the elbow, measured with the forearm horizontal and the individual standing erect. Standing elbow height defines the top of the optimal Comfort Zone (bottom is hand rest height).

Application Conveyor and access heights. A range should be selected, if possible. If fixed, choose large and provide platforms for smaller persons.



North American 38.2" (970 mm) 47.8" (1.21 m)

European 37.6" (955 mm) 47.5" (1.21 m)

Asian 35.3" (897 mm) 43.5" (1.10 m)

Latin American 36.8" (935 mm) 45.1" (1.15 m)

231


Standing Hand Rest Height

Figure 7.29 Standing Hand Rest Height

Definition Distance from the standing surface to the operator’s palm, measured with the arm held straight down and the hand extended to a horizontal position. Hand rest height defines the bottom of the optimal Comfort Zone (top is standing elbow height).

Application Hand rail heights can be designed from this measure.




European 27.0" (686 mm) 33.5" (851 mm)

Asian 26.6" (676 mm) 33.1" (841 mm)



232

© 2008 Humantech

Standing Knee Height

Figure 7.30 Standing Knee Height

Definition Distance from the standing surface to the top of the knee, measured with the individual standing erect. Knee height defines the bottom of the Comfort Zone (top is shoulder height).

Application Material handling tasks should be designed no lower than this height.

Percentile Selection Because this is a reach measure, accommodate the largest.



European 17.3" (439 mm) 22.0" (559 mm)

Asian 15.7" (399 mm) 20.1" (511 mm)


233


References 3D Static Strength Prediction ProgramTM (3D SSPP), University of Michigan, Ann

Arbor, MI.

Bhattacharya, A. & McGlothlin, J. (ed.), Occupational Ergonomics: Theory and Applications, Marcel Dekker, New York, 1996.

Chaffin, D.B., et al., Occupational Biomechanics, Wiley, New York, 1999.

Corlett, E.N. and Clark, T.S., The Ergonomics of Workspaces and Machines, 2nd ed., Taylor & Francis, London, 1995.

Department of Trade and Industry, Government Consumer Safety Research, “Strength Data for Design Safety – Phase 1,” October 2000, http://www.dti.gov.uk (January 2008).

Department of Trade and Industry, Government Consumer Safety Research, “Strength Data for Design Safety – Phase 2,” June 2002, http://www.dti.gov.uk (January 2008).

Diffrient, N., Tilley, A., Bardagjy, J., Humanscale 1/2/3, MIT Press, Cambridge, MA, 1974.

Eastman Kodak Company, Ergonomic Design for People at Work, 2nd ed., John Wiley & Sons, Inc., Hoboken, NJ, 2003.

Helander, M., A Guide to the Ergonomics of Manufacturing, Taylor & Francis, Philadelphia, 1997.

Human Factors and Ergonomics Society, BSR:HFES 100: Human Factors Engineering of Computer Workstations, Human Factors and Ergonomics Society, Santa Monica, CA, 2002.

Karwowksi, W., and Marras, W., The Occupational Ergonomics Handbook, CRC Press LLC, Boca Raton, FL, 1999.

Konz, S. and Johnson, S., Work Design – Industrial Ergonomics, Holcomb Hathaway, Scottsdale, AZ, 2000.

Kroemer, K., Kroemer, H., Kroemer-Elbert, K., Ergonomics – How to Design for Ease and Efficiency, Prentice Hall, Englewood Cliffs, NJ, 1994.

Kroemer, K.H.E. and Grandjean, E., Fitting the Task to the Human, Taylor & Francis, Philadelphia, PA, 1997.

Peebles, L. and Norris, B., ADULTDATA: The Handbook of Adult Anthropometric and Strength Measurements – Department of Trade and Industry, London, 1998.


234

© 2008 Humantech

Pheasant, S., and Haslegrave, C.M., Bodyspace: Anthropometry, Ergonomics, and the Design of Work, Taylor & Francis, Philadelphia, PA, 2006.

Salvendy, C., Handbook of Human Factors and Ergonomics, John Wiley & Sons, Inc., Hoboken, NJ, 2006.

Sanders, M. and McCormick, E., Human Factors in Engineering and Design, 7th ed., McGraw-Hill, Inc., New York, NY, 1993.

Woodson, W., Tillman, B., Tillman, P., Human Factors Design Handbook, McGraw-Hill, Inc., New York, NY, 1992.

235


Notes


236

© 2008 Humantech

Notes

237

8 hapter 8 Cost Justifying Ergonomic Improvements

About This Chapter................................................................................238 Introduction to Cost Justification ...........................................................239 Ergonomics and Value-Added Analysis ................................................241 Ergonomics and Motion Time Analysis – The STEP™.........................242 Estimating Ergonomic Improvement Benefits, Cost Recovery..............244 The Cost Justification Worksheet..........................................................246 Avoiding Potential Pitfalls When Cost Justifying With STEP ................253 References ............................................................................................253


238

© 2008 Humantech


��

� ��!��"��

��

��

��

�� !�"��

��#�� $!�"��

#��

�� %��

��&� ��%�

��'��'��(��)��

$�%��

��*��%+��'��%��

��&� ��!��


This chapter describes the STEP analysis, a tool that allows you to project motion savings from ergonomic improvements. You'll also learn how to estimate the benefits of improvements and how long it will take to recover the initial cost of your ergonomic investments. You'll find answers to these questions:

Why should I cost justify ergonomic improvements?

What is the function of cost justification?

How do I cost justify ergonomic improvements?

239

Chapter 8: Cost Justifying Ergonomic Improvements

Introduction to Cost Justification Cost justification is a normal business process in any company with mature financial systems. It is a means for managers and executives to weigh the costs and benefits of various improvement initiatives to optimize the company’s resource investment. By boiling everything down into a single metric (dollars), it ensures that all requests for funds are fairly considered with an apples-to-apples comparison.

Within a site, managers must consider the relative merit of ergonomic improvements against other potential improvements. In today’s ultra-competitive business environment, managers are much more likely to support ergonomic improvements if they can fit them into the accepted cost justification process. This allows them to do what they think is right without having to defend system decisions to others who only look at the numbers.

Cost justifying ergonomic improvements can have a major impact on site manager and staff enthusiasm. Managers are challenged every day to do more with less, yet are measured on how quickly they can improve productivity and quality. Ergonomics is an undiscovered tool managers can use to positively affect their performance measures.

Financial Benefits of Health and Safety Improvements Ergonomics has been proven to have positive effects on health and safety performance and the related costs. Improved health and safety has both direct and indirect financial benefits. Direct costs are those that can be tracked to a WMSD incident, including:

Direct medical costs

Workers’ compensation payments

Indirect costs are those that increase when WMSDs occur but aren’t considered a direct cost. Some suggest that indirect costs can be as much as four to seven times direct costs, but this is difficult to substantiate. Indirect costs may include:

Occupational health staff time costs for treating WMSDs, completing paperwork, and assisting with return to work

Costs associated with recruiting and training replacement workers

Supervisor time cost to complete incident investigations and paperwork

Unfortunately, while the direct and indirect health and safety costs can be substantial, they do not fit well into typical cost justification systems. Improved health and safety can dramatically impact the bottom line, but companies often do not track these costs to the plant, department, and workstation level.


240

© 2008 Humantech

The easiest way to use health and safety costs to justify ergonomic improvements is to gather historic data for the operation that will be affected. This may require working with various departments and outside vendors such as third party administrators, but it can be done in many cases.

Keep in mind that there are no simple, scientifically reliable means to predict and quantify health and safety cost reductions from reduced ergonomic risk. As illustrated by the case studies on your Applied Industrial Ergonomics Toolbox CD, experience has shown that reduced risk leads to lower workers’ compensation costs, but the equation simply doesn’t exist to use these financial benefits in a proactive manner to cost justify improvements at the workstation level.

Financial Benefits of Performance Improvements Ergonomics has been proven to impact production performance and the related costs. Improved production leads to cost savings in many areas including:

Quality

Delivery

Productivity

Using quality and delivery improvements to cost justify ergonomic improvements can be useful in some situations, such as when management’s attention is focused on quality or delivery challenges. However, these cost measures usually suffer from the same barriers as health and safety cost savings—they are not typically tracked to specific operations and there is no simple, scientifically reliable means to predict and quantify savings.

Productivity improvements have proven to be the most straightforward means of cost justifying ergonomic improvements. Productivity is measured at the workstation level, so it fits easily into typical cost justification processes. Also, it is simple to predict and quantify the productivity impact of ergonomic improvements.

Ergonomics can affect productivity in two main ways: elimination of non-value-added tasks and reduction in motion waste. Methods for identifying and quantifying time savings as a result of elimination or reduction of non-value-added motions are discussed in the next two sections.

241


Ergonomics and Value-Added Analysis Value-added work includes those tasks and operations that make the product more valuable to the customer. For example, joining two components with a fastener is considered a value-added step since the customer would be willing to pay more for the assembled product than for a bag of unassembled components.

Non-value-added work includes those tasks and operations that do not affect the dollar amount a customer is willing to pay for your product. An example of non-value-added work is conveying parts to the assembly line. Even though the activities involved in bringing the parts to the assembly line may be necessary in the production process, they are considered non-value-added because the conveyance does not directly affect the value to the customer.

It is estimated that as much as 95% of manufacturing time falls into the non-value-added category (Suzaki, 1987). The intention of value-added analysis is to identify those non-value-added activities that can be reduced or eliminated. It is not expected that any production process can achieve 100% value-added, but even incremental reductions in non-value-added tasks can reduce costs significantly.

Many ergonomic risks occur during non-value-added activities. Performing a value-added analysis on a job is one way to identify opportunities for ergonomic improvement.


242

© 2008 Humantech

Ergonomics and Motion Time Analysis – The STEP™ Motion study has long been used by industrial engineers to improve operations and determine appropriate workloads. This analysis method requires operations to be divided into tasks, task elements, and basic motions. Then, the basic motions can be used to generate a predicted time for the operation. Techniques for motion study such as Methods Time Measurement (MTM) are complex, require trained users to ensure accuracy, and often require special software packages to ensure data integrity as operations are modified over time.

Many tasks that can be improved for motion time also contribute to ergonomic risks. For example, tasks that require extended reaching can be improved from a motion time standpoint by moving the objects closer. This will also reduce ergonomic risk; back bending, raised shoulders, and extended elbows are all associated with extended reaching. Motion time analysis can be used to calculate time savings resulting from ergonomic improvements.

Humantech has developed the STEP Analysis (Standard Time Efficiency Process) as a simple alternative to industrial engineering methods. STEP, a motion economy tool, should not be used to set time standards. Rather, it is used to estimate the motion time savings from ergonomic improvements, given the improvements reduce a reach or eliminate walking steps. The method can be used to project the productivity impact of these improvements.

The strength of the STEP is its relative ease of use—within minutes, an ergonomics team can estimate motion time savings for a given improvement and the productivity impact can be calculated.

When to Use the STEP Analysis The STEP is best used when individual ergonomic improvements have been specified in enough detail that changes to reaching and working distances can be projected. It can be used to determine the relative effect of alternative improvements, or to estimate time savings from job improvements.

Limitations of the STEP Analysis The STEP evaluates only reaching and walking motions. It is not a replacement for Methods-Time Measurement (MTM) or time study to predict, establish, or modify cycle and Takt (theoretical target time to produce one product ordered by the customer) times.

243


How the STEP Works Motion time savings resulting from ergonomic improvements can be estimated in terms of:

Reductions in reaching

Elimination of walking

Figure 8.2 STEP Zones

Each STEP zone corresponds to a time penalty. Reaching to the farthest zone will take more time than reaching to the next closest zone. The time penalties were calculated using the MTM technique and vary by 0.2 seconds for each zone based on round-trip movements.

Table 8.1 STEP Zones

STEP Zone Neutral 0"–6" 6"–12" 12"–18" 18"–24" 24"–30"

Penalty (seconds) 0 0.2 0.4 0.6 0.8 1.0


244

© 2008 Humantech

STEP analysis assigns time savings for each step eliminated for walking tasks. The first step, used to begin walking, corresponds to 0.8 seconds. Subsequent steps correspond to 0.5 seconds.

Figure 8.3 STEP Penalties for Walking

Estimating Ergonomic Improvement Benefits, Cost Recovery Cost justification is based on a simple concept: the benefit of an improvement should outweigh the cost. This is referred to as the "benefit to cost ratio".

