Ech 5511 ergonomic control

Slide 1Semester 2 2011/2012

INDUSTRIAL HYGIENE AND ERGONOMIC CONTROLS


Ergonomics


Ergonomics

The study of man’s relationship with his or her workplace.

Fitting the task to the person rather than forcing him/her to adapt to the work environment.

Designing the workplace to prevent occupational injury and illness.

VARIOUS AUTHORS DEFINE ERGONOMICS AS:


Discovering the capabilities and limitations of the human body.

The art and science that addresses workers’ job performance and well-being in relation to their job tasks, tools, equipment and environment.

The study of the relationship between people and machines or between employees and their environment.


Ergonomics


The study of the interaction between the worker and the process at the workplace.


WHAT OTHER DEFINITIONS HAVE YOU HEARD?

Ergonomics


Improve quality. Improve absenteeism. Maintain a healthier work force. Reduce injury and illness rates. Acceptance of high-turnover jobs. Workers feel good about their work. Reduce workers’ compensation costs. Elevate OSHA compliance to a higher level of awareness.

ERGONOMICS PLAYS A ROLE IN APPROXIMATELY 50% OF ALL WORKPLACE INJURIES. ERGONOMICS WILL HELP:

Ergonomics


“It is estimated that in the United States, 97% of the money spent for medical care is directed toward treatment of an illness, injury or disability. Only 3% is spent on prevention.”

Self-help Manual for your BackH. Duane Saunders, MSPTby Educational Opportunities

Ergonomics


Historical progression of WMSDs (Work related Musculoskeletel disorders)


Ergonomics A Multi-disciplinary Approach

THINK ABOUT THE NUMBER OF WAYS ERGONOMICS

IMPACTS OUR DAILY LIFE!


The science of ergonomics is critically important in the

continuing development of the

AUTOMOBILE!

FOR EXAMPLE!



Economics Sociology Physiology Psychology Biomechanics Physical Sciences Management Philosophies Engineering, Industrial Design Safety & Health, Human Factors Engineering

THE FOLLOWING DISCIPLINES HAVE PLAYED A ROLE IN DEVELOPMENT OF THE AUTOMOBILE:



Program Implementation

Personal Interest Dedication Management Commitment

IMPLEMENTATION OF AN ERGONOMIC PROGRAM REQUIRES:

NOTE:UNDERSTANDING AND SUPPORT FROM THE WORK FORCE ISESSENTIAL, WITHOUT IT THE PROGRAM WILL FAIL!


Typical Applications

Work station design Tool selection and design Office safety improvement Video display terminals (VDT’s) safety Back injury reduction and prevention Manual material handling improvement Cumulative trauma disorder (CTD) reduction

APPLICATIONS


ENGINEERING CONTROLS 1st CHOICE Work Station Design Tool Selection and Design Process Modification Mechanical Assist

ADMINISTRATIVE CONTROLS 2nd CHOICE Training Programs Job Rotation/Enlargement Pacing Policy and Procedures

PERSONNEL PROTECTIVE EQUIPMENT LAST CHOICE

Gloves Wraps Shields Eye Protection Non-Slip Shoes Aprons

Industrial Hygiene And Ergonomic Controls


Source of ergonomic hazards

1. The work itself2. The workstation3. Workpiece / tools4. Working environment


INAPPROPRIATE

OCCUPATIONAL RISK FACTORS: Occupational risk factors are defined as any attribute of a job or

task that we know increases the probability of injury or illness.

1. Force - Including- Internal or External

2. Posture - Such as - Extreme Twisting or Bending

3. Repetition - Including- Muscle Group Overexertion

4. Insufficient Rest - Including- Muscle Group Overexertion



WORKSITE ANALYSIS IS DIVIDED INTO 4 MAIN PARTS:

1. Gathering information from available sources.

2. Conducting baseline screening surveys to determine which jobs need a closer analysis.

3. Performing ergonomic job hazard analyses of those work stations with identified risk factors.

4. After implementing control measures, conducting periodic surveys and follow-up to evaluate changes.



TANGIBLE INDICATORS: Accident Records Production Records Personnel Records Employee Surveys



WORKSITE ANALYSISContinued

FRONT BACK

SYMPTOM SURVEY

1. Note areas of pain or discomfort!

2. What do you feel is the source?

3. What environmental changes would help?

4. What other feedback can be gathered?


WHAT TANGIBLE INDICATORS

WOULD BE MOST USEFUL TO YOU?



INCIDENCE RATES: incidence rates for upper extremity disorders and/or back injuries should be calculated by counting the incidences of CTDs and reporting the incidences per 100 full time workers per year per facility.

