ball-check valve

A type of flow control valve used in a fluid power system to allow fluid to flow in one direction but not in the other. A ball check valve contains a spring-loaded ball that seats in one side of the valve. The ball is forced tightly against its seat by fluid entering the valve from the end containing the spring, and the fluid cannot flow through the valve. Pressure on the side of the valve containing the ball forces the ball off its seat and fluid flows through the valve. Fluid flowing through the valve is opposed only by the force of the spring.