Before going further let us understand first that what is a solenoid valve, why we need to study about solenoid valves, and where it is used – its applications. Then we will discuss how to identify a solenoid valve, its various components, the working procedures, and different types of solenoid valves.

What is a Solenoid Valve?

A Solenoid valve is an electromechanically operated valve which is used to regulate the flow of gas or liquid. It is controlled by electrical current which runs through the coil. The detailed working will be discussed further.

Why Solenoid Valves are used?

Solenoid valves are the most frequently used control elements in fluid mechanics. They are used to shut off, release, dose, distribute or mix fluids and found in many application areas. Solenoid present in the Solenoid valve promotes fast and safe switching, high reliability, long service life, good medium compatibility of the materials used, and low control power and compact design.

Where solenoid valves are used?

Solenoid valves are utilized in fluid power pneumatic and hydraulic systems to regulate cylinders, fluid power motors, or larger industrial valves. Domestic washing machines and dishwashers also use solenoid valves to control the amount of water into the machine. Solenoid valves are usually referred to as “solenoids.”
Solenoid valves are often used for a good range of commercial applications that incorporates general on-off control, calibration and test stands, pilot plant control loops, process control systems, and various equipment manufacturer applications.

How does a solenoid valve look?

These are some of the images of different types of solenoid valves based on their uses. A Solenoid Valve is mainly made up of two parts – solenoid and valve body as shown below in the fig.

Various Components of a Solenoid Valve:-

Various Parts of Solenoid Valve
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How does a Solenoid Valve work?

The sensor present in the Solenoid valve senses the process towards the outlet side of the solenoid valve. After sensing that certain quantity of the flow of the fluid is required, it allows the current to pass through the solenoid valve which energises the valve and the magnetic field is generated which triggers the movement of the plunger against the action of the spring. It makes the plunger to move in upwards direction, which allows the opening of the orifice. At this instant the flow of the fluid is allowed from the inlet port to the outlet port.

When the current passing through the solenoid valve remains constant, the position of the plunger and the opening of the orifice remains constant. And when the sensor senses that more flow of the fluid is required, it allows the increase in current through the solenoid valve, which creates more magnetic field and thus more upwards motion of the plunger. This results in further opening of the orifice and more flow of the fluid from the inlet port to the outlet port. And if the required flow of fluid is less, the sensor allows passage to reduce current to the solenoid valve.

If the sensor senses that the fluid is no more required in the process, it stops the flow of the current to the solenoid valve completely which de-energises the solenoid valve and the plunger reaches the bottom most position and closes the orifice completely stopping the flow of fluid from the inlet port to the outlet port.

Here I am attaching the link for working of Solenoid valve. Go through the video it will clear the concept of working of a Solenoid Valve.

Courtesy:- The Engineering Mindset, YouTube

Types of Solenoid Valves:-

  1. Direct Acting Solenoid Valves

In a direct-acting solenoid valve, a coil magnetically opens the valve in direct action which lifts the shaft and the seat of the valve without depending on outside pressure.

  1. Pilot-Operated Valves

In this type of valve, the solenoid activates a smaller “pilot” valve which in turn opens up a larger valve that is operating at much higher pressure, such as required in hydraulics, steam, etc., or at much greater volume flow – for releasing large quantities of liquids, gases, steam, or air.
Pilot-operated valves require less electrical energy to operate, they just need to maintain full power in order to stay in an open state, and they perform at a much slower rate than direct-acting solenoids. Direct-acting solenoid valves only need full power when opening the valve, as they will hold their open position even when operating on low power.

Types of solenoid Valves
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  1. Two-Way Valves
    Each of the two ports on a two-way valve is alternately used to permit flow as well as to close it off. A two-way valve is often specified to be either “normally open” or “normally closed” in its operation. Normally open valve – the valve remains open until some sort of current is applied to shut the valve. Suspension of the electricity causes the valve to automatically reopen to its normal state. A normally closed solenoid valve is the most common, works in the opposite fashion, remains closed until an electrical power source causes it to open.
Two Way solenoid valve
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4. Three-Way Valves

Three-way valves come with three ports. Used when alternate and exhaustive pressure are required for operation.

Three way solenoid valve
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5. Four-Way Valves

Four-Way valves can have four or more port connections. These valves are commonly used with a dual-acting cylinder or actuator. Half of the port connections supply pressure and the remaining connections provide exhaust pressure.

Four/Five way solenoid valve
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Symbolic Representation of Solenoid valves:-

Symbols of solenoid valves
Image Source: Internet, Courtesy:

Authored By:- Cdt. Aditee, TMI

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