Cost justification of capital improvements can be very complex, as the cost of money over time and the timing of savings realized from the benefits must be factored in. Typically, financial analysts can assist with these complex equations; they just need to know the costs and the benefits in dollar terms.

Costs are fairly simple to quantify, but calculating dollar benefits can be difficult. There may be reductions to historic costs associated with health and safety, quality, or delivery. These can be estimated if the current costs are understood and there is an acceptance that the ergonomic improvements will reduce these costs.

245


Projecting Productivity Impact The easiest and most effective way to estimate benefits of ergonomic improvements is to focus on productivity impact. Time savings from eliminating non-value-added tasks and reducing motion times can be used to project effects on productivity. A “conservative productivity impact” is calculated by multiplying the “projected productivity impact” by 65%. This accounts for the following:

Relative lack of precision of the STEP Analysis (compared to MTM and other motion analysis techniques)

Inefficiency of translating time savings into productivity gains

Projected (total time savings) Productivity Impact = (total operation time) x 100 = %

Conservative (total time savings x 0.65) Productivity Impact = (total operation time) x 100 = %

Figure 8.4 Productivity Impact Equation

Calculating the Payback Period To cost justify ergonomic improvements, you can calculate the payback period. Payback period refers to the amount of time that savings must accumulate to “pay back” the initial investment cost. Payback period is typically expressed in years or months.

To calculate a payback period, an annual savings calculation is needed as well as the cost of the investment. Calculate annual savings by multiplying the productivity impact by the fully burdened direct labor cost of the operation. Benefits burdens typically range from 25% to 33% of the hourly wage; a conservative measure is recommended.

Annual Savings = (productivity impact) x (annual direct cost) Payback Period (cost of improvement) (Years) = (annual savings)

Figure 8.5 Payback Period Calculation


246

© 2008 Humantech

The Cost Justification Worksheet Your Applied Industrial Ergonomics Toolbox CD contains the Cost Justification Worksheet, which combines the elements of non-value-added analysis and STEP Analysis to help you calculate a Payback Period.

The worksheet is divided into two sections:

Use the Job Improvements section to project time savings.

Use the Cost-Benefit Analysis section to calculate a payback period.

The worksheet also enables you to calculate several interim measures such as time savings per unit and time savings per day.

Note: Yellow areas in the worksheet indicate data input fields.

247


Using the Job Improvement Section The Job Improvement section of the Cost Justification Worksheet looks like this:

Figure 8.6 Cost Justification Worksheet – Job Improvement Section


248

© 2008 Humantech

To complete the Job Improvement section, you'll follow these four steps:

Step 1 Complete job description.

2 Complete job task information.

3 List job improvements.

4 Enter STEP zone information for each job improvement.

Step 1: Complete Job Description Fill in the job description information at the top left of the worksheet.

Figure 8.7 Job Description

249


Step 2: Complete Job Task Information Fill in the job task information at the top right of the worksheet.

Figure 8.8 Job Task Information

Step 3: List Job Improvements List job improvements on the left side of the worksheet. List all improvements that will reduce motion times (reaching and walking), and any tasks that will be eliminated.

Figure 8.9 Job Improvements


250

© 2008 Humantech

Step 4: Enter STEP Zone Information for Each Job Improvement For each job improvement, indicate the following:

Current and proposed STEP zones, Reach From and Reach To (reaching)

Current and proposed Position Step and Full Steps (walking)

Current and proposed Task Time in seconds (for eliminated job tasks)

Number of Times Per Cycle the reach, walk, or eliminated task occurs

Figure 8.10 STEP Zone Information

251


Interpreting Motion Time Savings Data The projected and conservative motion time savings are calculated based on the job improvement information you enter. The conservative motion time savings corresponds to 65% of the projected motion time savings. This reflects the lack of precision in the STEP Analysis, and the inefficiency of directly converting motion time savings into productivity impacts.

Figure 8.11 Motion Time Savings Projections


252

© 2008 Humantech

Using the Cost-Benefit Analysis Section The second half of the Cost Justification Worksheet calculates the payback period of the job improvements based on the projected motion time savings, the cost of the improvements.

Note that one additional data points is required, Cost of Improvement(s), which includes the cost of purchased items, cost of any contracted services and in-house services to complete the installation, and costs associated with operator training and production downtime.

Figure 8.12 Cost Justification Worksheet – Cost-Benefit Analysis Section

253


Interpreting Cost-Benefit Data The Cost-Benefit Analysis section provides you with six interim measures and two payback calculations.

Total Time Savings Per Unit – Amount of time saved per unit (seconds) per job.

Total Time Savings Per Day – Amount of time saved per day per job (minutes). Note that this may include multiple shifts, if applicable.

Additional Time Available – Total time savings (hours) when taking all jobs and all shifts into account.

Additional Volume Potential – Number of additional units that could be produced each year if all time saved is put toward additional production.

Potential % of Cycle Time Saved – Time savings divided by the cycle time (percentage).

Annual Motion Savings – Dollar value of motion savings, based on the fully burdened labor rate.

Payback Period (months) – Number of months it will take for the motion savings to pay for the improvements.

Payback Period (years) – Number of years it will take for the motion savings to pay for the improvements.

Avoiding Potential Pitfalls When Cost Justifying With STEP The following table lists potential pitfalls you may encounter when cost justifying ergonomic improvements using the STEP Analysis and a recommended approach for each.

Table 8.2 Potential STEP Cost Justification Pitfalls


After reducing the amount of reaching and walking, the cycle time hasn't changed.

Production standards reflect a variety of factors, including contractual obligations, and normal procedures should be used to change cycle times when motion and task time savings are realized.

Production demand is already being met, no need to increase production.

Making more product may not help because there is a bottle-neck elsewhere on the line.

Use the extra time resulting from your efforts to improve the process or product (additional quality checks, cleaning, etc.).

References Suzaki, Kiyoshi, The New Manufacturing Challenge, The Free Press, New York,

NY, 1987.


254

© 2008 Humantech

Notes

255

9 hapter 9 The Job Improvement Process

About This Chapter................................................................................256 Introduction to the Job Improvement Process.......................................257 Identify Feasible and Effective Improvements.......................................257 Implement Improvements ......................................................................266


256

© 2008 Humantech


��

� ��!��"��

��

��

��

�� !�"��

��#�� $!�"��

#��

�� %��

��&� ��%�

��'��'��(��)��

$�%��

��*��%+��'��%��

��&� ��!��


This chapter presents a variety of tools and techniques you can use in your organization to ensure that effective ergonomic improvements are identified and implemented. It follows a step-by-step process that uses the tools presented throughout this manual. You'll find answers to these questions:

Why should I use a process for improving problem jobs?

What is the function of the job improvement process?

How do I apply the job improvement process?

257

Chapter 9: The Job Improvement Process

Introduction to the Job Improvement Process The goal of ergonomics is to maximize productivity and reliability while eliminating work-related musculoskeletal disorders. Assessing jobs and risk factors and identifying improvements are important elements in this process, but these do not complete the journey; implementing effective improvements remains an important step.

The job improvement process consists of two primary activities:

Identify effective and feasible improvements

Implement the selected improvements

Ergonomic improvements are effective when they reduce the likelihood of WMSDs while improving productivity and reliability. This is best accomplished by reducing exposure to ergonomic risk factors. Consequently, ergonomic assessments are sometimes necessary to clearly identify the presence of risk factors; this becomes the problem statement to answer the question "Does the solution resolve the problem?"

Ergonomic improvements are feasible when they present an acceptable cost to the business. Improvements are often very inexpensive, in which case feasibility is a given. In other cases, improvements require funding and must be cost justified. A key step in cost justifying ergonomic improvements is productivity impact analysis. This answers the question "How do I pay for it?"

Once you have identified effective and feasible improvements, carefully consider the implementation process; starting with an action plan, the individual changes must be put into place and their use ensured. Then confirm the effectiveness of the improvements to ensure that the solution really does resolve the problem (and does not create any new problems). This implementation process answers the question "What are the steps to make it happen?"

Identify Feasible and Effective Improvements Figure 9.2 (on the next page) illustrates the steps involved in identifying feasible and effective improvements. A more detailed discussion of each step follows.


258

© 2008 Humantech





Prioritize Controls



Key: BEST Assessment - Prioritizes job/tasks based on exposure to WMSD risk factors STEP Analysis - Projects impact of job improvements on productivity NIOSH Lifting Equation - Determines limits for lifting and lowering tasks MMH Guidelines - Determine limits for push, pull, carry tasks Design and Build Guidelines - Provides criteria for dimensions and force Cost Justification Worksheet - Calculates payback period for improvements


259


Clearly Identify the Challenges The first step in the job improvement process is to clearly identify the root causes of the identified ergonomic issues. The goal is to establish an agreed-upon list of problems that contribute to the ergonomics challenges, usually identified using the BRIEF Survey.

Several of the ergonomic analysis tools used in this course can be useful to relate workplace factors to ergonomic issues. These tools enable an objective assessment of contributing task factors.

Table 9.1 Ergonomic Analysis Tool Uses

Analysis Tool Use to identify task factors that contribute to…

NIOSH Lifting Equation (Chapter 6)

Exceeding lifting limits, such as the horizontal distance or vertical travel distance.

Push/Pull/Carry Analysis (Chapter 6)

Exceeding material handling limits, such as carry distances or handle height for pushing.

Design and Build Guidelines (Chapter 7)

Exceeding dimension or strength limits, such as the horizontal reach distance or the type of grip used.

Two other ways to identify root causes and agree on the most important task factors are defined below. These techniques are subjective in nature; there is no right or wrong answer.

Employee involvement – Nobody knows the jobs like the operators. Employees in jobs with ergonomic issues should be asked to participate in identifying possible contributing factors. Supervisors, maintenance staff, and area engineers often can also add valuable insight.

Pareto analysis – This technique applies the "80/20" rule to determine the 20% of contributing factors that affect 80% of the ergonomic issues experienced by operators. The goal is to examine all potential contributing factors and agree upon the most import ones, those that, if improved, will substantially reduce the ergonomic issue.


260

© 2008 Humantech

Brainstorm Controls One useful technique for developing job improvements that address specific ergonomic challenges is brainstorming. Brainstorming involves bringing several people together to generate ideas. Careful process management and the absence of evaluation during the idea generation stage maximize creativity.

Here are some general guidelines for brainstorming:

Strive to generate as many high-quality recommendations as possible in an efficient manner. Set a time limit, generally no more than 45 minutes per operation.

The brainstorm team should include representatives from operators, supervisors, maintenance, engineers, and health and safety. Five to six people is an ideal number of participants.

A brainstorm leader is needed to provide information, keep people focused, and maintain the flow of ideas.

Begin the brainstorm session by viewing videotape of the job and assessment findings. Take into consideration the tasks performed, risk factors, critical dimensions, operator discomfort, and any other relevant information.

The leader should facilitate the group and write down all ideas on a white-board or flip chart so they are visible to everyone.

As the ideas begin to develop more slowly, the leader should prompt the group by focusing on specific issues. Slow motion video can help bring the focus in on a particular concern.

The golden rule in brainstorming is "No Idea is a Bad Idea". Respect everyone’s input and build on those ideas that are less than ideal to generate more effective improvements.

261


Hierarchy of Controls Control of ergonomic risk factors should follow this hierarchy:

1. Engineering controls – the preferred method for reducing or eliminating ergonomic risk factors. Engineering controls are changes to the equipment, tools, controls, piece presentation, workstations, and work flow that eliminate or significantly reduce risk factors.

2. Administrative controls – changes to task responsibilities that reduce exposure to ergonomic risk factors. Examples include job rotation, job task enlargement, work pace, alternative tasks, and rest breaks. These controls are dependent upon good planning and consistent implementation by leaders. They do not eliminate ergonomic risk factors but may reduce risk exposures to an acceptable level.

3. Work practices – changes to procedures and work methods that reduce exposure to ergonomic risk factors. Examples include appropriate use of material handling aids, proper positioning of adjustable work tables, and improved sequencing of tasks to minimize manual handling. These controls are dependent upon individual work behaviors and require continual and ongoing supervision, monitoring, and correction by leaders. They do not eliminate ergonomic risk factors but may reduce some contributing factors.

Pros and Cons Associated with Control Types The table below provides some advantages and disadvantages of each of the three control types. The overall goals should be the protection of workers from harm.

