Solenoid valves are used in a wide range of applications, from industrial machinery and automobiles to household appliances and systems. Pneumatic solenoid valves regulate the air passage in a circuit, while liquid solenoid valves control the flow of liquid media.

The widespread use of solenoid valves is not without reason. These valves offer the advantages of fast acting, virtually noiseless and accurate.

Manufacturing Systems

Solenoid valves are used in industry to control machines, dose, mix or restrict the flow of liquids or gases. For example, beverage plants use solenoid valves to measure the exact amount of beverage to be poured into a bottle.

These valves can also be used to mix different liquid substances using precise volumes. In automatic systems, solenoid valves are used to control the flow of fluids and create motion.

Agriculture

Most agricultural equipment contains solenoid valves for control systems. You will find them in irrigation equipment (e.g. automatic sprinklers) or electric farm machinery to meter substances.

Irrigation solenoid valves essentially control the flow of water and can be used to operate sprinkler functions autonomously.

Other uses include delivery systems for agricultural machinery used to regulate different fluids. You will also find these valves in equipment used to dispense chemicals. Milking machines use solenoid valves for solenoid valve functions.

Because of all these uses, these valve types are the most common types in the agricultural industry and are perhaps only comparable to pneumatic control valves.

Automotive applications

A range of solenoid valves are used in motor vehicle systems. They are typically used to regulate the flow of automotive fluids such as oil, anti-skid brake fluid and even fuel.

In some of these functions, a variable solenoid valve is often used. It allows to control the medium instead of closing it completely.

A good example is to restrict the flow of fuel to the engine to reduce the speed of the vehicle. Fuel solenoids are common in countries where there are regulatory requirements for speed.

Other automotive solenoid valves include the type used to cut off fuel flow and stop the vehicle, the type that automatically drains water from a water-fuel separator, and the coolant control solenoid in a vehicle's HVAC system.

Vacuum Systems

Solenoid valves are widely used in vacuum applications. Direct and semi-direct valve types are the most common. They do not require minimal pressure levels, which makes them most suitable for these situations. Vacuum solenoid valves are usually designed to be leak-free, which is a necessary requirement in this case.

Vacuum applications include the electronics industry where partial removal of air is required, vacuum manufacturing and automation systems, and vacuum pumps.

Domestic heating devices

Heaters use gas or wood to heat water and distribute it to a variety of fixtures such as bathroom shower heads, kitchen faucets and other devices. At the heart of heater operation are solenoid valves.

These automatically open and close to let in cold and hot water. The flow rate in the circuit is usually high, which makes pilot operated solenoid valves most suitable.

Refrigeration equipment and systems

An important use for solenoid valves is in refrigeration systems. Refrigeration solenoid valves have multiple functions in these installations. It prevents high pressure compressor start-up and protects the compressor from fluid hammer problems. The valve also closes and opens the refrigerant path as needed, helping to prevent refrigerant from entering the evaporator when the compressor stops.

Car Washes

Car wash equipment provides high-pressure water and cleaning agents to clean motor vehicles. To mix and lift the water and cleaning solution, these units use a series of automatic solenoid valves.

These valves are usually direct acting. To protect the valves from the corrosive chemicals in the cleaning solution, manufacturers use nickel-plated brass. 

Air Compressor Sets

The air compressor draws in air and compresses it before sending it to the compressed air storage tank. As the air enters the tank, it must remain under pressure. This is accomplished through the use of a solenoid valve.

The compressed air solenoid valve is energized to shut off the fluid flow, in this case for the air, and allows the built-up pressure to remain in the tank.

Compressed air pressure should not be left in the tank for long periods of time. When the coil is de-energized, the valve opens and releases the air into the system.

Hot beverage dispensers

These are machines that dispense coffee, tea and other beverages. They are usually found in offices and commercial establishments, although some can be used in private locations. Hot beverage dispensers typically use a direct acting solenoid valve system.

The valves open and close in a sequence to allow fluid to pass through the system.

Mixing water in a safety tap

Solenoid valves are used to automatically mix hot and cold water before it flows from a tap or faucet where sanitation is a strict requirement. Typically, these devices are equipped with a sensor to detect the presence of a person. It can be an infrared sensor or any other device.

Behind the unit are two water solenoid valves. They open simultaneously to allow hot and cold water to enter. The type used is usually a pilot operated solenoid valve due to the high flow rate involved.

Floor scrubber

The scrubber must dispense the right amount of water and detergent at the same time. To ensure this, a solenoid valve is used for each function.

Since the fluid being controlled is not under pressure, the valves used are mostly direct-acting.

Water metering devices

These are mechanical devices that regulate the amount of water dispensed. They are used in different places, such as the food industry, to measure the exact amount of water in a mixture. The solenoid valves used in these meters are usually pilot-operated.

These are easily adapted to the high flow rates common in installations. When the system pressure is low, these water solenoid valves contain an auxiliary lift.