(NUMBER OF NEW CASES (200,000 WORK HRS*) PER FACILITY

NUMBER OF HOURS WORKED/FACILITY/YR

INCIDENCE RATE

200,000 = approximate annual work hours for 100 workers. The same method should be applied to departments, production lines, or

job types within each facility.



• SAMPLE INCIDENCE RATE CALCULATION:

(Number of new cases (200,000 work hrs*) per facility

Number of hours worked/facility/yr

If you experienced 2 carpal tunnel cases last year, in a population of 100 employees. What is the incidence rate?

IR =2 X 200,000100 X (50 X 40 hrs)

IR =400,000200,000

IR = 2 CASES OF CARPAL TUNNEL PER 100 PERSON-YEARS OF EXPOSURE

* 200,000 = approximate annual work hours for 100 workers.* The same method should be applied to departments, production lines, or job types within each facility.



ANTHROPOMETRY

ANTHROPOMETRY:

The technology of measuring and quantifying various human physical traits such as size, weight, proportion, mobility and strength.


Engineering Anthropometry:

The application of anthropometric data to equipment, workplace and job design to enhance the efficiency, safety and comfort of the operator.

Anthropometry


Anthropometric Measurements

• When designing products it is important to remember that people come in many sizes and shapes.

• Anthropometric data varies considerably between regional populations.

• For example, Scandinavian populations tend to be taller, while Asian and Italian populations tend to be shorter.


The relative sizes of different percentile humans.



• It is common practice to design for the 5th percentile (5th%) female to the 95th percentile (95th%) male.

• The 5th% female value for a particular dimension (e.g. Sitting height) usually represents the smallest measurement for design in a population.

• Conversely, a 95th% male value may represent the largest dimension for which one is designing.

• The 5th% to 95th% range accommodates approximately 90% of the population.

• To design for a larger portion of the population, one might use the range from the 1st% female to the 99th% male.



Common Ranges Of Measurements (For Office

Furniture Design.



Common ranges of measurementsused in office furniture design.


Common Workplace Postures

There are common postures found in the office environment that can be considered when designing workplace products or space.

• Standing• Sitting• Reaching• Moving


StandingDesk height for a standing operator can range from 28 - 43“ (Grandjean, 1997) depending on whether the desk is for precision, light, or heavy work.


Sitting

• Knowing what parameters to design for while the user is seated can help increase the comfort of the user.

• Common seated anthropometric measurements can be seen in slide 17

• Spine and Lumbar– Maintaining the neutral, or standing shape of the lumbar, or

lower spinal area, is important for comfort and posture. – Chairs can give appropriate and correct lumbar support. – This seated lumbar support will help the spine maintain an S-

shaped curve similar to the spine’s shape when standing (as seen in Figure 5.)


Sitting


Sitting

• Posture– Correct seated posture is a continual debate with

ergonomic professionals.– Some say that users need to have a 90-90-90 degree

placement for the elbow, hip, and knee joints, respectively.

– Others feel that a variation in this placement is better, as long as it does not lead to slouching or hunching over.

– A good seated posture is one that is comfortable and does not put a lot of stress or strain on the user’s buttocks, back, or arm muscles, and allows the user’s feet to be on the floor.


Reaching

• The workstation, and parts that go with workstations (such as overhead storage and pedestals), should allow the majority of movement of the user’s body joints within healthy zones.

• When designing products, consider how much individuals will have to reach in order to minimize awkward or unhealthy positions.


Moving

• Users will move around in their environment to file papers, answer a phone, or stretch.

• An occasional break from sitting is encouraged because it helps to stimulate muscles, and increases blood flow, which decreases fatigue.

• The space in a cubicle or desk area should allow the chair to move around easily.

• Also, a wheelchair may need to turn around or move in the office space, requiring a 60" diameter turning radius and at least 36" of passage width


Moving

• Chairs and other devices in the workspace can allow the user to easily get up and move around without having to move armrests, adjust other chair settings, or put undue stress on the body.


Ranges of motion (ROM) for different joints.

• Zone 0 (Green Zone) Preferred zone for most movements.Puts minimal stress on muscles and joints.

• Zone 1 (Yellow Zone) Preferred zone for most movements.

Puts minimal stress on muscles and joints.

• Zone 2 (Red Zone) More extreme position for limbs. Puts greater strain on muscles and joints.

• Zone 3 (Beyond Red Zone) Most extreme positions for limbs, should be avoided if possible, especially with heavy lifting or repetitive tasks.


Repetitive Motions

• If repetitive tasks are necessary, minimizing the number of continuous movements can help reduce the risk of injuries.

