Check valve refers to a valve whose opening and closing part is a circular disc, which acts by its own weight and medium pressure to block the backflow of the medium. It is an automatic valve, also known as a check valve, one-way valve, return valve or isolation valve. The movement mode of the valve disc is divided into lift type and swing type. The lift check valve is similar in structure to the globe valve except for the valve stem that drives the 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 its flow resistance, the valve opens. Conversely, when the medium flows back, the valve closes. Rotary check valves have an inclined disc that can be rotated around an axis and work similar to lift check valves. 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.
working principle:
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 fluid flowing in one direction, it opens at the valve flap. When the fluid flows in the opposite direction, the fluid pressure and the weight of the valve disc 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, so that the valve disc and the valve seat are truly in full contact. Discs can be all metal or inlaid with leather, rubber or synthetic coverings, depending on performance requirements. 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 disc of the poppet check valve is located on the sealing surface of the valve seat on the valve body. Except that the disc can rise and fall freely, the rest of the valves are like globe valves. Fluid pressure lifts the disc from the seat sealing surface, 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 disc can be an all-metal structure, or it can be in the form of a rubber pad or rubber ring embedded in the disc frame. As with globe valves, the passage of fluid through lift check valves is narrow, so the pressure drop across lift check valves is greater than swing check valves, whose flow is rarely restricted.
Post time: Aug-20-2022