Natural gas installations and appliances

Solenoid valves are used in industrial and domestic gas systems to turn on or stop the flow of natural gas. Gas solenoid valves can also be found in installations that use pneumatic actuators for different functions. Natural gas solenoid valves control the flow of gas in a home gas heating system, indicating when the gas must be ignited to heat water and when it must be turned off.

Solenoid valves are a common device in today's workplace. From automated manufacturing systems, automobiles, refrigeration and air conditioning systems to pump and irrigation systems on farms, they are almost everywhere.

They can be found in most household appliances and fixtures as opposed to pneumatic valves or certain types of hydraulic valves.

In industrial and engineering systems, solenoid valves are the most commonly used.

The list of applications is by no means exhaustive; the examples explained here are the most common.

Selection Criteria

Before selecting a solenoid valve, it is critical to understand your application. Some important selection criteria are as follows.

Solenoid Valve Type: Determine if your application requires a 2-way or 3-way solenoid valve.

Housing Material: Determine the valve housing material based on the chemical properties and temperature of the media, and the environment in which the valve will be located. Brass is generally used for neutral media. Stainless steel has good chemical, temperature, and pressure resistance. PVC and polyamide are commonly used because they are cost effective. However, they are also used for high-end applications with aggressive chemicals. Mechanical components such as stainless steel plungers and springs must also be compatible considering that they are in contact with the media. Special media separation valves can be used, in which these parts are separated from the fluid by a membrane.

Seal Materials: Seal materials should be selected based on the chemical properties and temperature of the media. NBR, EPDM, FKM (Viton), and PTFE (Teflon) are common choices.

Voltage: Solenoid valves are available in AC and DC versions, each with its own advantages and disadvantages. See Selecting AC or DC Coils for Solenoid Valves for more information.

Valve Function: Depending on the time period of operation, either normally open or normally closed valves can be selected. Most solenoid valves are normally closed. Normally open valves are preferred if the valve is open for longer than it is closed, and vice versa. Bi-stable or latching is also an option.

Pressure: The valve must be able to withstand the maximum pressure required for your application. It is also important to note the minimum pressure, as high differential pressures can cause valve failure.

Type of operation: Determine if your application requires direct, indirect or semi-direct operation of the solenoid valve.

Temperature: Make sure the valve material can withstand the minimum and maximum temperature requirements of the application. Temperature considerations are also important in determining valve capacity, as it affects fluid viscosity and flow rate.

Response time: The response time of a valve is the time it takes for the valve to move from the open position to the closed position and vice versa. Small direct acting solenoid valves respond much faster than semi-direct or indirect acting valves.

Certification: Ensure that the valve is properly certified according to the application.

Protection: Ensure that the valve has the proper IP rating to protect against dust, liquids, moisture, and contact.

A solenoid valve is defined as an electromechanical valve, typically used to control the flow of a liquid or gas. There are several types of solenoid valves, but the main variants are pilot-operated or direct-acting. The most widely used pilot-operated valves use system line pressure to open and close the main orifice in the valve body. 

Direct-acting solenoid valves, on the other hand, open or close the main orifice directly, which is the only flow path in the valve. They are used in systems requiring low flow rates or in applications where the differential pressure across the valve orifice is low.

How Solenoid Valves Work

Solenoid valves work by controlling the flow of a liquid or gas in a positive, fully closed or fully open mode. They are often used in place of manual valves or for remote control. Solenoid valve functions include opening or closing an orifice in the valve body to allow or prevent flow through the valve. The plunger opens or closes the orifice by exciting the coil to raise or lower in the casing.

The solenoid valve consists of a coil, plunger, and sleeve assembly. In a normally closed valve, a plunger reset spring holds the plunger in place over the orifice and prevents flow. Once the solenoid coil is energized, the resulting magnetic field lifts the plunger, which allows flow. When the solenoid coil is energized in a normally open valve, the plunger seals the orifice, thus preventing flow.

Why use a solenoid valve?

In most flow control applications, the flow in the circuit must be started or stopped to control the fluid in the system. For this purpose, electronically operated solenoid valves are often used. With solenoid actuation, solenoid valves can be placed in a remote location and can be easily controlled with a simple electrical switch.

Solenoid valves are the most commonly used control element in fluidics. They are commonly used to shut off, release, meter, dispense, or mix fluids. As such, they exist in many applications. Solenoids typically provide fast and safe switching, long service life, high reliability, low control power and compact design.

How do I replace a solenoid valve?

For proper and accurate control function, the solenoid valve must be configured and selected for the specific application at hand. The most important parameters for selecting a solenoid valve are the Kv value (given in cubic meters per hour) and the pressure range of the application.

The lower the orifice of the valve, or the stronger the coil, the higher the pressure at which the valve can be closed. Based on the calculated Kv value and the pressure range of the planned application, the corresponding suitable valve type and its required orifice can be determined.