Check valve, also known as check valve, is an automatic valve, which relies on the pressure of the flowing medium in the pipeline to push the valve disc to achieve the closing and opening of the valve, when the medium stops flowing, the check valve disc is closed, it can effectively prevent the medium in the pipeline from backflowing, which plays a great role in ensuring the safety of the pipeline.
According to the structure, the check valve can be divided into three types: lifting check valve, swing check valve and butterfly check valve.
Lifting check valves can be divided into vertical and straight-through types.
There are three types of swing check valves: single-petal, double-petal and multi-petal.
Butterfly check valves are divided into butterfly double valve, butterfly single valve, the above check valves can be divided into four kinds of connection form: threaded connection, flange connection, welding and clamp connection.
The purpose of installing the check valve is 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, whether it is installed in front of the pump or behind the pump, can be divided into two situations:
One is installed at the end of the vertical suction pipe in front of the pump, also called the bottom valve. The purpose is to fill the pump with water without pumping water once, because the pump can only idle and pump water when there is no water in the pump and in the suction pipe in front of the pump, so the pump must be filled with water to pump out the water. This kind of pump is installed as a method when it is higher than the liquid level, also known as the negative pressure method.
The other is installed at the rear of the pump. This installation method is when the liquid level is higher than the pump, which is convenient to start and stop the pump without closing the pump outlet valve, especially for the mother tube pump system, to prevent the occurrence of backflow.
The check valve must be installed at the outlet of the pump, in front of the outlet control valve, in order to allow access to the check valve. Generally, the outlet channel of the pump is a soft connection (shock absorber), followed by a check valve, and then a partition valve (such as 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 the parallel pump, when one pump does not start, its outlet door is closed, and the other pump starts, the impact force is borne by the gate valve or butterfly valve. In the event of a check valve failure, the inlet and outlet valve isolation system can be closed for repair.
Disadvantages: Who will protect the gate valve or butterfly valve?
2. Install the gate valve or butterfly valve first and then install the check valve
Advantages: It can protect butterfly valves or gate valves, and the impact force is borne by the check valve.
Disadvantages: who will protect the check valve, the check valve is switched on and off by the pressure difference, if the main pressure is high, the pump will be opened if the pressure is high, if the flow rate used is unstable, then the check valve will be repeatedly switched and closed, which will affect the life of the check valve. Moreover, the check valve is broken, especially the parent control system, and the system needs to be shut down before it can be repaired.
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