Parts of a Solenoid Valve

Solenoid Valves

The Role of Solenoid Valves in Pneumatic and Hydraulic Power Systems

What is a Solenoid Valve?

A solenoid valve is an electrically operated valve that is mainly used to regulate the flow of air or a liquid in pneumatic and hydraulic power systems. It is mostly configured to a spool or a poppet that is in turn connected to a ferrous metal plunger that may be spring-centered or spring offset. The plunger itself moves inside a core tube of non-ferrous metal that in turn is surrounded by a coil comprised comprising of electrical windings.

How Solenoid Valves Work

The coil of a solenoid valve can carry an electric current within the range of 12-48 V DC and 110-220 V AC. As soon as power is sent through it, a magnetic field gets created which pushes and pulls the plunger in the process of moving the valve. 

The simplest solenoid valves are the two-way, two-position poppet valves that merely open and close to permit flow when their coil is provided with energy. Then there are the three-way two-position poppet valves which are also quite commonly found in use. These allow the diversion of fluid from one channel to another. This kind of valve can be deployed for both pneumatic and hydraulic operations.

Parts of a Solenoid Valve

We can get a good idea of the components of a solenoid valve described a little earlier in this article, by looking at the illustration below that depicts a normally closed direct-acting valve. This type of valve typifies the operation of a solenoid valve.

Parts of a Solenoid Valve

Types of Solenoid Valves

As mentioned earlier in the article the most in-use solenoid valve is a two-way valve, which as the name suggests has two ports. More advanced solenoid valves may have three or more ports, but common to all is the fact that they will either be designed to be a direct-acting one or a pilot operated one used in leak prevention.

Two-Way Valves

In the case of these valves, one alternatively uses either of their two ports to allow flow as well as close it. One can specifically go for the normally open or normally closed position. The normally open valve remains open until an electric current is applied to close it. On one’s switching off the electrical power, the valve reopens. The normally closed solenoid valve is the more used one and operates in the opposite manner from the normally open one. It remains closed until the switching on of the power causes it to open.

Three-Way Valves

These, as one would imagine come with three ports and find use in circumstances where one needs to use alternate and exhaustive pressure to operate something. Coffee machines and dishwashers are good examples of three-way solenoid valve deployment. 

Four-Way Valves

Four-way valves come with four or more ports and largely see use in dual-acting cylinders or actuators. Half of the ports are deployed to provide supply pressure and the other half to provide exhaust pressure. These valves can be of the normally closed, normally open, or universal types.

Direct-Acting Valve

In this kind of solenoid valve, a coil will be able to magnetically open the valve by pulling up the shaft and set of the valve without relying on any outside pressure. The good thing about direct-acting valves is the fact that they require full power only when opening the valve, after which they can pretty much operate on low power. 

Pilot-Operated Valve

This involves the solenoid activating a considerably smaller pilot valve which on its part opens up a larger valve capable of operating at a much higher pressure. This is ideal in a scenario involving the use of hydraulics or steam-anything that has to do with dealing with much higher volume flow. A typical example would be the release of large quantities of gasses, air, steam, or liquids. 

Though pilot operated valves don’t require all that much power to operate, they do need to run on full power to remain in an open state. They also perform at a rate that is lower than that of direct-acting valves.

You can get some of the most highly regarded brands of solenoid valves from SafeRack including those from Brodie International who provide a range of solenoids and pilots that see diverse applications including back pressure control and differential control.

