Check Valves Only Allow Flow In One Direction

Check valves only allow flow in one direction and, as such, are similar in operation to electronic diodes. The simplest construction is the ball and seat arrangement of the valve, commonly used in pneumatic systems. The right angle construction is better suited to the higher pressures of a hydraulic system. Free flow direction is normally marked with an arrow on the valve casing.

Check valves are self-actuating valves that minimize the reversal of fluid flow in a piping system. Fluid flow in the desired direction opens the valve, while backflow forces it closed. Check valves are used to

minimize return flow into a system,

enable reciprocating pumps and compressors to start at no load,

prevent centrifugal pumps and compressors from operating in reverse when power is lost.

Check valves are used in lines feeding a secondary system in which the pressure can rise above the primary system. They are classified by the way the seating element moves onto the seat.