• There is no specific number for minimum daily repetitions.

• The factors affecting repetitive tasks include user’s muscle strength, amount of force required, and type of task.

• Decreasing the amount of force required to perform a task will also lower the risk of pain and musculoskeletal disorders.


Neutral and awkward wrist postures


Neutral and awkward elbow postures


Neutral and awkward shoulder postures


Neutral and awkward back postures


Wrist posture with the keyboard placed at different positions, including flat, positive, and negative tilt


When body joints are in awkward postures, maximum force produced decreases.

Muscle fatigue will occur earlier when working in an awkward posture instead of a neutral posture.

Hand dynamometer


Pinch grip & power grip

A power grip curls the fingers toward the palm; a pinch grip presses the thumb against the fingers of the hand or an object, and does not involve the palm.

The amount of force that can be generated depends on the type of grip and the width of the grip.


Fatigue Failure

The vertebrae of the back can have multiple sub-failures that are not visible but can result in complete failure over time.

The number of cycles that lead to failure of the vertebrae varies across the population.

Endplate fractures usually occur through repeated loading, by a process known as fatigue failure


Moment Arms And Lifting

Principles • Reduce the weight of the object being lifted. • Keep loads close to the body when lifting.


The length of the moment arm and weight of the object both affect the forces exerted by the lower-back muscles.

The size and shape of the object lifted or carried, existence of barriers, and design of workstations are all factors that affect the moment arm of an object being lifted or carried.

Moment Arms And Lifting


Ergonomic Risk Factors

PERSONAL RISK FACTORS

1. Age2. Gender3. Attitude4. Training5. Strength6. Work Method7. Anthropometry



JOB RISK FACTORS

1. Weight of load2. Location/size of load3. Frequency of the Task4. Duration and pace of cycle5. Stability of load6. Coupling of load7. Travel distances of worker8. Reach distances of worker9. Symmetry between worker and the object

held


10. Static work posture a) Standing b) Sitting

11. Work platforms or stairs12. Torso flexion (bending)

a) Mild (up to 45 degrees) b) Severe (greater than 45 degrees)

13. Work heights (too high or too low)14. Floor surfaces (wet, smooth, vibration)

JOB RISK FACTORS



15. Environmenta) Hot (sweat, reduced grip, fatigue)b) Cold (gloves reduce grip by as much as 30%)

16. Lighting a) posture problems (because of inability to see)17. Noise/vibrationa) Frequency very importantb) Can amplify through the body

JOB RISK FACTORS



WHAT ARE THE PRIMARY RISK

FACTORS ASSOCIATED WITH

YOUR JOB?



Job And Task Analysis

UNIT LOADS:

DEFINED AS:The unit to be moved or handled at any one time.

THE CONTAINER, CARRIER, OR SUPPORT USEDTO MOVE MATERIALS MUST BE INCLUDED AS PART OF THE UNIT LOAD.


FACTORS AFFECTING UNIT LOADS

The material to be utilized

The quantity of material to be handled

The susceptibility of the material to damage

The number of times the unit load is handled

The receiving, storing, shipping, and handling methods

The environmental conditions to which the load is exposed



DESIGNING THE UNIT LOAD

Optimize the weight of the load

Reduce the size of the load

Insure stability of the load

Optimize load coupling

- HAND TO LOAD- FOOT TO FLOOR



DEFINITION OF TERMS:

Fundamental Movements or acts

- Search - Inspect- Select - Assemble- Grasp - Disassemble- Reach - Delay (unavoidable)- Move - Delay (avoidable)- Hold - Plan- Position - Rest (overcome fatigue)

“ELEMENT”



“CYCLE” Example:

1. Assemble new box 2. Put bottles in box from conveyor 3. Stack boxes on pallet 4. Go to step 1

The time required to complete one sequence of tasks sub- tasks, or elements.

DEFINITION OF TERMS:



TASK ANALYSIS

Identify the job to study

Collect the data

Evaluate the data

Formulate control measures



IDENTIFYING THE JOB TO STUDY

Accident investigations

Accident statistics

Complaints & operator feedback

Production bottlenecks, high errors

High employee turnover jobs



COLLECTING THE DATA

Direct observation

Video tape

Action photographs

Documentary accounts

Accident statistics



EVALUATING THE DATA

Task description

Sub-task description

Element description

Risk factor/hazard identification



FORMULATING CONTROL MEASURES

Application of ergonomic principles

Corrective action for non-compliance

Eliminate or reduce exposure



TASK ANALYSIS FORM

TASK DESCRIPTION - Action Being Performed LEFT HAND - Usage RIGHT HAND - Usage FREQUENCY - Usually per minute NOTES - Supporting information POSTURE - Acceptable to extreme FORCE - High, Medium, Low DURATION - Length of Stressor



