Experimental Study of Fluid Forces on Direct-Acting Relief Valves

Safety valves as the last barrier of the pressure vessel and piping system ensure the stability of the whole system. However, there are specific situations where valves may not operate properly, which can have a significant impact on the safety of the entire system. The reason for this is a lack of understanding of the dynamic characteristics of valves, of which fluid forces are the most critical factor. In this paper, a high-precision test rig was built to test steady-state fluid forces of a direct-acting relief valve, where proportional-integral-derivative control (PID) control was applied in order to obtain more accurate multi-stage flow rates adjustments. In addition, a adjustment mechanism has been designed to obtain a more accurate valve opening. Based on this test rig, the steady-state fluid force at different openings and different flow rates are conducted, the relationship between fluid forces, flow rates and pressure drop of the valve is analyzed from the test data, which provide an in-depth understanding of the dynamic characteristics of the valves.