Asahi/America, Inc. Manual Plastic Check Valve Options, Swing Check Options - Assist Assemblies

Swing check valves have the option to install an external spring assist assembly. This spring is made from 316SS and is mounted external to the valve. When fluid pressure starts to drop, the spring retracts the swing arm and brings the disc back into the seat position. This effectively reduces the speed of the fluid flowing back towards the check valve, reducing the shock caused by water hammer. The spring returns the disc to the seat, but does not accommodate sealing. Hence, minimum backpressure requirements still apply for swing check valves with spring assists. The lever and weight assembly for swing check valves achieve the same function as a spring assist. The exception is that the closing action is provided via a weight connected to the swing arm of the valve. Because lever and weight assemblies rely on gravity to provide their assistance on a closed stroke, they tend to work better in vertical installations.