Pneumatic vs. Hydraulic Solenoid Valves

Pneumatic Solenoid Valves

Hydraulic Solenoid Valves

  1. Pneumatic Valves are characterized by their 5 ported making it possible for 5/3 solenoid valve enabling control of cylinder operations. A pneumatic valve also incorporates exhaust ports (usually 2 of them).
  2. They mainly have a spooled design and comprise of an aluminum body with a cylindrical hole with the ports of the valve connecting to the cylinder. With the process of moving the spool within the cylinder, the different ports can be made to open and close.
  3. Pneumatic valves are more conducive to situations where very high pressure is not required. It is ideally suited to something like pressurized internal control systems that use low-pressure oil-free air.
  4. Pneumatic systems are best suited in situations of lighter automation.
  1. Hydraulic Solenoid Valves are deployed to use electric power to direct hydraulic fluid to and out of an actuator by moving a spool of poppet within the valve.
  2. The valves can be configured as 2-, 3-,4- or 5-way and can be moved by one or two electric coils.
  3. As hydraulic fluid is not compressible, there is lower likelihood of a mishap at a higher pressure, when compared with a pneumatic system at a similar pressure.
  4. Hydraulic systems are better suited to high performance-oriented industries.

Choosing the Right Solenoid Valve

When it comes to choosing the right solenoid valve, you have got to know what sort of environment it will be operating in. This is important because such valves are designed to work in an environment that is free of solid particles.  Typically a solenoid valve would be used in an environment comprised comprising of water, heat transfer fluids, petroleum by-products, compressed air, and steam. It is important to possess this information for it will help you determine the material that your solenoid valve should be made of- For instance stainless steel is ideal in the case of food product liquids and corrosive liquids or gasses. In the case of fuel, inert gas, fuel, and air brass are the material of choice. In the case of the food and chemical sectors, it is plastic.

One’s choice of solenoid valve depends upon what one intends to use it for. If you want to obtain the ideal amount of supply time with the help of a solenoid valve, you may have to choose between a normally closed solenoid valve and a normally open solenoid valve, while a ball float valve or check valve is used in dispensing avenues for gas pumps.  There are a few other parameters that help decide on the kind of solenoid valve to use:

  • You also have also got to know as to whether you should be going for a standalone type or manifold mounted. In the case of standalone the inline valves have to be mounted near the actuator to enhance performance and all the ports happen to be a part of an inland port’s body. In the case of manifold mounted units, the valves share both exhaust and supply channels.
  • One should have a firm handle on the prevailing flow rate so as to choose the right kind of solenoid valve. If the valve is too large there would be wastage of liquid or gas, thereby impacting the bottom line of a company. If on the other hand, if it is too small, you will have a case of the actuator not working at all.
  • The amount of power required too also has a bearing on the type of solenoid valve chosen for a specific application. The extent of electric current needed to move the core of the orifice is determined by the size of the opening. It is important that one selects a valve that is able to work in tandem with the amount of power supplied. The bigger the orifice the more the power consumed.

If one is looking at a high flow rate and low power consumption situation one should go with a pilot operated valve.

  • The operating pressure as described in the manual of the solenoid valve manufacturer will also determine the right kind of valve best suited for a specific application.
  • You also need to examine the port size so as to ensure that you procure the right size of valve fittings. The valves need to be installed in either a single base or a multiple-station manifold in accordance with the method used to allow air into the circuit.

Application of Solenoid Valves

Solenoid valves are used across industries. They are for example used to run a host of household appliances like ice cube makers, dishwashers, washing machines, and refrigerated water dispensers. These also see use in more commercial industries like automatic irrigation sprinklers, air conditioners, medical equipment, and car transmission. Given below are a few other examples of industrial applications of solenoid valves-

  • Dentist’s Chairs
  • Hot Drinks Dispenser
  • Air Compressors
  • Press Safety Valves
  • Metering Devices
  • Vibrating Feeders
  • Industrial Ironing Boards
  • Coffee Dispensers
  • Dryers
  • Car Washing Systems
  • Electronic Mixers
  • Floor Washing Machines
  • Foam Makers
  • Hydro Saunas
  • Sewing Machines
  • Thermoelectric Heaters
  • Exposure Units
  • Water Meters
  • Vacuum Packers
  • Refrigerant Loading Systems
  • Vacuum Pumps

As one can see the applications that solenoid valves are put too are diverse and many. Let us now look at a few broad categories encompassed by these –

Automobile Industry 

Solenoid valves are an integral part of the starting system of all motor vehicles. Whenever a driver turns on the ignition switch he or she causes an electric current to be conveyed to the solenoid valve. That, in turn, makes the solenoid valve to cause the current to start the motor of the automobile. Once that happens the driver no longer uses the ignition switch causing the flow of current to the solenoid valve and from there to the motor of the car to stop.

