Regulating valves, also known as control valves, are composed of actuators and valves. Their medium are suitable for air and water. Steam corrosive medium, mud, oil and so on. According to the different power used by the actuator, the regulating valve can be divided into three types: electric, pneumatic and hydraulic. Now we introduce pneumatic control valve as an example. The control valve consists of valve body, seat, valve spool, valve stem, packing, valve stem, thrust rod, lower membrane cover, compression spring, diaphragm, upper membrane cover and other components.
Fault analysis, when valve action, check whether there is air supply, if there is air supply, check whether the valve is jammed, generally we can take knock valve body if it can be solved. If not, the valve body needs to be removed for inspection.If Valve action is unstable, check whether the pressure of air supply is stable, if air supply unstable, check whether there is leakage from air source pipe, check nozzle, location plate and spring, check whether the valve packing is too tight, check whether the front valves and behind valves of the control valve are open at the same time, If there are too much gap pressure,It will be cause valve instability, when the valve is not fully opened, It should be checked whether the air pressure can meet the pressure requirements for valve opening, when the valve is not closed, it should be checked whether the air pressure can meet the pressure requirements for valve closing, and check the stem if it located in closing state. If the valve is still leaking when the stem locating in the closing state, it may be the problems with the valve spool, or seat corrosion or valve spllo falling off, So it need to open the valve body for inspection