As the solenoid is controlling much smaller openings, it requires much less power to move compared to a directing acting solenoid valve.Įxternally piloted solenoid valves work in a similar way to internally piloted valves, but use air from an external source to assist valve movement, rather than pressure within the valve. When this is opened, pressure in the line pushes the spool across, opening the valve. In internally piloted valves, the solenoid gates a smaller passage between the line and a cavity behind the spool. This makes them capable of controlling air flow using less power than is exerted by pressure in the line. Unlike direct acting solenoids, internally piloted valves work with system pressure to aid control, rather than against it. This is because flow can be limited, and they consume a large amount of electrical power. In a N/O valve, the opposite happens – the spring keeps the spool in the open position.ĭirect acting solenoid valves are of limited use and are only seen in about 10% of applications. When the solenoid is charged, the magnetic field causes the solenoid rod to lift, moving the spool and allowing air to pass through to the other side. With direct acting, N/C valves, the solenoid rod is attached to a spool and kept in place by spring. They do not require any line pressure to work, and can operate in vacuum conditions. In the case of direct acting solenoid valves, the force generated by the solenoid must be greater than the force exerted by the pressure of the air. Solenoid piloted valves can be further divided into internally or externally piloted valves, and are sometimes referred to as servo-assisted solenoid valves. What are the different types of solenoid valve?Īs we shall see, solenoid valves can be split into the following broad categories: direct acting or solenoid piloted.

Solenoid valves eliminate the need for manual or pneumatic control of a pneumatic circuit and only require an electrical input (and air pressure for piloted valves) to operate, this makes them easy to program and install in a wide variety of applications.

Pneumatic electric solenoid valve