Job And Work Station Design

GOOD JOB DESIGN

REDUCES Discomfort, Fatigue, Aches & PainsInjuries & Illnesses, Work Restrictions

AVOIDS Absenteeism, Turnover, Complaints,Poor Performance, Poor Vigilance

ABATES Accidents, Production Problems,Poor Quality, Scrap/Rework


GOOD JOB DESIGN

PREVENTS Economic Loss, Loss in Earning Power,Loss in Quality of Life, Pain & Suffering

PREVENTS Economic Loss, Loss in Expertise,Compensation Costs, Damaged Goods& Equipment

EMPLOYEE:

EMPLOYER:



Design for the Range-of-Motion of the Worker Design for the Field of Vision of the Worker Design out Extreme Ranges-of-Motion Reduce Force in Job Accomplishment Reduce the Frequency of Motions Required Reduce the Duration of a Specific Task Design to Provide Adequate Support to Back, and Legs

DESIGN CONSIDERATIONS



Incorporate Adjustable Work Surfaces Design Delivery Bins to Accommodate Various Heights Design Delivery Bins to Accommodate Various Reaches Design Work Platforms with Ranges-of-Movement Incorporate the use of Mechanical or Powered Assists Incorporate the use of Suspension Devices for Tools Incorporate the use of Floor mats to Reduce Leg Trauma




Do not design for the average! Do not design for yourself! The large must be able to fit! The small must be able to reach! Design for a range! Design for adjustability!

THE BOTTOM LINE



WHAT ADDITIONAL DESIGN

CONSIDERATIONS CAN YOU THINK OF

FOR WORK STATIONS?



Consider the Gender and Age of Users. The Specific Use of the Tool Is Critical. Contact Manufactures for Their Assistance. Make Informed Decisions Before You Buy. Don’t be Fooled by Misleading Advertising. Any Other (than its intended) Use Negates Possibly All

Benefits and May Prove to be Detrimental to an Ergonomic Program.




REMEMBER

A TOOL WHICH IS CALLED AN

“ERGONOMIC TOOL”IS ONLY AN ERGONOMIC TOOL

WHEN IT IS USED FOR ITS INTENDED PURPOSE



Tool Design And Selection

CONSIDERATIONS

STRAIGHT WRIST

FIRM GRIP

WEIGHT

SAFE BALANCE

VIBRATION

TORQUE

PINCHPOINTS


Tools come in endless variety, the next few slides provide some considerations to think about.



HANDLE CONSIDERATIONS

Criteria consideration

Diameter - avoid one size fits all

Hand fit - avoid grooves and contours that cause pressure points

Handle - non-conductive Material - textured to avoid slip or twist

- Consider thickness



Tools whose handles are sized and shaped to complement the hand, require less effort to use, thereby reducing the muscle fatigue that leads to discomfort.


HANDLE CONSIDERATIONS


Orientation - accommodates straight wrist?

Span - not too large to grasp easily?

Grip strength - consider powered tools when operator has difficulty with

forces or high repetition!



Adjustability in tools, or multiple tool designs, is important because it allows for neutral postures to be adopted

When selecting or purchasing a tool, consider the ability of the tool’s handle to be adjusted in multiple positions to keep the wrist in a neutral posture


GUARDING CONSIDERATIONS


Pinch points - pinch and nip points covered?

- Stopper to avoid closing fingers?

Exhaust - pointed away from hand and body?



FREE HAND CONSIDERATIONS


Free hand use - jigs and fixtures to hold work

- Fixtures can even hold tool



When purchasing heavy power tools, consider features that allow the tool to be held with both hands.

When operating heavy tools, take advantage of features that allow for greater control of the tool and less fatigue.


STORAGE OF TOOL BETWEEN CYCLES


Between cycles - suspend if frequently grasped or released

- Consider workstation or waist mounted holster



POWER TOOLS


Center of - should be near fist Gravity - avoid nose-heavy tools Weight - support or counterbalance

if over two pounds



POWER TOOLS


Trigger location - placed with grip so digits don’t have to reach

Trigger tension - light enough to avoid fatigue, heavy enough to avoid

accidental activation

Size - preferably large enough to span multiple fingers



POWER TOOLS


Power - torque and speed should be adequate to match fastening requirements

Hose connection - swivel connection reduces “moment” created by dangling hose


Ech 5511 ergonomic control

Education

puts minimal

power toolscriteria

authors define

office furniture

force required

industrial

designing

moment arm