Table 9.2 Pros and Cons of Control Types

Control Approach Pros Cons

Engineering controls

Eliminate or reduce the hazard, reduce long-term cost

Can require a high initial expense and can be slow to achieve

Administrative controls

Can be immediately implemented, reduce employee risk exposure

Do not eliminate the risk, effectiveness depends on correct implementation, can be disruptive to management practices

Work practices modifications

Involve more personnel in reducing ergonomic risk exposure

Do not eliminate the risk, can require ongoing training expenses, effectiveness depends on employee acceptance


262

© 2008 Humantech

An example list of refined brainstorm ideas for a packing operation is shown in Figure 9.3. This list summarizes the best ideas, eliminating those determined to be infeasible.

Refined Brainstorm Ideas 1. Powered flipper to eliminate manual flipping 2. Pad table edge to eliminate soft tissue compression 3. Pop up ball table to reduce force required to transfer packed boxes 4. Self-inking stamp to eliminate reach to ink pad 5. Height adjustable table to enable comfortable working heights 6. Diverter arm on table to minimize reach distance 7. Foot rail to increase operator comfort

Figure 9.3 Example List of Refined Brainstorm Ideas

Evaluate Impact of Controls Once a list of engineering, administrative, and work practices controls has been developed, determine the impact of each for both ergonomic risk reduction and motion time savings. You can use the tools listed below to evaluate the impact of controls.

Table 9.3 Ergonomic Analysis Tool Uses

Analysis Tool

Use to evaluate impact of controls on…

BEST Assessment (Chapter 5) Reducing WMSD exposures

STEP Methodology (Chapter 8) Estimating motion and cycle time

NIOSH Lifting Equation (Chapter 6) Lifting and lowering tasks

Push/Pull/Carry Analysis (Chapter 6) Material handling tasks

Design and Build Guidelines (Chapter 7) Meeting human performance design criteria

263


Prioritize Controls Compare the impact of each control to the cost (time and money) for implementation planning. The Recommendation Priority Matrix (Figure 9.4) is based on four regions described in the table below. Improvements are typically implemented in the order of the regions—easy and high impact (Region 1), easy and low impact (Region 2), difficult and high impact (Region 3), and finally, if new designs are being implemented, difficult and low impact (Region 4).

Table 9.4 Recommendation Priority Matrix Regions

Region Description

1 Region 1 controls eliminate or significantly reduce exposure to major ergonomic hazards within a relatively short time, and can be implemented at a relatively low cost. Implement these controls immediately.

2 Region 2 controls eliminate or reduce exposure to moderate and minor ergonomic hazards within a relatively short time, and can be implemented at a relatively low cost. They are designated as continuous improvements due to the lower ergonomic impact.

3 Region 3 controls eliminate or significantly reduce exposure to major ergonomic hazards within a longer time period, or at a higher implementation cost. Implementation should proceed based on site capital improvement plans.

4 Region 4 controls eliminate or reduce exposure to moderate and minor ergonomic hazards within a longer time period, or at a higher implementation cost. They are typically implemented when considering new designs.

Figure 9.4 Recommendation Priority Matrix


264

© 2008 Humantech

An example recommendation priority matrix (using the refined list of brainstorm ideas presented in Figure 9.3) is shown below.

Refined Brainstorm Ideas 1. Powered flipper to eliminate manual flipping 2. Pad table edge to eliminate soft tissue compression 3. Pop up ball table to reduce force required to transfer packed boxes 4. Self-inking stamp to eliminate reach to ink pad 5. Height adjustable table to enable comfortable working heights 6. Diverter arm on table to minimize reach distance 7. Foot rail to increase operator comfort

Figure 9.5 Example Recommendation Priority Matrix

1

6

2

7

4

3

5

265


Financial Approval Region 1 improvements (easy and high impact) can typically be approved without detailed financial analysis. Region 3 improvements (difficult and high impact) often require a capital appropriations request to secure funding. While different in every company, financial approval requires:

A reasonable estimate of the total cost of the improvement, including purchased items, installation services, lost production for downtime, and operator training.

A reasonable estimate of the annual savings anticipated from the improvement. This typically includes workers’ compensation costs, labor costs, and costs related to poor quality.

Humantech’s Cost Justification Worksheet is provided on the Applied Industrial Ergonomics Toolbox CD to assist with this step. This tool focuses on productivity impact, projected savings from quality, workers’ compensation, absenteeism, etc. You can sometimes estimate these figures based on company experience. Refer to Chapter 8, Cost Justifying Ergonomic Improvements, for information about how to calculate payback periods resulting from motion time savings.


266

© 2008 Humantech

Implement Improvements This section includes a step-by-step procedure for implementing improvements. The procedure begins with a clear understanding of the problem and an agreed-upon set of improvements.

Figure 9.6 The Implementation Process

267


Develop an Action Plan An action plan combines an implementation schedule with task responsibilities. It can be used to plan and communicate job improvement activities.

A responsibility matrix with milestone goals is a useful way to chart an action plan. Following is an example of a responsibility matrix using the Region 1 improvements from the previous example.

Table 9.5 Responsibility Matrix

Action Item

Benefits

Person to Complete

Target Completion Date

Powered flipper Eliminate manual flipping J. Fox Feb. 28

Pad table edge Eliminate soft tissue compression

W. Smith Feb. 4

Diverter arm on table

Minimize reach distance J. Fox Mar. 15


268

© 2008 Humantech

Implement Controls Implementation can range from simple adjustments, to existing work cells, to procurement of customized tools and equipment. Use the Ergonomics Action Form (Chapter 3) for simple solutions.

For improvements beyond simple solutions, you may need to work with an outside vendor. Following is a list of activities that may be necessary to design, build, and install vendor-supplied custom solutions.

Set initial performance specifications – Document the performance expectations in terms of production rate, quality expectations, and ergonomic risk. This activity should include input from both the health and safety and manufacturing groups.

Draft bid documents – Include illustrations of the intended approach with human performance specifications such as reach dimensions and force applications.

Identify vendors and distribute bid documents – Use existing vendors that you have found to be effective, and solicit interest from specialty vendors if appropriate.

Evaluate vendor concepts – Evaluate against the bid documents as well as the initial performance expectations.

Develop final concept and performance specifications – Based on vendor bids, draft final concept and performance expectations. This activity should include input from both the health and safety and manufacturing groups.

Select vendor – Identify the best solution using normal vendor evaluation protocols.

Work with vendor on final design – Ask the selected vendor to tour the area where the solution will be installed. This activity should include input from both EHS and manufacturing groups.

Prototype performance test and improvement – Perform an ergonomic design review during prototype performance testing. Be sure to capture operator feedback for enhancements. Work with the vendor to specify design improvements.

Equipment documentation – Obtain the necessary documentation from the vendor to support the operation phase:

Spare parts Maintenance schedule Operational instructions

Install hard goods – Coordinate with the vendor to install the hardware and perform final run-off tests.

269


Ensure Use Ergonomic solutions are most effective when supported by mechanisms to ensure they are used as intended. These mechanisms typically include:

1. Operator training in the process changes and how to use the added equipment to ensure that all personnel have the information they need to meet production and quality goals with the modified tool, equipment, and workstation components.

2. Supervisory support during the learning curve period to ensure that all personnel are successful in meeting production and quality goals with the modified tool, equipment, and workstation components.

3. Updated process documentation such as work instructions and Job Safety Analyses.

Confirm Effectiveness The final step in the implementation process is confirming effectiveness of engineering, administrative, and work practices controls. A formal evaluation against the final performance specifications (production rate, quality expectations, and ergonomic risk) is recommended, along with feedback from operators. Tools used to confirm risk reduction include those listed in table 9.3 (page 262).

If improvements do not resolve the ergonomic issues, revisit the job as a whole using the steps in the Identify Feasible and Effective Improvements phase (page 257). If the improvements are confirmed to be successful, revisit the list of prioritized challenges and initiate the job improvement process once again.

Apply continuous improvement procedures to improved workstations to assist in working out any production issues that may arise from changed processes. In addition, take advantage of successful improvements and leverage your efforts by applying the FORM (Fix Once, Repeat Many) philosophy (page 78) to similar challenges.


270

© 2008 Humantech

Notes

271

10 hapter 10 Performing an Ergonomics Review

About This Chapter................................................................................272 What is an Ergonomics Review?...........................................................273 Step 1: Select a Job to Review ............................................................274 Step 2: Gather Data..............................................................................275 Step 3: Analyze the Data......................................................................298 Step 4: Complete the Job Improvement Process.................................299


272

© 2008 Humantech

About This Chapter Chapter 10 is part of Putting it All Together.

��

� ��!��"��

��

��

��

�� !�"��

��#�� $!�"��

#��

�� %��

��&� ��%�

��'��'��(��)��

$�%��

��*��%+��'��%��

��&� ��!��


This chapter describes the steps involved in completing an ergonomics review of a job. It also describes where the various tools discussed in this manual come into play during the review process. We'll address these questions:

Why should I perform an ergonomics review?

What is the function of an ergonomics review?

How do I apply the steps involved in an ergonomics review?

273

Chapter 10: Performing an Ergonomics Review

What is an Ergonomics Review? An ergonomics review is an assessment of job/tasks that leads you through the Recognition, Evaluation, Control process to achieve effective and efficient ergonomic improvements.

Performing an ergonomics review includes these four steps:

Step 1 Select a job to review

2 Gather data

3 Analyze the data

4 Complete the job improvement process

Following these steps will ensure that ergonomic improvements are implemented according to the principles of ergonomics (described in Chapter 1). The ergonomics review applies accepted management tools in a consistent process to achieve repeatable results.

Risk management – a clear problem statement ensures that solutions reduce risks.

Continuous improvement – a participative problem solving process captures the best insight from everyone involved, from shop floor operators to maintenance and engineering staff.

Engineering design – human performance specifications ensure that all operators (not just those present at the time) will benefit from the ergonomic improvements.

Cost justification – savings are projected in advance of investments, providing a means for fulfilling cost justification requirements.


274

© 2008 Humantech

Step 1: Select a Job to Review In the ergonomic sense of the word, we will describe a "job" as a certain set of tasks that must be completed regularly in a set amount of time.

There are several ways to determine if a job is a good candidate for an ergonomic review:

Examine medical data from the past. If numerous injuries or illnesses have resulted from performing the job, the job may benefit from a review.

Interview operators and get their opinions as to which job is the most difficult in the plant and why.

Visually assess jobs in the plant, looking for awkward postures (like those found on the BRIEF), high forces, frequencies, and/or durations of these awkward postures or high forces.

Ideally (as is the case in the EASY), we would use all of this information to help determine which job or jobs are the ones most in need of an ergonomics review.

275


Step 2: Gather Data Whether you are going to perform a BRIEF, an EASY, or a BEST assessment, it will be necessary to gather several pieces of information about the job. You will need to:

Obtain job information

Perform task analysis

Videotape the job

Take still pictures

Interview the operator

Gather medical data

Take workplace measurements

Obtain Job Information In order to document the job under review, obtain the following pieces of information from the supervisor of the department in which the job is located.

Job name

Department

Shift length

Production standards (i.e., number of parts produced per shift)

Production mix (the types of parts made at the workstation)

Rotation schedule (Do the operators at this workstation participate in a rotation schedule?)

Total exposure time at this workstation per shift (not including breaks, lunch, time at other jobs)


276

© 2008 Humantech

Perform Task Analysis Task analysis is simply dividing one individual’s job into its main tasks. For example, a person feeding a molding machine may complete the following tasks for one job cycle:

1. Pull material on table

2. Cut material with knife

3. Transfer cut material to molding machine

4. Activate molding machine

5. Return to work bench

We can examine each task for the requirements that may pose ergonomic risks. This points us further to identifying the source of the risk factors identified in the BRIEF Survey. For example, in the job described above, one of the risk factors cited was wrist flexion > 45°. It may be obvious that cutting the material with the knife is a source of this risk factor, but the task analysis reveals that activating the molding machine is also a source of this risk factor. Therefore, to eliminate this risk factor from the job, both of these sources must be addressed.

Videotape the Job A good videotape is often the most important piece of job documentation you can obtain during an ergonomics review. The videotape of a job gives you information about the postures the operator assumes, the methods used, and the cycle length. Videotape can also show you any difficulties that the operator has in performing the job. Played back in slow motion, videotape provides, by far, the best means to analyze hand manipulations and postures.

Videotapes are also a valuable source of audio information recorded during the analysis, for example, questions about job and injury history, job changes, operator comments, etc. It is essential to get a high-quality videotape record of any job being analyzed.

