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Pump classification: A pump is a machine that converts the mechanical energy of a prime mover into the energy of a liquid. The prime mover (electric motor, diesel engine, etc.) drives the impeller to rotate through the pump shaft, doing work on the liquid and increasing its energy (including potential energy, pressure energy and kinetic energy), thereby transporting the liquid to high places or places requiring pressure. Types and technical performance of pumps According to the principle of action, pumps can be divided into power pumps, positive displacement pumps and other types of pumps. 1． Centrifugal pump The basic performance parameters of a centrifugal pump are flow Q (m3/h, L/h), head H (m), allowable NPSH Δhr (m), speed n (rev/min), shaft power N and efficiency eta. This type of pump has a simple structure and is light in weight. It can transport clean water with a temperature not exceeding 80°C and liquids with physical and chemical properties similar to water. 2． Axial flow pumps Most axial flow pumps are single-stage and can be divided into fixed vane type and adjustable vane type. 3． Compared with centrifugal pumps, under the same impeller diameter and speed, the head of vortex pumps is 2 to 4 times higher than that of centrifugal pumps, but its efficiency is lower, generally only 20% to 50%. The liquid delivered by the vortex pump is clean, has low viscosity and does not contain solid particles. 4． Reciprocating pumps There are four types of reciprocating pumps: electric pumps, direct-acting pumps, diaphragm pumps, and metering pumps. 5. Screw pump Screw pump is characterized by small flow and pressure pulsations, low noise, long life, self-priming ability, and simple and compact structure. There are single screw pumps, twin screw pumps and three screw pumps. 6． Gear pump The gear pump has a simple structure, is easy to manufacture, works reliably, is easy to maintain, and can be self-priming, but the pulsation and noise of flow and pressure are large. Gear pumps are suitable for transporting a variety of liquids that do not contain solid particles. They have a wide viscosity range and can transport high-pressure liquids. 7. Liquid ring pump The liquid ring pump is a fluid machine that transports gas. The working fluids of liquid ring pumps often include water, sulfuric acid, oil, etc. Liquid ring vacuum pumps are often used for vacuum evaporation, drying, water pump water absorption, etc. Liquid ring compressors are mainly used to pressurize gas, ethylene, chlorine, oxygen, etc. 8. There are many types of vacuum pumps, including reciprocating vacuum pumps, rotary vacuum pumps, Roots vacuum pumps and jet vacuum pumps.