UNIVERSITI TEKNIKAL MALAYSIA MELAKA Analysis of Working Postures of Operator in Mixing Department of an SMI in Malaysia Thesis submitted in accordance with the requirements of the Malaysia Technical University of Malacca for the Degree of Bachelor of Engineering Manufacturing (Process) By Saidah binti Khalid Faculty of Manufacturing Engineering May 2007
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UNIVERSITI TEKNIKAL MALAYSIA MELAKA
Analysis of Working Postures of Operator in
Mixing Department of an SMI in Malaysia
Thesis submitted in accordance with the requirements of the Malaysia Technical
University of Malacca for the Degree of Bachelor of Engineering Manufacturing
(Process)
By
Saidah binti Khalid
Faculty of Manufacturing Engineering
May 2007
DECLARATION
I hereby declare this thesis entitled “Analysis of Working Postures of Operator in Mixing
Department of an SMI in Malaysia” is the results of my own research
except as cited in the references.
Signature : ……………………………............
Author’s Name : ……………………………………
Date : ……………………………………
APPROVAL
This thesis submitted to the senate of UTeM has been accepted as
fulfillment of the requirement for the degree of Bachelor of Engineering
Manufacturing (Process). The members of the supervisory committee
are as follows:
…………………………………….
Main supervisor
Faculty of Manufacturing Engineering
i
ABSTRAK Projek ini dijalankan untuk menganalisa postur kerja pekerja-pekerja di Jabatan
Percampuran di sebuah kilang IKS (Industri Kecil dan Sederhana) di Malaysia. Daripada
kajian-kajian yang telah dibuat sebelum ini, didapati bahawa sakit belakang dan CTDs
(Cumulative Trauma Disorders) adalah jenis kcedaraan yang berkaitan dengan postur
bekerja seseorang pekerja. Projek ini dijalankan untuk mengenalpasti sebab-sebab
terjadinya kecedaraan akibat postur yang tidak betul semasa mengangkat beban yang
berlaku di industri. Selain itu, kajian ini difokuskan untuk mengkaji postur kerja pekerja-
pekerja di Jabatan Percampuran menggunakan RULA dan REBA. Selain itu, kajian ini
juga menggunakan 1991 NIOSH Lifting Equation untuk mencari beban yang sesuai dan
selamat untuk kerja yang sedia ada. RULA akan dijalankan menggunakan perisian
CATIA manakala REBA analisis dijalankan menggunakan REBA Employee
Assessment Worksheet. Untuk menjalankan analisis ini, data antropometri, gambar dan
rakaman aktiviti diperlukan. Data yang didapati akan digunakan untuk analisis RULA
dan REBA. Untuk projek ini, syarikat yang menerima kajian ini untuk dijalankan di
kilang mereka terletak di Kuala Selangor. Kilang ini menghasilkan barangan
berunsurkan plastik, system takungan air hujan dan paip. Jabatan Percampuran, bahan
mentah dalam bentuk serbuk dicampurkan untuk digunakan dalam mesin Extruder.
Dalam jabatan ini, pekerja terpaksa mengangkat beban 25kg setiap hari. Aktiviti yang
dianalisa ialah proses memindahkan guni resin ke dalam corong mesin. Akitiviti ini
dibahagikan kepada empat sub proses untuk mengkaji sub proses yang mana paling
berisiko. Hasil daripada analisis menunjukkan bahawa tempat bekerja bagi proses ini
harus diubah untuk mengurangkan risiko kecederaan kepada pekerja.
ii
ABSTRACT
The purpose of this project is to analyze working posture in of operator in mixing
department in an SMIs (Small Medium Industry) in Malaysia. From previous study, it is
found that back pain and CTDs (Cumulative Trauma Disorders) are the types of injury
occurred associated to working postures. This project is done to identify the risk factors
for lifting activity in the manufacturing industry. Furthermore, the research is focus on
analyzing the working postures of the mixing department operators using RULA and
REBA methods. Other than that, the 1991 NIOSH lifting equation is used to find the
(RWL) recommended work limit of the current workstations. RULA analysis is done
using CATIA software while REBA analysis is done using the REBA Employee
Assessment Worksheet. In order to do the analysis, the anthropometry data, image and
video recording of the activity are taken. The data are used to do the RULA and REBA
analysis. In this project, the company that accepted the research is an SMI factory
located in Kuala Selangor. This factory produces plastic based product, rain gutter
system and pipes. Mixer department is one of the production sections in this company.