There are three major considerations when videotaping a job:

Viewing angle

Field of view (wide-angle or close-up)

How much footage to shoot

277


Viewing Angle Viewing angle is simply where you position the camcorder relative to the operator when you shoot the tape. Some viewing angle choices are to the operator’s side, in front of the operator, behind the operator, and above the operator when possible. Unfortunately, the viewing angles used are often dictated by the workstation layout. In general, the more views you can get of a job, the easier and more thorough the analysis.

Side View When videotaping a job, use at least two different viewing angles. Choose one of the angles so that the operator is seen from the side (as shown below). A side view of the operator is useful for measuring forward bending of the back and neck, and forward reaching with the arms.

Figure 10.2 Side View


278

© 2008 Humantech

Front or Rear View A front or rear view of the operator is useful for assessing lateral bending of the neck, elevation of the arms to the side (elbows out), and neck twisting. In addition, the front view is often the most useful view for analyzing hand manipulations and postures.

Figure 10.3 Front View

279


Overhead View Sometimes a catwalk or upper floor will allow you to capture an overhead view so that the operator is seen from the top. Overhead views can help you determine work reach requirements, process flow, and workstation layout.

Figure 10.4 Overhead View


280

© 2008 Humantech

Field of View In addition to the angle of view, you must also choose the field of view. This is simply the choice between taking a wide-angle shot or a close-up shot. In all cases you should use both types of view, but the nature of the job will often determine which type you will emphasize. Both options have their pros and cons.

Wide-Angle View Wide-angle views show most or all of the operator’s body. They are required to assess trunk, arm, and neck postures. If a job consists of whole-body exertions, such as lifting and carrying, the wide-angle view is the view of choice.

A wide-angle view also allows you to capture the overall workstation layout, part bins, and tool storage areas. Even when a job involves mostly light hand work while seated at a bench, use at least one wide-angle view to record the posture of the operator’s body in relation to the workbench and the seat.

Figure 10.5 Wide-Angle View

281


Close-Up View A close-up view zooms in and concentrates on one small part of the operator or workstation. The close-up view is ideal for analyzing hand exertions and postures or a specific feature of the workstation. If a job involves fine hand manipulations, get a close-up view of the operator’s hands for at least one complete job cycle.

A potential drawback to the close-up view is that body parts other than those singled out are not visible. For example, a close-up of an operator’s hands might reveal that a pinch grip was being used, but the analyst would not be able to see that the operator’s elbows were raised to shoulder height at the same time.

Figure 10.6 Close-Up View


282

© 2008 Humantech

How Much Footage to Shoot Consider these guiding principles when determining the appropriate amount of footage to shoot:

Obtain enough footage to see all aspects of the job you want to analyze. Be sure to include tasks that may not be performed on every single cycle, such as getting new boxes of stock and disposing of empty boxes. In some cases, it may be necessary to ask the operator to stage one or more of their infrequent activities, such as changing stock, if you think it may present a hazard. Some of the most stressful aspects of jobs occur during the irregularly-performed tasks.

Represent all of the different working conditions encountered on the job. For example, consider a job in which an operator unloads boxes stacked several layers high on a pallet. Ideally, you would like to have a continuous tape of the operator unloading an entire pallet since the operator’s back and arm postures will be much different depending on how high the boxes are stacked. Unfortunately, these types of jobs often have such long cycle times that it is impractical to videotape an entire cycle uninterrupted. As a compromise, shoot some footage when the pallet is nearly full, some when the pallet is about half full, and some when the pallet is nearly empty. This system will show you the range of postures and lifting conditions.

Try to tape at least three complete cycles of a job from two different viewing angles. For short-cycle jobs, such as taking a part off a line and putting it into a box, this is easy. For long-cycle jobs, such as the pallet unloading job described above, try changing the angle of view several times while taping the same cycle of the job.

It is better to take too much tape than too little. If you have too much tape, you can edit some out; if you don’t have enough, it’s back out to the plant floor for more.

Additional Videotaping Tips A few more ideas for effective videotaping are:

Talk through the operation to the camera. Describe the operation as you are taping it. Mention any concerns you have, or any solution ideas that come to you. Interview the operator on tape; ask them about problems with the job and any potential solutions.

Either use the time and date feature on the camcorder to annotate the tape, or hold up cards with the job name and other relevant information written on them. This comes in handy when you want to use the tape for future reference to compare a "before and after" job change.

Auto-focus cameras often change focus when stray people or vehicles enter the field of view. If you must shoot across an aisle or in a high-traffic area, you may want to turn off the auto-focus once you have focused in on your subject.

283


Videotaping Tip Summary Keep these general tips in mind when videotaping:

Use at least two viewing angles, preferably the side view and front (or back) view.

Use both wide-angle and close-up views.

Videotape at least three job cycles for each view, if possible.

Always videotape more of the job than you think you need.

Videotaping Do's and Don'ts

Do… Don't… Always ask the operator before

taping Use high quality video tape Get at least three job cycles on tape Have extra disks and batteries for

camera Videotape in sequence of job

production Record date and time on tape or film Thank the operator for participating

Start shooting video without asking the operator

Use only one shot/view of workstation

Force operators to participate in review

Move camera unnecessarily Interfere with normal job operation Stand in high-traffic aisles while

taping Forget to charge the batteries

Videotaping Tools The tools you'll need for videotaping are:

8mm, VHS, or VHS-c video camera

Battery charger

Charged batteries

Blank videotapes

Some examples of video camera models with all of the necessary functions and features are:

Sony Handycam® Model CCD TRV 308

Sharp Hi-8 Viewcam Model VL-AH151U

Canon Hi-8 Camcorder Model ES8400V

Video cameras are widely available at retail stores. You may also find the following three Web sites helpful in locating a video camera:

www.bestbuy.com

www.walmart.com

www.target.com


284

© 2008 Humantech

Take Still Photos Good photos are very important in the analysis documentation process. They will allow you to illustrate your results and observations in meetings and presentations. Digital photos prove to be the most useful because they can be modified and easily included in reports and presentations. Photos provide close-ups of body postures and part manipulations. It is, therefore, important to obtain as many photos as possible.

The major considerations when taking photos of a job are:

Lighting and viewing angles/field of view

Photo quality

Number of photos to shoot

Lighting and Viewing Angles/Field of View Good photos are typically the result of good equipment. A high quality digital camera with auto-focus is a must for consistently high quality photos.

First, make sure there is sufficient light on the subject matter. Most digital cameras have a built-in flash. Place the camera in "auto-flash" mode so that you always have the proper lighting. A flash is usually necessary when shooting slides because the ambient lighting at most industrial operations is insufficient for taking photos.

Once assured of your light source, you can concentrate on the viewing angles and fields of view needed. The viewing angles and fields for photos are identical to those used for videotape footage (i.e., side, front, rear, and overhead angles). The auto-focus feature allows you to quickly center on an object and capture a series of postures or movements in rapid succession.

Photo Quality Most digital cameras give you a choice as to the quality of the photo. Standard and Fine are two common settings. In most cases, the Standard setting will allow you to get the most photos on the disk (or memory stick) while still maintaining adequate quality. Some cameras also allow you to choose image size, ranging from 640 x 480 pixels (standard) to 1216 x 912 pixels; 640 x 480 will usually suffice. However, if you will be editing the photo, you may want to choose a higher quality/higher image size.

Number of Photos to Shoot As many as 100 photos and as few as 15 may be taken during an ergonomic analysis; however, about 30 photos per analysis is usually sufficient. Two or three shots from each angle and field of view are a minimum. Also, be sure to take photos of parts bins, tools, personal protective equipment, and displays. As a general rule of thumb, obtain as many photos as possible because you can always use extra photos when presenting your solutions or when training other personnel.

285


Still Photo Do's and Don'ts

Do… Don't… Have extra disks and batteries for

camera Zoom in on various body areas

(hands, back, neck) Take photos of the workstation (front

and side views) Take photos of tools and all

equipment

Use only one shot/view of workstation

Force operators to participate in review

Take only a few pictures Take only close-up pictures Forget to charge the batteries

Still Photo Tools The tools you'll need for taking still photos are:

Digital camera (with blank disks or memory stick)

Battery charger

Charged batteries

Some examples of digital cameras with all of the necessary functions and features are:

Sony Mavica® Model MVC-FD75

Fuji FinePix® Model A200

Canon PowerShot® Model A40

Digital cameras are widely available at retail stores. You may also find the following three Web sites helpful in locating a digital camera:

www.bestbuy.com

www.walmart.com

www.target.com


286

© 2008 Humantech

Interview the Operator Communicating with operators can dramatically increase the effectiveness of the ergonomics review. Let them know what you are going to do and try to relieve any apprehension associated with recording their job. Always try to be as non-disruptive as possible. Operators are excellent sources of information about jobs. They can typically provide information about the following:

The most difficult part of the job

Improvements that have been made in the past

New improvement ideas

Length of time (months/years) at the job

Discomfort or pain associated with the job

Tasks that are normally repeated throughout the process

Tasks that occur only occasionally

Interviewing Do's and Don'ts

Do… Don't… Introduce yourself and explain what

you hope to do Ask the operator to walk you through

the job tasks Ask the operator for improvements Step through each body part when

asking about pain or discomfort Ask open-ended questions

Interfere with normal job operation Discuss personnel/staffing issues Ask leading questions about pain or

discomfort Ask general questions Interview the operator in a group

setting

287


Interviewing Tools Humantech has developed an Employee Survey to help in the interviewing process (see Figure 10.7). This form is the same form used to complete the EASY methodology of risk prioritization. However, two additional pages are available on which you can record more than one operator’s pain or discomfort data and the operators' typical tasks (see Figures 10.8 and 10.9).

Figure 10.7 Employee Survey


288

© 2008 Humantech

Figure 10.8 Employee Survey, Second Page

289


Figure 10.9 Routine Job Elements Form


290

© 2008 Humantech

Gather Medical Data Although medical information may be disclosed during the operator interview, a good place to get more detailed and accurate information is the OSHA 300 Log. Just as in the EASY methodology, focus on recordable WMSDs that have occurred in the last 24 months.

Medical Data Do's and Don'ts

Do… Don't…

Enlist the help of plant medical personnel

Focus only on WMSDs as opposed to acute injuries like trips and falls

Determine which body areas were affected and indicate left and/or right sides of the body

Focus on the person to which the injury/illness happened

Discuss medical data with anyone not directly involved in the ergonomics review process

291


Medical Data Tools Humantech has developed a Medical Data form to help in gathering medical information. This form is the same form used to complete the EASY methodology of risk prioritization.

Figure 10.10 Medical Data Form


292

© 2008 Humantech

Take Workplace Measurements Another important aspect of data collection is taking accurate measurements of the workplace. The measurements fall into two categories:

Dimensions Weights and forces

Dimensions Measurements of workplace dimensions are needed for many aspects of ergonomic analysis, including judging the suitability of the workplace for operators of different sizes, assessing the placement of critical objects relative to preferred work reach zones, and accurately describing lifting tasks for analysis using the NIOSH lifting calculation.

Because workplace dimensions are central to most ergonomic analyses, one of the first steps in performing an ergonomic analysis is to prepare a detailed plan and elevated sketch of the workplace, showing the important dimensions. Following are some of the dimensions that should be measured:

Bench height Control locations Reach distances Part stacking/palletizing Carry distances

Seat height Cart locations Sight distances Lift locations and distances Product dimensions

This list is by no means exhaustive. Measure any dimension that you think might be useful to know!

The most useful tool for taking these measurements is a 20-foot retractable metal measuring tape. It is often a good idea to take these measurements while the operator is on break, so that you can take as many as you like without interrupting the operator. However, some measurements, like reach distances and most of the NIOSH Lifting Equation variables, must be taken when the operator is present at the workstation.

293


Weights and Forces Weight and force measurements are essential for performing lifting analyses using the NIOSH Lifting Equation, and for applying the push/pull guidelines and the BRIEF.

Some weights and forces that should be measured are:

Part weights

Tool weights

Grip forces

Push/pull forces (sliding or dragging objects such as carts, etc.)

Control manipulation forces (levers, palm buttons, triggers, etc.)

These weights and forces can be taken with strain gauges, force measuring equipment, and scales.

To measure the grip forces that the operator must exert during the job, you can do either of the following:

Have the operator squeeze or pinch the grip dynamometer as hard as he or she normally would have to in order to complete the task. Get the force requirements from several operators and use the average. Note that the operator might squeeze or pinch a little harder than necessary.

