Abstract:
A two way fluid flow check valve includes a plug movable reciprocally lengthwise of the valve against either of respective valve seats within a valve housing. A fixed partition which acts as a piston is located within a cylindrical cavity of the plug. The plug is slidable on a pair of hollow tubes centrally of the housing, the tubes supporting the fixed partition therebetween. The tubes provide respective fluid passages from either end of the housing into the plug cavity on the opposite side of the partition. Upon leakage in the pipe on either side of the valve, the plug will move in response to internal and external fluid pressures from the opposite side, towards the direction of lowered fluid pressure, and will seat against a mating valve seat at that end of the housing, thereby closing the valve. When the leak is repaired and the line pressure is restored, the valve will automatically reopen in response to renewed fluid pressure within the plug cavity on the one side of the fixed partition and the bleeding of fluid from the cavity on the opposite side of the partition, until equalized pressure obtains.