Safety Valve Reaction Forces

Abstract

Translate Article

A combination of back pressure and sudden impulses generate reaction forces when the safety valve is open and blowing. Although the reaction forces at the inlet are relatively small, the majority of the reaction forces are generated at the outlet. This is due to the fact that high velocity and an increase in outlet pressure are expected. Particularly in the case of gas (compressible) service, the main reaction force is generated at the outlet. Taking into account the impact of the pressure safety valve (PSV) load, ensure that the pipework is adequately supported. It is important to note that reaction forces in safety valves are determined by the pressure of the fluid or gas flowing inside the valve as well as the size of the valve. Two safety valve standards explain how reaction forces are calculated: ISO 4126-9 and API 520. In accordance with ISO 4126-9, PSV reaction forces should be calculated based on steady-state flow conditions. A steady state flow is characterized by constant fluid properties throughout the system. According to API 520, different equations are provided for the calculation of reaction forces for gas, vapor, and steam services open discharge into the environment. To calculate the safety valve loads for open discharge of liquids and two-phase fluids, two separate equations are provided based on API 520. A limit for the acceptance of safety valve reaction forces is provided at the end of the chapter in accordance with ASME B31.3.