Try the job yourself and then squeeze or pinch the grip dynamometer as hard as you had to in order to complete the task. Try it several times and use the average.

Remember that it is not critical to get an exact measurement. For the BRIEF, you only need to know if the pinch grip exceeds two pounds (0.9 kg) or if the power grip exceeds ten pounds (4.5 kg). You may want to obtain a more accurate measurement if you are planning on taking force measurements both before and after the ergonomic "fix" is put into place.

Workplace Measurement Do's and Don'ts

Do… Don't… Record the dimensions and weight of

any item with which the operator interfaces

Note if the operator is outside the 5th to 95th percentile range

Record the forces required to perform each task involved in the job

Estimate when measurement is possible

Ask to measure the operator Forget to measure and weigh

equipment, tools, or parts that are not used frequently


294

© 2008 Humantech

Workplace Measurement Tools The tools you'll need to take workplace measurements are:

20-foot tape measure

Scale

Push/pull gauge (see below)

Grip meter (pinch and power grips, Figures 10.14 through 10.16)

Sketch pad (or "Current Workstation Drawing" forms, Figures 10.17 through 10.19)

Some examples of push/pull gauges with all of the necessary functions and features are shown below:

Figure 10.11

AliMed Pocket Push-Pull Force Gauge (www.alimed.com)

Figure 10.12 Chatillon Force Gauge DFM Series (www.itinscale.com)

Figure 10.13 HMC Int'l. Div. Inc. Push-Pull

Gauge Model DPG-PP* (www.hmc-international.com)

*This force gauge only measures forces up to 35 pounds (15.9 kg).

295


Some examples of Jamar® grip dynamometers are shown below. All three are available at www.rehaboutlet.com.

Figure 10.14 Jamar Hand

Dynomometer

Figure 10.15 Jamar Pinch Gauge

Figure 10.16 Jamar Hand Evaluation Kit

The figures on the following pages show examples of data collection forms that will aid in drawing workstations.


296

© 2008 Humantech

Figure 10.17 Current Workstation Drawings – Plan View

297


Figure 10.18 Current Workstation Drawings – Elevation View


298

© 2008 Humantech

Figure 10.19 Current Workstation Drawings – Tool/Part Detail

Step 3: Analyze the Data Once you have gathered all the necessary information, you can analyze the data to determine the ergonomic acceptability associated with the job. The following tools are available for this purpose:

BRIEF Survey (Chapter 4) to identify ergonomic acceptability on a task-by-task basis

EASY (Chapter 5) to determine priorities in work environments in which operators perform the same job/task for at least 20 hours per week

BEST assessment (Chapter 5) to determine priorities in work environments in which operators perform the same job/task for less than 20 hours per week

299


Step 4: Complete the Job Improvement Process Now it's time to complete the rest of the job improvement process.


ErgonomicsHit ListTM


Simple, effectivesolutions?

Clear risks withsimple, effective

solutions?

IdentifyJob/Tasks

BRIEFTM

Survey

EASYTM Prioritizationor

BESTTM Assessment


Job/tasks withpotential risks

Job/tasks withrisks identified

Yes

Highest riskjob/tasks

Yes

No

No





Prioritize Controls





300

© 2008 Humantech

Remember that Chapter 9, The Job Improvement Process, presented a variety of tools and techniques to ensure that effective improvements are identified and implemented. It follows a step-by-step process that uses the tools presented throughout this course. The steps are divided into two primary activities:

Identify feasible and effective improvements

Implement the selected improvements

The following two sections are a review of these activities.

Identify Feasible and Effective Improvements Ergonomic improvements are feasible when they present an acceptable cost to the business. Ergonomic improvements are effective when they reduce the likelihood of WMSDs while improving productivity and reliability.

The first step is to clearly identify the root causes of the identified ergonomic issues. The goal is to establish an agreed-upon list of problems that contribute to the ergonomics challenges, usually identified with the BRIEF Survey. Other tools that can be used in this step include:




The next step is to brainstorm controls. Implement engineering controls first, administrative controls next, and finally, work practice controls. The goal of brainstorming is to generate as many ideas as possible. See chapter 9 for a list of brainstorming guidelines.

Once the ideas are written down, evaluate the impact of each idea. Tools you can use for this purpose are:

BEST Assessment (Chapter 5)

STEP Methodology (Chapter 8)




301


The impact of each control should be compared to the cost (time and money) for implementation planning (prioritize controls). The Recommendation Priority Matrix has four regions:

High impact/easy to implement ideas (Region 1)

Low impact/easy to implement ideas (Region 2)

High impact/difficult to implement ideas (Region 3)

Low impact/difficult to implement ideas (Region 4)

Implement the ideas in Region 1 first, moving then to the ideas in Region 2 while, at the same time, beginning work on the ideas in Region 3. Consider Region 4 ideas only if a new line or new facility is being planned.

Most likely, you will need to obtain financial approval for Region 3 ideas. A reasonable estimate of the total cost of the improvement should include purchased items, installation services, lost production for downtime, and operator training. Managers may also require a reasonable estimate of the annual savings anticipated from the improvement. This typically includes workers’ compensation costs, labor costs, and costs related to poor quality.


302

© 2008 Humantech

Implement Improvements At this stage, the ideas are actually put into place.

Figure 10.21 From Job Improvement to Implementation

The first step in this phase is to develop an action plan. An action plan combines an implementation schedule with task responsibilities. It can be used to plan and communicate job improvement activities. A responsibility matrix with milestone goals is a useful way to chart an action plan.

The next step is implementation. Implementation can range from simple adjustments to existing work cells to procurement of customized tools and equipment. Use the Ergonomics Action Form (Chapter 3) for simple solutions.

303


For improvements beyond simple solutions, you may need to work with an outside vendor. The following activities may be necessary to design, build, and install vendor-supplied custom solutions. For more detailed information about these steps, see Chapter 9, The Job Improvement Process.

Set initial performance specifications

Draft bid documents

Identify vendors and distribute bid documents

Evaluate vendor concepts

Develop final concept and performance specifications

Select vendor

Work with vendor on final design

Prototype performance test and improvement

Equipment documentation

Install hard goods

Ergonomic solutions are most effective when supported by mechanisms to ensure they are used as intended. These mechanisms typically include operator training in the process changes and added equipment, close supervision during the learning curve period, and updating process documentation such as work instructions and Job Safety Analyses.

The final step in the implementation process is to confirm effectiveness of engineering, administrative, and work practices controls. A formal evaluation against the final performance specifications (production rate, quality expectations, and ergonomic risk) is recommended, along with feedback from operators. Tools available for this purpose include the following:

BEST Assessment (Chapter 5)

STEP Methodology (Chapter 8)





304

© 2008 Humantech

Notes

305

11 hapter 11 Surviving the First 90 Days

About This Chapter................................................................................306 The First 90 Days ..................................................................................306 Structuring the Ergonomics Process (Plan) ..........................................308 Initiating Job Improvement, Demonstrating Success (Do) ....................313 Adding Strength and Longevity to the Ergonomics Process.................319


306

© 2008 Humantech

About This Chapter Chapter 11 describes key activities for the first 90 days of implementing an effective ergonomics process.

��

� ��!��"��

��

��

��

�� !�"��

��#�� $!�"��

#��

�� %��

��&� ��%�

��'��'��(��)��

$�%��

��*��%+��'��%��

��&� ��!��


Upon completion of this chapter, you'll be able to answer these questions:

Why should I be concerned about the first 90 days?

What are key activities in the first 90 days?

How do I ensure an excellent start to an ergonomics process?

The First 90 Days After implementing an ergonomics process, the first 90 days should move you toward your goal of an effective, efficient, and sustainable ergonomics process that follows the Plan-Do-Check-Act continuous improvement cycle.

During the first three months of an ergonomics initiative, you'll make critical decisions (Plan), and initiate the job improvement process and demonstrate success (Do). It is important not to expect a world-class ergonomics process at the end of 90 days, but you can expect to be moving toward that goal.

This chapter is geared toward a facility that does not already have an ergonomics process in place. If you already have an ergonomics process in place, use this chapter to help you develop your process further. Also refer to the next section, Determining Process Maturity Level.

307

Chapter 11: Surviving the First 90 Days

Determining Process Maturity Level If you already have an ergonomics process in your facility, it is useful to know how mature that process is. Use the table below to determine the level of maturity and where you would like the process to be. The levels are defined as follows:

Level 5 = World-Class Level 3 = Systematic Level 1 = Basic Level 4 = Excellent Level 2 = Fundamental

Table 11.1 Process Maturity Level Characteristics

Level Typical Characteristics

5 Non-manufacturing areas (offices, laboratories, product design for manufacturing) are fully integrated into the ergonomics process

Management leads by example Ergonomics is viewed as a competitive advantage Ergonomics is integrated into processes of support organizations

4 An Ergonomics Management System is in place with these elements: activities are part of performance criteria for key individuals (engineers, operations managers) all people in key roles are trained an information system supports solution sharing an annual ergonomic improvement plan is established and followed

Ergonomics activities are predominately proactive A change management system is functioning and effective Top management sets expectations for a high level of performance

3 Policies and line management drive the ergonomic improvement activities to: follow a risk management approach apply a phase design review process for new equipment and processes apply a job improvement process with impact vs. difficulty evaluation

Formal ergonomics methods are applied to support an effective improvement process: application of ergonomic design criteria productivity impacts can be projected risk reduction can be projected

Some ergonomic improvements are shared within facilities Employees are trained and there is an employee involvement process Line organization is responsible for ergonomics activities

2 Ergonomics organization/team, engineers, supervisors/managers are trained with skills to: analyze methods that enable problem job prioritization apply anthropometry data to fit jobs and the workplace to people follow step-by-step job improvement process to ensure solutions are directed at problems

Ergonomic improvement efforts are primarily reactive (incidents drive improvement activities) WMSD incident information is systematically collected and shared

1 An organization for managing ergonomics (committee) exists with basic awareness training A return-to-work process is in place WMSD statistics are gathered but data may not be shared New employee training exists and addresses ergonomics Regulatory requirements are being met Management is aware of WMSD issues


308

© 2008 Humantech

Structuring the Ergonomics Process (Plan) The key elements of the Plan phase are:

Identify applicable regulations and define current status

Identify trends and site needs

Establish goals and measures

Establish improvement plans

Provide adequate resources to support the process

This section describes important considerations in how you structure your ergonomics process, and details to consider in formulating your approach.

There are different ways to structure the ergonomics process. Regardless of how the process is structured, an Ergonomics Process Owner is necessary. The Ergonomics Process Owner has a different role and a different set of responsibilities depending on whether a team is formed to help support the Ergonomics Process Owner.

When the Ergonomics Process Owner is supported by a team, he or she is responsible for coordinating and facilitating all elements of the ergonomics process. Some responsibilities include the following:

Develop a plan to direct the implementation of the ergonomics process

Ensure all applicable components of the process are implemented and sustained

Track metrics and progress regularly

Report progress to site management at least quarterly

Periodically review and analyze workplace incident data to determine trends

309


The ergonomics team is responsible for risk assessment and identification, and the individuals on the team serve as resident subject matter experts. The team’s responsibilities include the following:

Evaluate workstations and tasks for ergonomic risk factors

Rank and select jobs or operations with the most risk factors

Develop and prioritize corrective actions for the presence, severity, or exposure to the risk factors

Confirm reduction of identified risk factors

Provide information and assistance to area employees and managers to address risk factors

Document improvements

Assist with the investigation of WMSD injuries by conducting risk evaluations

Note: If the Ergonomics Process Owner is not supported by a formalized team, he/she takes on the responsibilities of the Ergonomics Process Owner and the ergonomics team, delegating to appropriate personnel.

Which path is right for you? There are several considerations to take into account when making this decision. For example:

The size of your facility

The number of different products leaving the facility

Whether your plant is unionized (unions usually require a team, or at least a union representative along with the Ergonomics Process Owner)

The amount of time the Ergonomics Process Owner can devote to ergonomics

The amount of time others in the plant can to devote to ergonomics


310

© 2008 Humantech

Key Questions for the Plan Phase Depending on which path your organization takes, there are several questions (listed in Table 11.2 below) that the Ergonomics Process Owner must answer during the Plan phase. Further discussion follows to help you find answers to some of these questions.

Table 11.2 Key Planning Questions

Ergonomics Process Owner Ergonomics Process Owner + Team

Who should be involved in the process? Does the facility have medical

personnel on site? Does the facility have a dedicated

maintenance person or staff? Is there a union? Involve a cross section of the plant

What can I expect from each person? How much time can each person

dedicate to the ergonomics process?

