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Solenoid operated valve

Solenoid valve

A solenoid valve or SOV is an electro mechanically operated valve.

 This is controlled by an electric current through a solenoid coil, a magnetic field is produced in the electrical coil which mechanically operates the plunger of the valve and hence changes the path of air or fluid from one direction to another direction.

Types of solenoid valve:

2/2-way solenoid valve

This type of valve has 2 ports and it acts in  2 positions. 

It means the solenoid valve has two ports one is the inlet port and another port is the outlet port, material passing through the solenoid valve either pneumatic or fluid is applied to the inlet port and exhausted through the outlet port.

Two-position of solenoid valve means that its piston or plunger has two-position, either valve is open or close.




3/2-way solenoid valve

 This type of valve has 3 ports and 2 acting positions.









5/2 way solenoid valve

 This type of valve has 5 ports and 2 positions.




Types of a solenoid valve according to operation 

Direct-acting

Any Medium air (pneumatic) or fluid (oil or water etc), flows through the orifice of SOV and the path is closed or open when the valve is activated through an electric signal or by a manual lever.





Indirect operated SOV

 (Servo or pilot operated)

A diaphragm is operated to change the path of fluid, like auto drain valve, etc.








Types of a solenoid valve according to valve normal position

Normally open

This is a type of solenoid valve in which at the normal position when the solenoid valve is not energized and there is no power at coil then the valve is open and fluid or air can pass through the valve from one port to another.

Normally close


This is a type of solenoid valve in which at the normal position when the solenoid valve is not energized and there is no power at the coil then the valve is closed and fluid or air can not pass through the valve from one port to another port.

Types of SOV according to supply

Ac  supply  usually 220v or 110 volts

or dc supply usually 24 or 12 volts

Parts of solenoid valve








Common faults in solenoid valve








  • Coil burnt or open circuit — usually caused by continuous over voltage, a stuck plunger preventing the coil from de-energizing properly, or simple end-of-life failure. Check coil resistance with a multimeter against the manufacturer's rated value; an open or drastically low reading confirms a burnt coil.
  • Plunger stuck — dirt, rust, or scale buildup inside the sleeve can jam the plunger in either the open or closed position. This is one of the most common SOV faults in dusty or humid plant environments and is usually fixable by cleaning without replacing the whole valve.
  • No supply voltage reaching the coil — check upstream at the terminal block, junction box, and control relay/PLC output before condemning the valve itself.
  • Diaphragm or seal damaged (pilot-operated types) — a torn or worn diaphragm prevents the valve from fully opening or closing, often showing up as a partial or sluggish response rather than a complete failure.
  • Debris or scale in the orifice — contamination in the pneumatic or fluid supply can lodge in the small internal orifice, causing partial blockage, slow response, or valve chatter.
  • Wrong voltage/frequency coil installed — a common field mistake after replacement; a 220V AC coil installed where a 24V DC coil is specified (or vice versa) will either fail to actuate or burn out quickly. Always confirm the coil rating matches the original before swapping.
  • Valve chatter/humming — usually caused by low supply voltage, a worn plunger assembly, or AC ripple on a coil that should be receiving clean DC.

Field tip: Before replacing a solenoid valve outright, isolate whether the fault is electrical (coil) or mechanical (plunger/diaphragm/orifice) — energize the coil and listen/feel for the plunger click. A valve with a healthy audible click but no flow change points to a mechanical blockage or seal issue; a valve with no click at all points back to the coil or its supply.


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