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Examples of pump selection: First, understand the process parameters involved in choosing a pump: ① Flow rate Q: Process engineers should specify the normal, minimum, and maximum flow rates; when selecting a pump, its rated flow rate should be no less than the maximum flow rate of the system, or it should be 1.1 – 1.15 times the normal flow rate. ②Head H: The head value required by the process unit; the rated head of the pump is generally 1.05 to 1.1 times the head required by the unit. ③Import and export pressures: Affect the pressure resistance requirements of the housing and the shaft seal requirements. ④Temperature T: The normal, minimum, and maximum temperatures of the medium at the pump inlet should be specified. ⑤Device net positive suction head available NPSHa: that is, the effective net positive suction head available. ⑥Operation mode: divided into continuous and intermittent operation. ⑦Site conditions: include the pump installation location (indoor, outdoor), ambient temperature, relative humidity, atmospheric pressure, degree of atmospheric corrosion, and hazard zone classification, etc. I. Key Points for Pump Selection 1. Selection Criteria Physical and chemical properties of the fluid to be transported: including the type of fluid, its corrosiveness, abrasiveness, toxicity, the content and size of solid particles, density, viscosity, vapor pressure, gas content, and whether it tends to crystallize. These parameters have a significant impact on the performance, materials, and structure of the pump, and must be taken into consideration during selection. For example: The discharge pump of the three-effect evaporator transports an aqueous solution containing sodium chloride; chloride ions are corrosive, and the slurry is abrasive, with a solid content of about 10% and particle sizes of around 0.12 mm. 2. Selection of pump type: Centrifugal pumps have a simple structure, produce no pulsation in the fluid flow, and allow for easy flow regulation; they should be given priority over other types, except in special cases. Choose a metering pump if metering requirements are present. When a high head and low flow rate are required and no suitable centrifugal pump is available, a reciprocating pump should be chosen; or when the requirement for cavitation resistance is not high, a vortex pump is an option. For low head and high flow rates, axial flow pumps and mixed-flow pumps are chosen. For media with high viscosity (greater than 650 – 1000 mm²/s), use rotary pumps (such as screw pumps) or reciprocating pumps ； When the viscosity is particularly high, a specially designed high-viscosity pump should be used. When the gas content in the medium is >5%, the flow rate is low, and the viscosity is less than 37.4 mm²/s, a vortex pump should be chosen; a reciprocating pump can be used if flow rate fluctuations are acceptable. In situations where startup is frequent or pumping is inconvenient, choose pumps with self-priming capabilities (such as self-priming centrifugal pumps, vortex pumps, and positive displacement pumps). II. Selecting the appropriate pump based on the properties of the medium 1. Freshwater pump: In urban water supply systems, the medium transported is ordinary clean tap water that does not possess any corrosive or toxic properties; in such cases, a freshwater pump can be used. For example, the IS type clean water centrifugal pump is suitable for transporting clean water at temperatures below 80°C or liquids with physical and chemical properties similar to those of clean water. It has a simple structure and can meet the basic requirements for transporting tap water. 2. Corrosion-resistant pumps: For transporting sulfuric acid in chemical plants, corrosion-resistant pumps are required due to the strong corrosive nature of sulfuric acid; examples include centrifugal pumps made of fluoroplastic alloys. Its overcurrent components are made of fluoroplastic alloys, which offer excellent corrosion resistance and can effectively resist the corrosion caused by sulfuric acid, ensuring the proper operation and longer service life of the pump. 3. Leak-free pumps: In pharmaceutical factories, when transporting highly pure, highly toxic, or valuable liquid medications for which leaks are not permissible, shielded pumps can be used. For example, in the case of shielded pumps used for transporting insulin solutions, the motor and the pump body are integrated together; a shielding sleeve separates the motor rotor from the stator, keeping the medium completely enclosed within the pump body and thus eliminating any possibility of leakage. This meets the strict requirements of the pharmaceutical industry regarding the transportation of media during drug production. 4. Pumps with low net positive suction head: In the LPG transportation systems of petrochemical enterprises, LPG is a volatile liquid. To prevent cavitation from affecting the proper operation of the pump, a cylindrical pump can be used. Tubular pumps have a low net positive suction head, which enables them to effectively avoid cavitation issues caused by the vaporization of liquids when transporting volatile liquids, thus ensuring the stable transport of LPG. III. Selecting the pump type based on installation conditions 1. Horizontal pumps: Horizontal pumps have a low center of gravity, making them easy to install and maintain; they are suitable for horizontal installation in indoor environments with favorable space conditions. 