Solenoid valves

A solenoid valve is an electrically driven valve that controls the flow of media such as air, water, or oil. Using an electrical signal, a magnetic field is generated that opens or closes the valve. This technology offers fast and reliable control, which is essential in many industrial processes.

Solenoid valves, also known as magnet valves, are controlled by means of electromagnetism. They generally consist of a valve body, a piston, and a coil. As soon as an electrical current flows through this coil, a magnetic field is generated that moves the piston and in so doing opens or closes the valve.

The construction of a solenoid valve can vary depending on the application, however, they are generally made from high-quality materials such as brass, stainless steel, or plastic so as to meet the varying requirements in industry. The choice of material should depend on the type of media flowing through the valve and the ambient conditions.

Fig. 1: Flow rate control with solenoid valves

Advantages of solenoid valves

Solenoid valves offer numerous advantages over other valve types:

• Fast response time: they react very quickly to electrical signals.
• Precision: they enable the precise control of the flow rate.
• Reliability: they are designed for continuous use in industrial environments.

As such, solenoid valves impress with their diverse range of advantages, which make them a key component in many industrial processes. These properties make them perfectly suited for use in the most varied of industrial applications. But where exactly are these versatile components used?

Areas of application of solenoid valves

Solenoid valves are used in many sectors and industries. The list below offers a brief insight into the numerous application possibilities:

• Process instrumentation
• Water and waste water
• Chemicals industry
• Food industry
• Pharmaceuticals industry

Function of solenoid valves

Solenoid valves are also known as way valves. Here, the precise designation is supplemented with two numbers, which provide information as to the exact design of the valve. For instance, names such as "2/2-way valves", 3/2-way valves" and "5/2-way valves" are common. But what exactly do the numbers before "-way valve" mean?

Alongside 2/2-way valves, 3/2-way valves also play an important role in industry. These valves have three connections and two switching positions, which allows them to not only open and close off the flow, but also to redivert or vent. This additional flexibility makes them particularly useful in applications in which switching between different lines is required. In pneumatic systems, 3/2-way valves are often used to control the air supply or discharge compressed air, which contributes to the safe and efficient control of machines and processes. In the chemical and pharmaceutical industry, they are used to divert the flow of reagents or solvents, which is particularly important in sample preparation and analysis. In process control, 3/2-way valves can also be used to discharge excess pressure or safely vent systems. This versatility makes them an essential component in many industrial systems where complex control tasks are required.

In industry, 5/2-way valves can be put to versatile use, playing a crucial role in the control of pneumatic cylinders and actuators. In automated production cycles, they enable precise movements of grippers, conveyor belts, and lifting tables, which guarantees the efficient positioning and transport of workpieces. In the packaging industry, these valves are used to control machines, for example machines that cut, fold, seal, or stack packaging materials, thus achieving a more synchronised and faster packing process. 5/2-way valves are also used in robotic technology, as they can control the movements of pneumatic end-effectors, which are responsible for the gripping or positioning of parts in automated systems. Automated storage and conveyor systems also make use of 5/2-way valves to lift pallets, sort products, and control conveyor belts, which guarantees continuous and efficient operation.

Overall, 5/2-way valves make a significant contribution to ensuring efficiency, productivity, and safety in a wide range of industrial applications. Many 5/2-way valves from the manufacturer Bürkert can also be used as 3/2-way valves. Thus, the retroactive changing or expanding the number of connections from 3 to 5 is possible without any problem. A wide range of 5/2-way pneumatic valves are available at Automation 24!

There are two main operating modes for solenoid valves: direct-controlled and servo-controlled. The main difference between direct-operated and servo-operated solenoid valves lies in the way they are opened and closed. Servo-assisted valves are a third type that represents a mixture of the first two. Below you will find an explanation of the advantages of the designs and when they should be used.

• Directly controlled (also known as direct-acting): Directly controlled solenoid valves open and close by means of a direct mechanical connection between the actuation element, in this case an electromagnet, for example, and the valve stem. When the electromagnet is activated, it directly attracts the valve stem and moves it, as a result of which the valve can be opened or closed. This process takes place independently of the pressure of the flowing liquid or gas, meaning that a pilot operated valve also functions reliably in case of very low or even no differential pressure. For this reason, they are particularly well suited for applications in which precise and immediate control is required, regardless of the pressure conditions in the system. A direct acting valve is typically larger, heavier and more expensive than a servo-controlled valve. A direct acting valve is used primarily where there is insufficient differential pressure or where the flow conditions are not clear. For this reason, it is particularly useful in applications in which precise and instant control is required necessary, regardless of the pressure conditions in the system.
• Servo-assisted (also referred to as pilot-operated): Compared to a force pilot operated valve, a servo-assisted valve is generally smaller, lighter, and less expensive. It is also often designed for higher pressure, while simultaneously consuming less electricity. However, these advantages are not sufficient for all intended purposes, as a servo-assisted valve still requires a differential pressure to open and close reliably. Here, the differential pressure is stated as the minimum pressure. If this differential is no longer provided by means of pressure equalisation, the function of the servo-assisted valve can be significantly restricted.
• Force pilot operated: A force pilot operated solenoid valve is a hybrid of the two control types "directly controlled" and "servo-assisted". Here, the force pilot operated valve combines the reliable direct control of the directly controlled valve with the efficiency of control provided by a pilot opening, as is used in servo-assisted valves. This enables it to perform accurately at low pressure conditions while also providing the ability to efficiently control larger flows.

Brief selection guide for Bürkert solenoid valves

Below you will find an overview of the Bürkert solenoid valves found in the Automation24 product ranges, as well as a list of the respective features. These can be used as an initial guide to help you quickly find the product that suits your needs.