A gas actuator is a pneumatic device that makes use of gas pressure to move a piston or similar mechanism to provide actuation movement. Most gas actuators are used in industries such as petroleum refinement, where a ready supply of natural gas is available as part of the system process. Some variants do, however, use a captive gas source in applications such as explosion suppression. Gas actuators use either gas alone as a motivator or a combination of gas and hydraulic fluid. These devices may, dependent on design and application purpose, supply linear or rotary actuation outputs.
Actuators are devices used to remotely operate or switch a secondary mechanism. They are generally used in applications where the actuated mechanism is a long distance from staff stations, where large numbers of mechanisms are involved or in hazardous environments which preclude operator proximity. All actuators require a power source to operate and, in the case of the gas actuator, this comes in the form of high pressure gas. The gas is used to press against a piston or vane, which moves as a result. This movement is harnessed to supply the required actuation.
Most gas actuators are used in systems where a ready supply of high pressure gas is present as part of the normal process. A good example of this type of application is the petroleum and natural gas refinement industry. In these applications, gas actuators are used extensive as valve and process machinery activators with the gas actuation source often tapped directly from the line on which the valve or mechanism is located. The high pressure nature of the gas, often exceeding 1,000 pounds per square inch (PSI), make the gas actuator one of the more powerful actuator types, with output values frequently exceeding one million inch pounds. These high-power values are generally needed to operate valves in the aggressive, high-pressure systems involved.
Strictly speaking, a gas actuator uses only gas as a power source. The term is, however, often applied to gas over oil actuators. These devices utilize a high pressure gas source to compress hydraulic oil, which is then used to drive the actuator mechanism. The identifier is also used to describe a family of captive gas actuators used in explosion and fire suppression systems. These actuators are single-duty cycle devices which use a small captive gas cylinder to instantly deploy suppressants in the event of a fire or explosion.
Gas actuator outputs may be supplied as linear or rotary movement. Piston-type actuators are used to generate straight line or linear outputs, while canted scotch yoke-type actuators supply rotary motion. Rotary actuators are usually of the quarter-turn type and used to operate high-pressure butterfly valves.