2. Vertical pumps (submersible pumps): In the wastewater tanks of sewage treatment plants, it is necessary to pump out the wastewater at the bottom of the tanks for treatment. A vertical submersible sewage pump can be installed directly in the sewage tank, with its pump body submerged in the liquid, and it is connected to the motor above via a long shaft. Such an installation method not only saves space but also prevents critical components such as motors from being corroded by sewage, ensuring the proper operation of the pump. 3. Vertical pumps (pipeline pumps): In the fire water supply systems of high-rise buildings, it is necessary to pressurize the fire water and transport it through pipeline systems. To facilitate direct connection to piping systems and reduce floor space, a pipeline pump can be used. It can be installed directly on fire protection pipelines, has a compact design, and allows for easy and quick connection to pipes, thus meeting the requirements of high-rise buildings regarding space constraints and ease of installation for fire protection water supply. IV. Selection of pump type based on flow rate 1. Single-suction pump: In small-scale agricultural irrigation systems, where the area to be irrigated is small and the amount of water required for irrigation is relatively low, the flow rate is generally around 5 – 20 m³ per hour. Single-suction pumps have a simple structure and low cost, making them suitable for irrigation needs with low flow rates; they can meet the daily irrigation water requirements of small farms. 2. Double-suction pumps: In the process of supplying water to cities by large urban water treatment plants, a high flow rate is required to meet the water needs of numerous urban users; generally, the flow rate can reach several hundred cubic meters per hour or even higher. Double-suction pumps are characterized by their high flow rate; they have suction inlets on both sides of the impeller, allowing water to be drawn in from both sides simultaneously, which meets the high-flow requirements for large-scale water supply in cities. 3. Low-flow centrifugal pumps: In laboratories, it is often necessary to transfer small amounts of liquid with precision; for example, in chemical experiments, certain reagents need to be transferred, and the flow rate is generally below 1 m³ per hour. This pump features low flow rate and high precision, meeting the laboratory’s needs for precise transfer of small volumes of liquid. Additionally, its magnetic drive mechanism ensures leak-free transfer of the liquid, satisfying the special requirements regarding reagent transfer in laboratories. V. Selecting the pump type based on head requirement. Single-stage pumps: In typical residential community water supply systems, where water is supplied from the community’s reservoir to residential buildings, and these buildings are usually multi-story structures (6–8 floors), the required head is relatively low, around 20–40 meters. In this case, a single-stage centrifugal pump can be used, such as the CDLF type lightweight stainless steel vertical multi-stage centrifugal pump (operated in single-stage mode). 2. Multi-stage pumps: In the water supply systems of high-rise buildings (30 floors and above), due to the great height of these buildings, water needs to be lifted to a significant altitude, requiring a high head pressure, typically around 80 – 150 meters. 3. High-speed centrifugal pumps: In the special process flows of some petrochemical enterprises, it is necessary to raise liquids to high pressures and elevations in a short time, with a relatively low flow rate. In the lubricant delivery systems of petrochemical plants, in order to rapidly transport lubricant to high-pressure equipment at specific process stages, a high head (around 100 – 150 m) and certain pressure are required. VI. Selection of Pump Series and Manufacturing Inspection Standards 1. Selection of pump series and manufacturer: For the corrosion-resistant pumps used in hydrochloric acid transmission systems in chemical enterprises, market research has shown that the IHF series of fluoroplastic alloy centrifugal pumps meets the requirements. These pumps offer reliable quality, enjoy a good reputation in the chemical industry, and have numerous successful application cases. 2. Selection of manufacturing inspection standards: If a chemical company has high requirements regarding the quality and performance of pumps – for example, if it demands high standards for the quality of the products it produces, as well as high standards for the reliability and safety of the pumping equipment – and if its procurement budget permits it, then the API610 standard can be chosen. Pumps manufactured in accordance with this standard adhere to strict specifications and requirements in terms of design, materials, manufacturing processes, and inspection procedures, ensuring their stable and reliable operation under long-term, complex conditions in chemical production. VII. Selection of diaphragm metering pumps based on medium properties 1. Transporting highly toxic liquids in chemical enterprises: In a pesticide manufacturing plant, it is necessary to transport liquid raw materials containing highly toxic organophosphorus pesticide components. Due to the highly toxic nature of this liquid, any leakage can cause serious harm to people and the environment; therefore, a diaphragm metering pump is used for its transfer. Specifically, a double-diaphragm metering pump was selected, equipped with a diaphragm rupture alarm. When the inner diaphragm ruptures, the alarm device immediately emits a warning to alert operators to take action promptly, preventing the leakage that could result from the mixing of highly toxic liquids with hydraulic oil, thereby ensuring production safety and the health of personnel. 2. Transportation of flammable and explosive liquids in the petrochemical industry: Refineries often need to transport flammable and explosive liquids such as gasoline and liquefied petroleum gas. Taking gasoline transportation as an example, diaphragm metering pumps are used to ensure safety. 3. Transporting valuable liquids in the pharmaceutical industry: When biopharmaceutical companies produce high-value monoclonal antibody drugs, certain components of the liquid substances used in the production process are extremely expensive. To prevent economic losses due to leaks during the delivery of the liquid medication, a diaphragm metering pump is used.