An Easy and Accurate Design Of Safety Relief Valve Inlet Piping Systems For Gas/Vapor Relief

Safety relief valves used to protect against overpressure require well-designed inlet piping for proper operation. The un-recoverable pressure loss of the inlet piping of a pressure relief valve is required to be less than 3% of the set pressure to avoid chattering and reduction of the flow capacity of the valve. Therefore, the design of proper inlet piping system needs lots of fluid mechanic calculations of trial-and-error to reach the goal of 3% rule and capacity requirement. This article presents an easy and accurate method to design inlet piping systems without any trial-and-error and iteration calculations. According to the required mass flowrate and 3% rule, the maximum velocity head loss of inlet piping system can be easily calculated from classical one-dimensional adiabatic compressible fluid flow principles for gas/vapor relief. Then the inlet piping system (including pipe length, diameter, elbows, Tees, etc.), accordingly velocity head loss, can be easily adjusted to satisfy both 3% rule and capacity requirement. One case study with selection of safety relief valve for gas relief validates the proposed method.