In the production process, in order to make the medium pressure, flow and other parameters in line with the process requirements, the need to install the adjustment mechanism to adjust the above parameters. The main working principle of the adjusting mechanism is to change the valve disc and the flow area between the valve disc and valve seat to achieve the purpose of adjusting the above parameters. Belong to this type of valve collectively referred to as the control valve, which is divided into rely on the media itself driven by self-driven control valves such as pressure relief valves, pressure regulators, etc., where the leading power-driven (such as electricity, compressed air and liquid Power) called his drive control valves, such as electric control valve, pneumatic control valve and hydraulic control valve.