Does RP 521 require the pressure safety valve on our electrostatic treater to be sized for two-phase relief in a fire case?
This question is related to an offshore facility processing oil with density from 27 to 31°API. The facility comprises a horizontal crude oil electrostatic desalter with an internal diameter of 5 meters, a tangent-to-tangent length of 20 meters and a design pressure of 12 barg. The electrostatic desalter is provided with a pressure safety valve. The governing relief scenario for sizing of the pressure safety valve is a fire case for the liquid filled electrostatic desalter. For this relief scenario, section 18.104.22.168 of API Recommended Practice 521 applies.