Work Study and Ergonomics - Cambridge University Pressassets.cambridge.org/97811075/03366/frontmatter/9781107503366... · This textbook studies the fundamentals of work study and

Work Study and Ergonomics

This textbook studies the fundamentals of work study and ergonomics in a single volume. It examines the theories of human physiology and cognitive sciences and also evaluates the application of these theories to design a work environment that optimizes work potential and reduces threats of work-related disorders. It discusses the strategies to design effective work processes and congenial work environment in order to enhance human well-being and efficiency. The book also explains the ergonomic tools and techniques including biomechanics, work posture assessment tools, anthropometry and work physiology.

Using live examples from the industry, the author discusses the principles of work study including string diagram, method study, work sampling and man-machine system. He illustrates why it is important to ‘fit the job to the man’ rather than continuing with conventional practices that ‘fit the man to the job’. Multiple choice questions, exercises and case studies are interspersed throughout the book for better understanding and assessment.

Lakhwinder Pal Singh is a faculty in the Department of Industrial and Production Engineering, Dr B R Ambedkar National Institute of Technology Jalandhar. He has more than fifteen years’ experience in teaching and research, and has published nearly forty-five papers in national and international journals and conferences. His research interests include human factors engineering, production and operations management, lean manufacturing, occupational health and environment, logistics and supply chain management.

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Work Study and Ergonomics

Lakhwinder Pal Singh






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© Lakhwinder Pal Singh 2016

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Library of Congress Cataloging-in-Publication DataSingh, Lakhwinder P., author. Work study and ergonomics / Lakhwinder Pal Singh. pages cm Includes index. ISBN 978-1-107-50336-6 (pbk.)1. Work design. 2. Human engineering. I. Title. T60.8.S56 2016 620.8--dc23 2015030275

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To my parents











Contents

List of Figures xiiiList of Tables xviiiPreface xxiAcknowledgments xxiii

1. Productivity and Work Study 1 1.1 Introduction 1 1.2 Definition of Productivity 3 1.3 Productivity of the Individual Organization 4 1.4 The Role and Responsibility of the Management of an Organization 5 1.5 Work Study and Productivity 6 1.6 Interrelationship of the Various Methods Used to Reduce Ineffective Time 10 2. Human Factors in Work Study 16 2.1 Introduction 16 2.2 Historical Glimpse Related to Work 16 2.3 Objectives of Work Study 17 2.4 Importance 17 2.5 Segments of Work Study 18 2.6 Human Factors Consideration in the Application of Work Study 19 2.7 The Role of Management and Supervisor in Work Study 19 3. Method Study (Motion Study) 24 3.1 Introduction and Background 24 3.2 Definition of Method Study 25 3.3 Procedure of Method Study 25 3.4 Develop the Best Method 30 3.5 Install the Best Proposed Method 30 3.6 Maintain the Installed Method 31 3.7 Process Analysis 31 3.8 Principles of Motion Economy 45 3.9 Operation Analysis 49 3.10 Therbligs 52 3.11 Work Simplification 60






viii Contents

4. Work Measurement 63 4.1 Introduction to Work Measurement 63 4.2 Stopwatch Time Study 63 4.3 Essentials for Time Study 64 4.4 Time Study Procedure 64 4.5 Applications of Time Study 64 4.6 Selecting the Job for Time Study 65 4.7 Selection of Worker for Time Study 65 4.8 Time Study Equipment 66 4.9 Element Break-down in Time Study 69 4.10 Determination of Number of Observation 71 4.11 Recording Observation on Time Study Form 76 4.12 Performance Rating 76 4.13 The Qualified Worker 77 4.14 Comparison of Observed and Standard Ratings 78 4.15 Work Content 80 4.16 Calculations of Standard Time 86 4.17 Synthesis 89 4.18 Pre-determined Motion Time Standards (PMTS) 90 4.19 Work Sampling Process 94 5. Wages and Incentive Plans 116 5.1 Introduction 116 5.2 Types of Wage Incentive Plans 117 6. Introduction to Ergonomics 133 6.1 Background of Ergonomics 133 6.2 Historical Evolution of Ergonomics 134 6.3 Introduction 135 6.4 Definitions of Ergonomics 136 6.5 An Ergonomist 136 6.6 Significance of Ergonomics in Society 137 6.7 The Scope of Ergonomics 137 6.8 Ergonomics and Related Disciplines 138 6.9 Aspects of Ergonomics 139 6.10 Application Areas of Ergonomics 139 6.11 Man and Machine Interaction 139 6.12 Man–Machine Closed Loop System 140 6.13 Man–Machine System (MMS) 140 6.14 Determinants of MMS System Performance 141 6.15 Limitations of Human Beings 142 7. Work Physiology 145 7.1 Introduction 145 7.2 Muscle Structure 145 7.3 Metabolisms (Aerobic and Anaerobic) 146






