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 known as non return valve, is an automatic valve. It 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 and the check valve disc closes, it can effectively prevent the medium from flowing back in the pipeline, which plays a role in ensuring the safety of the pipeline.
According to the structure, 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, double-petal and multi-petal. Butterfly check valves are divided into butterfly double disc and butterfly single disc. 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 water flow inside the pump, so as to ensure the normal operation of the pump. Therefore, the installation position of the check valve can be divided into two situations: before or after the water pump.
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 not need to fill the pump once with every pumping water. Because when there is no water in the pump and the suction pipe in front of the pump, the water pump can only be idle and cannot pump water, so the water 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 main pipe water 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: gate valve or butterfly valve has nothing to protect
2. Install gate valve or butterfly valve first and then install the check valve
Advantages: It can protect the butterfly valve or gate valve, and the impact force is borne by the check valve.
Disadvantages: check valve has nothing to protect. The check valve is switched by the pressure difference. If the main pipe pressure is high, it will be closed, and if the pump pressure is high，it will be opened. If the flow rate used is unstable, the check valve will be opened and closed repeatedly, which will affect the life of the check valve. Moreover, the check valve is broken, especially the main control system, which needs to be shut down before it can be repaired.
In general, due to the frequent opening and closing actions of the check valve, the internal connection parts and sealing components are prone to damage. To facilitate repairs and prevent the entire system from being shut down due to a check valve failure, from this perspective, the check valve will be installed before the outlet gate valve or butterfly valve, is it basically the same as what you see?