Air operated valve is a type of power-operated valve that uses air pressure against a piston or diaphragm to produce linear or circular movement to operate a valve. The air-operated valve is commonly used in applications, which require a valve to open and shut quickly and that must be placed in fail-safe position. A fail-safe position refers to the state that a given component would revert to, in order to minimize plant equipment damage and personal endangerment, if that component were to become damaged or faulted. Air operated valve are typically designed to stroke using an incoming air pressure between 40 and 80 psig, are relatively inexpensive and are easy to install and maintain.
Air pilot switch consists of a high-pressure sensor operator connected directly to a three-way air valve that can be operated either normally open or closed. The spring in the sensor applies a counteracting force to the switch and is adjustable within the spring range. All air pilot switches are subject to dead band conditions, which should be considered when using the valve. A dead band is described as the difference in pressure between a set point of sensing pressure and a pressure at which the air valve returns to the original position. Dead band conditions vary by pressure range in percentage with high-pressure conditions reducing the dead band range. Air pilot switch valves are most commonly used to control automatic turn on and shut off of a gas booster or pump system and are used in conjunction with a remote pilot on the booster or pump.