LEC IEC60079-29-3 Edition1.02014-03 INTERNATIONAL STANDARD NORME INTERNATIONALE colour nside Explosiveatmospheres Part 29-3: Gas detectors - Guidance on functional safety of fixed gas detection systems Atmospheresexplosives- Partie29-3:Detecteursdegaz-Recommandations relativesalasecurite fonctionnelledessystemesfixesdedetectiondegaz IEC 60079-29-3:2014-03(en-fr - 2 - IEC60079-29-3:2014@IEC2014 CONTENTS FOREWORD. 5 INTRODUCTION.. 1 Scope. 2 Normative references 11 3 Terms and definitions. .11 4 Requirements. 13 4.1 General.. .13 4.2 Demand rate. 13 5 Gas detection unique features ... .13 5.1 Objective 13 5.2 Features.. 5.2.1 General 5.2.2 Sensor location.. 14 5.2.3 Sensorfilterelements (passive). 5.2.4 Sensor filterelements (active) 14 5.2.5 Sensor principles. 14 5.2.6 Poisoning and adverse chemical reaction. 15 5.2.7 ppm.hr or %vol.hr lifetime. .15 5.2.8 Negative gas readings 5.2.9 Hazard and risk analysis.. .15 5.2.10 Preventative effectiveness or mitigation effectiveness 16 5.2.11 Cross sensitivities.. .16 5.2.12 Special states. 16 5.2.13 Metrological performancestandards. 5.2.14 Fault signal handling... 16 5.2.15 Over-range indication.. 5.2.16 Surrogate calibration .16 5.2.17 Maximum/minimumalarm setpoints 17 Functional safety management.. 6 .17 6.1 Objective 17 6.2 Requirements 17 6.3 Competence 18 7 General requirements. 19 7.1 Objective 19 7.2 Requirements 19 7.2.1 .19 7.2.2 Safetyandnonsafetyfunctions 7.2.3 Safety functions of different integrity targets .19 7.2.4 Behaviour under dangerous failure conditions. 7.2.5 Behaviour under safe failure conditions 7.2.6 Behaviour under special state conditions .20 7.2.7 Power supply.... .21 7.2.8 Gas detector... 7.2.9 Gas detection control unit (logic solver). ..21 7.2.10 Final element (actuator).. .22 7.2.11 Visual indication 22 - 3 - IEC60079-29-3:2014IEC2014 7.2.12 Switching outputs .22 7.2.13 Protocol outputs . .24 7.2.14 Protocol inputs. 24 7.2.15 Systemarchitecture,PFDandPFHvalues .24 Gas detection unique requirements 8 .24 8.1 Objectives. ..24 8.2 Requirements ..25 8.2.1 Introduction to gas sampling 8.2.2 Gas sampling... 8.2.3 Gasmultiplexer .26 8.2.4 Gas multiplexer control system.. .27 8.2.5 Conditioning of measured gas ..27 8.2.6 Gas sampling by diffusion mode.. 8.2.7 Automatic calibration and adjustment.. ..28 8.2.8 Automatic calibration and adjustment control system.. .29 9 Alternative control units (logic solvers) ... 9.1 Objectives .30 9.2 Requirements 9.2.1 Performance (metrological) .30 9.2.2 Programming of logic. .30 10 Factory acceptance testing. ..30 10.1 Objectives .30 10.2 Requirements ..30 10.2.1 Planning. .30 10.2.2 Execution .31 Installation and commissioning 11 31 11.1 Objectives. 31 11.2 Requirements 11.2.1 Planning ... 11.2.2 Execution .32 12 System validation .33 12.1 Objectives .33 12.2 Requirements 12.2.1 Planning .... 12.2.2 Execution ..33 13 Operation and maintenance .34 13.1 Objectives .34 13.2 Requirements .34 13.2.1 Planning ... 13.2.2 Execution ..34 14 System modification .35 14.1 Objectives ..35 14.2 Requirements .35 14.2.1 Planning .... 14.2.2 Execution ..35 15 System decommissioning .36 ..36 15.1 Objectives. 15.2 Requirements .36