How does a single solenoid valve work?

Dec 04, 2025

What is a single acting solenoid valve?

A single solenoid valve is a type of valve that uses an electromagnetic coil to control the flow of air, gas, or liquid in a system. It is widely used in automation and fluid control applications due to its simple structure, fast response, and reliable on/off operation.

Single-acting solenoid valves are used in both pneumatic and hydraulic systems due to their simple structure and low cost. Solenoid valves with a more robust structure and stronger pressure resistance, used in hydraulic systems, are called single-acting hydraulic solenoid valves; similarly, solenoid valves with weaker pressure resistance, used in pneumatic systems, are called single-acting pneumatic solenoid valves.

The main components of a solenoid valve

To understand how it works, we first need to learn about its key parts:

Coil: An electromagnet that generates a magnetic field when energized.

Valve Core/Plunger: A movable metal rod inside the coil that is attracted by the magnetic force.

Spring: Provides a force opposite to the electromagnetic force, used to reset the valve core.

Valve Orifice: The opening through which fluid (air, water, oil, etc.) flows.

Seal: Typically attached to the valve core, used to open or close the valve orifice.

How does a single solenoid valve work?cid=861

The Working Principle of Single-acting Solenoid Valve

The operation of a single-acting solenoid valve is not complicated; it will be explained in two main states.

State 1: Power off state

No power supply: The coil is not powered, and the electromagnet does not work.

Spring force action: The spring is in an extended or natural state, pushing the valve core downwards.

Sealed closure: The valve core tightly presses the seal onto the valve port, blocking the fluid passage.

Result: The valve is in the closed state. The fluid cannot flow from the inlet (P) to the outlet (A).

State 2: Power on state

Electrification: When current passes through a coil, a strong magnetic field is generated.

Electromagnetic force effect: Magnetic force will attract the valve core and overcome the spring force to move upward.

Spring compression: The movement of the valve core compresses the spring.

Seal opening: The valve core is lifted, driving the seal away from the valve port and opening the fluid channel.

Result: The valve is in the open state. The fluid can now flow freely from the inlet (P) to the outlet (A).

Advantages and disadvantages of using single acting solenoid valves

Advantages:

Simple and reliable structure: few parts, low failure rate, and low cost.

Fault safety: It can automatically restore to the default state when power is cut off, with high safety.

Low energy consumption: Usually only consumes electricity when changing state (in one direction).

Disadvantages:

Spring limitation: Electromagnetic force must overcome spring force, which limits the working pressure range of the valve and is usually not suitable for ultra-high pressure applications.

Single function: can only control one action. For devices that require precise control of two directional movements (such as double acting cylinders), dual electronic control solenoid valves are required.