Valve controller

Valve controller

Valves are driven in a variety of ways. Valves with smaller nominal diameters can be electromagnetically opened by electromagnets and coils. They are generally closed with a spring force. For larger valves, the required coil is very large and generates a lot of heat. After the coil is energized, the current can be reduced by internal electronic controls to prevent overheating of the drive. Despite this, valves larger than DN 40 are rarely powered by electromagnetic power.

Pneumatically operated valves are driven using air pressure. The required control pressure is usually in the range of 0.4 to 0.8 MPa. The pneumatic cylinder transmits its motion to the valve plate. If one direction is operated by compressed air and the opposite direction is reset by a spring, this type of drive is called “single acting pneumatic”. If compressed air is required in both directions, it is called "double acting pneumatic". An electropneumatic drive is used if the pneumatic drive head has an electromagnetic control valve that compresses the air inlet and outlet. Here, the air pressure must be applied and must be controlled by a control valve with a control voltage (typically 24 V DC). For conventional pneumatic drives, solenoid valves are also commonly used to control compressed air. However, for example, it is located in the cabinet or, if many valves are connected, it is located on the so-called valve end that houses the control valve. If the control fails, it is usually advantageous when the valve with the return spring falls into the specified valve position. There is a difference between the "normally closed" and "normally open" designs, where the standard is the closed position. In addition to this, the valve can be operated by an electric motor. The intermediate position is also possible if the design permits.

Most valves have an "on/off" optical position indicator that indicates the position of the valve. For automated processes, it is useful or even necessary to obtain actual valve position feedback information, regardless of the switch state. For this purpose, the valve is equipped with a valve position indicator that directly indicates the position of the valve plate. It indicates a fault, such as a compressed air fault or a control valve fault.