The water pump is the main equipment of the pump station, and it is also the main technical basis for the selection of other equipment and buildings in the pump station. Therefore, the determination of the type and quantity of the pump directly affects the size and investment of the pump station. Therefore, the reasonable choice of the type and number of pumps is a very important task for the design of the pump station.

First, the principle of pump selection

1) Traffic

　　The flow rate of the pump must be selected according to the user's water demand, water source conditions and usage. If the water source is sufficient, the pump only needs to determine the pump specifications according to the maximum water demand.

2) Head

　　The lift on the nameplate of the selected pump should be larger than the actual lift. Under normal circumstances, it should be 5%-10% larger than the actual required lift. Similarly, the pump suction head (allowing the suction of the vacuum lift) should also be larger than the actual lift, otherwise the pump will be difficult to pump. (Note: the higher the required lift, the more attention should be paid to the lift)

3) The average efficiency is high

　　In the long-term operation of the pump station, the average efficiency of the pump operation is high, and it is often best to operate on the right side of the highest efficiency point.

4) Less management costs

　　According to the selected pump type and number of units, it should be easy to install, easy to operate, easy to maintain and manage, and less administrative and operating costs.

5) The possibility of comprehensive utilization

　　When conditions permit, we must try to achieve comprehensive utilization and give full play to the benefits of equipment.

Second, the pump selection and steps

　1. List the basic data:

　　1) Characteristics of the medium: medium name, specific gravity, viscosity, corrosivity, toxicity, etc.

　　2) The particle diameter and content of the body contained in the medium.

　　3) Medium temperature

　　4) The required traffic

　　5) Pressure: suction tank pressure, drain pressure, pressure drop in the piping system (head loss).

　2. Determine the flow and lift:

　　1) Flow rate is one of the important performance data of the pump selection, which is directly related to the production capacity and conveying capacity of the entire unit. For example, the normal, minimum and maximum flow rates of the pump can be calculated in the design of the design institute. When the pump is selected, the normal flow rate is based on the maximum flow rate. When there is no maximum flow rate, 1.1 times the normal flow rate can be taken as the maximum flow rate.

　　2) The head required for the installation system is another important performance data of the pump selection. Generally, the head should be selected by amplifying the 5% to 10% balance.

　3. Determine the material of the pump:

　　1) The material of the pump must meet the requirements of the media characteristics: liquid properties, including the name of the liquid medium, physical properties, chemical properties and other properties. The physical properties are temperature c density d, viscosity u, solid particle diameter and gas content in the medium, etc., which involves the head of the system, the calculation of the effective cavitation margin and the type of suitable pump; the chemical properties, mainly the chemistry of the liquid medium. Corrosion and toxicity are important basis for selecting pump materials and selecting the type of shaft seal.