Solenoid Actuated Valves:

Solenoid actuated valves gives for automatic open-close valve positioning as described in Figure. Most solenoid actuated valves also have a manual override that permits manual positioning of the valve for as long as the override is manually positioned.

Solenoids position the valve through attracting a magnetic slug attached to the valve stem. Within single solenoid valves and spring pressure acts against the motion of the slug while power is applied to the solenoid. These valves could be arranged such in which power to the solenoid either opens or closes the valve. While power to the solenoid is erased that the spring returns the valve to the opposite position. Two solenoids could be used to gives for both opening and closing through applying power to the suitable solenoid.

Figure: Solenoid Actuated Valve

One solenoid valves are termed fail open or fail closed depending on the position of the valve within the solenoid de-energized. Fail open solenoid valves are opened through spring pressure and closed through energizing the solenoid. Fail closed solenoid valves are closed through spring pressure and opened through energizing the solenoid. Double solenoid valves classically fail "as is." That is, a valve position does not modify while both solenoids are de-energized. A single application of solenoid valves is within air systems such as those used to supply air to pneumatic valve actuators. A solenoid valves are used to control the air supply to the pneumatic actuator and therefore the position of the pneumatic actuated valve.