Contents ix

7.4 Circulatory and Respiratory Systems 148 7.5 Energy Expenditure and Workload 155 7.6 Occupational Kinesiology 157 7.7 Conclusion 160 8. Biomechanics of Manual Lifting Tasks 162 8.1 Introduction to Musculoskeletal System 162 8.2 Functions of the Muscular System 162 8.3 Bones and Connective Tissues 163 8.4 Bone Joints 163 8.5 Biomechanics 164 8.6 Biomechanical Models 164 8.7 Lever Systems 165 8.8 Single-Segment Planer Static Model 166 8.9 Low–Back Problems 167 8.10 The Revised Lifting Equation 172 8.11 Lifting Task Limitations 174 9. Risk Assessment for Distal Upper Extremities (DUE) Disorders 185 9.1 Introduction 185 9.2 Carpal Tunnel Syndrome (CTS) 186 9.3 Cubital Tunnel Syndrome 186 9.4 Thoracic Outlet Syndrome 186 9.5 Rotator Cuff Syndrome 187 9.6 Tendinitis 187 9.7 Tenosynovitis 188 9.8 Trigger Finger 188 9.9 Ganglion Cyst 188 9.10 Cumulative Trauma Disorder (CTDs) 189 9.11 Distal Upper Extremities Disorder Risk Factors 189 9.12 Wrist Posture in Daily Life Activities 189 9.13 Introduction to Strain Index Method 193 9.14 Case Study 196 10. Work Related MSDs Risk and Work Postures Assessment 203 10.1 Introduction 203 10.2 Assessment of Work Postures Using RULA Method 204 10.3 Work Posture Assessment Using Rapid Entire Body Assessment Tool (REBA) 214 11. Office Ergonomics 228 11.1 Introduction 228 11.2 Issues in Workstation Design 228 11.3 Seat Design 233 11.4 Engineering Anthropometry and Workspace Design 237 11.5 A Case Study: An Investigation on Passenger Seat Design (Lower Side Berth)

in Sleeper Class Coaches in Indian Trains 239






x Contents

12. Physical Stresses 251 12.1 Introduction 251 12.2 Vibration 251 12.3 Occupational Noise Exposure 260 13. Occupational Noise Exposure 265 13.1 Introduction to Noise 265 13.2 Sound 265 13.3 Sources of Noise and Vibration 267 13.4 Basic Theory of Noise Measurement 268 13.5 Noise-measuring Meters 271 13.6 Basic Sound Level Meters 271 13.7 Integrating Meters 272 13.8 Noise Control 273 13.9 Permissible Limits for Exposure with respect to Occupational Noise 273 13.10 Assessment of Exposure 276 13.11 Adding Decibels 276 13.12 Hearing Conservation Program (HCP) 277 13.13 Noise Control Programmes 278 13.14 Administrative Controls 279 13.15 Hearing Protective Devices (HPD) 279 13.16 Occupational Noise Exposure Assessment: A Case Study 280 14. Occupational Noise Induced Hearing Loss (NIHL) 287 14.1 Introduction 287 14.2 Hearing Threshold Shift Due to Occupational Noise Exposure 288 14.3 Hygiene Standards for Noise-induced Hearing Loss 289 14.4 Cause of Noise-induced Hearing Loss 289 14.5 Measuring Hearing Loss-Audiometry 291 14.6 Hearing Impairment Criteria 293 14.7 Protocol and Procedure for Pure Tone Audiometry 294 14.8 Effect of Occupational Noise Exposure on Latency Time (Brainstem

Auditory Evoked Potentials Response, BERA) 294 14.9 Assessment of Latency Time using Brainstem Auditory Evoked Potentials

Response (BERA) 295 14.10 Method for Latency Time (Brainstem Auditory Evoked Potentials) 295 14.11 Protocol and Procedure for the BAEP 296 14.12 Case Study: Investigation of Auditory Functions of Steel Industry Workers 297 14.13 Comparison of Exposed Group v/s Control Group for Latency Time 301 14.14 Effect of Workplace Conditions on Hearing Threshold 301 14.15 Effect of Workplace Conditions on Latency Time 302 14.16 Effect of Work Exposure on Hearing Threshold 302 14.17 Conclusions 302 15. Occupational Heat Stress Exposure 304 15.1 Introduction 304 15.2 Heat Stress and Human Performance 304






