How Does a Solenoid Valve Work

What is a solenoid valve

A solenoid valve (solenoid valve) is an electromechanically operated valve used to control the flow of a medium, such as gas or liquid. The valve operates based on an electromagnetic coil (the solenoid) that controls a movable core (the plunger).

Main component

• Solenoid (coil): A copper wire coil that generates a magnetic field when electric current passes through it.
• Plunger (core): A metal cylinder attracted to the solenoid's magnetic field. This mechanism opens or closes the valve.
• Valve body: This is the part where the plunger moves and the medium flows. It can be made of brass, stainless steel, or plastic.
• Spring: Ensures the plunger returns to its original position (usually closed) when the magnetic field is turned off.
• Connection Ports: Inlets and outlets through which the medium enters and leaves the valve.

Operation

• In the 'closed' position: When no current flows through the coil, a spring holds the plunger in place, blocking the flow.
• In the 'open' position: When current flows through the coil, it creates a magnetic field that pulls the plunger up. This opens the valve and allows the medium to flow.

Applications

• Industrial processes: include chemical processing, the oil and gas industry, and food production.
• Household appliances: For example, washing machines, dishwashers and coffee machines.
• Medical equipment: Control of gas and liquid flows in medical applications.
• Irrigation systems: Automatic water control in garden and agricultural applications.

Different types of solenoid valves

Different types of solenoid valves

Solenoid Valves come in different types and configurations depending on the application and how they work. Below is an overview of the main types of solenoid valves :

1. Based on the default position

Normally Closed (NC)

• Description: The valve remains closed when the coil is not activated. When activated (electric current), the valve opens.
• Applications: Most common type, used in applications where flow is only required when the valve is activated.

Normally open (NO)

• Description: The valve remains open when the coil is not activated. When activated, the valve closes.
• Applications: Used in systems where flow is required as standard and only occasionally needs to be shut off.

2. Based on the operating method

Directly operated solenoid valve

• Description: The plunger opens or closes the valve directly without external pressure.
• Advantages:
• Suitable for low pressures.
• Fast response.
• Applications: Low pressure systems, such as small water flows.

Indirectly operated (servo-controlled) solenoid valve

• Description: Uses the pressure of the medium itself to open or close the valve. A small amount of force from the solenoid controls a diaphragm or pilot orifice, opening or closing the main valve.
• Advantages:
• Suitable for higher pressures and flow rates.
• More energy efficient.
• Applications: Industrial installations, irrigation systems.

Semi-direct operated solenoid valve

• Description: Combines elements of both direct and indirect operated valves. The solenoid directly assists in opening the central orifice and simultaneously uses the medium pressure.
• Advantages: Suitable for a wider pressure range.
• Applications: General industrial applications.

3. Based on the number of ports

2/2 way solenoid valve

• Description: Two ports, one inlet and one outlet. The valve opens or closes the flow completely.
• Applications: Water, oil and gas controls.

3/2 way solenoid valve

• Description: Three ports and two positions. Allows the flow to be diverted or released.
• Applications: Air operated cylinders, pneumatic systems.

4/2 way and 5/2 way solenoid valves

• Description: Multiple ports and positions for complex flow control. Often used in combination with pneumatic actuators.
• Applications: Industrial automation and hydraulic systems.

4. Based on the medium

Fluid solenoid valves

• Designed for water, oil, and other fluids, it is made of materials that are resistant to corrosion and chemical interactions.

Gas or air solenoid valves

• Suitable for compressed air, nitrogen or other gases. Often used in pneumatic systems.

Special solenoid valves

• For aggressive chemicals or high-pressure applications, often made from specialised materials such as PTFE or stainless steel.

5. Based on the design

Single acting solenoid valve

• The solenoid opens or closes the valve and returns to the default position by a spring.

Double acting solenoid valve

• Uses two coils to open and close the valve without a spring.