Safe Design Consideration for Overpressure Protection via Depressuring Valves

Abstract

Depressuring valves are used in the oil and gas industry to release fluid in a controlled manner in the event of an overpressure, upset, or shutdown of a plant. API 521 provides guidance on how and when to utilize depressuring valves but do not clearly indicate cases where a plant might prefer to configure multiple depressuring valves instead of a single depressuring valve. Refining and offshore oil explorations are two areas where knowing a reasonably optimum configuration of the number and set point of the valves could meet the constraints of operation while meeting the safety requirements and disposal system design limitations. This paper provides basic guidelines for consideration and highlights the theory behind depressuring through valves, so that practitioners can make preliminary safe design assessments. In addition, the impact of depressuring valves design on disposal system, such as flare header system, is presented.