Pneumatically operated valves are comprised of two basic units:

• an actuator with a piston assembly or diaphragm which develops applied force when pressurized;
• a valve with an orifice to stop or permit air flow via an air pressure plug or disc.

What are Pneumatically Operated Valves?

Controlled air for the actuator is totally isolated from the main input line by a valve with a unique seal arrangement, so that any pressure within its overall range will allow the valve to operate. This permits a degree of pressure fluctuation in the main input line. Two forms of pneumatically operated valves are generally used. Direct acting valves have a drive operator stem, moved by a piston or diaphragm which directly closes or opens the valve orifice, while systems with internal pilot valves use the input line pressure for operating a secondary work valve.

Two styles of pneumatically operated valves are commonly available:

Valves also come in different operating types:

• 2-Way Valves (either Normally Closed or Normally Open), often used in safety applications;
• 3-Way Valves (NC, NO and universal), normally used for spring-return and single drive cylinders;
• 4-Way Valves using two 3-way functions at the same time. This type have one NC and one NO, two alternating pressurised and exhausted outlet ports, and are used to control two-directional air motors and double drive cylinders.