analysis of working postures of operator in mixing...

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


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


5

Number of Accidents of the Upper Limb 2004

8,678, 29%16,560, 55%

164, 1%

43, 0%2,260, 7%

1,009, 3%

442, 1%

326, 1%

771, 3%

SHOULDER UPPER ARMELBOW FOREARMWRIST HANDFINGERS UPPER LIMB, MULTIPLE LOCATIONSUPPER LIMB, UNSPECIFIED LOCATION

Figure 1.4: Number of Accidents of the Upper Limb 2004


Number of Accidents of the Trunk 2004

1,463, 33%

790, 17%412, 9%

271, 6%

1,466, 32%

117, 3%

BACK CHESTABDOMEN PELVISTRUNK, MULTIPLE LOCATIONS TRUNK, UNSPECIFIED LOCATION

Figure 1.5: Number of Accidents of the Trunk 2004


6

1.2 PROBLEM STATEMENT

From the statistics produced by Social Organizational Safety Malaysia (PERKESO),

industrial sector gives the biggest number of accidents which are 26,690 cases from

69,132 cases. In 2004 there are about 58247 cases of injury from 4,567,365 active

workers is related to lifting task activities resulted of overexertion or repetitive motion.

Most of the cases affected the back and the pain on the upper extremity of the body such

as shoulder, neck, hand, and wrist. Generally, this entire problem occurred along the

warehouse workers as they involved directly to the repetitive lifting task activity.

Repetitive tasks, especially if forceful, can temporarily make many musculoskeletal

disorders more painful. (Davis T.R.C., 1999). Repetitive task that involving heavy loads

contributes to the developing of back pain and CTDs (Cumulative Trauma Disorders).

CTDs develop overtime due to repetitive stress applied to a joint, typically the upper

extremities. (Gangopadyay S. et al, 2003).

Generally, human only can lift an object as long as they have enough energy to support

the load. The energy needs to lift the object depends on the weight of the object. The

heavier the object, the more energy needed. Human energy will count on the

biomechanics of work and it relate to human physical body capability. Other than

weight, the frequency of lifting also affects human body. Performing lifting task

repetitively will also affect the human physical body. This is lifting frequency has a

relationship with the duration of work. Naturally, human will get tired out after

sometimes.

This study is very important to find the types of injury that could happened according to

the repetitive picking task activity. In this study, the causes of injury will be recognized.

The picking activity will be analyzed using RULA method, REBA method and the 1991

NIOSH Lifting Equation. This study will also try to find the preventive actions or

solutions for long term negative affects to this work related problem.

7

1.3 OBJECTIVES

The objectives of the study are:

· To identify the causes of injury may happen during lifting an object.

· To analyze working postures due to lifting activities.

· To provide suggestions on how to improve workstation in order to reduce

back pain and CTDs.

1.4 SCOPE

The scope of the project is to find the types of injury that usually occurs during the

lifting activity in manufacturing warehouse. In industry, the workers still do not aware of

the long term effect because of the picking task activity that is done repetitively and not

following the RWL (recommendation work limit).

The study will be carried along the mixer department operator at an SMIs (Small

Medium Industry) company as they involved in the repetitive picking task of heavy

loads everyday. The study is carried out in a company producing plastic products such as

rain gutter system, pipes and fittings, and cable slab. The company is located at Kuala

Selangor.

The tools that are going to be used are the RULA (Rapid Upper Limit Assessment),

REBA (Rapid Entire Body Assessment) and the 1991 NIOSH Lifting Equation. The

tools will be used to analyze the working posture while performing the picking task

activity.

8

CHAPTER 2 LITERATURE REVIEW

2.1 MANUAL MATERIAL HANDLING

More than a third of all over-three-day injuries reported each year to HSE and local

authorities are caused by manual handling - the transporting or supporting of loads by

hand or by bodily force. The pie chart shows the pattern for over-three-day injuries

reported in 2001/02. The most recent survey of self-reported work-related illness

estimated that in 2001/02, 1.1 million people in Great Britain suffered from

musculoskeletal disorders (MSDs) caused or made worse by their current or past work.

An estimated 12.3 million working days were lost due to these work-related MSDs. On

average each sufferer took about 20 days off in that 12-month period. Figure 2.1 shows

the kind of accident causing over three-day-injury in the year 2001/02. (Health and

Safety Executive, 2006)

Manual handling injuries can occur wherever people are at work - on farms and building

sites, in factories, offices, warehouses, hospitals, banks, laboratories, and while making

deliveries. Heavy manual labour, awkward postures, manual materials handling, and

previous or existing injury are all risk factors implicated in the development of MSDs.

(Health and Safety Executive, 2006)

9

Figure 2.1: Kind of Accident causing over three-day-injury, 2001/02

(Source: Health and Safety Executive (2006) Getting to Grip with Manual Handling: A

Short Guide (2006) INDG143(rev2))

The word lift means raise up, pick up or take up. Lifting something up means lift, take

up, gather up or snatch up. For this study, picking task is referred to lift or pick some

amount of an object to move or store them in the required position. This activity usually

practiced in the in the production department in the manufacturing company. The

materials usually are solids that come as bags, boxes or containers with or without

handle. There are many ways to pick an object but usually the workers practiced wrong

techniques to lift or pick an object.

Picking or lifting is defined as moving or bringing something from a lower level to a

higher one. The concept encompasses stresses resulting from work done in transferring

objects from one plane to another as well as the effects of varying techniques of patient

handling and transfer. Forceful movements include movement of objects in other ways,

such as pulling, pushing, or other efforts.

Several studies included in this review used indices of physical workload that combined

lifting/forceful movements with other work-related risk factors (particularly heavy

10

physical work and awkward postures). Some studies had definitions for lifting which

include criteria for number of lifts per day or average amount of weight lifted (Bernard

et al, 1997).

According to Kroemer et al, 2001, while doing lifting activity, our body will strained as

we have to bend, stretch, move or strengthen our body parts. Usually the body parts that

involved during picking task are the back, shoulder, hand, and wrist. Heavy loads pose

an additional strain on the body, owing to their mass or bulk or their lack of handles.

The back is directly involved while picking and the part that affected is the disc of the

lumbar spine. Kroemer et al, 2001 suggested that when one considered all the

musculoskeletal structures within the trunk, a variety of elements may be strained, either

singly or combined, including the spinal vertebrae (primarily their disc or facet joints),

but also connective tissues such as ligaments and cartilage, as well as their muscle with

their tendons.

2.2 THE SKELETAL SYSTEM

The Skeletal System serves many important functions; it provides the shape and form for

our bodies in addition to supporting, protecting, allowing bodily movement, producing

blood for the body, and storing minerals. The skeletal system consists of the bones,

connectives tissues, joints, spinal column and the muscle.

Bodily movement is carried out by the interaction of the muscular and skeletal systems.

For this reason, they are often grouped together as the musculo-skeletal system. Muscles

are connected to bones by tendons. Bones are connected to each other by ligaments.

Where bones meet one another is typically called a joint. Muscles which cause

movement of a joint are connected to two different bones and contract to pull them

together. An example would be the contraction of the biceps and a relaxation of the

analysis of working postures of operator in mixing...

Documents