A solenoid valve actuator is a device that can open or close a valve by applying an electrical current to an electromagnet coil, causing a control rod or arm to move. Actuators are used wherever valves are controlled in remote locations or when continuous valve control is needed. Valve actuators are operated by manual switches in a control room, or by control systems connected to sensors in a manufacturing process. The term solenoid refers to the electric coil magnet, or electromagnet, used to control the valve.
Valves are used to control air, water and nearly all other gases and liquids. They can be as simple as a one-quarter turn ball valve used on a water line to complex control valves connected to software monitoring a chemical reaction. Any time a valve needs to be controlled from another location, a solenoid valve actuator can be used.
The solenoid valve actuator contains an electromagnet surrounding a control arm with a magnet attached at the end. Electric power sent to the electromagnet creates a magnetic field around the control arm. The control arm can move because the magnet is attracted or repelled by the electromagnet.
These controls may turn a separate valve stem or wheel, or can act directly as the stem. A spring normally keeps the valve stem closed until the electric field is applied and the valve opens. The amount of valve opening is dependent on the electrical current applied, and control software can be used to move the valve in small amounts.
Gate valves use a flat plate that opens and closes with a geared shaft; the solenoid can control a valve wheel that operates the gate. A ball valve normally requires one-quarter turn on or off, and can be solenoid controlled. Globe valves use a valve stem fitted in a machined seat that can be controlled with the solenoid valve actuator.
Needle valves are used in equipment requiring lower flow rates, using small needle-shaped valve stems controlled by a solenoid. Larger butterfly valves can be controlled to supply water to generators in dams, creating hydroelectric power. Similar valves can control cooling water to chemical processes. Anywhere a valve needs to be controlled rather than simply turned on and off, a solenoid valve actuator may be used.
Electric circuits can create problems in explosive environments, or when flammable chemicals are present. Air pressure can be used to control valves in these environments. Not considered solenoids because of the lack of an electric current, pneumatic or air actuators can be controlled similarly to a solenoid valve actuator.