Critical Valve Analysis
A critical valve analysis comprises an assessment of the increased consequences to a facility caused by failure to close of an emergency shutdown valve when there is a fire in one of the hydrocarbon segments. Failure to isolate will drain the adjacent segment volume into the segment that leaks and consequently give increased fire duration.
This assessment will rank the emergency shutdown valves in terms of criticality. The results are used to set requirements to testing, e.g. test frequency, closing time and requirement to maximum internal leakage in the valve.