Contents xi

15.3 Assessment of Heat Stress at Workplace 305 15.4 Permissible Limits for Exposure with respect to Heat Stress in India 307 15.5 Case Study 307 16. Dust Fumes and Respiratory System 312 16.1 Introduction 312 16.2 Definitions Relevant to Dust and Fumes 312 16.3 The Behavior of Dusts 312 16.4 Physiology of the Human Lung 313 16.5 Physiological Mechanisms of Dust Movement 313 16.6 Human Body’s Protective Mechanisms 314 16.7 Sources of Dust 315 16.8 Dust Control Measures 315 16.9 Dust Control Strategies 316 16.10 Dust Explosion 317 16.11 Fumes 319 16.12 Procedure for Assessment of Respirable Suspended Particulate Matter

(RSPM) at Workplace 320 16.13 Dust Formation 322 16.14 Case Study 322 16.15 Materials and Methods 323 16.16 Lung Functions Measurement using Spirometry 326 17. Occupational Health and Safety 332 17.1 Introduction 332 17.2 Environmental Law – Legal Control of Hazardous Substances and Processes 332 17.3 Indian Penal Code 334 17.4 Management of Safety at Enterprise Level 334 17.5 Factors Relating to Work Environment 336 17.6 Occupational Health and Safety 337 17.7 Deprived Work Environment 337 17.8 Significance of Occupational Health and Safety 338 17.9 Indian Scenario of Steel (Casting and Forging) Industry 338 17.10 Present Scenario of Occupational Health and Safety in Developing Countries 338 17.11 Scarcity of Occupational Health Specialist in India 340 17.12 Need for Research on Occupational Health and Ergonomics in Steel Industry 341 17.13 Case Study: An Exploratory Study for Assessment of Awareness with respect to

Occupational Health, Safety and Environment in SMEs 341 18. Cardiovascular Health of Steel Workers 354 18.1 Introduction 354 18.2 Statistical Tools used for Analysis 354 18.3 Cardiovascular Autonomic Control (HRV) and Work Conditions 354 18.4 Effect of Work Conditions, Alcohol and Smoking on Blood Pressure 356 18.5 Heart Rate Variability (HRV) 357 18.6 Method for HRV Assessment 357 18.7 Protocol and Procedure for HRV Recording 358






xii Contents

18.8 Blood Pressure (BP) Measurement 359 18.9 Equipment for BP Measurement 360 18.10 Protocol and Procedure for BP Measurement 360 18.11 Comparison of Exposed Group v/s Control Group for Cardiac Autonomic

Control (HRV) 361 18.12 Comparison of Exposed Group v/s Control Group for Blood Pressure (BP) 362 18.13 Effect of Workplace Conditions on Cardiovascular Autonomic Control

(HRV and BP) 362 18.14 Effect of Workplace Conditions on BP Parameters 362 18.15 Effect of Work Exposure on Cardiovascular Autonomic Control (HRV and BP)

Within Exposed Group 364 18.16 Effect of Work Exposure on BP Parameters 365 18.17 Discussion 366 18.18 Summary 370

References 372






List of Figures

1.1 (a) Cutting of wire in standard size, (b) Bending of wire into shape of hanger, (c) Final shape of hanger after paint/plastic coating. 2

1.2 Role and responsibility of management in coordinating the resources of an enterprise. 6 1.3 Constituents of operation time. 7 1.4 Wastage of material due to bad design of product. 8 1.5 Basic and added work content. 11 1.6 Management techniques to reduce the added work content. 12

2.1 Productivity improvements through work study. 18

3.1 Method suggested by Frank Gilbreth. 24 3.2 Flow diagram of method study. 26 3.3 Analysis of existing method using questioning technique. 28 3.4 Outline process chart. 33 3.5 Outline process chart of repairing a punctured wheel (tubeless) for a car. 34 3.6 Material type flow process chart for cutting of mild steel rod. 35 3.7 Material flow process chart for manufacturing of spanner. 36 3.8 Two-handed process chart. 37 3.9 Summary of two-handed process chart. 37 3.10 Man-machine type multiple activity chart. 38 3.11 Flow diagram. 40 3.12 String diagram (M-1 stands for Machine-1) 41 3.13 Travel chart. 42 3.14 Block templates for layout. 43 3.15 Cyclegraph and chrono-cyclegraph. 44 3.16 A tool (claw hammer) can carry out two operation namely

