An electric solenoid valve is a fluid or gas control device that relies on a solenoid to raise or lower a valve from its seat. The solenoid works in conjunction with a return spring designed to return the valve to its neutral position when the solenoid is deactivated. This type of valve is used to remotely open and close valves in inaccessible locations, in multi-valve systems, and in proximity to hazardous environments. Solenoid valves offer only fully open or fully closed functions, and can't be used to throttle or incrementally control a flow of gas or fluid. The coils used in electric solenoid valves may be rated for alternating current (AC) or direct current (DC) in a range of voltages and duty cycle durations.
Solenoids are a very useful and convenient source of remote actuation of fluid and gas control valves. A solenoid operates on an electromagnetic principle where an electric current is passed through a coil that generates a strong magnetic field. A solenoid plunger made of ferrous metal is attracted by this magnetic force and is pulled into the center of the coil, thereby providing the linear motion needed to actuate the valve. This linear motion is used to lift a valve plug onto or off of a seat that either opens or closes the valve. These two modes of operation are known as normally open or normally closed.
Once activated, the electric solenoid valve will keep the valve open or closed until the supply of power to the coil is cut. At that point, a strong spring that surrounds the solenoid plunger pulls it back into the neutral position and reinstates the valve's secondary status. The fact that no direct, physical operator action is required makes the electric solenoid valve an ideal solution for fluid or gas flow control in inaccessible locations or where environments featuring high temperatures, dangerous chemicals, and gasses or moving machinery make for hazardous working conditions.
The electric solenoid valve can only function as a open or closed device and cannot be used to incrementally open or close the valve in applications where a throttle function is required. The valves may feature coils rated for continuous or limited duty cycles depending on the intended end use. A wide range of AC and DC voltages are catered for, with DC voltages typically ranging from 12 to 24 volts and AC varieties from 24 to 600 volts. Electric solenoid valve coils may also be enclosed in flameproof and explosion-proof enclosures for use in hazardous environments.