Solenoid Valves Archives

Solenoid valves are key parts of many systems in which the flow of material needs to be controlled remotely. This type of valve opens and closes in response to an electrical charge, so they are perfect for machinery and systems operated by control panels, or in automated systems. In this article, we will describe a few examples of solenoid valve uses, and the types of SV best suited to the application.

To name a few examples, solenoid valves are used in:

Automated Irrigation/Sprinkler systems
Air Compressor systems
Electric Showers
Drinks Dispensers
Automatic Door Locking systems

In each of these systems, an electrical signal controls the valve, allowing simple, immediate and accurate control, and enabling programmable systems.

What is a Solenoid Valve?

A solenoid valve is an electromagnetically-operated gate used to control the flow of gasses and liquids in pressurised systems. The valve can be either “normally open” or “normally closed” and is moved from its normal position when the solenoid receives an electrical current. A solenoid is a coil of copper wire around a rod (or core, or plunger) of ferrous (iron-containing) metal. When electrical energy passes through the coil, it creates a magnetic field, moving the rod. When this happens, the rod opens or closes the valve, starting or stopping the flow of the medium (substances) through the system.

Working Principles: Direct Acting vs Pilot Operated Valves

There are two main types of solenoid valves: directly or pilot operated. In a direct-acting solenoid valve, the core or rod is the part which blocks the opening, sealing the valve. It is the simplest working principle and adequate for many systems.

Pilot-operated valves, on the other hand, are quite complex. They are also known as indirect-acting valves and rely on the pressure differential between the inlet and outlet ports. The rod of a pilot-operated valve moves when the coil is electrified and causes a rubber membrane or ‘diaphragm’ to open the orifice. To do this, there must be a minimum pressure differential of approximately 0.5 bar. between the inlet and outlet ports.

The diaphragm has a small opening, allowing the medium (water, gas, etc.) to flow from the inlet port into the upper compartment, where the diaphragm is supported by a spring.

The rod in the solenoid acts upon a pilot hole, a narrow opening which connects the upper compartment to the low-pressure port.

In the closed position, the rod closes this pilot hole, but in the open position, a small amount of the medium can flow through, causing the pressure above the diaphragm to drop.

This allows the spring to contract, lifting the diaphragm away from the main opening. The medium can then flow freely from the inlet port to the outlet port.

The engineers at Instrumentation Academy have made an informative video explaining with diagrams and simple terms how pilot-operated solenoid valves work.

Different Solenoid Valve Applications

There are many systems in which solenoid valves are applied. These valves can be two-way, three-way or more, and specially adapted for use with gas, water, liquid chemicals or for general purpose use. Here we’ll discuss some different systems that use solenoid valves.

Automated Irrigation & Sprinkler Systems

Controlling water flow through sprinkler systems can be achieved with normally-closed solenoid valves. When irrigation is triggered, an electrical charge causes the ferromagnetic core to move, opening the valve and allowing water to pass through the system.

This works because the system is pressurised. When the valve opens, the water flows through at a high rate and is expelled through small holes in the sprinkler head, creating the familiar shower effect over a wide area.

Depending on the size of the area to be irrigated, consider whether 2-way or 3-way valves are the best option. A 3-way valve will enable multiple sprinklers to have one point of control, making these perfect for large areas such as sports pitches, parks and arable fields. It is also important to have a high flow-rate valve for this application.

Air Compressor systems

Air compressors use air-tight solenoid valves to control air pressure within the circuit. When the compressor is running, the electric motor drives the compressor, drawing in filtered air. The air is compressed, refrigerated and stored in the tank. During this phase, the solenoid is powered, closing the circuit to prevent air from escaping. When there is enough compressed air in the tank, a pressure switch stops the motor. To avoid over-pressurising the system, the power stops and the solenoid valve opens, allowing excess air to escape.

It’s important to use high-pressure solenoid valves for compressors as they have stronger seals to withstand the build-up of pressure required. The 21A-PW series can support pressures up to 15 bar.

Shower Systems

Similar to the sprinkler system, An electric shower system uses a solenoid valve to control the flow of water. When the shower turns on, the electric current enters the coil of the solenoid, pulling the valve open immediately and releasing the flow of water through the shower system.

