Check Valves

Check valves are self-activating safety valves that permit gases and liquids to flow in only one direction, preventing process flow from reversing. They are classified as one-way directional valves. Fluid flow in the desired direction opens the valve, while backflow forces the valve closed. The mechanics of check valve operation are relatively simple. Most check valves contain a ball that sits freely above the seat, which has only one through-hole. The ball has a slightly larger diameter than that of the through-hole. When the pressure behind the seat exceeds that above the ball, liquid is allowed to flow through the valve; however, once the pressure above the ball exceeds the pressure below the seat, the ball returns to rest in the seat, forming a seal that prevents backflow.