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Solenoid valves - Everything you need to know

What is a solenoid valve?

A solenoid valve is an electromechanical valve operated by the control of an electric current. It consists of a cavity containing a movable valve controlled by an electromagnet. This solenoid is a coil with a ferromagnetic core, a housing and an armature.

When electric current flows through the solenoid, a magnetic field is created which exerts force on the ferromagnetic armature. This opens or closes the valve to control the pressure and flow of liquids or gases in a pipe system.

Solenoid valves are used in a wide range of applications, including automotive, medical, aerospace, heating and air conditioning control and industrial automation. They provide a reliable and fast way to control liquids or gases in piping systems and are usually easy to install.

How does a solenoid valve work?

There are various operating principles of solenoid valves that can be selected depending on the area of application and requirements, for example:

There are various operating principles of solenoid valves that can be selected depending on the area of application and requirements, for example:

• 1. direct-acting solenoid valves are the simplest form of solenoid valves. They consist of an electromagnet that acts directly on the valve spool. Applying current activates the magnetic field, causing the valve to open. When the current is switched off, the valve falls back to its initial position or its end position and shuts off the flow. Direct-acting solenoid valves are suitable for small flow rates and for low as well as high pressures.
• Indirect-acting solenoid valves require a pressure difference of at least 0.5 bar and use this to open and close the valve. The medium can flow from the inlet into the upper chamber through a small opening in the diaphragm. When the solenoid coil is energised, the pressure over the diaphragm drops and the diaphragm is lifted. An additional pressure chamber above the diaphragm amplifies the flow so that even small valves can control large volumes. Indirect solenoid valves are only suitable for media flow in one direction and are used in applications with sufficient pressure difference and high flow rate.

Solenoid valve properties

Switching functions

Switching functions" in solenoid valves refers to the way the valve controls the flow of liquids or gases (closing, opening, dosing, distributing). There are different switching functions, which can vary depending on the application. Two examples are:

• Two-way switching function: The valve consists of an inlet and an outlet where the flow direction is indicated by an arrow. This valve is used to open and close the flow.
• Three-way switching function: The valve has three ports and can divert flow between different channels or containers and is used to open, close, distribute or mix different media.

Advantages of solenoid valves

• Electrical control: By applying an electrical control voltage, solenoid valves can be both opened and closed. Thus, fast and precise control is possible.
• Reliability: Solenoid valves have a long service life and are very reliable. They are also capable of handling a large number of cycles without malfunctioning.
• Flexibility: There are a variety of solenoid valves in different designs and sizes to meet different requirements. They can be designed for different media such as liquids or gases, as well as for high or low pressures and temperatures. Flow rates can also vary and be adapted to the specific application
• Fast response time: Due to their fast opening and closing speed, solenoid valves are ideally suited for applications that require a fast response time.
• Easy installation: Solenoid valves are easy to install and usually require no special tools or knowledge.
• Energy efficiency: By means of electrical voltage control, solenoid valves only require energy during opening or closing. No energy is consumed in the holding position, which leads to higher energy efficiency. Permanent magnets or economy circuits can be used here, for example.
• Low-noise: As arule, solenoid valves are low-noise and do not produce any audible vibration or noise when opening and closing. This makes them ideal for applications where a quiet and trouble-free working environment is required.
• High pressure: They are able to withstand high pressures, making them ideal for applications where high pressures are encountered.
• Manual override: In many applications it is important that the valve can be opened or closed even in the event of a power failure or other malfunction in the electrical control system. Many solenoid valves therefore have a manual override function that allows the valve to be operated manually.
• Position feedback: Many solenoid valves are equipped with valve position feedback. This can be in the form of position sensors that make it possible to monitor the exact state of the valve. Position feedback can help to quickly detect and rectify possible malfunctions or faults, which increases operational safety.
• Adjustable reaction time: Some solenoid valves have the option of adjusting the reaction time. This means that the time it takes for the valve to fully open or close can be adjusted to the requirements of the specific application. An adjustable response time can help to improve the performance and accuracy of the valve and avoid possible errors or malfunctions.

Applications of solenoid valves

Solenoid valves are used in many different areas of application and have become indispensable in many industries. An important area of application is, for example, heating and air conditioning systems. Here, solenoid valves are used to regulate the flow of water or air and thus enable precise control of the temperature.

Solenoid valves are also frequently used in the automotive industry to control the fuel supply in the various areas of the engine. Another area of application is medical technology, where solenoid valves are used, for example, in the dosage of medicines.

In the food industry, solenoid valves are often used to regulate the flow rate of liquids in production. By using stainless steel or plastic materials that are approved for food contact, solenoid valves meet the highest hygiene requirements here.

Solenoid valves are also used in the chemical industry to regulate the flow rate of chemical liquids or gases. Here, the valves usually have to be particularly resistant to aggressive chemicals.

In water treatment and waste water treatment, solenoid valves are also used to control the flow of water or other liquids. By using special materials, they can also be used in aggressive environments.