Detail of GB/T 21109.2-2007

Introduction of GB/T 21109.2-2007

1 Scope This part provides guidance on the specification, design, installation, operation and maintenance of safety instrumented functions and related safety instrumented system as defined in GB/T 21109.1. To facilitate use of GB/T 21109, the clause and subclause numbers provided are identical to the corresponding normative text in GB/T 21109.1 (excluding the annexes). 2 Normative references See GB/T 21109.1. 3 Terms, definitions and abbreviations See GB/T 21109.1 for the terms, definitions and abbreviations. The following terms in GB/T 21109.1-2007 are explained in this part. 3.2.68 safety function A safety function shall prevent a specified hazardous event. For example, “prevent the pressure in vessel #ABC456 exceeding 100 bar.” A safety function may be achieved by a) a single safety instrumented system (SIS), or b) one or more safety instrumented systems and/or other layers of protection. In case b), each safety instrumented system or other layer of protection shall be capable of achieving the safety function and the overall combination has to achieve the required risk reduction (process safety target). 3.2.71 safety instrumented function Safety instrumented functions are derived from the safety function, have an associated safety integrity level (SIL) and are carried out by a specific safety instrumented system (SIS). For example, “close valve #XY123 within 5 s when pressure in vessel #ABC456 reaches 100 bar”. Note that components of a safety instrumented system may be used by more than one safety instrumented function.

Contents of GB/T 21109.2-2007

Foreword I Introduction II 1 Scope 2 Normative references 3 Terms, definitions and abbreviations 4 Conformance to GB/T 21109 5 Management of functional safety 5.1 Objective 5.2 Requirements 6 Safety life-cycle requirements 6.1 Objectives 6.2 Requirements 7 Verification 7.1 Objective 8 Process hazard and risk assessment 8.1 Objectives 8.2 Requirements 9 Allocation of safety functions to protection layers 9.1 Objective 9.2 Requirements of the allocation process 9.3 Additional requirements for safety integrity level 4 9.4 Requirement on the basic process control system as a layer of protection 9.5 Requirements for preventing common cause, common mode and dependent failures 10 SIS safety requirements specification 10.1 Objective 10.2 General requirements 10.3 SIS safety requirements 11 SIS design and engineering 11.1 Objective 11.2 General requirements 11.3 Requirements for system behaviour on detection of a fault 11.4 Requirements for hardware fault tolerance 11.5 Requirements for selection of components and subsystems 11.6 Field devices 11.7 Interfaces 11.8 Maintenance or testing design requirements 11.9 SIF probability of failure 12 Requirements for application software, including selection criteria for utility software 12.1 Application software safety lifecycle requirements 12.2 Application software safety requirements specification 12.3 Application software safety validation planning 12.4 Application software design and development 12.5 Integration of the application software with the SIS subsystem 12.6 FPL and LVL software modification procedures 12.7 Application software verification 13 Factory acceptance testing (FAT) 13.1 Objectives 13.2 Recommendations 14 SIS installation and commissioning 14.1 Objectives 14.2 Requirements 15 SIS safety validation 15.1 Objective 15.2 Requirements 16 SIS operation and maintenance 16.1 Objective 16.2 Requirements 16.3 Proof testing and inspection 17 SIS modification 17.1 Objective 17.2 Requirements 18 SIS decommissioning 18.1 Objective 18.2 Requirements 19 Information and documentation requirements 19.1 Objectives 19.2 Requirements Annex A (Informative) Example of techniques for calculating the probability of failure on demand for a safety instrumented function Annex B (Informative) Typical SIS architecture development Annex C (Informative) Application features of a safety PLC Annex D (Informative) Example of SIS logic solver application software development methodology Annex E (Informative) Example of development of externally configured diagnostics for a safety-configured PE logic solver Figure 1 Overall framework of GB/T 21109 IV Figure 2 BPCS function and initiating cause independence illustration Figure 3 Software development life cycle (the V-model) Figure B.1 Model used to achieve SIL Figure C.1 Logic solver Figure E.1 EWDT timing diagram Table 1 Typical Safety Manual organisation and contents Table B.1 Typical SIS lifecycle steps