Working principle of check valve

Check valves can also be used on pipelines that provide supply to auxiliary systems whose pressure may rise above the system pressure. Check valves can be mainly divided into swing check valves (rotating according to the center of gravity) and lift check valves (moving along the axis).

The function of a check valve of this type is to only allow the medium to flow in one direction and prevent flow in the opposite direction. Usually, this type of valve operates automatically, and under the pressure of fluid flowing in one direction, the valve disc opens; When the fluid flows in the opposite direction, the valve seat is cut off by the fluid pressure and the self weight of the valve disc, which acts on the valve seat.

Among them, check valves belong to this type of valve, which includes swing check valves and lift check valves. The swing check valve has a hinge mechanism and a valve disc that is like a door, freely leaning against the inclined valve seat surface. In order to ensure that the valve disc can reach the appropriate position on the valve seat surface every time, the valve disc is designed in a hinge mechanism, so that the valve disc has sufficient swing space and truly and comprehensively contacts the valve seat. The valve disc can be made entirely of metal, or it can be embedded with leather, rubber, or synthetic covering on the metal, depending on the performance requirements. When the swing check valve is fully open, the fluid pressure is almost unobstructed, so the pressure drop through the valve is relatively small. The disc of the lift check valve is located on the sealing surface of the valve seat on the valve body. Except for the valve disc, which can be freely raised and lowered, the rest of the valve is like a globe valve. Fluid pressure lifts the valve disc from the sealing surface of the valve seat, and the medium reflux causes the valve disc to fall back onto the valve seat, cutting off flow. According to the usage conditions, the valve disc can be an all metal structure, or it can be in the form of a rubber pad or rubber ring embedded on the valve disc holder. Like globe valves, the passage of fluid through lift check valves is also narrow, so the pressure drop through lift check valves is greater than that of swing check valves, and the flow rate of swing check valves is limited very little.

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