How a Solenoid Valve Works ~ Learning Instrumentation And Control Engineering Learning Instrumentation And Control Engineering

How a Solenoid Valve Works

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As shown above, a solenoid valve is made up of two basic functional units. They are
(1) The solenoid, an electro-magnet with a plunger.
(2) A valve containing an orifice in which a disc or plug is positioned to stop or allow flow.
The valve is opened or closed by movement of the magnetic plunger, or core, which is drawn into the solenoid when the coil is energised (an electric current is passed through it). In A above, the solenoid valve opens when energized allowing instrument air to pass through. In B, the valve closes when the solenoid is de-energized preventing instrument air from passing through but vented to the atmosphere
Solenoid valves have a solenoid mounted directly on the valve body with the solenoid core attached to the valve stem. The core is enclosed and free to move in a permanently sealed tube inside the solenoid coil. This construction provides a compact, leak tight assembly.

Solenoid Valve Configurations And Ratings
Solenoids are often used in valve pneumatic controls to activate the valve. In their simplest form, there are 2-way, 3-way and 4-way pneumatic valves. A 2-way pneumatic valve typically has two outlet ports for instrument air flow in and out. A 3-way valve has two outlet ports and one exhaust or vent port. A 4-way valve has two outlet ports and two exhaust ports and it switches air supply between the two outlet ports. 2-way can be normally open (NO) or normally closed (NC), terms that refer to their normal states without power applied.

Solenoid operated valves use an electrical coil to control the position of a poppet, plunger or spool to open or close a valve. Typical solenoid control voltages are 12VDC, 24 VAC/DC, 120VAC or 240VAC.