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PST
Identify hazards and
potential safeguards
• May have several cases
• Identify the most
conservative case
(shortest PST)
Establish approach
• Qualitative
• Simplified Quantitative
• Rigorous Quantitative
Use design or
operating data
• Basic process information
• Equipment design
limitations
• Design data
Calculate PST
• Required for all SIFs with
SIL 1 and above
Slide 6
Challenges in Achieving Safety Instrumented Function Response Time for a Fast-Acting Process• K. Rampaul, A.
Barnwell & S. Sookhoo