How can I keep people involved? Does your company have an intranet? Does the plant have bulletin boards

that people read? Does the plant have a weekly or

monthly newsletter?

How involved should participants be? How much time can you devote to

ergonomics? How much time can others devote to

ergonomics?

Who should be on the team? Does the facility have medical personnel

on site? Does the facility have a dedicated

maintenance person or staff? Is there a union? Involve a cross section of the plant

How many people are on the team? How large is the plant? Are there entirely separate departments

making different products? Are there many different types of

products made at your facility?

What should the team be doing? How involved in the planning process do

you want them to be? Do you want the team to focus only on

job improvements? Do you want the team to also focus on

risk assessment and prioritization?

What should be done in a meeting and how long should it last? Are you planning to do ergonomics

activities between meetings? Does the team have time between

meetings to complete assignments? Is there an agenda for the meeting?

How often should the team meet? Are you planning to do ergonomics

activities between meetings? Does the team have time between

meetings to complete assignments? Is there an agenda for the meeting?

311


Finding the Answers This section may help you find answers to questions presented in Table 11.2.

Who should be on an ergonomics team? The ergonomics team should include a representative from each of the following departments:

Hourly employees. Hourly employees are valuable assets because they are the experts at the jobs you are trying to improve. They know the details of each task, the order in which the task must be performed and, most importantly, what can be done to improve the job.

Maintenance. Maintenance personnel are also vital to the ergonomics team because they often make physical changes to workstations, or build new ones.

Engineers. Engineers can help the ergonomics team design the work area and provide specifications for existing workstations. Engineers also understand the inner workings of the machinery and tooling in a facility.

Environmental Health and Safety. EH&S personnel can provide essential information on known safety issues. Ergonomics is often based in Health and Safety. For this reason, it is especially important to include a representative from this department on the team.

Quality. A strong ergonomics process and effective ergonomics team can improve product quality, while a poorly functioning team may adversely affect it. It is important to have a quality professional available to ensure the continued excellent quality of your product.

Medical. If your plant has a nurse, he or she will be able to tell the team which jobs have a track record of WMSDs. One of the tools you can use to prioritize jobs is the EASY. The EASY uses the BRIEF data, employee data, and medical data for a given job. The medical data is available only from those in the medical department. If the plant is small, Human Resources may also act as recordkeeper of ergonomic injuries and illnesses.

Labor/union leadership. If your facility is unionized, a union/labor representative on the team can ensure that no union regulations are violated.

Department management. Managers can help with cost justification and can shed light on how to sell improvements to other managers.

What should the ergonomics team be doing? As mentioned earlier, the purpose of the ergonomics team is to support the Ergonomics Process Owner. The team should focus mostly on the Plan and Do phases of the Plan-Do-Check-Act continuous improvement cycle.


312

© 2008 Humantech

What should be done in a meeting and how long should it last? Because this time together is valuable, be careful how you spend it; plan ahead of time what you will be discussing and deciding in meetings so that they are the most productive they can be.

How often should the ergonomics team meet? At first, the ergonomics team should meet frequently until each person is comfortable with how the process works and understands his or her role and responsibilities. Once the ergonomics process is underway, the team may meet less frequently.

Example Company ABC is a small medical device manufacturing facility with 200 employees. The Ergonomics Process Owner is part of the Health and Safety Department and has decided to form an ergonomics team to share some of the responsibilities. Following are her answers to the questions above.

Who should be on the team? "We have an on-site nurse and a maintenance department. We are not unionized. I will also include two operators, an engineer, a quality manager, and two managers from the areas that I feel will benefit the most from the ergonomics process."

How many people should be on the team? "My list above includes a cross section of the plant. Including myself, there are nine people."

What should the team be doing? "I want to include the team in the planning phase to ensure that all ideas are heard and there is support among the team members. I would like the team to perform assessments and prioritize the jobs in the facility."

What should be done in a meeting and how long should it last? "I’ve talked with the managers of all team members and they are prepared to allow the team members to spend at least one day per month on ergonomics. I will have the team members complete the videotaping and risk assessment outside of the meeting so that we can use the meeting to brainstorm ideas and give progress reports. I anticipate that most meetings will take about an hour. I will ensure that there is an agenda for every meeting and that we stick to the agenda."

How often should the team meet? "During the first 90 days, I plan to hold meetings twice per month to make sure that everyone is clear on their roles and responsibilities. After the 90-day period, I plan to hold meetings once per month."

313


Mission Statements Creating a mission statement for those involved in the ergonomics process keeps everyone on track and should be completed early in the Plan phase. Take a few moments at the beginning of the ergonomics process to draft a mission statement. Following are a few tips for drafting a mission statement.

A good mission statement should accurately explain why the ergonomics team exists and what it hopes to achieve in the future. It articulates the team's essential nature, its values, and its work.

The mission statement should be a brief paragraph that is free of jargon. Avoid the kind of shorthand that you may be in the habit of using with others who work in your facility, but is unfamiliar to anyone outside the team.

At a minimum, the mission statement should answer three key questions:

What are the opportunities or needs that we exist to address? What are we doing to address these needs? What principles or beliefs guide our work?

Initiating Job Improvement, Demonstrating Success (Do) The key elements of the Do phase are:

Establish a support infrastructure

Provide training for skills and awareness

Ensure corrective action plans are implemented to reduce risk factors

Evaluate new products, technologies, and workstations

Manage WMSD health effects

This section describes important factors to consider to leverage the enthusiasm that will be generated. It describes how to achieve initial success, and the importance of broadcasting that success to ensure that it will happen again.

Start Small Start with a small project that has some "low-hanging fruit" (low cost, high impact solutions). Choose a workstation that is fairly high profile that you know can be fixed quickly and inexpensively, and at which you can lower the ergonomic risk to the operator.

Start small so that you (and your team) can have a success under your belt before tackling more difficult and more complicated problems. It is not recommended that you start the process by completing a BRIEF on every job in your facility. Doing so will require a substantial amount of time and has been known to cause "paralysis by analysis."


314

© 2008 Humantech

You can prioritize the jobs in your facility by determining which jobs are high risk (a posture coupled with either a force, frequency, or duration), if there has been an ergonomic related injury at the job, and if the job is known to cause pain to employees. Once that basic information has been gathered, it is easy to prioritize the jobs in the facility in broad terms. Once you (or the team) have a good idea which jobs pose the highest risk, you can perform the EASY or BEST assessment on those jobs, and continue with the job improvement process.

Leverage Enthusiasm to Amplify Ergonomic Success Excitement and enthusiasm are critical components for any ergonomic improvement initiative. Without them, an initiative becomes just another "program of the month," failing to drive measurable improvements and lacking the resources to be successful.

Ergonomics is perfectly positioned in many companies to disappoint—but can be turned around to exceed expectations with the alignment of three critical groups:

Shop floor operators

Engineering and maintenance personnel

Business leadership

Although enthusiasm for ergonomics often extends well beyond these groups, the active participation and support of these particular functions will amplify the success your ergonomics initiative is already achieving.

Build Shop Floor Enthusiasm Ergonomics is relatively simple—find workplace challenges and fix them. Yet many ergonomics initiatives end up complicated by tricky assessment forms and costly software programs. The majority of the workforce is left out of improvement activities because individuals lack specialized knowledge or computer access to participate in the ergonomics process.

Observation-based ergonomics assessments like the "Find It and Fix It" approach (Chapter 3) allow all levels of employees to participate in ergonomics and contribute to immediate, evident improvements. The pride and satisfaction that comes from contributing to improvement breeds enthusiasm and spreads involvement, leading to a greater impact without requiring individual heroic effort.

Observation-based assessments combine simple observation methods with cost-effective solution strategies. They focus on the most important ergonomic issues—awkward postures, forceful exertions, and high rates of repetition—and create a common language, enabling the entire organization to work together to solve problems. Most importantly, the assessments ensure that improvements target the most critical ergonomic issues to optimize the impact of every dollar spent.

315


Tap into Excitement for Enhanced Performance Engineering and maintenance personnel are often the missing link in a struggling ergonomics program. Identifying the greatest ergonomic hazards and formulating high impact improvement plans have no affect if the plans are never implemented. Engaging representatives from these critical functions is an important strategy for success.

Engineers and maintenance staff must balance their work demands for health and safety projects, manufacturing excellence initiatives, and routine "daily improvements." They are focused on performance metrics—typically productivity and quality measures—that the company deems important. Consequently, it can be challenging to generate excitement among these individuals for health and safety projects. Capturing the impact of ergonomics on productivity and quality has proven to be an effective means for generating the missing excitement.

An effective ergonomics initiative includes techniques for quantifying productivity and quality gains in addition to driving health and safety improvements. These techniques are fully integrated into ergonomics training courses and become part of every improvement project. Simple tools, such as the Standard Time Efficiency Process (STEP) methodology (Chapter 8), turn projecting the impact of improvement on performance from a chore into a celebration.

Amplify Ergonomic Success Another important strategy for success is aligning business leadership with the ergonomics initiative. Shop floor enthusiasm will drive improvements and engineers and maintenance staff will invest in performance-enhancing projects, but management systems integration is necessary for sustained success. After all, management controls the budget and determines where resources will be deployed.

Management systems integration requires developing an ergonomics process that can be managed like any other initiative, which typically requires widened accountability and clear role definitions. In addition, leveraging Human Resources mechanisms, such as performance plans and promotion criteria, ensures that ergonomics is seen as important to the business and treated as such.

Achieving this integration with management systems requires looking at your ergonomics initiative in a whole new light. Become familiar with management's goals and priorities, and determine where ergonomics fits in. Companies with a successful ergonomics process have positioned ergonomics as a contributor to a wide variety of critical business goals including these:

Workers’ compensation costs

Injury and illness rates

Productivity improvements

Lean Manufacturing metrics

"Employer of choice" initiatives

First-time yield (quality)


316

© 2008 Humantech

Broadcast Victories Once the small project you started with is complete, it’s time to broadcast your victories to the rest of the plant and to other related facilities. There are several ways to do this, including the following:

Highlight the project in your company newsletter.

Post before and after photos with a small explanation on bulletin boards around the plant.

Present to management the risks identified and what you did to control them using before and after pictures.

Post a red flag at the workstation while it is being improved, and change the flag to green when improvements are complete. Rely on word of mouth or post pictures so that others in the plant know the success you and your team achieved.

Post the project (with photos) on the company Web site, explaining what the ergonomic risks were and how you reduced/eliminated them.

One or any combination of these ideas will broadcast your success. Be sure not to overlook broadcasting, as future funding for other ergonomics projects may depend on how well you perform this step.

Example Below is an example of a case study that can be placed in a company newsletter or on your Web site. A shorter version may be placed on a bulletin board in the plant.

Ergonomic Improvements Reduce Cycle Time and Increase Productivity A plant assembles laptops on a continuous-flow line. At one particular workstation, the operator installs one laptop display screen every 35 seconds, eight hours per day. The job consists of five distinct tasks.

An ergonomic risk analysis identified that the left hand, right hand, right elbow, neck, and back are at significant ergonomic risk. Two workstation improvements were recommended to reduce ergonomic risk:

Provide two auto-fed screwdrivers.

Move the parts storage within easy reach.

317


The workstation design template is shown below along with the projected time savings in Table 11.3.

��,+3(,�)+,

�<=��=

��>��'��/)+,��/,*5+

(��%�*6��/,*5+

Figure 11.2 Existing Workstation Layout

*>�/!-+(��,+3(,�)+,

��>��'��/)+,��/,*5+

(��%�*6��/,*5+/)+,��.+

�?=�2*@��=

Figure 11.3 Improved Workstation Layout


318

© 2008 Humantech

Table 11.3 Projected Time Savings from Ergonomic Improvements

Task

Current Task Time

Task Time with Improvements

Install center hinge cover 4.6 4.6

Drive two screws to center hinge cover 9.4 2.3

Install display 8.6 8.3

Drive two screws to display clutches 9.4 2.3

Close display and activate line 0.8 0.8

Operator recovery (rest) 2.2 2.7

Total time for the display install job 35 seconds 21 seconds

The job improvements will decrease the cycle time by 40% and significantly reduce the ergonomic risk for the right wrist, right elbow, and back. Assuming the cost of operators to this company is $10 per hour ($8 per hour wage plus a 25% benefits burden), these simple improvements can save the company $160 per week in labor costs. That’s $8,000 per year in productivity gains, providing a return on investment of 167% in the first year on a $3,000 investment.

