Handbook of Reliability, Availability, Maintainability and Safety in Engineering Design - Part 67 studies the combination of various methods of designing for reliability, availability, maintainability and safety, as well as the latest techniques in probability and possibility modelling, mathematical algorithmic modelling, evolutionary algorithmic modelling, symbolic logic modelling, artificial intelligence modelling, and object-oriented computer modelling, in a logically structured approach to determining the integrity of engineering design. . | 644 5 Safety and Risk in Engineering Design Fig. High-integrity protection system HIPS Table Component functions for HIPS system Component Code Function Failure modes A and mean repair time Maint. interval Main PCV V1 Stop high-pressure surge passing through system Valve fails open PCV-M 4 360 Sub-PCV V2 Stop high-pressure surge passing through system Valve fails open PCV-S 4 360 ESD valve V3 Stop high-pressure surge passing through system Valve fails open V-ESD 4 360 HIPS1 V4 Stop high-pressure surge passing through system Valve fails open VH1 4 360 HIPS2 V5 Stop high-pressure surge passing through system Valve fails open VH2 4 360 Solenoid Sol Supply power to valves Fails energised PCVs M S and ESD and SH1 SH2 4 360 Relay contacts RC Supply power to solenoids 2 per solenoid Fails closed R1-R10 10-6 4 360 Pressure sensors PrS Indicate the level of pressure to the computer Fails to record actual pressure P1-P6 10-6 4 360 DCS DCS Reads information sent from pressure sensors and acts to close values Fails to read or act on information 10-5 4 360 a high-pressure surge originating from process circulation pumps to protect equipment located downstream of the process. The first level of protection is the emergency shutdown ESD sub-system. This comprises three pressure sensors P1 P2 P3 for which two out of three must indicate a high pressure to cause a trip. Two pressure control valves PCVs a main Theoretical Overview of Safety and Risk in Engineering Design 645 PCV a subsidiary PCV and an emergency shutdown ESD valve V1 V2 V3 activate to trip. If a high-pressure surge is detected the ESD sub-system acts to close the main PCV the sub-PCV and the ESD valve. To provide an additional level of protection a second sub-system is included the high-integrity protection sub-system HIPS . This sub-system also comprises three pressure sensors P3 P4
