Relief Valves in Parallel

摘要

It has become standard practice in some facilities to open the block valves to identical and parallel, 100%-sized relief valves thus leaving both relief valves in service when that was not the design intent. During a recent Hazards and Operability Study, (HazOp), block valves under dual relief valves were shown as CSO and CSC, (Car-Seal Open or Closed) on the Piping & Instrumentation Diagram, (P&ID). The intent was to keep a fresh spare relief valve closed to the process thus facilitating maintenance and testing. This is a common design practice.