Check valve is to rely on the media itself activity and active open, closed disc, used to avoid medium backflow valve, also known as check valve, one-way valve, reverse flow valve, and back pressure valve. The check valve is classified as an active valve whose primary effect is to avoid media backflow, to avoid pump and drive motor reversals, and to discharge vessel media.

The check valve may also be used in the supply line for auxiliary systems where the pressure may rise above the system pressure. Check valve the effect of this type of valve is to allow only one direction of movement of the medium and to obstruct movement in the opposite direction. Usually this valve is active, in one direction of the fluid pressure effect, the disc open; When the fluid moves in the opposite direction, the pressure of the fluid and the self-coincidence of the disc act on the seat and then cut off the movement.

Check valves can be divided into swing check valve (rotating according to the center of gravity) and lift check valve (moving along the axis). Swing check valves have a meso-hinge mechanism and a disc like a door resting freely against the skewed seat surface. To ensure that the disc reaches the proper orientation of the seat face each time, the disc is designed in a hinged mechanism so that the disc meets with swing space and the disc truly and fully touches the seat. The disc may be made entirely of metal or may be inlaid with leather, rubber or perhaps with a composition covering, depending on the performance of the application. Swing check valve in the case of full open, the fluid pressure is simply not stopped, so the pressure drop through the valve is relatively small.

The disc of the elevating check valve is located on the seat sealing surface of the valve body. This valve except that the disc can rise and fall freely, the rest of the valve seems to be the same as the globe valve, the fluid pressure causes the disc to be lifted from the seat sealing surface, the media backflow causes the disc to fall back to the seat and cut off the movement. Depending on service conditions, the disc may be of an all-metal construction or may be inlaid with a rubber pad or ring on the disc holder. Like globe valves, the passage of fluid through the lift check valve is narrow, so the pressure drop through the lift check valve is larger than the swing check valve, and the flow of the swing check valve is less constrained.

Check valve test status

Elevating check valve disc axis in a straight horizontal direction; The axis of the swing check channel and disc are approximately parallel to the horizontal line.

During the strength test, the test medium shall be introduced from the inlet end to the specified value, and the other end shall be closed, and the valve body and cover shall be qualified without leakage.

For sealing test, it is qualified to introduce experimental medium from the outlet end and check the sealing surface at the inlet end. No leakage is found in the packing and gasket.