A 2-way, normally closed, direct-acting water solenoid valve is suitable for use in shower systems, as long as materials can work well with hot water. The 21A solenoid valve series is suitable for use with showers, and other systems using pressurised and heated water.

Drinks Dispensers

The office coffee machine, the water dispenser and the car wash all operate using vending solenoid valves in a very specific configuration, controlled by programmed timers. For a basic cup of coffee, a metred amount of hot water from the heater tank is released via the first solenoid valve into an internal container. Ingredients such as coffee and milk powder are dispensed by similar valves into the same container, where they are mixed with the water before being released into the dispenser head. A final valve dispenses the finished product into a cup, and you walk away with a cup of coffee.

All of the solenoid valves in an automated coffee machine are normally closed, water-resistant and made from high-grade materials to withstand the heat of the hot water and prevent contamination.

Vending Solenoid Valves, such as those in the JM series and 21A series, are designed for vending hot water in applications such as this.

Dentists’ Chairs

It may surprise you to know that the automated hydraulic function which raises and lowers some dentists’ chairs is controlled using solenoid valves. Most dentists’ offices are equipped with a fully-integrated system, enabling the chair height to be adjusted from the same control panel as the dental equipment.

A hydraulic chair is lifted by the thrust of a hydraulic cylinder, providing a smoother movement than mechanical systems. The hydraulic system works by pumping oil from a basin into the circuit and pressurising it to 12-13 bar. When a button is pressed, the solenoid valve works to divert the oil from the pump into the cylinder, which is pushed up by the force of pressurised fluid, lifting the chair to the required height. A second button sends an electrical current to a second solenoid valve which opens to exhaust the pressurised oil from the cylinder, pulling the chair back down.

High-pressure solenoid valves are perfect for a hydraulic system such as this, as it requires a valve that can cope with the viscous medium and high pressure, such as the 4731 series.

All types of Solenoid Valves Available from Avalco

There are solenoid valves in many systems in industry, medicine, agriculture and in the home. We hope that this article has given an overview of the wide range of applications solenoid valves have, and the differences in how certain valves are more suited to each application. Whether you’re looking for 2 or 3-way valves or something that can cope with harsh chemicals, heat or high pressure, you’ll find it in our solenoid valve online shop. Avalco Ltd is a supplier of almost every range of solenoid valves, for air, water, fuel and more. We operate throughout the UK for all types of industry. On our website, you can find the exact spec for each valve we supply, or you can speak to a solenoid valve expert for more friendly advice.

Whether you’re installing a solenoid valve in a gas, water or chemical system, the working principles are similar enough that the process is largely the same. In this how-to guide, we aim to give you a clear set of basic installation instructions for solenoid valves. We’ll also cover what to remember, what to avoid, and the differences between solenoid valve types.

How Does A Solenoid Coil Work?

A solenoid is a coil of copper wire which produces a magnetic field when charged with an electrical current. It is a relatively weak type of electromagnet which does not always have an iron core.

The working principle is as follows:

Electrical Energy flows through the coil
The coil produces a Uniform Magnetic Field
The magnetic field provides energy for linear motion through the centre of the coil

The linear motion is what makes solenoids so mechanically useful. In a solenoid valve, the rod or plunger moves instantly in a straight line along the magnetic field to open or close the valve. Because electrical energy is used to create the field, it is easy to control remotely and programme for automation. The uniform magnetic field causes instant linear motion of a ferromagnetic rod or plunger, and when the current is removed, the magnetic field disappears and the motion is reversed. This is how solenoid valves control the flow of the medium proportional to the voltage applied.

The voltage required varies depending on the application but is most often supplied by a control unit installed remotely from the valves. In irrigation, a relatively low, 24-volt AC is enough.

A Few Do’s and Don’ts

When installing any equipment, it’s important to avoid mistakes that are easy to make but render the operation useless. For example, did you know that any contamination inside the solenoid valve can cause problems that may affect the whole system? Here are a few tips to help you install a solenoid valve perfectly every time.

