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RELATIONSHIP BETWEEN PST AND SIFRT
• Design margin should account for:
• Inaccuracies in the design
• Degradation in performance over the SIF lifetime
• Not clearly defined in industry standards
• Industry rule of thumb is SIFRT should respond in
less than half the PST
• Should be evaluated and defined early
• An iterative process
Slide 9
Challenges in Achieving Safety Instrumented Function Response Time for a Fast-Acting Process• K. Rampaul, A.
Barnwell & S. Sookhoo