Refrigeration Industry

Solenoids are used extensively in the refrigeration industry. For instance, they are used in air conditioners to help control the direction of the flow of the refrigerant to enable them to be used for cooling in the summers and for heating in the winters.

Hydraulics and Pneumatics

In hydraulic systems, solenoid valves control the direction of the flow of the hydraulic fluid inside the cylinder that controls the motion of the piston. In the case of hydraulic systems, the solenoid valves control the pressure of air that flows to the actuator and thereby exercises control over the action caused by the actuator.

Locking Systems

Solenoid valves find use in locking systems deployed in offices, hotels, and other areas that need to be secured. The solenoid valves in these cases are part of the locking devices installed in the doors. In the event of the door being locked, there is no consumption of power by the solenoid valve. Such locking systems are used at car parks, access barriers, remote access systems, vending machines, and so on.


You could call solenoids actuator devices that make magnetic material move with the help of the magnetic field that is created by an energized solenoid coil. The main parts of the solenoid valve comprise the valve body, the inlet port, the outlet port, solenoid, solenoid winding, lead wires, piston spring, and orifice.

Solenoids are deployed in a large number of gas and oil applications. These are also used in our cars, boats, and myriad home appliances. Solenoid valves are extensively used because these come with a host of advantages. For starters, these are extremely versatile and see use in a large number of diverse systems that encompass applications pertaining to air, water, gas, steam, and other myriad gasses and liquids.

Then there is the fact that these are extremely efficient at managing automatic flow control when it comes to liquids and gasses. As compared to other kinds of valves, these valves require very little wiring or effort. These are cheaper as well

An inordinately large number of industrial processes involve the movement of gas or liquid and for that purpose using a valve to regulate the flow is a must. That is not something that human beings can manage very efficiently doing it manually. An automated system is the best way to do it, hence the need and importance of solenoid valves. A solenoid valve therefore in a layman’s language is a device that automatically regulates the flow of a liquid or a gas. 

This ability of theirs lets them control fuel flow in an engine and the water-flow in dishwashers. A solenoid valve that is used to regulate the flow of hydraulic fluid is referred to as a hydraulic solenoid valve. When it is used to regulate the flow of pressurized gas it is called a pneumatic solenoid valve. A solenoid valve is put to use across a very wide array of industrial and commercial processes. These include controlling hydraulic operations, managing air pressure, RO plants that treat water, managing the fuel supply in automobiles,  manufacturing companies, blood analysis instruments, and oil refineries.

Given the importance of these valves in the efficient management of applications across industries, it is important that one sources them from the best suppliers. Among the suppliers out of the top tier SafeRack, whose valves see the application in pressure control, pump control, and tank safety operations. These are used extensively across loading terminals, aircraft refueling facilities, and other such operations. 

Solenoid valves may not be something that most people think of in their daily lives, but it is something that is an important part of it, on account of the innumerable applications it lends itself too. Even though most of us don’t quite understand what they are all about, they are an important part of the processes and systems that make up modern life. From helping run automobiles and enabling planes to fly and from securing hotel premises to help power our washing machines and air-conditioners solenoid valves make our lives so much better without our knowing it. 

Solenoid valves are so popular because they are simple, highly effective, and economical. They are an integral part of most industrial projects on account of their ability to enhance efficiency and thereby increase profitability. The fact that there is a wide range of solenoid valves to cater to the diverse needs of a slew of industries ensures that their presence in the industry and commercial enterprises are ubiquitous.