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Sun 14 Aug 2022

What is a pneumatic solenoid valve?

A pneumatic solenoid valve – also known as an electrically-operated valve – is a valve that uses electromagnetic energy to direct or stop the flow of compressed air in a pneumatic system. They’re used in automation and control applications to actuate cylinders, tools and industrial valves. If you’d like to know more about pneumatic solenoid valves, how they work and their different types, continue reading BM Engineering’s helpful guide.

How does a pneumatic solenoid valve work?

So, what is a pneumatic solenoid valve and how does it work? A pneumatic solenoid valve, occasionally called a directional control valve, uses an electric current to pass through a solenoid coil. This generates a magnetic field that causes a metal rod to move. This opens the valve and works either directly or indirectly on the compressed air within a system.

The main purpose of a pneumatic solenoid valve is to make processes much more efficient. Pneumatic solenoid valves are at the heart of many modern systems and applications because they can be easily programmed to turn processes on or off without human interference. Modern industry relies on automation to complete production using a wide range of technological and computer-controlled systems, hence the use of solenoid valves.

Because pneumatic solenoid valves can be installed easily and are simple to operate, they can be positioned in remote and inaccessible locations to be activated electronically.

Compressed air systems, vacuum systems, ventilation systems, and air-operated equipment rely on pneumatic solenoids to control their application.

Different types of solenoid valves

There are a few different types of solenoid valves, and they can be split into direct-acting or piloted categories. Piloted solenoid valves can then be divided into internally or externally piloted valves, and are often referred to as servo-assisted solenoid valves.


In direct-acting solenoid valves, there must be a greater force generated than the force exerted by the pressure of the compressed air. They don’t require any line pressure to work and can operate in vacuum conditions.

With direct-acting solenoid valves, the solenoid rod is attached to a spool and kept in place by a spring. When the solenoid is charged, the magnetic field causes the rod to lift. This moves the spool and allows air to pass through to the other side.

Direct-acting solenoid valves are not seen in many applications, though. This is because the flow can be limited and they consume a large amount of power.

Internally Piloted

Internally piloted solenoid valves work with system pressure to aid control rather than against it, as opposed to direct-acting solenoid valves. This makes them capable of controlling air flow using less power than is exerted by pressure in the line.

There is a smaller passage between the line and a cavity behind the spool of the solenoid and once this is opened, pressure in the line pushes the spool across. When this happens, it allows the valve to open. 

The solenoid requires much less power to move compared to a direct acting solenoid valve while it is controlling smaller openings.

Externally Piloted

Externally piloted solenoid valves work in a similar way to internally piloted valves. What separates them is that externally piloted valves use air from an external source to assist valve movement, rather than pressure within the valve.

This has to come from upstream of the valve. Although, it can also be provided from a separate circuit. The external air source is then fed into an extra port. 

Externally piloted valves are commonly used in low-pressure porting scenarios where there is low, negative or no pressure in the valve to facilitate movement.

Solenoid valves at BM Engineering

BM Engineering offers a variety of solenoid valves from industry-leading manufacturer, Bürkert.

Bürkert solenoid valves from BM Engineering are applicable for a wide variety of functions, such as general on/off control and process control systems, to name but a few. As with our other valve types, all of the solenoid-operated valves we stock are designed to provide industrial applications based in Scotland and the wider UK with a high-performance flow control solution. 

Here at BM Engineering Supplies, we primarily stock two types of solenoid valves: pneumatic and general-purpose solenoid valves.

If you’d like to know more about the solenoid valves we stock at BM Engineering, don’t hesitate to contact us today on 0141 762 0657 or email us at sales@bmengineering.co.uk.

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