In this department, the raw materials in powder are mixed in order to be processed using
the extruder machines. In this section, the workers have to lift load 25kg everyday. The
activity that analyzed is the process of transferring the sacks of resin to the funnel. The
activity is divided into four sub processes to in order to determine which activity is the
worse. Based on the analysis of the project, the result of the research recommended
improvements of the workstation. This improvement intended to decrease the risk of
injury of the workers.
ii
ACKNOWLEDGEMENT
In the name of Allah, Most Gracious, Most Merciful. All praise to the Almighty Allah for giving me the strength, patience and
guidance throughout the process of completing this Projek Sarjana Muda (PSM). I am
grateful to have the support and motivation from a lot of people in accomplish this
research. I would like to take this opportunity to thank those who are either directly or
indirectly involve during this research is conducted.
Mostly a special gratitude goes to my respective supervisor, Prof.Madya Dr. Adi
Saptari from Faculty of Manufacturing Engineering. Thank you so much for the precious
time, advices, contributions, comments and guidance in every stage of this research.
My token appreciation also goes to my beloved family members who never
failed to be there for their love, support and prayers. Last but not least, I would like to
thank to all my friends, especially my classmates and housemates for the never ending
supports.
Thank you very much.
iii
DEDICATION
To all my siblings;
For your love, encouragement, and support on this project was absolutely
invaluable.
To my respectful Supervisor;
Prof Madya Dr. Adi Saptari
For your guidance and help in completing this project. You are always in my mind.
To my special partner;
Syahrul Affendi bin Ismail
For all your support and motivation during the completion of this research
Especially to my father
Khalid bin Tomi
And the memory of my late mother
Manisah bt Suratman
For your support, love and demonstration of the values of education since I’m still
a little kid. Love you so much.
iv
TABLE OF CONTENTS
Abstract i
Acknowledgement ii
Dedication iii
Table of contents iv
List of tables viii
List of figures x
List of Abbreviation xi
1. INTRODUCTION
1.1 Background of Study 1
1.2 Problem Statement 6
1.3 Objectives 7
1.4 Scope 7
2. LITERATURE REVIEW
2.1 Manual Material Handling 8
2.2 The Skeletal System 10
2.2.1 The Bones 11
2.2.2 Connective Tissue 12
2.2.3 Muscle 12
2.2.4 Facet Joints 12
2.2.5 Spinal Column 12
2.3 Anatomical System of the Back 14
2.3.1 Fifth Lumbar Vertebrae (of the Spine) 15
2.3.2 Erector Spine Muscle 16
2.3.3 Upper Extremity 17
2.4 Type of MSDs 18
2.4.1 Low Back Musculoskeletal Disorders 18
v
2.4.2 Neck Musculoskeletal Disorders 22
2.4.3 Shoulder Musculoskeletal Disorders 22
2.4.4 Elbow Musculoskeletal Disorders 23
2.4.5 Hand/Wrist Musculoskeletal Disorders 23
2.4.6 Tendon Related CTDs 24
2.4.7 Neuritis 24
2.4.8 Ischemia 24
2.5 The Risk Factor 25
2.5.1 Posture 25
2.5.2 Repetition 26
2.5.3 Load 27
2.5.4 Horizontal and Vertical Multipliers 27
2.5.5 Non occupational Risks 28
2.6 Ergonomic Assessment Tools 28
2.6.1 The 1991 NIOSH Lifting Equation 29
2.6.2 REBA (Rapid Entire Body Assessment) 30
2.6.3 RULA (Rapid Upper Limb Assessment) 31
2.6.4 OWAS 31
2.6.5 Various Methodology Used in Previous Ergonomic Study 31
3. METHODOLOGY
3.1 Overview of Methodology 33
3.2 Description of Methodology 35
3.2.1 Problem Identification 35
3.2.2 Problem Formulation, Objectives and Scope 35
3.2.3 Literature Review 35
3.2.4 Collecting Data 35
a) Anthropometry Data 36
b) Video Recording 36
3.2.5 Analysis Data 36
a) RULA (Rapid Upper Limb Assessment) 37
vi
b) REBA (Rapid Entire Body Assessment) 37
b) The 1991 NIOSH Lifting Equation 37
3.2.6 Recommendations 38
4. RESULTS AND ANALYSIS
4.1 Overview 40
4.2 Approach 41
4.2.1 Image Capturing 41
4.2.2 Measurement of Working Magnitude 42
4.3 Analysis of Working Postures 43
4.3.1 RULA Analysis 43
4.3.1.1 Results 48
4.3.1.1.1 Standing Position 48
4.3.1.1.2 Untie Position 50
4.3.1.1.3 Lifting Position 51
4.3.1.1.4 Unloading Position 53
4.3.2 REBA Analysis 54
4.3.2.1 Results 56
4.4 The 1991 NIOSH Lifting Equation 60
4.4.1 Data 64
4.4.2 Results 65
5. DISCUSSION 71
6. CONCLUSION 72
