How does a lift check valve work? 

Lift check valve refers to the valve which automatically opens and closes the valve disc by replying on the flow of the medium itself to prevent the back-flow of the medium, it is also known as one way valve, non return valve, back pressure valve, cut off valve.

The working principle of the lift check valve is that when the medium flows into the valve body from the direction indicated by the arrow marked on the valve body, the pressure of the medium acts on the valve disc to generate upward thrust. When the medium thrust is greater than the gravity of the valve disc, the lift check valve opens. When the force of the medium pressure behind the valve acting on the valve disc plus the weight of the valve disc itself is greater than the force of the pressure before the valve acting on the valve disc, the lift check valve is closed to prevent the medium from flowing back.