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Nov. 16, 2021
A check valve is a kind of automatic valve. It relies on the pressure of the flowing medium in the pipeline to push the valve flap to close and open the valve. When the medium stops flowing, the check valve flap closes, which can effectively prevent the backflow of the medium in the pipeline, which plays a great role in ensuring the safety of the pipeline.
The check valve must be installed in a position after the pump outlet and before the outlet control valve in order to service the check valve. The first general pump outlet is a soft connection (damper), followed by a check valve, followed by a shut-off valve (such as a butterfly valve, gate valve, globe valve, etc.).
Advantages: can protect the butterfly valve or gate valve, the impact force by the check valve to bear.
Disadvantages: lack of protection for the check valve. The check valve is dependent on the pressure difference to switch, if the main pipe pressure is high to close, the pump pressure is high to open, if the use of unstable flow, then the check valve will repeatedly switch, will affect the check valve life. And the check valve is broken, especially the master control system, need to stop the system before repair.
Advantages: can protect the check valve, especially in parallel pumps, when a pump does not start, its outlet door closed, another pump start, the impact is gate valve or butterfly valve bear. After the failure of the check valve, the inlet and outlet valves can be closed to isolate the system for repair.
Disadvantages: gate valve or butterfly valve lack of protection. There was a case that the valve plate of the butterfly valve was broken.
The check valve is installed to ensure the flow of water inside the pump, so as to guarantee the normal work of the pump. So about the installation position of the check valve, whether it is installed in front of the pump or after the pump, it can be divided into two cases.
This installation method is the case that the liquid level is higher than the pump so that it is convenient to start and stop the pump without closing the pump discharge valve. Especially for the mother control pump system, to prevent the backflow situation.
The purpose of this installation method is to fill the pump with water without pumping once. Because there is no water in the pump or in the suction pipe in front of the pump, the pump can only idle and pump no water. Therefore, the pump must be filled with water in order to pump out water. This kind of pump installation is a method when it is above the liquid level, also called the negative pressure method.
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