(i) hammering, (ii) drawing outs nails. 47 3.17 Normal and maximum working areas in the workplace design for the average user.* 48 3.18 Workplace layout for assembly of small components. 49 3.19 Operation chart for the assembly of nuts and bolts by use of existing method. 50 3.20 Operation chart for the assembly of nuts and bolts by use of improved method. 52 3.21 Micro-motion film analysis record sheet. 57 3.22 SIMO chart for a simple chiselling operation. 58






xiv List of Figures

4.1 Non-fly backstopwatch. 67 4.2 Fly back stopwatch. 67 4.3 A motion picture camera. 68 4.4 Time study board used for making observations. 68 4.5 Proforma for time study. 69 4.6 Normal distribution of workers. 77 4.7 Procedure for determination of allowances. 81 4.8 Calculation of standard time. 82 4.9 Constituents of standard time. 87 4.10 Basic motion of a body: at rest (begin), movement and rest at end point. 91 4.11 Classifications of basic motions. 92 4.12 Proportional distribution of ‘heads and tails’ after 100 tosses of coins at a time. 97 4.13 Distribution of ‘heads and tails’ after a huge number of tosses

of coins at a time to make a normal distribution of data. 97 4.14 Curve of normal distribution. 98 4.15 Work sampling procedure for making observations. 102

5.1 Merrick’s differential piece rate system. 119 5.2 Earning rate versus percentage of performance. 126 5.3 Earning rate versus percentage of performance. 128

6.1 Historical evolution of ergonomics. 135 6.2 Ergonomics and interaction with other disciplines. 139 6.3 Closed loop of man-machine system. 140 6.4 Human and technical subsystems user interface. 141

7.1 Detailed structure of muscle. 146 7.2 Working of various systems to meet the requirement of energy expenditure

for physical work. 147 7.3 The circulatory system. 149 7.4 Human respiratory system. 150 7.5 Diffusion of oxygen into the blood in alveolis. 151 7.6 Anatomy of human heart. 152 7.7 Total energy expenditure rate in response to level of physical activity. 157

8.1 The composition of muscles. 162 8.2 A typical type of lever system. 165 8.3 A person lifting weight on forearm and biceps. 166 8.4 Human spine and muscles supporting the lower spine. 168 8.5 Loads (A–D) on spinal motion segments and E) the mechanism

of disc compression with respect to time. 168 8.6 Mechanism of disc degeneration. 169 8.7 The person lifting a weight at a distance of 20 inches from L5/S1. 170 8.8 The person lifting a weight at a distance of 10 inches from L5/S1. 171 8.9 A simplified biomechanical model of low back. 171 8.10 Procedural steps for analysis of lifting task. 177






List of Figures xv

8.11 A worker lifting load in hand tool industry. 178

9.1 Mechanism of carpal tunnel syndrome. 186 9.2 Mechanism for the cubital tunnel syndromes. 187 9.3 Mechanism for the thoracic outlet syndrome. 187 9.4 Ganglion cyst at the wrist. 188 9.5 Flow diagram for development of DUE disorder. 189 9.6 Various wrist postures 190 9.7 Various types of grips in daily life. 190 9.8 Various types of pinch grasp. 191 9.9 Palm-up grasp. 191 9.10 Directions of object weight and pinch force. 192 9.11 Overall average SI of casting, forging and car assembly line. 193

10.1 Flow chart for calculation of RULA score. 204 10.2 Movements of upper arm and allocation of score*. 205 10.3 Movements of lower arm and allocation of score*. 205 10.4 Movements of wrist and allocation of score*. 206 10.5 Movements of neck and allocation of score*. 206 10.6 Movements of trunk and allocation of score*. 207 10.7 Worker A and B are engaged in grinding jobs. 208 10.8 Assessment of RULA score for worker A. 209 10.9 Assessment of RULA score for worker B. 210 10.10 Score with respect to variations in posture of neck. 214 10.11 Score with respect to variation in posture of trunk. 215 10.12 Score with respect to variation in posture of legs. 215 10.13 Score with respect to variation in posture of upper arm. 216 10.14 Score with respect to variation in posture of lower arm. 217 10.15 Score for various wrist positions. 217 10.16 Flow chart for calculation of REBA scores. 219 10.17 Worker (WA) in a bending posture at pouring task. 220 10.18 Worker (WB) in relatively better posture at pouring task. 220 10.19 Calculations of REBA score for workers WA and WB engaged in pouring operation. 224 10.20 Work postures WC and WD of a worker engaged in molding operation. 225 10.21 Calculation of REBA scores for WC and WD. 226 10.22 A worker engaged in pouring operation with relatively safe posture. 226