6.1 Conclusion 78
6.2 Recommendation 79
REFERENCES
APPENDICES
A Project Gantt Chart PSM 1
B Project Gantt Chart PSM 2
C REBA Employee Assessment Worksheet
D RULA analysis for different sub processes
xi
LIST OF ABBREVIATIONS
PSM = Projek Sarjana Muda
PERKESO = Social Security organizational of Malaysia
RWL = Recommended Weight Limit
LI Lifting Index
RULA = Rapid Upper Limit Assessment
REBA Rapid Entire Body Assessment
MSD = Musculoskeletal Disorders
CTD = Cumulative Trauma Disorder
CAD Computer Aided Design
NIOSH National Institute for Occupational Safety and Health
SMI Small Medium Industry
OWAS Ovako working posture analysis system
viii
LIST OF TABLES
2.1 Various methodologies used in previous study 33
4.1 Anthropometry data of the subjects 45
4.2 Magnitudes of every subject for different sub process 48
4.3 Description of RULA action level 49
4.4 RULA score or standing position 50
4.5 RULA score for untie position 51
4.6 RULA score for lifting position 53
4.7 RULA score for unloading position 54
4.8 REBA action level 57
4.9 Summary of results for REBA analysis 58
4.10 Definition of Components of NIOSH Lifting Equation 63
4.11 Frequency Multiplier (FM) (Note: 75cm = 30 inches) 64
4.12 Coupling Multiplier 64
4.13 Results for the value of RWL and LI for different heights 71
5.1 Results of RULA, REBA analysis and the 1991 NIOSH 73
Lifting Equation
ix
LIST OF FIGURE
1.1 Statistic of Accidents Reported to Perkeso from 1999 to 2004 3
1.2 Number of Accidents by Cause of Accidents 2004 4
1.3 Number of Accidents by Location of Injury 2004 4
1.4 Number of Accidents of the Upper Limb 2004 5
1.5 Number of Accidents of the Trunk 2004 5
2.1 Kind of Accident causing over three-day-injury, 2001/02 10
2.2 Vertebral column 14
2.3 Division of the Skeleton 15
2.4 Typical lumbar vertebrae 17
2.5 Division of the Upper Extremity 18
2.5 Low-back biomechanical model of static coplanar lifting 20
3.1 Methodology of project 35
4.1 The workers is unloading the material to the funnel 42
4.2: Image of an operator pulling the sack from the pallet. 43
4.3 Two lines were constructed to determine upper arm and forearm angles. 44
4.4 A manikin that created using the anthropometry data measured 45
4.5 The worker pulling the sack from the pallet 46
4.6 The worker untied the sack of resin 46
4.7 The worker lifts the sack from the floor 47
4.8 The workers unload the resin into the funnel 47
4.9 A complete RULA analysis 48
4.10: Flow of REBA analysis 56
4.11 REBA employment assessment worksheet 60
x
4.12 The required distance of the workstation that is measured 65
4.13 Recommended vertical lifting height 71
5.1 Figure of the tilt table 75
5.2 The application of the tilt table 75
5.3 The result of RULA analysis 76
5.4 The data for the redesign workstation 77
1
CHAPTER 1 INTRODUCTION
1.1 BACKGROUND OF STUDY
Lifting is done every day no matter in working neither condition nor the usual activity
that we do everyday. We need to lift something in order to move it to the desired place.
While performing the activities, people managed to get injured internally or externally.
This study is done to identify the types of injury that usually happens during lifting. In
this chapter, the reader will be introduced with the problem and the theoretical
background. The objective and scope of the project also is also stated here.
Injury is one of the problems that always happened to human being. Injury can be
defined as hurt, pain, and suffering. Usually injury is realized automatically when we
hurt by something that sharp such as knife or when involved in accidents. But the injury
that happened in the body system such as the skeletal system, muscle and joints is not
noticed until the person faced serious problem such as back pain and injury to the
muscle. One of the factors that contribute to this problem is picking task.
Everyday, people will do this activity either when it necessary to do that or it is their job
to lift anything. Lifting task can be defined as picking something with both hands that
required bending of the body posture. Usually, lifting task will affect human being if
they lift load that are too heavy for the body and done repetitively. This activity usually
happened to the worker at the warehouse as they have to perform this activity everyday.
