What is Solenoid Valve? Working Principle & Function | Linquip
Solenoid Valve

What is Solenoid Valve? Working Principle & Function

A Solenoid Valve is an electrically controlled valve. Solenoid valves differ in terms of the properties of the electric current they utilize, the strength of the magnetic field they generate, the mechanism they use to govern the fluid, and the type and qualities of fluid they control. Because solenoid valves are solenoid operated, they can be placed in remote locations and controlled by simple electrical switches. Solenoid valves are control units that shut off or allow fluid flow when electrically energized or de-powered. An electromagnet is used as the actuator. When electrified, a magnetic field forms, pulling a plunger or pivoted armature against the spring's action. Solenoid valves are the most often used control devices in fluidics. They're typically utilized to turn liquids off, release, dose, distribute, or mix. 

What Is Solenoid Valve | Linquip

An overview of a solenoid valve configuration (Reference: researchgate.net)

What Is Solenoid Valve?

Solenoid valves are electromechanically operated valves. As a control element, solenoid valves are among the most commonly used in fluidics. Their tasks include releasing, administering, distributing, mixing, or shutting off fluids. Different solenoid valves come in a variety of sizes, shapes, and configurations, with different types of electric current, magnetic fields, pressure regulation mechanisms, and fluid types and characteristics. "Solenoids" are the generic terms for solenoid valves.

Many different applications rely on them. They are fast, reliable, and safe switching devices, able to operate for a long time, compact in design, medium compatible, and use minimal power.

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Working Principle of Solenoid Valves

A solenoid valve is a control unit that shuts off or allows fluid flow when electrically energized or de-energized. Electromagnets serve as actuators. When energized, magnetic fields pull a plunger or pivot armature against the force of a spring. It can be categorized into three types of valves based on the mode of actuation: direct-acting, internally piloted and externally piloted valves. Flow paths ("ways") or the number of port connections are other distinguishing features.

The principle that solenoid valves use to open and close is basically this: The valve contains a solenoid, a coil consisting of a ferromagnetic core (plunger) at its center that can move. The plunger closes off the orifice in the rest position. The coil creates a magnetic field when an electric current flows through it. An upward force pushes the plunger upwards, opening the orifice.

Function of Solenoid Valves

When the flow of fluid needs to be controlled automatically, solenoid valves are applied. Their use has increased in a wide range of plants and equipment. With all the options on offer, it is possible to select the valve that is most suited to the application at hand. A solenoid valve is an electrically activated valve that controls the flow or direction of liquids or air in fluid power systems.

Pneumatic and hydraulic systems commonly use solenoid valves, which have either a poppet or a spool configuration. In some solenoid valves, switching and staying in that position (depending on the type) can result in hot spots.

Solenoid valves use a variety of actuator mechanisms, ranging from linear action actuators, plunger-type actuators, and pivoted-armature actuators. Valve designs can consist of two ports to regulate a flow or three or more ports to switch flows between ports. It is possible to group several solenoid valves in a manifold.

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Components of a Solenoid Valve

Components of a Solenoid Valve | Linquip

Components of a solenoid valve (Reference: valveproducts.net)

Choosing the correct solenoid valve can have a significant impact on how the machine, system, or process will perform in the long run. This control valve has many functions, and understanding its basic parts will make it easier to understand how it works. The following figure shows an illustration of a normally closed, direct-acting solenoid valve.

According to the figure, the valve contains the following parts:

  1. Valve body: The valve body is the part to which the solenoid valve is attached.
  2. Inlet port: Fluid enters the automatic valve through the inlet port, gaining access to the eventual process.
  3. Outlet port: By connecting the outlet port to the process necessitating fluid, the fluid flowing through the automatic valve is discharged.
  4. Coil Solenoid: A steel-covered cylindrical coil of wire that is inside the valve acts as a current-carrying coil as the current passes through it.
  5. Coil windings: In completed solenoid coil assemblies, enameled wires are wrapped around the ferromagnetic material like steel in a tightly packed spiral. Within the hollow section of the coil, there may be a plunger or piston. Plunger movement is controlled by the spring within the coil.
  6. Lead wires: These are the connections on the outside of the valve, through which the current from the power supply is passed. When the power is turned off, the current flow stops.
  7. Plunger or piston: When current passes through the control valve, it creates a magnetic field within the hollowed-out space of the valve in which the metallic plunger or piston is positioned.
  8. Spring: This makes the plunger control the fluid and moves the plunger or piston only when the current passes through the solenoid valve.
  9. Orifice: The inlet and outlet ports are connected by this. The spring and the current moving through the valve control the motion of the plunger or piston, which in turn controls the orifice's opening.

In the beginning, the sensor detects the process going through the valve outlet. The sensor ends the current flow to the valve as soon as it identifies no need for the fluid. This, in turn, causes power loss in the valve and the plunger or piston to move towards the bottom, closing the orifice. By doing this, fluid flow will be interrupted between the inlet and outlet ports.

Usage of Solenoid Valves

In a pipe, solenoid valves control gas or liquid flow by closing, opening, dosing, distributing, or mixing. Solenoid valves serve specific purposes determined by their circuit functions.

The solenoid valve is commonly employed in systems used for fluid power pneumatics and hydraulics to control cylinders, motors, and large industrial valves. Solenoid valves are also applied in automatic irrigation sprinkler systems. Solenoid valves control water entry to domestic washing machines and dishwashers. These are also commonly used in paintball gun triggers to act as the CO2 hammer valve.

The solenoid valve is a versatile component used in many industries, including on-off control, calibration and test stands, control loops in pilot plants, process control systems, as well as various OEM (Original Equipment Manufacturer) applications.

Common Applications of Solenoid Valves

Common Applications of Solenoid Valves | Linquip

Application of solenoid valve in water supply system (Reference: pinterest.com)

Applications of solenoid valves include the following items:

  • Solenoids are only used for liquids or gases that are clean.
  • By using a solenoid valve, media can be closed, opened, dosed, distributed, or mixed with two or more inlets or outlets.
  • Solenoids are fast-acting valves.
  • Solenoids can be used for overrides, ATEX, gas approval, and media separation, among other things.
  • Solenoids are commonly found in heating systems, compressed air, vacuums, irrigation, and car washes.

Material of Solenoid Valves

Valve materials are carefully selected according to the different types of applications for which the valves are used. Materials for body parts, seals, and solenoids are selected so as to maximize durability, fluid compatibility, and lifespan.

Various housing materials are available for solenoid valves. Typical materials are Nylon, PVC, Brass, Nickel plated brass as well as Stainless Steel. Chemical properties and medium temperature play a large role in material selection.

There must be compatibility between the seals and the fluid. Seal materials should be selected based on the mechanical, thermal, and chemical conditions of the application.

Because the plugnut, core, springs, shading ring, and other components would often be exposed to fluid, they also must be compatible. Several issues arise from the requirements. For the solenoid field to pass through the core and the plugnut, the core tube needs to be non-magnetic. The plugnut and core need to be made of a material with good magnetic properties, such as iron. Iron, however, is prone to corrosion. Instead, the use of stainless steel is possible because it is available in both magnetic and non-magnetic varieties.

FAQ about Solenoid Valve

  1. What is a solenoid valve used for?

The solenoid valve is the most frequently used control element in fluidics. In general, they are applied to shut off, release, dose, distribute, mix or distribute fluids. Because of that, they are found in many fields.

  1. How does a solenoid valve work?

By electrically energizing or de-energizing solenoid valves, they shut off or allow fluid flow. An electromagnet is used as the actuator. A magnetic field is generated that pulls a plunger or pivot against the spring's action.