Today we will discuss the installation position of check valve. Check valve is usually used with other valves, so when it is used with other valves, where should the check valve 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 disc to close and open the valve. When the medium stops flowing and the check valve disc is closed, it can effectively prevent the medium in the pipeline from backflow, which plays a great role in ensuring the safety of the pipeline.
According to the structure, the check valve can be divided into lift check valve, swing check valve and butterfly check valve. Lift check valve can be divided into two types: vertical type and straight type. Swing check valve is divided into three types: single disc, double disc and multi disc. Butterfly check valve can be divided into butterfly double disc and butterfly single disc. The above check valves can be divided into four connection forms: threaded connection, flange connection, welding and wafer connection.
The installation of check valve is to ensure the flow direction of water inside the pump, so as to ensure the normal operation of the pump. Therefore, as for the installation position of check valve, whether it is installed in front of or after the water pump, there are two situations:
One 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 not to pump primary water to fill the pump with primary water, because the pump can only idle without water in the pump and the suction pipe in front of the pump, 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 at the rear of the water pump. When the liquid level is higher than the water pump, it is convenient to start and stop the water pump without closing the water outlet valve of 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 and in front of the outlet control valve to facilitate the maintenance of the check valve. Generally, the first outlet of the pump is a soft connection (shock absorber), followed by a check valve, followed by a block valve (such as butterfly valve, gate valve, stop valve, etc.)
1. Install check valve first and then gate valve or butterfly valve
Advantages: it can protect check valve, especially in parallel pump. When one pump does not start, its outlet valve is closed, and the other pump starts, the impact force is borne by gate valve or butterfly valve. After the check valve fails, the isolation system of inlet and outlet valves can be closed for repair.
Disadvantages: who will protect the gate valve or butterfly valve? In one case, the valve plate of butterfly valve was broken.
2. Install gate valve or butterfly valve first and then check valve
Advantages: it can protect butterfly valve or gate valve, and the impact force is borne by check valve.
Disadvantages: who will protect the check valve? The check valve is opened and closed by the pressure difference. If the main pipe pressure is high, the pump pressure is high. If the flow used is not stable, the check valve will be opened and closed repeatedly, which will affect the service life of the check valve. And the check valve is broken, especially the main control system, which needs to be stopped before repair.
Generally speaking, due to the frequent opening and closing action of check valve, the internal connecting parts and sealing parts are easy to be damaged. In order to facilitate repair and prevent the whole system from being shut down due to the failure of check valve, from this point of view, check valve will be installed before the outlet gate valve or butterfly valve. Do you see that basically?