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©ABBGroup
October23,2016|Slide11
Three Criteria for a SIL Compliant Design
§ The Control/ Instrument / Electrical engineer has to demonstrate three
criteria are met for a compliant SIF design:
1. Control of Random Hardware Failures – these are the PFDavg
calculations
2. Meet Architectural Constraints – Hardware Fault Tolerance
3. Control of Systematic Faults
§ The issue with the certificate seemed to be related to claims for
Hardware Fault Tolerance (HFT)
©ABBGroup
October23,2016|Slide12
Ways to Address Hardware Fault Tolerance
§ BS EN 61511-1 Ed 1 Tables 5 and 6
§ BS EN 61508-2 Ed 2 Route 1H - Type A/ Type B and Safe
Failure Fractions
§ BS EN 61511-1 Ed 1 Prior Use
§ BS EN 61508-2 Ed 2 Route 2H