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Where to install check valve before or after the outlet valve

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Update time : 2020-06-12 10:33:15

Today we will discuss the installation position of the check valve. So how to determine the installation position of the check valve? What is the difference between the installation before the pump and the installation of the check valve after the pump, and where does the installation before the pump apply?
Check valves are usually used in conjunction with other valves, so when used with other valves, where should the check valves be installed? Let's discuss it together.
Check valve, also called 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 and the check valve flap closes, it can effectively prevent the medium from flowing back in the pipeline, which plays a role in ensuring the safety of the pipeline. Great effect.

 Check valves can be divided into three types: lift check valves, swing check valves and butterfly check valves.
Lift check valve can be divided into two types of vertical and straight. The swing check valve is divided into three types: single-petal type, double-petal type and multi-petal type. 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: threaded connection, flange connection, welding and wafer connection.
The check valve is installed to ensure the flow direction of the internal water flow of the pump, so as to ensure the normal operation of the pump. So regarding the installation position of the check valve, whether it is installed in front of the pump or after the pump can be divided into two situations:
One is to install the end of the vertical suction pipe in front of the pump, also called the bottom valve. The purpose is to charge the pump once without pumping water. Because the pump and the suction pipe in front of the pump are empty, the pump can only idling to 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 negative pressure method.

 The other is installed behind the water pump. This installation method is convenient for starting and stopping the pump without closing the pump outlet valve when the liquid level is higher than that of the pump, especially for the female control pump system to prevent backflow.

 The check valve must be installed at the outlet of the pump and before the outlet control valve in order to repair the check valve. Generally, the first outlet of the pump is a soft connection (shock absorber), followed by a check valve, and then a blocking valve (such as a butterfly valve, gate valve, globe valve, etc.)

 1. Install the check valve first and then install the gate valve or butterfly valve
Advantages: It can protect the check valve, especially in parallel pumps. When one pump is not started, the outlet door is closed, and the other pump is started, the impact force is borne by the gate valve or the butterfly valve. After the check valve fails, you can close the inlet and outlet valve isolation system for repair.
Disadvantages: who will protect the gate valve or butterfly valve? There was a case where the valve plate of the butterfly valve was smashed.

 2. Install gate valve or butterfly valve first and then check 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 switched by the pressure difference, if the main pipe pressure is high, it will be closed, and the pump pressure will be opened, if the flow rate used is unstable, then the check valve will be switched repeatedly. Affect the life of the check valve. And the check valve is broken, especially the female control system, which needs to be shut down before repairs can be made.
In general, due to the frequent opening and closing actions of the check valve, the internal connection parts and sealing parts are prone to damage. In order to facilitate repair and prevent the entire system from being shut down due to the failure of the check valve, from this perspective, the check The valve will be installed before the outlet gate valve or butterfly valve.

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