11.1 A workstation for computer user. 229 11.2 Workstation with arm/wrist support, standing workstation, split and traditional

keyboard. 231 11.3 Human spine viewed from the left side. 231 11.4 Supine curvature produced in different postures adopted by an individual. 232 11.5 Various anthropometric considerations while designing a seat or chair for workstation. 234 11.6 A work chair as per the anthropometric considerations. 236 11.7 Image showing offset along thickness, gap along length and offset

in width of two halves of the seat. 239






xvi List of Figures

11.8 (A) One senior citizen indicating back pain due to design of the berth, and (B) a young passenger filling feedback questionnaire. 240

11.9 Present design 3-D model of lower side berth (A) while sleeping and (B) while sitting. 240

11.10 (A) Position of joint exactly at lumber position of the back and (B) improved proposed design, the joint is under the hamstring muscles. 249

12.1 Frequency and amplitude of vibration in sinusoidal form. 252 12.2 Vibration coordinates in (a) standing, (b) seated and (c) laying position. 253 12.3 (A) Head to feet transmissibility, (B) eye to head transmissibility. 258 12.4 Vertical vibration exposure limits for fatigue decreased proficiency (FDP). 260

13.1 (A) Pure tone sound, (B) different frequencies, (C) broad band noise and (D) impulsive noise. 266

13.2 Equal loudness curves for pure tones. 269 13.3 Type 1 Integrating Sound Level Meter (right) and

Type 2 Integrating Sound Level Meter (left). 271 13.4 Different types of hearing protective devices (HPD). 280 13.5 Noise level and noise dose assessment at onsite location. 281

14.1 Anatomy of human ear. 290 14.2 Sectioned view of cochlea with (A) normal hair cells and (B) damaged hair cells. 290 14.3 Flowchart of occupational audiometry. 292 14.4 Arphi model 500 MK-III portable audiometer. 293 14.5 Audiometry test conducted in a sound proof audiometry room. 293 14.6 A typical audiogram of a group of workers exposed to

high noise in forging section versus control group. 294 14.7 Latency time assessed by brainstem auditory evoked potential test using RMS

BERA Mark-II. 296 14.8 Wave forms produced after recording. 296 14.9 Audiogram of left and right ear of exposed group v/s control group. 298 14.10 Audiogram of left and right ear of workers engaged in various sections and

control group. 300

15.1 Heat stress monitoring at onsite locations in forging industry. 306 15.2 Heat stress monitoring at onsite locations in casting industry. 306 15.3 Comparison of average WBGT (°C) recorded at various sections in casting

industry with respect to recommended WGBT criteria. 309 15.4 Comparison of average WBGT (°C) recorded at various sections in forging

industry with respect to recommended WGBT criteria. 309

16.1 Structure of human respiratory system. 313 16.2 Explosion suppression using an explosion detector, electrical

power unit and a hemispherical suppressor. 319 16.3 Leland Legacy pumps with sampler for RSPM. 321 16.4 Respirable suspended particulate matter assessment. 321 16.5 Dust concentration in various sections. 324






List of Figures xvii

16.6 Respiratory symptoms in various sections. 325 16.7 Sampling on shop floor in grinding section, workers without complete PPE. 325 16.8 RMS Helios 401 Spirometer, reusable mouth piece and nose clip. 328 16.9 Spirogram plot after performing FVC test. 329

17.1 Safety management at an enterprise level. 335 17.2 Questionnaire survey and interview conducted with the industry workers. 341 17.3 Percentage distribution of workers with respect to fatigue/noise induced syndromes. 344 17.4 Fatigue, noise induced syndromes at a 0–4 point scale. 344 17.5 Percentage distribution of workers with respect to shift and work schedule. 345 17.6 Distribution of workers with respect to overtime per week, N (%). 345 17.7 Percentage distribution of workers with respect to various intake. 346 17.8 Distribution of workers with respect to musculoskeletal complaints, N (%). 347 17. 9 Workers working in bending postures at different workplaces. 348 17.10 Distribution of workers with respect to various reasons for non-use of PPEs. 351

