The check valve, also called a check valve, is an 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, it can be effective to prevent the medium in the pipeline from flowing back, which plays a great role in ensuring the safety of the pipeline.
According to the structure of the check valve, it can be divided into stainless steel lifting check valve, stainless steel swing check valve, and butterfly check valve. Lift check valves can be divided into two types: vertical and straight-through. Swing check valves are divided into three types: single, double, and multiple. Butterfly check valves are divided into butterfly double flaps and butterfly single flaps. The above types of check valves can be divided into four types in connection form: threaded connection, flange connection, welding, and wafer connection.
The check valve is installed to ensure the flow direction of the water flow inside the pump, so as to ensure the normal operation of the pump. Therefore, regarding the installation position of the check valve, whether it is installed before or after the water pump, there are two situations:
One is installed at the end of the vertical suction pipe in front of the pump, also called a bottom valve. The purpose is to fill the pump without pumping water once, because when there is no water in the pump and the suction pipe in front of the pump, the pump can only be idling and cannot pump water, so the pump must be filled with water to pump out water. The installation of this kind of water pump is a method when it is higher than the liquid level, also called the negative pressure method.
The other is installed behind the pump. This installation method is that when the liquid level is higher than the water pump, it is convenient to start and stop the water pump without closing the water pump outlet valve, especially for the main control water pump system to prevent backflow.
Butterfly check valve must be installed at the outlet of the pump and before the outlet control valve in order to check the check valve. Generally, the first outlet of the pump is the soft connection (shock absorber), the next is the check valve, and then the isolation valve (such as butterfly valve, gate valve, stop valve, etc.)
1. Install the check valve first and then the gate valve or butterfly valve
Advantages: It can protect check valves, especially in parallel pumps. When one pump does not start, its outlet door is closed, and when the other pump starts, the impact force is borne by the gate valve or butterfly valve. After the check valve fails, the inlet and outlet valve isolation system can be closed for repair.
Disadvantages: Who will protect the gate valve or butterfly valve? There has been a case where the valve plate of a butterfly valve was broken.
Stainless Steel Swing Check Valve
2. Install a gate valve or butterfly valve first and then check the valve
Advantages: It can protect the butterfly valve or gate valve, and the impact force is borne by the check valve.
Disadvantages: Who will protect the check valve? The check valve is opened and closed by the pressure difference. If the pressure of the main pipe is high, it will be closed, and the pressure of the pump will be opened. If the flow rate used is unstable, the check valve will switch repeatedly. Affect the life of the check valve. And the check valve is broken, especially the mother control system, it needs to be shut down before repairing.
Generally speaking, due to the frequent opening and closing actions of the check valve, the internal connecting parts, and the sealing parts are prone to damage. In order to facilitate repairs and prevent the entire system from shutting down due to the failure of the check valve, from this perspective, check The valve will be installed before the outlet gate valve or butterfly valve. Do you see this basically?
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