Analysis of Working Postures of Operator in Mixing Department of an SMI in Malaysia

Transcription

1 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

2 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 :... : :

3 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

4 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 pekerjapekerja 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. i

5 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

6 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. ii

7 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. iii

8 TABLE OF CONTENTS Abstract Acknowledgement Dedication Table of contents List of tables List of figures List of Abbreviation i ii iii iv viii x xi 1. INTRODUCTION 1.1 Background of Study Problem Statement Objectives Scope 7 2. LITERATURE REVIEW 2.1 Manual Material Handling The Skeletal System The Bones Connective Tissue Muscle Facet Joints Spinal Column Anatomical System of the Back Fifth Lumbar Vertebrae (of the Spine) Erector Spine Muscle Upper Extremity Type of MSDs Low Back Musculoskeletal Disorders 18 iv

9 2.4.2 Neck Musculoskeletal Disorders Shoulder Musculoskeletal Disorders Elbow Musculoskeletal Disorders Hand/Wrist Musculoskeletal Disorders Tendon Related CTDs Neuritis Ischemia The Risk Factor Posture Repetition Load Horizontal and Vertical Multipliers Non occupational Risks Ergonomic Assessment Tools The 1991 NIOSH Lifting Equation REBA (Rapid Entire Body Assessment) RULA (Rapid Upper Limb Assessment) OWAS Various Methodology Used in Previous Ergonomic Study METHODOLOGY 3.1 Overview of Methodology Description of Methodology Problem Identification Problem Formulation, Objectives and Scope Literature Review Collecting Data 35 a) Anthropometry Data 36 b) Video Recording Analysis Data 36 a) RULA (Rapid Upper Limb Assessment) 37 v

10 b) REBA (Rapid Entire Body Assessment) 37 b) The 1991 NIOSH Lifting Equation Recommendations RESULTS AND ANALYSIS 4.1 Overview Approach Image Capturing Measurement of Working Magnitude Analysis of Working Postures RULA Analysis Results Standing Position Untie Position Lifting Position Unloading Position REBA Analysis Results The 1991 NIOSH Lifting Equation Data Results DISCUSSION CONCLUSION Conclusion 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 vi

11 LIST OF ABBREVIATIONS PSM PERKESO RWL LI RULA REBA MSD CTD CAD NIOSH SMI OWAS = Projek Sarjana Muda = Social Security organizational of Malaysia = Recommended Weight Limit Lifting Index = Rapid Upper Limit Assessment Rapid Entire Body Assessment = Musculoskeletal Disorders = Cumulative Trauma Disorder Computer Aided Design National Institute for Occupational Safety and Health Small Medium Industry Ovako working posture analysis system xi

12 LIST OF TABLES 2.1 Various methodologies used in previous study Anthropometry data of the subjects Magnitudes of every subject for different sub process Description of RULA action level RULA score or standing position RULA score for untie position RULA score for lifting position RULA score for unloading position REBA action level Summary of results for REBA analysis Definition of Components of NIOSH Lifting Equation Frequency Multiplier (FM) (Note: 75cm = 30 inches) Coupling Multiplier Results for the value of RWL and LI for different heights Results of RULA, REBA analysis and the 1991 NIOSH 73 Lifting Equation viii

13 LIST OF FIGURE 1.1 Statistic of Accidents Reported to Perkeso from 1999 to Number of Accidents by Cause of Accidents Number of Accidents by Location of Injury Number of Accidents of the Upper Limb Number of Accidents of the Trunk Kind of Accident causing over three-day-injury, 2001/ Vertebral column Division of the Skeleton Typical lumbar vertebrae Division of the Upper Extremity Low-back biomechanical model of static coplanar lifting Methodology of project The workers is unloading the material to the funnel : Image of an operator pulling the sack from the pallet Two lines were constructed to determine upper arm and forearm angles A manikin that created using the anthropometry data measured The worker pulling the sack from the pallet The worker untied the sack of resin The worker lifts the sack from the floor The workers unload the resin into the funnel A complete RULA analysis : Flow of REBA analysis REBA employment assessment worksheet 60 ix

14 4.12 The required distance of the workstation that is measured Recommended vertical lifting height Figure of the tilt table The application of the tilt table The result of RULA analysis The data for the redesign workstation 77 x

15 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. 1

16 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 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 About 7663 locations of injury is head, 194 cases of the neck, 4519 cases of the trunk, 2

17 35253 cases of upper limb, 8186 cases of multiple locations, 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 Accidents 100,000 80,000 60,000 40,000 20, ,074 95,006 85,229 81,81073,858 69, Year Accidents Reported Figure 1.1: Statistic of Accidents Reported to Perkeso from 1999 to 2004 Source: Statistics taken from 3

18 Number of Accidents by Caused of Accidents , 12% 316, 0% 70, 0% 1159, 2% 8882, 13% 1435, 2% 18379, 27% Falling Crushed by Falling Objects Step On/Crushed by Objects (except falling objects) Stuck in an Object or Between Two Objects Exposed/Touched to Hot/Cold Environment Exposed to Electric Current 22409, 32% 8524, 12% Exposed to Chemicals Others Heavy Movements Figure 1.2: Number of Accidents by Cause of Accidents 2004 Source: Statistics taken from Number of Accidents by Location of Injury , 1% 7663, 11% 194, 0% 683, 1% 16818, 24% 4519, 7% 8186, 12% 30253, 44% HEAD TRUNK MULTIPLE LOCATIONS GENERAL INJURIES NECK UPPER LIMB LOWER LIMB UNSPECIFIED LOCATIONS Figure 1.3: Number of Accidents by Location of Injury 2004 Source: Statistics taken from 4

19 Number of Accidents of the Upper Limb ,260, 7% 43, 0% 326, 1% 442, 1% 164, 1% 771, 3% 1,009, 3% 16,560, 55% 8,678, 29% SHOULDER ELBOW WRIST FINGERS UPPER LIMB, UNSPECIFIED LOCATION UPPER ARM FOREARM HAND UPPER LIMB, MULTIPLE LOCATIONS Figure 1.4: Number of Accidents of the Upper Limb 2004 Source: Statistics taken from Number of Accidents of the Trunk , 3% 1,466, 32% 1,463, 33% 271, 6% 412, 9% 790, 17% BACK ABDOMEN TRUNK, MULTIPLE LOCATIONS CHEST PELVIS TRUNK, UNSPECIFIED LOCATION Figure 1.5: Number of Accidents of the Trunk 2004 Source: Statistics taken from 5

20 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 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. 6

21 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. 7

22 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) 8

23 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 9

24 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 10