18.1 ECG recording of a subject in spine rest position. 358 18.2 Normal ECG recording with P, QRS and T waves. 359 18.3 Tachogram plotted for 300 sec recoding of ECG. 359 18.4 FFT Power Spectral Density (PSD) spectrum. 360 18.5 Mercury sphygmomanometer and stethoscope. 360






List of Tables

3.1 Primary and secondary questions for analysing the job. 28 3.2 Primary and secondary questions for handling raw material for blank cutting in

a hand tool manufacturing unit. 29 3.3 Description of five basic symbols used in process chart. 32 3.4 Description of process chart symbols being used for combined activities. 32 3.5 Summary of symbols used in outline flow process charts for repairing a punctured

wheel of a car. 34 3.6 Summary of symbols used in material flow process chart. 36 3.7 Summary of multiple activity chart. 39 3.8 Normal and maximum working area dimensions as shown in Figure 3.17 49 3.9 Gilbreth’s seventeen therbligs. 53 3.10 Classification of effective and ineffective therbligs. 54 3.11 Therbligs with symbols, word code and interpretation. 54

4.1 Number of cycles to be timed for a job of particular cycle time. 71 4.2 Observations taken with snap back method. 72 4.3 Calculations of required parameters for calculation of number of observations. 73 4.4 Calculations of required parameters when cycle time is relatively less as compared

to the initial observations. 74 4.5 Elemental times to be calculated by subtraction. 75 4.6 Different types of rating scales. 79 4.7 Personal/fatigue allowances for male workers. 83 4.8 Showing the observations and rating for each cycle and element respectively. 88 4.9 Calculation of average observed time and basic time for each element. 88 4.10 Different tolerances values and respective distances. 93 4.11 Random table for making observations. 100 4.12 Work sampling schedule on basis of random observations. 101 4.13 Work sampling record sheet showing observation when machine is running and idle. 102 4.14 Work sampling record sheet showing observation for machine

running and distribution of machine idle time. 102 4.15 Work sampling record sheet showing observation on distribution of

machine idle time of nine elements of operation performed. 103 4.16 Group sampling sheet with rating factors. 105






List of Tables xix

7.1 Blood flow distribution (percentage) throughout different body organs in rest and working conditions. 155

7.2 Estimates of energy expenditure rates for various activities. 156

8.1 The formula for calculation of multipliers for each of the six variables of NIOSH lifting equation (1991). 175

8.2 Coupling multiplier. 175 8.3 Frequency multiplier. 175

9.1 Various types of grip strength. 191 9.2 Ratings for intensity of exertion. 194 9.3 Ratings for percentage duration of exertion. 194 9.4 Rating for efforts per minute. 195 9.5 Rating for various positions of hand/wrist. 195 9.6 Ratings for different categories of speed of work. 195 9.7 Ratings for various categories of duration of task per day. 196 9.8 Combined rating for all six variables. 196 9.9 Value of multipliers w.r.t. rating scores variables. 197 9.10 Strain Index score associated with various processes in forging unit. 199 9.11 Strain Index score associated with various processes in automated casting unit. 200 9.12 Average SI score associated with various processes in automated car assembly unit. 200

10.1 Various load/force score for RULA*. 207 10.2 Upper limb posture score table-A of RULA*. 211 10.3 Neck, trunk, and legs posture score table-B of RULA*. 212 10.4 Grand score table–C of RULA*. 212 10.5 Distribution of risk level and their corresponding action levels for RULA. 213 10.6 Distribution of RULA score process-wise. 213 10.7 Distribution of scores and their corresponding action levels according to REBA*. 218 10.8 Neck, trunk and leg score Table-A of REBA*. 221 10.9 Upper arm, lower arm and wrist score Table-B of REBA*. 222 10.10 Overall grand score category-C (Table-C) of REBA. 223

11.1 Suggestions offered by the passengers for improvements in the seat dimensions and design. 241

11.2 Dimensions of side lower berth while seat is laid for sleeping (N = 50). 241 11.3 Dimensions while seat is folded for sitting (N = 50). 243 11.4 Gap along: length, breadth and thickness. 245 11.5 Anthropometric dimensions for seat design according to NASA athropometric

source book (NASA, 1978). 247

12.1 Resonant frequencies for different parts of seated bodies. 254 12.2 Frequency-dependent health effects. 254

13.1 Addition of decibels. 269 13.2 Standard range of octave bands. 270 13.3 Methods of noise control. 273 13.4 Various occupational noise exposure standards. 274 13.5 Permissible limits for occupational noise exposure as per Indian Factory Act 1947. 274






xx List of Tables

13.6 Occupational noise dose criteria. 275 13.7 Permissible exposure levels of impulsive or impact noise

(Schedule – xxiv, Indian Factory Act 1947). 276 13.8 Estimation method for calculation of noise level for two or more sources of noise. 277 13.9 Prevailing noise levels at various sections of casting units. 282 13.10 Prevailing noise levels at various sections of forging units. 282 13.11 Prevailing noise levels Leq (A) dB and mean noise dose (% age). 284