319


Adding Strength and Longevity to the Ergonomics Process Once the initial project is complete, documented, and broadcasted, do not let the process stall. Use the same excitement that was generated at the end of that project to start the next one. It is vital that the process does not lose momentum. You now need to add strength and longevity to ensure that ergonomics is a continuous process, not a program.

How to Sustain Your Process To add strength to your ergonomics process, review what worked well in the project and what did not. With that knowledge, you can repeat the project successes and change the aspects of the project that could have gone better.

Following is a list of activities that may have been part of your process. Use the list to judge how well each part worked for your organization.

1 = Strongly Disagree 3 = Neutral 5 = Strongly Agree 2 = Somewhat Disagree 4 = Somewhat Agree

Activity Rating

1. Risk factors for WMSDs were identified accurately. 1 2 3 4 5

2. Signs and symptoms for WMSDs were recorded. 1 2 3 4 5

3. Shop floor employees were interviewed for possible ideas to reduce ergonomic risk factors.

1 2 3 4 5

4. The BRIEF was filled out accurately and in a timely manner. 1 2 3 4 5

5. Jobs were prioritized using the EASY or BEST, and high risk jobs were controlled first.

1 2 3 4 5

6. The NIOSH Lifting Equation was used to determine the level of risk in the lifting task.

1 2 3 4 5

7. A brainstorm session, including representatives from a cross section of the plant, was held to identify controls that would help reduce or eliminate ergonomic risk factors.

1 2 3 4 5

8. Workstation design guidelines were used to determine proper heights, reaches, and forces.

1 2 3 4 5

9. Brainstorm ideas were prioritized according to impact and difficulty. 1 2 3 4 5

10. Cost justification models were used to cost justify improvement ideas. 1 2 3 4 5

11. An implementation plan was formed describing who is doing what and when it will be done.

1 2 3 4 5

12. The job improvement process was followed and completed. 1 2 3 4 5

13. All successes were documented and repeated as often as possible. 1 2 3 4 5

14. Successes were broadcast to the plant and other related facilities. 1 2 3 4 5

15. All data was gathered in a timely fashion. 1 2 3 4 5


320

© 2008 Humantech

Potential Pitfalls That May Stall an Ergonomics Process The following table lists potential pitfalls you may encounter as you move ahead with your ergonomics process, and a recommended approach for each.

Table 11.4 Potential Ergonomics Process Pitfalls


The structure of the ergonomics process is not formalized.

Use either the team approach or assign an ergonomics process owner. Formalize the process, describing the roles and responsibilities for each person.

An ergonomics team or process owner is not aware of the process goal.

Create a mission statement that describes the goals of the ergonomics process.

Ergonomics team members take on more responsibility that they have time for.

Ensure that participants understand their roles and responsibilities and have the time to commit to the process. If they don’t, consider another person.

Ergonomics process owners take on more responsibility that they have time for.

Ensure that the ergonomics process owner can devote at least one day per week to the ergonomics process.

There are too many people on the ergonomics team.

Limit the team to 5-10. If more people are needed on the team, try dividing the team into groups that function separately but report to a steering committee.

Meetings are not productive. Set an agenda for the meeting and stick to it. Ensure that all team members are participating in a positive way.

Management is not willing to support the ergonomics process with money for improvements.

Cost justify all improvements using the STEP methodology or by showing how many dollars were spent on injuries in the past.

The ergonomics process has lost momentum.

Jump-start the process by getting the employees involved. Use the Find It and Fix it approach to quickly find and solve ergonomic challenges. Highlight the results on bulletin boards throughout the plant.

We (I) don’t know where to start.

Refer to the flowcharts presented in Chapter 1 ("Using the Right Tool for the Job") and Chapter 9 ("The Job Improvement Process").

Meetings do not occur due to time constraints.

Schedule meetings at the same date, time, and place each month. Take into consideration production schedules. For example, if you know that the end of each month is very busy, hold meetings either at the beginning of the month, or toward the middle.

321


Notes


322

© 2008 Humantech

Notes

323

Appendices

Appendix A: Basis for the BRIEF ..........................................................324 Appendix B: Basis for the Design and Build Guidelines........................328


324

© 2008 Humantech

Appendix A: Basis for the BRIEF Humantech’s BRIEF Survey is based on published scientific references. The sources for these references are listed for each risk factor and assumptions made to simplify the survey. For full reference information, see References on page 120.

Risk Factors for the Hands and Wrists

Category Risk Factor References

Flexed > 45° Barnhart, S. et al., 1991 Punnett, L. and Keyserling, W.M., 1987

Extended > 45° Barnhart, S. et al., 1991 Kuorinka, I. and Forcier, L., 1995

Ulnar Deviation Muggleton, J.M. et al., 1999 Punnett, L. and Keyserling, W.M., 1987

Posture

Radial Deviation Armstrong, T.J. et al., 1982 Kuorinka, I. and Forcier, L., 1995

Pinch Grip > 2 lb (0.9 kg)

Putz-Anderson, V., 1988 Roquelaure, Y. et al., 1997

Finger Press > 2 lb (0.9 kg)

Armstrong, T.J. and Chaffin, D.B., 1979 Putz-Anderson, V., 1988

Force

Power Grip > 10 lb (4.5 kg)

Armstrong, T.J. et al., 1987 Stetson, D.S. et al., 1993

Duration > 10 seconds Chaffin, D.B. and Andersson, G.B.J., 1988 Putz-Anderson, V., 1988

Frequency > 30/minute Kuorinka, I. and Forcier, L., 1995 National Research Council and the Institute

of Medicine, 2001

Risk Factors for the Elbows


Rotated Forearm Feldman, R.G. et al., 1983 Silverstein, B.A., 1985

Posture

Fully Extended Feldman, R.G. et al., 1983 Silverstein, B.A., 1985

Force > 10 lb (4.5 kg) Nicholson, A.S. et al., 1997

Duration > 10 seconds Putz-Anderson, V., 1988

Frequency > 2/minute Kuorinka, I. and Forcier, L., 1995

325

Appendices

Risk Factors for the Shoulders


Arm Behind Body Putz-Anderson, V., 1988

Arm Raised > 45° Kuorinka, I. and Forcier, L., 1995 Sommerich, C.M. et al., 1993

Posture

Shoulders Shrugged Kuorinka, I. and Forcier, L., 1995

Force > 10 lb (4.5 kg) Nicholson, A.S. et al., 1997

Duration > 10 seconds Putz-Anderson, V., 1988

Frequency > 2/minute Chiang, H-C, et al., 1993 Kuorinka, I. and Forcier, L., 1995

Risk Factors for the Neck


Flexed > 30° Bernard, B.P., 1997 Ohlsson, et al., 1995

Extended Dartiques, J.F. et al., 1988 Hales, T.R. and Bernard, B.P., 1996

Sideways Bernard, B.P., 1997

Posture

Twisted > 20° Bernard, B.P., 1997

Force > 2 lb (0.9 kg) Bernard, B.P., 1997 Chaffin, D.B., et al., 1999

Duration > 10 seconds Bernard, B.P., 1997 Viikari-Jantara, E.R.A., 1997

Frequency > 2/minute Bernard, B.P., 1997 Kuorinka, I. and Forcier, L., 1995


326

© 2008 Humantech

Risk Factors for the Back


Flexed > 20° Burdorf, A. and Sorock, G., 1997 Punnett, L. et al., 1991

Sideways Punnett, L. et al., 1991 Genaidy, A.M. et al., 1993

Extended Keyserling, W.M., 1986

Twisted Burdorf, A. and Sorock, G., 1997 Punnett, L. et al., 1991

Posture

Unsupported Chaffin, D.B., et al., 1999 Grandjean, E. and Hunting, W., 1977

Force > 25 lb (11.3 kg) Macfarlane, G.J. et al., 1997 National Research Council and the

Institute of Medicine, 2001

Duration > 10 seconds Keyserling, W.M., 1986 Punnett, L. et al., 1991

Frequency > 2/minute Kuorinka, I. and Forcier, L., 1995 Punnett, L. et al., 1991

Risk Factors for the Legs


Squat Feldman, R.G. et al., 1983

Kneel Buckle, P.W., et al., 1986 Feldman, R.G. et al., 1983

Posture

Unsupported Chaffin, D.B., et al., 1999

Force Foot Pedal > 10 lb (4.5 kg)

Van Cott, H.P., and Kinkade, R.G., 1972

Duration > 30% of day Buckle, P.W., et al., 1986

Frequency > 2/minute Kuorinka, I. and Forcier, L., 1995

327

Appendices

Physical Stressors

Risk Factor References

Vibration Kuorinka, I. and Forcier, L., 1995 National Research Council and the Institute of

Medicine, 2001

Low Temperatures Kuorinka, I. and Forcier, L., 1995 Muggleton, J.M. et al., 1999

Soft Tissue Compression Kuorinka, I. and Forcier, L., 1995 Moore, J.S. and Garg, A., 1994

Impact Stress Kuorinka, I. and Forcier, L., 1995 Muggleton, J.M. et al., 1999

Glove Issues Kuorinka, I. and Forcier, L., 1995 Keyserling, W.M., 2000


328

© 2008 Humantech

Appendix B: Basis for the Design and Build Guidelines Humantech’s Design and Build Guidelines are based on published scientific references. The textbook sources for these references are listed for each set of design criteria and assumptions made to simplify the checklists. For full reference information, see References on page 233.

Work Reach Guidelines

Criteria Dimension References


Max. 11" (279 mm)


Max. 16" (406 mm)


Max. 22" (559 mm)


Max. 62" (1.58 m)


Max. 74" (1.88 m)

3D Static Strength Prediction Program (3D SSPP), University of Michigan

Diffrient, N., Tilley, A., Bardagjy, J., 1974

Eastman Kodak Company, 2003 Konz, S. and Johnson, S., 2000 Kroemer, K., Kroemer, H.,

Kroemer-Elbert, K., 1994 Kroemer, K.H.E. and Grandjean,

E., 1997 Pheasant, S., and Haslegrave,

2006 Woodson, W., Tillman, B.,

Tillman, P., 1992

329

Appendices

Standing Workstation Guidelines


A. Hand Working Height

Optimal Zone Adj. 38" – 47" (0.97 – 1.19 m) Fixed: 42" (1.07 m)

Acceptable Zone Adj. 30" – 57" (0.76 – 1.45 m) Fixed: 42" (1.07 m)

Precision or Visually Demanding Tasks

Adj. 40" – 51" (1.02 – 1.30 m) Fixed: 45" (1.14 m)

B. Display Height Adj: 58" – 71" (1.47 – 1.80 m) Fixed: 66" (1.68 m)


Adj: 18" – 30" (457 – 762 mm) Fixed: 23" (584 mm)

D. Knee Space Depth Min. 6" (152 mm)

E. Foot Rail Height 6" (152 mm)

Knee Space Width Min. 30" (762 mm)


Corlett, E.N. and Clark, T.S., 1995

Eastman Kodak Company, 1983 Eastman Kodak Company, 2003 Human Factors and Ergonomics

Society, 2002 (Industry standard)

Konz, S. and Johnson, S., 2000 Kroemer, K.H.E. and

Grandjean, E., 1997 Pheasant, S., and Haslegrave,


Tillman, P., 1992

Seated Workstation Guidelines


A. Hand Working Height – Precision or Visually Demanding Tasks

Adj. 27" – 36" (686 – 914 mm) Fixed: 36" (914 mm)

B. Display Height Adj. 35" – 46" (0.99 – 1.17 m) Fixed: 46" (1.17 m)


Adj: 18" – 30" (457 – 762 mm) Fixed: 23" (584 mm)

D. Work Surface Thickness

Max. 2" (51 mm)

E. Knee Space Depth Min. 18" (457 mm)

Knee Well Width 30" (762 mm)


Corlett, E.N. and Clark, T.S., 1995

Diffrient, N., Tilley, A., Bardagjy, J., 1974

Eastman Kodak Company, 2003 Helander, M., 1997 Human Factors and Ergonomics

Society, 2002 Konz, S. and Johnson, S., 2000 Pheasant, S., and Haslegrave,

2006 Sanders, M. and McCormick, E.,


Tillman, P., 1992


330

© 2008 Humantech

Material Handling Guidelines


A. Hand Working Height – Comfort Zone Bottom

Min. 24" (610 mm)

