Safety with machinery

Contents Preface ix Part I Safeguarding philosophy and strategy 1 1 Safeguarding of work equipment 3 1.1 Introduction 3 1.2 Design considerations 4 1.3 ‘Cradle to the grave’ concept 4 1.4 Designer’s responsibility 5 1.5 Safeguarding principles 6 1.6 Guarding strategy 7 1.7 Standard-making bodies 8 1.8 European approach to machine guarding 8 1.9 Unit vs holistic approach to safeguarding 9 2 Factors affecting the selection and effectiveness of machine safeguards 10 2.1 Introduction 10 2.2 Basic factors 10 2.3 Quality assurance 13 2.4 Reliability 14 2.5 Integrity 16 2.6 Validation 17 2.7 Summary 17 3 Typical hazards of machinery 18 3.1 Identification 18 3.2 Agents of hazards 18 3.3 Hazards from parts of machinery and work equipment 20 4 Risk assessment, risk reduction and selection of safeguards 35 4.1 Introduction 35 4.2 What is a risk assessment 35 4.3 Risk reduction strategy 36 4.4 Determining a Safety Integrity Level for machinery hazards 40 4.5 Selecting a safeguarding system 49 4.6 Summary 53 vi Contents Part II Guarding techniques 55 5 Mechanical guarding 56 5.1 Introduction 56 5.2 Guard selection 56 5.3 Guard types 57 5.4 Other factors to consider 68 5.5 Other techniques 69 6 Interlocking safeguards 71 6.1 Introduction 71 6.2 Interlocking devices 71 6.3 Guard locking 75 6.4 Interlocking systems 76 6.5 Levels of risk 76 6.6 Interlocking media 77 6.7 Two hand controls 79 6.8 Hold-to-run controls 80 6.9 Limited movement control 80 6.10 Person sensing devices 80 6.11 Lasers 85 6.12 Pressure sensitive mats 86 6.13 Pressure sensitive edges and wires 88 6.14 Grab wires 88 6.15 Emergency stop switches 89 6.16 Telescopic trip switches 90 6.17 Proximity switches 91 6.18 Key exchange systems 91 6.19 Key interlock switches 93 6.20 Delayed start 93 6.21 Other interlocking devices 94 7 Ergonomic aspects of machinery safeguarding 95 7.1 Introduction 95 7.2 Physiology 95 7.3 Controls 96 7.4 Machine layout 98 7.5 Colours 98 7.6 Lighting 99 7.7 Noise 100 7.8 Vibrations 100 7.9 Rate of working 100 7.10 Temperature and humidity 101 7.11 Ventilation 101 7.12 Repetitive actions 101 7.13 Warnings 101 7.14 Vision 101 7.15 Radiations 102 7.16 Indicators and instruments 102 7.17 Coda 104 Contents vii Part III Safeguarding systems 105 8 Mechanical safety arrangements 107 8.1 Introduction 107 8.2 Guards 107 8.3 Distance fencing 113 8.4 Safety gaps 115 8.5 Feed and take-off stations 117 8.6 Work-holding devices 118 8.7 Counterweights 118 8.8 Safety catches 118 8.9 Braking systems 119 8.10 Clutches 121 8.11 Summary 124 9 Electrical safety circuits 125 9.1 Introduction 125 9.2 Effect on safety 126 9.3 Basic safety requirements 126 9.4 Selection of interlocking switches 127 9.5 Switching contact requirements 128 9.6 Factors influencing the selection of interlocks 129 9.7 Circuit fault protection 129 9.8 Safety control circuits 133 10 Hydraulic safety circuits 153 10.1 Introduction 153 10.2 Hydraulic systems for safety circuits 153 10.3 Hydraulic safety circuits 154 11 Pneumatic safety circuits 162 11.1 Introduction 162 11.2 Pneumatic installations 162 11.3 Pneumatic safety circuits 164 11.4 Summary 169 Part IV Other safety-related arrangements 175 12 Safety in the use of lifting equipment 177 12.1 Introduction 177 12.2 Common safety features of lifting equipment 177 12.3 Additional features for particular lifting equipment 178 12.4 Lifting accessories 182 12.5 Circumstances requiring special precautions 182 12.6 Precautions when handling lifting equipment 183 13 Safety with pressure systems 184 13.1 Introduction 184 13.2 Compressed air 185 13.3 Hydraulic installations 190 13.4 Steam 193 viii Contents 14 Safe working with equipment 201 14.1 Introduction 201 14.2 Systems of work 201 14.3 Protection from electric shock 202 14.4 Locking off 203 14.5 Ergonomics 205 14.6 Anthropometrics 206 14.7 Openings in guards 206 14.8 Operating instructions and manuals 206 14.9 Labels on equipment 207 14.10 Supervision 207 14.11 Use of jigs and fixtures 207 14.12 Safety clothing 208 14.13 Stored energy 208 14.14 Signs and signals 208 15 Plant layout and the working environment 210 15.1 Introduction 210 15.2 Space 210 15.3 Buildings 211 15.4 Services 211 15.5 Ventilation 211 15.6 Lighting 212 15.7 Temperature 212 15.8 Machine layout 213 15.9 Noise 213 15.10 Vibrations 214 15.11 Materials handling 214 15.12 Maintenance 214 15.13 Waste 214 15.14 Access 215 15.15 Lubrication 215 15.16 Dust and fumes 215 15.17 Floors and foundations 216 15.18 Hygiene 216 15.19 Notices and signs 216 Part V Appendices 217 1. Published standards 219 2. Glossary of terms 227 3. Abbreviations 232 4. Smooth shaft pick-up 234 5. Pipeline colour codes 235 6. Permit-to-work 236 7. Protection of enclosures 238 Index 241