14.1 Tabular audiogram in which hearing thresholds were recorded. 292 14.2 Hearing impairment criteria. 293 14.3 The ‘t’-test results of exposed v/s control group for hearing threshold. 297 14.4 The ‘t’-test results of exposed v/s control group for latency time (LT) 299

15.1 Categories of job activities on the basis of workload*. 306 15.2 Permissible heat stress criteria for acclimatized workers (WBGT °C)*. 307 15.3 Permissible limits for exposure with respect to heat stress as per the Indian

Factory Act, 1947. 307 15.4 Average WBGT at various sections in forging industry with respect to

ACGIH-2001 standards. 308 15.5 Permissible heat stress criteria for acclimatized workers (WBGT values in °C). 308 15.6 Degree of comfort for humidex range. 309

16.1 Classification of dust deposition locations in the respiratory tract. 315 16.2 Prevailing RSPM level in various sections of a casting industry. 321

17.1 Distribution of industry workers with respect to age, N (%). 342 17.2 Distribution of industrial workers with respect to education level, N (%). 342 17.3 Distribution of workers with respect to marital status and exposures to

working conditions environment (years), N (%). 342 17.4 Distribution of workers interviewed in each section of SMEs, N (%). 343 17.5 Distribution of workers with respect to various health symptoms. 347 17.6 Distribution of workers with respect to work posture N (%). 349 17.7 Distribution of workers with respect to auditory, visual and overall health, N (%). 349 17.8 Distribution of workers with respect to awareness of health and safety,

use of PPEs and work place injuries, N (%). 350 17.9 Details of score at five point scale with respect to use of PPEs by the workers (%). 350

18.1 The ‘t’-test results of exposed v/s control group for HRV (cardiac autonomic control). 361 18.2 The ‘t’-test results of exposed v/s control group for BP. 362 18.3 ANOVA results for effect of work conditions on HRV (autonomic control). 363 18.4 Tukey’s analysis multiple comparison for mean HR (SD) for group 2 with others. 363 18.5 Effect of occupation on BP parameters using ANOVAs results. 364 18.6 Tukey’s Analysis multiple comparison for SBP, DBP and MBP. 364 18.7 Effect of work exposure on autonomic control in exposed group. 365 18.8 Post hoc Tukey’s analysis for multiple comparisons for HRV components

among various subgroups. 365 18.9 Effect of work exposure on BP among industry workers. 366 18.10 Post hoc Tukey’s analysis for multiple comparison of SBP, DBP and MBP

w.r.t. work exposure. 366






Preface

This book has been especially written and prepared for undergraduate and post-graduate students of industrial engineering, production engineering, industrial and production engineering, mechanical and industrial engineering or mechanical engineering, pursuing a one semester course on work systems design, work safety and ergonomics, work design and ergonomics, work study and ergonomics, industrial ergonomics, occupational health and ergonomics, or industrial engineering and ergonomics. Normally the course is offered as a single semester course. But in the present text it has been the author’s endeavour to cover not only what can be taught in a single semester but also provide some additional material needed by an ergonomist or an occupational safety engineer. The present text is supplemented with the case studies and live examples from the industry. Hence, human factor engineers or occupational safety engineers or work study engineers will benefit from the knowledge on practical applications of Work Study and Ergonomics.

Chapter 1 explains the basic concepts, definitions, scope and importance of productivity, reasons for lower productivity, and methods to improve the same followed by integration of work study and productivity. Chapter 2 describes the role of human factors in work study, and the qualities of a good work study man. Chapter 3 deals with the concepts, definitions and applications of method study, procedural steps to conduct methods’ study, different tools and techniques for methods’ study; followed by principles of motion economy, therbligs and work simplification. Subsequently Chapter 4 focusses on basic techniques of work measurement, work sampling, and stopwatch time study procedure, equipment and forms for time study, allowances, rating scales, calculation of basic and standard time; followed by some numerical problems. As the standard time calculated through work sampling or stopwatch time study is useful for deciding wage rates and incentives for the workers and employees, hence Chapter 5 is dedicated to various wage and incentives schemes and programmes.

