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Pumps play a very important role in both environmental protection and construction projects in contemporary times. A water pump is a machine that transports liquids or increases their pressure. It transfers the mechanical energy of a prime mover or other external energy to the liquid, thereby increasing its energy level. It is primarily used for transporting liquids such as water, oil, acids, alkalis, emulsions, suspensions, and liquid metals; it can also be used to transport mixtures of liquids and gases, as well as liquids containing suspended solids. A characteristic of pumps is that their speed can vary according to the water demand in the pipeline network, thereby ensuring that the water output of the pump matches the demand and maintaining a stable flow rate. Pumps play a very important role in both environmental protection and construction projects today. A water pump is a machine that transports liquids or increases their pressure. It transfers the mechanical energy of a prime mover or other external energy to the liquid, thereby increasing its energy level. It is primarily used for transporting liquids such as water, oil, acids, alkalis, emulsions, suspensions, and liquid metals; it can also be used to transport mixtures of liquids and gases, as well as liquids containing suspended solids. The characteristic of this pump is that its speed can vary in accordance with the water demand in the piping network, thereby ensuring that the water output of the pump matches the demand in the network and maintaining a relatively constant pressure at the pump’s outlet (or at the most unfavorable point in the network). The variable-speed motor is what distinguishes a constant-speed pump from a variable-speed pump. Due to the aforementioned characteristics of variable-speed pumps, in particular the ability of such pumps to synchronize the water delivery volume of the pump with the water demand of the pipeline network. So how should we choose a water pump? It is recommended to consider five aspects: liquid flow rate, head, liquid properties, pipeline layout, and operating conditions. 1. Flow rate is one of the important performance parameters for selecting a pump; it is directly related to the production capacity and conveying capacity of the entire system. If the design calculations allow, the normal, minimum, and maximum flow rates of the pump can be determined. When selecting a pump, the maximum flow rate should be taken as the basis, with consideration also given to the normal flow rate. In cases where a maximum flow rate is not available, 1.1 times the normal flow rate can generally be used as the maximum flow rate. 2. Head is another important performance parameter for selecting a pump; generally, the head value should be increased by 5%–10% as a margin when making the selection. 3. Properties of the liquid, including the name of the liquid medium, its physical properties, chemical properties, and other characteristics. Physical properties include temperature C, density d, viscosity u, as well as the diameter of solid particles present in the medium and the amount of gas contained within it; these factors are relevant to determining the system’s head pressure, calculating the effective net positive suction head, and selecting the appropriate type of pump. Chemical properties refer mainly to the chemical corrosiveness and toxicity of the liquid medium, and they serve as important criteria for choosing the material for the pump as well as the type of shaft seal to use. 4. The pipeline layout conditions refer to data such as the liquid delivery height, distance, and direction; the lowest liquid level on the suction side and the highest liquid level on the discharge side; as well as details regarding pipe specifications, length, material, fitting specifications, and quantity. These are needed to calculate the system head and to verify the net positive suction head. 5. There are many aspects related to operating conditions, such as the operating temperature of the liquid, the saturated vapor pressure P, the suction side pressure PS (absolute), the pressure in the discharge side container PZ, altitude, ambient temperature, whether the operation is intermittent or continuous, and whether the pump’s location is fixed or movable.