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Challenge for SIL assessment - frequency
• Frequency will depend on number of opportunities and operator error rate
• Clear definition of sequence of events which initiate the hazard essential
• What is the correct Operating Procedure? (not yet developed)
• Restart from different valve positions – e.g. which valves are closed in PSD or
ESD logic…. Requires C&E logic which may be subject to change
It’s important to later verify that the Operating Procedures written match the
assumptions made in the SIL assessment.
Very much the same questions for the multiple Cargo pump cases…