Bench Set Impact Analysis on Fail-Safe Condition of Fail to Closed Type Control Valve with Spring-Diaphragm Actuator

Control valve is one of key elements in processing of a chemical industry and it is one of its important functions is as a flow control of chemical process. The accuracy of control valve opening or traveling is proportional to flow capacity. On the other hand, a leakage of a control valve on its failed position especially for Air to Open-Fail Closed (ATO-FC) type valve can become a disaster. One of critical parameters in Control Valve that impacts to performance and fail-safe position is Bench set range spring in valve’s actuator. This work analyzed this Bench set range impact to the fail-safe position. The force in spring is defined by control valve specification verified by force balance method of control valve. Then the impact of bench set range was analyzed by displacement of spring from spring force equation. At the end, the outcome is displacement data in correlation to the change of bench set range. It helps the repair technician on the maintenance workshop of permissible range when they adjust the bench set range by adjusting spring compression.