B. Hand Working Height – Comfort Zone Top

Max. 62" (1.58 m)

C. Hand Working Height – Optimal Comfort Zone Bottom

Min. 38" (965 mm)

D. Hand Working Height – Optimal Comfort Zone Top

Max. 49" (1.25 m)


Eastman Kodak Company, 2003 Helander, M., 1997 Pheasant, S., and Haslegrave,

2006 Sanders, M. and McCormick, E.,

1993

Finger Force, Grip Force, and Arm Strength References: Bhattacharya, A. & McGlothlin, J., 1996 Department of Trade and Industry, Government Consumer Safety Research, 2000 Eastman Kodak Company, 1986 Karwowski, W., Marras, W., 1999 Konz, S. and Johnson, S., 2000 Peebles, L. and Norris, B., 1998

Finger Force Guidelines Frequent (≥ 2/min) Infrequent (< 2/min) Force Exertions:

Finger Push Recommended Acceptable Recommended Acceptable

1 index finger 3.4 lb (1.5 kg)

5 lb (2.3 kg)

8.6 lb (3.9 kg)

11.2 lb (5.1 kg)


5.0 lb (2.3 kg)

7.5 lb (3.4 kg)

12.5 lb (5.7 kg)

16.3 lb (7.4 kg)

2 fingers on different hands

11.0 lb (5.0 kg)

16.5 lb (7.5 kg)

27.5 lb (12.5 kg)

35.8 lb (16.3 kg)

Frequent (≥ 2/min) Infrequent (< 2/min) Force Exertions: Finger Pull Recommended Acceptable Recommended Acceptable

1 finger 3.9 lb (1.8 kg)

6.0 lb (2.7 kg)

9.6 lb (4.3 kg)

12.5 lb (5.7 kg)


8.4 lb (3.8 kg)

12.5 lb (5.7 kg)

20.9 lb (9.5 kg)

27.1 lb (12.3 kg)

Frequent (≥ 2/min) Infrequent (< 2/min) Force Exertions: Thumb Push Recommended Acceptable Recommended Acceptable

1 thumb 5.3 lb (2.4 kg)

8.0 lb (3.6 kg)

13.3 lb (6.0 kg)

17.3 lb (7.8 kg)

2 thumbs 10.0 lb (4.5 kg)

15.0 lb (6.8 kg)

25.0 lb (11.3 kg)

32.5 lb (14.7 kg)

331

Appendices

Grip Force Guidelines Frequent (≥ 2/min) Infrequent (< 2/min) Force Exertions:

Pinch Grip Recommended Acceptable Recommended Acceptable

Chuck pinch grip (with wrist deviation)

2.0 lb (0.9 kg)

2.4 lb (1.1 kg)

4.0 lb (1.8 kg)

5.1 lb (2.3 kg)

Chuck pinch grip (no wrist deviation)

3.2 lb (1.4 kg)

4.7 lb (2.1 kg)

7.9 lb (3.6 kg)

10.3 lb (4.7 kg)

Key pinch grip (with wrist deviation)

2.0 lb (0.9 kg)

2.9 lb (1.3 kg)

4.8 lb (2.2 kg)

6.3 lb (2.9 kg)

Key pinch grip (no wrist deviation)

3.9 lb (1.8 kg)

6.0 lb (2.6 kg)

9.7 lb (4.4 kg)

12.6 lb (5.7 kg)

Frequent (≥ 2/min) Infrequent (< 2/min) Force Exertions: Power Grip Recommended Acceptable Recommended Acceptable

1 hand (with wrist deviation)

6.4 lb (2.9 kg)

9.5 lb (4.3 kg)

15.9 lb (7.2 kg)

20.7 lb (9.4 kg)

1 hand (no wrist deviation)

12.7 lb (5.8 kg)

19.1 lb (8.7 kg)

31.8 lb (14.4 kg)

41.3 lb (18.7 kg)

2 hands (with wrist deviation)

9.0 lb (4.1 kg)

13.5 lb (6.1 kg)

22.6 lb (10.2 kg)

29.3 lb (13.2 kg)

2 hands (no wrist deviation)

18.0 lb (8.2 kg)

27.1 lb (12.3 kg)

45.1 lb (20.5 kg)

58.6 lb (26.7 kg)

Frequent (≥ 2/min) Infrequent (< 2/min) Force Exertions: Push/Pull Recommended Acceptable Recommended Acceptable

With 1-handed grip on plastic surface

6.7 lb (3.1 kg)

10.1 lb (4.6 kg)

16.9 lb (7.7 kg)

21.9 lb (10.0 kg)

With 1-handed grip on rubber surface

8.0 lb (3.6 kg)

12.0 lb (5.4 kg)

20.0 lb (9.1 kg)

25.9 lb (11.8 kg)


332

© 2008 Humantech

Standing Arm Strength Guidelines

Frequent (≥ 2/min) Infrequent (< 2/min) Force Exertions Recommended Acceptable Recommended Acceptable

A. Push out at shoulder height – 1 hand

6.8 lb (3.1 kg)

10.2 lb (4.6 kg)

17.0 lb (7.7 kg)

22.1 lb (10.1 kg)

B. Push out at elbow height – 1 hand

7.4 lb (3.4 kg)

11.1 lb (5.1 kg)

18.5 lb (8.4 kg)

24.1 lb (11.0 kg)

C. Push out at elbow height – 2 hands

11.8 lb (5.4 kg)

17.7 lb (8.0 kg)

29.5 lb (13.4 kg)

38.3 lb (17.4 kg)

D. Pull in at shoulder height – 1 hand

7.0 lb (3.2 kg)

10.5 lb (4.8 kg)

17.6 lb (8.0 kg)

22.8 lb (10.3 kg)

E. Pull in at elbow height – 1 hand

7.5 lb (3.4 kg)

11.2 lb (5.1 kg)

18.7 lb (8.5 kg)

24.3 lb (11.1 kg)

F. Pull in at elbow height – 2 hands

13.1 lb (5.9 kg)

19.6 lb (8.9 kg)

32.7 lb (14.8 kg)

42.4 lb (19.2 kg)

G. Pull down from overhead – 2 hands

17.9 lb (8.1 kg)

26.8 lb (12.2 kg)

44.7 lb (20.3 kg)

58.1 lb (26.4 kg)

H. Pull up from knee height – 1 hand

6.3 lb (2.9 kg)

9.5 lb (4.3 kg)

15.8 lb (7.2 kg)

20.5 lb (9.3 kg)

I. Pull across body (lateral) at waist height – 1 hand, elbow fully extended

2.5 lb (1.1 kg)

3.8 lb (1.7 kg)

6.3 lb (2.9 kg)

8.2 lb (3.7 kg)

J. Pull across body (lateral) at waist height – 1 hand, elbow at 90º

3.3 lb (1.5 kg)

5.0 lb (2.3 kg)

8.4 lb (3.8 kg)

10.9 lb (4.9 kg)

K. Lift up at shoulder height – 2 hands

4.7 lb (2.1 kg)

7.0 lb (3.2 kg)

11.7 lb (5.3 kg)

15.3 lb (6.9 kg)

L. Lift up at elbow height – 2 hands

7.7 lb (3.5 kg)

11.5 lb (5.2 kg)

19.1 lb (8.7 kg)

24.9 lb (11.3 kg)

M. Press down at elbow height – 1 hand

12.8 lb (5.8 kg)

19.2 lb (8.7 kg)

30.0 lb (13.6 kg)

41.6 lb (18.9 kg)

333

Appendices

Tool Guidelines


A. Handle Length 3.8" – 6.0" (95 – 152 mm)

B. Power Grip


Tool Weight Max. 4 lb (1.8 kg)

C. Precision Grip


Tool Weight Max. 1 lb (0.5 kg)

D. Handle Span Fully Closed Min. 2" (51 mm)

E. Handle Span Fully Open Max. 3.5" (89 mm)

Chaffin, D.B., Andersson, G.B.J., and Martin, B., 1999

Eastman Kodak Company, 2003

Helander, M., 1997 Karwowksi, W.,and Marras,

W., 1999 Konz, S. and Johnson, S.,

2000 Kroemer, K.H.E. and

Grandjean, E., 1997 Salvendy, G., 2006 Woodson, W., Tillman, B.,

Tillman, P., 1992


334

© 2008 Humantech

Notes

335

Index

Index

Back anatomy, 52 biomechanics, 53, 106 disorders, 53 injury facts, 10 risk factors, 108, 162

Baseline Risk Identification of Ergonomic Factors (BRIEF), 95 and physical stressors, 111 applying, 97 completing, 114 limitations, 96 potential pitfalls, 120 scoring, 113 survey form, 95, 144 when to use, 96

BRIEF Exposure Scoring Technique (BEST), 128 and physical stressors, 134 completing, 131 limitations, 130 potential pitfalls, 138 scoring, 130 survey form, 128 when to use, 130

Continuous Improvement Process and the Hit List, 77

Controls hierarchy, 261 pros and cons, 261

Cost Justifying Ergonomic Improvements payback period, 245 productivity impact, 245 worksheet, 246

Design and Build Guidelines force, 210 limitations of, 204 material handling, 209 potential pitfalls, 218 seated workstations, 208 standing arm strength, 215 standing workstations, 207 tools, 217 when to use, 204 work reaches, 206

Disorders back, 52 nerve, 49 neurovascular, 51 tendon, 45

Ergonomic Assessment Survey (EASY), 139 completing, 147 limitations, 141 potential pitfalls, 156 scoring, 142 survey form, 139 when to use, 141

Ergonomics and value-added analysis, 241 as a business agenda, 10 cost justifying improvements, 239 defined, 5 evaluating risk factors, 93 fire triangle, 37 four-step review process, 273 identifying issues, 59 in design, 201 prioritizing risks, 127 process overview, 4 regulatory compliance, 13 risk vs. hazard, 127 tools overview, 16

Ergonomics Action Form, 79 completing, 81 limitations, 80 potential pitfalls, 88 when to use, 80

Ergonomics Process adding strength and longevity, 319 overview, 4 structuring, 308

Forms BEST assessment, 128 BRIEF, 95 EASY, 139 employee survey, 146 ergonomics action, 79 medical data, 145


336

© 2008 Humantech

Hit List, 59 "find it" items, 60 "fix it" items, 71 ask the operator, 76 bad vibes, 69 butts up, 65 comfort zone, 73 contact, 70 continuous improvement process, 77 don't give me static, 75 elbows out, 62 horizontal distance, 67 hungry head, 64 limitations, 59 shoulder too high/low, 63 sit vs. stand, 68 tool/target, 72 twist and shout, 66 wash rag, 61 when to use, 59 Work Doesn't Need to be a Pain!, 35 Would you do it this way?, 36

Job Improvement Process, 257

Lifting Index (LI), 172

Manual Material Handling example, 192 introduction, 161 NIOSH composite lifting index, 178 NIOSH Lifting Equation, 162 push, pull, carry guidelines, 181 spreadsheet, 174

NIOSH Lifting Equation, 162 applying, 174 composite lifting index, 178 interpreting results, 173 lifting index (LI), 172 potential pitfalls, 180 recommended weight limit (RWL), 164 uses for, 179 variables, 165 when to use, 163

Physical Stressors, 44 and the BEST, 134 and the BRIEF, 111

Push/Pull/Carry Guidelines, 181 for carry tasks, 186

for push/pull tasks, 183 limitations, 191 measuring improvement with, 190 potential pitfalls, 191

Recommended Weight Limit (RWL), 164

Risk Factors back, 108 defined, 93 elbow, 102 hand and wrist, 100 legs, 110 neck, 104 shoulder, 103

Standard Time Efficiency Process (STEP) cost justification worksheet, 246 how it works, 243 limitations, 242 potential pitfalls, 253 when to use, 242 zones, 243

Workplace Design Dimensions sitting buttock-calf length, 223 sitting elbow rest height, 224 sitting eye height, 225 sitting height, 219 sitting knee height, 221 sitting leg clearance, 220 sitting popliteal height, 222 sitting shoulder height, 226 standing elbow height, 230 standing eye height, 228 standing hand rest height, 231 standing height, 227 standing knee height, 232 standing shoulder height, 229

Work-Related Musculoskeletal Disorders (WMSDs) back, 52 defined, 38 in industry, 40 injury facts, 10 nerve, 49 neurovascular, 51 risk factors, 93 tendon, 45

Applied Industrial Ergonomics 4.3_tcm1038-133720

Documents