2
This activity can lead to back pain problem and CTDs (upper-extremity cumulative
trauma disorders).
Social Organizational Security of Malaysia (PERKESO) is an organization that is
committed to ensure socio-economic security of all working Malaysian citizens
including their dependants. Most of the workers in Malaysia are registered with
PERKESO that will cover them if they experienced any injury during the duration of
working. From the statistic by PERKESO for the year 2004, they are about 10,238,554
registered workers but only 4,567,365 are active workers. From the statistic, they are
about 69,132 registered accidents with 9,381 cases of permanent disable and 846 of
death cases. This means that there are many cases of injury that are not reported to
PERKESO.
From the statistics, industrial sector gives the biggest number of accidents which are
26,690 cases. This numbers shows that the workers in the industry face the highest risk
of injury compare to other sectors. In Figure 1.1, the histogram shows the statistic of
injury from year 1999 to 2004. The statistic shows that number of accidents decrease
every year. According to Figure 1.2, the accidents are divided to the causes of accidents.
The causes of accidents are falling, crushed by falling objects, crushed by object (except
falling objects), stuck in an object or between two objects, exposed to hot or cold
environment, exposed to electric current and chemicals, heavy movements and others.
One of the causes of accidents is heavy movements which divided into four categories;
injury when lifting objects (591 cases), injury when pulling and pushing objects (268
cases), injury when managing objects (287 cases), and heavy movements (289 cases).
Heavy movement is one of the factors of accidents that frequently happened in the
industrial sector especially in the production line where these activities are practiced
everyday.
In Figure 1.3, the pie chart shows the number of accidents by locations of injury in 2004.
About 7663 locations of injury is head, 194 cases of the neck, 4519 cases of the trunk,
3
35253 cases of upper limb, 8186 cases of multiple locations, 16818 cases of the lower
limb and 683 cases of general injuries. From the statistic, the most frequent injury
happened are at the upper limb which included the shoulder, upper arm, elbow, forearm,
wrist, hand, fingers, and upper limb. The statistics shows the number of pain for the
upper limb where the locations that give higher reading are shoulder (2,260 cases), wrist
(1,009 cases), hand (8,678 cases) and fingers (16,560 cases).
Figure 1.5 shows the number of accidents for the trunk. The locations are divided into
back, abdomen, chest, pelvis, trunk and multiple locations and unspecified locations.
The highest number of injury of the trunk happened at the back estimated 1,463 cases.
From the statistics, it shows that the workers who involve in the material handling and
lifting task activities especially at the production line have the highest possibilities to
experienced injury especially the lower back pain and MSDs for upper extremity. It is
very important for them to know their rights as the workers so that they could learn to
prevent the injury in the warehouse. This analysis is conducted in order to find the types
of injury they could experienced and what are the preventive actions can be conducted.
Statistic of Accidents Reported to Perkeso
92,07495,00685,22981,810
73,85869,132
0
20,000
40,000
60,000
80,000
100,000
1999 2000 2001 2002 2003 2004
Year
Acc
iden
ts
Accidents Reported
Figure 1.1: Statistic of Accidents Reported to Perkeso from 1999 to 2004
Source: Statistics taken from http://www.perkeso.gov.my/statistikpage1.htm
4
Number of Accidents by Caused of Accidents 2004
8524, 12%
22409, 32%
8882, 13%
1159, 2%
70, 0%
316, 0%
7958, 12%
1435, 2%
18379, 27%
Falling
Crushed by Falling Objects
Step On/Crushed by Objects(except falling objects)Stuck in an Object or BetweenTwo ObjectsExposed/Touched to Hot/ColdEnvironmentExposed to Electric Current
Exposed to Chemicals
Others
Heavy Movements
Figure 1.2: Number of Accidents by Cause of Accidents 2004
Source: Statistics taken from http://www.perkeso.gov.my/statistikpage1.htm
Number of Accidents by Location of Injury 2004
16818, 24%
8186, 12%30253, 44%
4519, 7%
194, 0%7663, 11%683, 1%
816, 1%
HEAD NECK
TRUNK UPPER LIMB
MULTIPLE LOCATIONS LOWER LIMB
GENERAL INJURIES UNSPECIFIED LOCATIONS
Figure 1.3: Number of Accidents by Location of Injury 2004
Source: Statistics taken from http://www.perkeso.gov.my/statistikpage1.htm