Check valve refers to a valve whose opening and closing part is a circular disc, which blocks the backflow of the medium by its own weight and medium pressure. It is an automatic valve, also known as check valve, check valve, return valve or isolation valve. The movement mode of the valve disc is divided into lifting type and swing type. The lift check valve is similar in structure to the globe valve, but lacks the valve stem that drives the valve disc. The medium flows in from the inlet (lower side) and flows out from the outlet (upper side). When the inlet pressure is greater than the sum of the weight of the disc and the fluid resistance, the valve opens. Conversely, when the medium flows back, the valve closes. The pendulum check valve has a tilting disc that can be rotated around the axis, and the working principle is similar to that of the lift check valve. The check valve is often used as the bottom valve of the pumping device, which can prevent the backflow of water. The check valve is used in conjunction with the globe valve, which can play the role of safety isolation.
Check valves may also be used on lines supplying water to auxiliary systems where the pressure may rise above the system pressure. Check valves can be divided into swing check valves (rotating according to the center of gravity) and lift check valves (moving along the axis).
The purpose of this type of valve is to allow the medium to flow in only one direction and prevent flow in the opposite direction. Usually, such valves work automatically. Under the pressure of the fluid flowing in one direction, the valve flap opens; when the fluid flows in the opposite direction, the pressure of the fluid and the self-coincident flap of the flap act on the valve seat, thereby cutting off the flow.
The check valve belongs to this type of valve, including swing check valve and lift check valve. The swing check valve has a hinge mechanism, and the door-like disc is free to rest on the inclined valve seat surface. In order to ensure that the valve disc can reach the proper position of the valve seat surface every time, the valve disc is designed in the hinge mechanism, so that the valve disc has enough swing space, and the valve disc can really fully contact the valve seat. Depending on the performance requirements, the valve can be made of all metal, or inlaid with leather, rubber or synthetic materials. In the fully open state, the fluid pressure of the swing check valve is almost unimpeded, so the pressure drop across the valve is relatively small. The poppet check valve disc is located on the sealing surface of the valve seat on the valve body. The rest of the valve acts like a globe valve, except that the disc can rise and fall freely. Fluid pressure lifts the disc from the sealing surface of the seat, and the backflow of the medium causes the disc to fall back to the seat, cutting off flow. Depending on the conditions of use, the valve disc can be an all-metal structure, or it can be in the form of a rubber gasket or rubber ring embedded in the valve disc frame. Like globe valves, the passage of fluid through lift check valves is narrow, so the pressure drop across lift check valves is greater than that of swing check valves, whose flow is rarely restricted.
Post time: Aug-26-2022