Does anyone know of any situation where it would be required (or beneficial) for process reasons or otherwise, to have a pressure safety valve set at significantly less than MAWP, and hence allow overpressure to exceed 10% (for single, non fire case valve).
To allow overpressures >10% when...
Does anyone have any info. on the following:
1. What is the basis for the 10% allowable overpressure specified by API520? Is it to do with the 0.9 derating factor used by vendors to determine capacity?
2. What is the basis for 21% allowable overpressure for 'fire case' relief valves.
3. Why...
