This paper describes methodology used to determine the SIL of a partial final element consisting of an Emergency Release Coupling (ERC) assembly and the effect that the remaining final element devices have on the SIL of the final element. The paper addresses the effect that the configuration of the final element has on PFDavg.
The results are presented in the form of tables that demonstrate the SIL that can be achieved using various proof test coverages and mission times. The 1H and 2H approaches to architectural constraints are addressed along with a reference to table 6 of IEC61511 section 11.
Whitepapers in the Series:
→ Analysis of a Ball Valve / ERC Assembly
→ Analysis of Architectural Constraints Applied to an ERC Assembly
→ Comparison of ETT and DTT Interface Designs for an ERC Assembly