A piston check valve is self actuated ,one way valve,essentially a lift type check valve which allows flow in one direction only. This valve is also Non-return Valve (NRV).
Construction and Operation of Piston Check Valve
Construction of the seat and disk of a piston check valve is the same as for lift check valves. Main component of piston check valve is its dashpot. Dashpot of piston check valve consists of a piston and cylinder that provides a cushioning effect during operation.
As the design of piston check valve is similar to lift check valve, the flow characteristics through a piston check valve are also same as through a lift check valve.
Installation of this NRV(non-return valve) is the same as for a lift check in that the flow must enter from under the valve seat.