Do:

Install the valve the right way around. There is usually an arrow on the housing which indicates the direction of flow, so make sure you check this first.
Install the valve upright with the solenoid housing vertically upward where possible. This will protect the solenoid in the event of leaks and support its proper function.
Keep the valve clean during installation. This may mean keeping it in the packaging until you are ready to install it, avoiding using oily cloths or placing it in dusty environments.
Tighten the Solenoid Properly. Leaving it loose can mean misalignment, causing leaks.
Check the parameters. Use the correct voltage, within the fluctuating scope of the voltage.
If you’re installing the valve in a water system such as for irrigation or water dispensing, ensure you use waterproof gel connectors to attach the low-voltage leads.
Place a Filter to clean the medium of any suspended particles before the valve. If there is dust or impurities in the medium, whether gas or liquid, this could cause a blockage over time.
Leave Space around the valve for maintenance access and to allow it ventilation for cooling.
Use a fuse. Whether you choose to use a fuse wire or a fused switch, this will protect your circuitry from surges.

Do Not:

Connect a power supply at a higher voltage than the rating on the valve’s specification, as this could burn out the solenoid coil.
Allow dirt to enter the valve during installation. This could block the valve and cause problems.
Connect too many valves. There should be a maximum of 3 valves for each control unit terminal.
Remove the solenoid casing in dirty or wet areas, as contaminants can potentially enter the coil and impede the working.

Checking Solenoid Valve Properties

You’ll likely have checked this when ordering a solenoid valve, but it is essential to make sure you have the correct valve for the application. Valves will have a label which shows the valve’s specifications, including:

Product Code e.g. 21H11K0B120. This is unique to the product.
Power (W) e.g. 12W. It is extremely important to use the correct voltage. Too high will burn out the coil, and too low will not create a strong enough magnetic field to move the plunger.
Port connection (e.g. G ⅜). This shows the diameter of the pipe thread in inches.
Operating Pressure (min-max) for AC/DC current e.g. 0-(16/10) bar, in which 16 is the maximum pressure with AC and 10 is the same for DC.

The main specifications to check include the operating power and Port connection and operating pressure. Attempting installation when these details are incorrect will unfortunately just lead to a broken valve. For all solenoid valves supplied by Avalco, specifications are also available on the product page as PDF files.

How To Install A Solenoid Valve

This guide is a basic “how to”, supporting installation as a quick-look cheat sheet. However, there are many different types of solenoid valves available, and we encourage you to check the product manual before you start. This is to ensure you do not miss vital steps specific to that valve model.

Check the valve voltage matches the supply voltage.
Isolate the supply pressure and ensure the system has cooled before you start.
Unscrew the connection where the valve is to be installed and clear any debris or residue from the pipeline, such as sealant, oil or dust.
Check the directional flow indicated on the valve body by an arrow (→). Position the valve this way around in line with the pipeline.
Connect the valve. Usually, this will involve a threaded connection at both the inlet and outlet. You may want to hold the valve steady with a wrench while you fasten it.
Wire the solenoid.
1. Connect wires to the two vertical pins on the coil housing using spade connectors or another type of connector.
2. Connect another wire to the third, horizontal pin and connect this to ground (usually the negative terminal of the power supply).
3. Connect the positive wire to the switch or control panel. Then connect this to the power supply.
4. Connect the negative wire to the power supply. When the switch is activated, the valve will work.
Test the circuit to make sure the valve is fitted correctly. Turn on the supply and test again, checking for leakage.

Solenoid Valves for All Purposes

In conclusion, we hope this installation guide has provided you with clear and concise instructions for solenoid valve installation. At Avalco, we are a solenoid valve supplier, trusted by a wide range of industries and tradespeople across the UK. Our commitment to quality and reliability ensures that you have access to the finest solenoid valves for any application, including explosion-proof solenoid valves for high-pressure or hazardous environments.

From automated irrigation to gas and fuel lines, our comprehensive stock of solenoid valves provides a solution with optimal performance for your projects. Browse our full range of products and find the right valves for the job, or get in touch and let us help you find a solenoid valve that fits your requirements.

5 Ways Solenoid Valves are Used