Is the check valve installed in front of or behind the outlet valve?

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 installing a check valve in front of a pump and installing a check valve after a pump, and where is the pump front installation applicable? Check valves are usually used in conjunction with other valves, so where should the check valve be installed when used in conjunction with other valves? Let's explore together.

A check valve, also known as a check valve, is an automatic valve that relies on the pressure of the flowing medium in the pipeline to push the valve disc to close and open the valve. When the medium stops flowing, the check valve disc closes, effectively preventing the medium from flowing back in the pipeline, which plays a significant role in ensuring the safety of the pipeline.

Check valves can be divided into three types according to their structure: lift check valves, swing check valves, and butterfly check valves. Lift check valves can be divided into two types: vertical and straight through. Swing check valves are divided into three types: single disc, double disc, and multi disc. Butterfly check valves are divided into butterfly double disc and butterfly single disc. The above types of check valves can be connected in four ways: threaded connection, flange connection, welding, and wafer connection.

The installation of a check valve is to ensure the flow direction of water inside the water pump, thereby ensuring the normal operation of the water pump. So, regarding the installation position of the check valve, whether it is installed in front of or behind the water pump can be divided into two situations:

One type is installed at the end of the vertical suction pipe in front of the water pump, also known as the bottom valve. The purpose is to fill the water pump with water without having to pump it once, because when there is no water inside the pump and the suction pipe in front of the pump, the pump can only idle and cannot pump water. Therefore, the pump must be filled with water in order to pump out water. The installation of this type of water pump is a method above the liquid level, also known as negative pressure method.

Another type is installed behind the water pump. This installation method is convenient for starting and stopping the water pump without closing the water outlet valve when the liquid level is higher than the water pump, especially for the main pipe water pump system to prevent backflow.

The check valve must be installed at the outlet of the pump, in front of the outlet control valve, in order to facilitate maintenance of the check valve. The first outlet of a general pump is a soft connection (shock absorber), followed by a check valve, and then an isolation valve (such as butterfly valve, gate valve, globe valve, etc.)

1. Install the check valve first and then the gate or butterfly valve

Advantages: It can protect the check valve, especially in parallel pumps. When one pump does not start and its outlet valve is closed, and when the other pump starts, the impact force is borne by the gate valve or butterfly valve. After the check valve malfunctions, the isolation system of the inlet and outlet valves can be closed for repair.

Disadvantage: Who will protect the gate valve or butterfly valve? There was once a case where the valve plate of a butterfly valve was broken

2. Install gate or butterfly valves first, then check valves

Advantages: It can protect butterfly or gate valves, 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 pressure difference. If the main pipe pressure is high, it will close, and if the pump pressure is high, it will open. If the flow rate used is unstable, the check valve will repeatedly open and close, which will affect the service life of the check valve. And the check valve is broken, especially in the main control system, which needs to be shut down before repair can be carried out.

Generally speaking, due to the frequent opening and closing actions of check valves, the internal connection parts and sealing components are prone to damage. In order to facilitate repair and prevent the entire system from being shut down due to check valve failure, from this perspective, check valves will be installed before the outlet gate valve or butterfly valve. Is this basically what you see?

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