By the end of Chapter 5 the students would have acquired an understanding of work study, its importance and its role in industry. Consequently they will be able to conduct motion studies, time studies, set time standards and apply them in fixing wages and incentives for the employees/workers of an organization. Given this, Chapter 6 of the book will introduce the students to the basic concept of ergonomics, to the historical evolution, scope and objectives of ergonomics, and then follow up the discourse by introducing the man machine system and its performance determinants. After an introduction to ergonomics, students need to be introduced to concepts of work physiology. Chapter 7 describes the structure and features of the human body, metabolism and measurement of physiological functions followed by work load and energy consumption. Chapter 8 focuses upon the musculoskeletal






xxii Preface

system and work related musculoskeletal disorders (MSD), followed by the biomechanics of lifting, and revised National Institute of Occupational Safety and Health (NIOSH) lifting equation. Thereafter, Chapter 9 elucidates the assessment of distal upper extremities disorders using staring index method. It is also important to enable the students to assess the work related MSD risk due to work posture; Chapter 10 is dedicated to work posture assessment tools like Rapid Upper Limb Assessment (RULA), rapid entire body assessment (REBA), the procedural steps to apply these tools and is supplemented by a case study from the small scale industry. Ergonomics interventions are very important in offices; Chapter 11 explains work place design, seat design and anthropometry followed by a case study.

Chapter 12 probes the effect of vibration, noise and temperature on performance. Occupational noise exposure assessment is taken up in Chapter 13, where the basic theory of noise, its measurement, and hearing protective devises, are introduced. The effect of occupational noise exposure mainly results in NIHL ; Chapter 14 gives a brief introduction to noise induced hearing loss (NIHL), assessment of hearing loss, procedures for audiometry, followed by a case study. After assessing occupational noise exposure and noise induced hearing loss the student needs an introduction to heat stress and respirable suspended particulate matter (RSPM). Chapters 15 and 16 are dedicated to an assessment of heat stress and RSPM levels in the industry. Chapter 17 describes occupational health and safety, present scenario of research into occupational health in India. At the end of this book, Chapter 18 presents a case study on the cardiovascular health of steel industry workers.

The author hopes that the information provided in the book will be useful for an appreciation of the importance (and application) of work study and ergonomics, in the industry and a variety of occupations.






Acknowledgments

This project would not have been possible without the support, advice and suggestions of colleagues, friends and family members. It is my moral and divine duty to acknowledge the contribution of every person whose effort has made this project possible. Before acknowledging anyone else, I bow my head in worship to my spiritual Guru and the almighty God for giving me the internal strength and self discipline for this assignment. I take this opportunity to express gratitude to the reviewers for their valuable suggestions for the book. I extend sincere thanks to Professor Debkumar Chakrabarty (IIT Guwahati), Dr D. Majumdar (DIPAS, Delhi), Professor S. Gangopadhya, Professor K.K. Deepak (AIIMS, Delhi), Professor A. Bhardwaj (NIT, Jalandhar) for their scholarly advice and encouragement. I owe sincere gratitude to Professor S. K. Das (Ex. Director NIT Jalandhar), Professor I. K. Bhatt (Director, NIT Jalandhar), Ajit Singh (Registrar, NIT Jalandhar) for providing a positive work environment. I am also grateful to my head of department, colleagues and friends for their continuous moral support. My family deserves a special mention: my parents, brothers and sister, my better half Poonam, my lovely kids Isha and Vansh, my niece and nephews, who stood behind me as a pillar of strength. I also extend my gratitude to the management of different SMEs for providing me the opportunity to conduct some case studies for supplementing the text.

I express my gratitude to the team at Cambridge University Press: Gauravjeet Singh Reen for his excellent ground work and syllabus research, that facilitated in finalizing the table of contents. I always turned to him for suggestions wherever I was stuck and he was always available to answer my queries. Members of the academic editorial team Hardip Grewal and Shikha Vats were also very cooperative and gave me advice and suggestions as and when required. Last but not the least I am thankful to all my students and teachers who have taught me and made me what I am today.






Documents

Work Study and Ergonomics - Cambridge University Pressassets.cambridge.org/97811075/03366/frontmatter/9781107503366... · This textbook studies the fundamentals of work study and