Check valves,non-return valves,are designed to prevent the reversal of flow in a piping system. These valves are activated by the flowing material in the pipeline.The pressure of the fluid passing through the system opens the valve

API598 check valve,swing check valve designed and manufacturered according to ASME B16.34,test and inspect to API598,API6D.

That opening has to be clear in order for anything to pass through. The disc is attached to a hinge, so the disc can swing open or closed when liquid hits the disk. It's kind of like a circular door. The direction of the flow is the most important thing when using these valves.

When liquid is traveling in the desired direction, the pressure of the flow pushes the door open, allowing liquid to pass through. When liquid travels in the wrong direction, the opposite happens. The force of liquid coming back through the valve pushes the disc against its seat, closing off the valve. When installing a swing check valve, it is vital that it opens when liquid is passing through the desired direction. If you install one of these valves and no water goes through, then it is the wrong way around and must be reinstalled. If your swing check valve has a true union design, it can easily be removed from the pipeline.