Pneumatic (air) assisted control valves are used to control the flow of water and liquid food products, petroleum products, and other chemicals through large piping. These types of valves are opened and closed by an electrical signal that is converted to air pressure. Pneumatic-operated valves became popular prior to the advent of electronic and solid-state components being used in industrial electronics. Pneumatic systems could provide analog control to open and close very large valves smoothly. The pneumatic-controlled valves allowed the valve opening to be anywhere between full closed and full open. The signals for these systems were transmitted over long distances throughout a factory or process plant by transmitting air through plastic tubing or copper tubing. Pneumatic technology has proven so dependable it has been incorporated with modern electronic systems and controls. Hence, new technology today can use an electronic or microprocessor controller and use an electronic-to-pneumatic converter that changes a milliamp signal to a pneumatic signal. The electrical signal is proportional 4-20 mA and the air pressure is proportional 3-15 psi.
These types of valves are commonly used as loads in the process industries. They're also used in applications where explosive atmospheres exist such as in spray painting and chemical processing.
