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I. Selection Steps I) List the basic data: 1. Required flow rate 2. Medium temperature: (°C) 3. Particle diameter and concentration of particles in the medium. 4. Properties of the medium: name of the medium, specific gravity, viscosity, corrosivity, toxicity, etc. 5. Pressure: pressure in the water intake tank, pressure in the water discharge tank, and pressure drop (head loss) in the piping system. 6. Pipeline system data (pipe diameter, length, types and quantities of pipeline accessories, geometric parameters from the suction tank to the pressure tank, etc.). If necessary, the device characteristic curve should also be prepared. When designing and arranging pipes, the following points should be taken into account: A. The discharge pipe and its fittings must be designed to withstand the maximum pressure they will experience. B. The pipe layout should be arranged as straight as possible; accessories within the pipes should be minimized, and the length of the pipes should also be reduced as much as feasible. When bends are necessary, the radius of curvature of those bends should be 3 to 5 times the diameter of the pipes, with the angle being as large as possible, exceeding 90°. C. A valve (such as a ball valve or globe valve) and a check valve must be installed on the discharge side of the pump. Valves are used to adjust the operating point of the pump, while check valves prevent the pump from rotating in reverse when the liquid flows backward, thus protecting the pump from water hammer effects. (When the liquid flows back, a huge reverse pressure is generated, which can damage the pump.) D. Choose the pipe diameter appropriately: a larger pipe diameter results in a lower flow velocity at the same flow rate, thereby reducing resistance losses; however, it increases costs. A smaller pipe diameter leads to a sharp increase in resistance losses, which in turn increases the head required of the pump, as well as its power consumption, thus raising both costs and operating expenses. Therefore, it should be considered from both technical and economic perspectives. II) Determining flow rate and head Determination of flow rate a. If only the mass flow rate is provided as basic data, it should be converted to volume flow rate. b. If only the normal flow rate is given in the production process, a certain margin should be taken into account. c. If minimum, normal, and maximum flow rates are specified in the production process, the maximum flow rate should be taken into consideration. II. Selection Principles Pumps are a type of general-purpose mechanical equipment that is widely used in various sectors such as petroleum, chemicals, power and metallurgy, mining, shipbuilding, light industry, agriculture, civil use, and national defense; they hold an important position in the national economy. According to statistics from 1979, China’s pump production reached 1.256 million units. The electrical energy consumption of pumps accounts for over 21% of the country’s total electrical energy consumption. Therefore, significantly reducing the energy consumption of pumps is of great importance for saving energy. In recent years, our pump industry has designed and developed many high-efficiency and energy-saving products, such as pump models of the IHF, CQB, FSB, UHB series, which have played a positive role in reducing the energy consumption of pumps. However, at present in various sectors of the national economy, due to improper selection, many pumps are operating under suboptimal conditions, resulting in low efficiency and significant energy waste. There are also pumps that, due to improper selection, cannot be used at all, or whose operation and maintenance costs are high, resulting in low economic efficiency. It can be seen that choosing the right pump is also of great significance for saving energy. The so-called rational selection of pumps involves taking into account a range of technical and economic factors, such as the investment and operating costs associated with the pump units and pumping stations, in order to ensure that the choice meets the principles of economy, safety, and suitability. Specifically, there are the following aspects: It is necessary to meet the requirements regarding flow rate and head; in other words, the operating point of the pump (the intersection of the device’s performance curve and the pump’s performance curve) must remain within the high-efficiency range as much as possible. This not only saves energy but also reduces the risk of damage to the pump’s components. The selected pump should be small in size, light in weight, and inexpensive, while also possessing good performance characteristics and high efficiency. It has excellent cavitation resistance, which not only reduces the excavation depth required for the pump house but also prevents cavitation in the water pump, ensuring stable operation and a long service life. Pump stations are built using the selected water pumps, resulting in low project investment and low operating costs.