Replacement solenoid coils for pneumatic control valves are needed when the electric solenoid in the valve control system wears out or breaks. Solenoids are a type of electromagnet comprising a coil wrapped around a magnetic core that generates a uniform magnetic field. They are often used as a control mechanism, and in this case they provide an interface between the pneumatic system and the electrical controller.
Solenoid coils form part of the control system of some types of pneumatic control valves. When an electric current is applied to the solenoid, it is active and the valve is therefore open. When there is no electric current the valve remains closed.
The main difference between different types of solenoid coils for pneumatic control valves is their operating power supply voltage, and their power consumption. They can also be specifically designed for use use with a particular type or brand of control valve.