The objective is to specify the requirements for the safety instrumented functions.
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To define the safe state of the process for each identified safety instrumented function;
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The assumed sources of demand and demand rate on the safety instrumented function;
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Requirement for proof-test intervals;
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Response time requirement for the sis to bring the process to a safe state;
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The safety integrity level and mode of operation(demand/continuous) for each safety instrumented function;
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A description of SIS process measurements and their trip points;
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Requirements relating to energize or de-energize to trip;
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Requirement for resetting the SIS after a shutdown.
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Maximum allowable spurious trip rate ; as per IEC 61511.