First, the principle of selection of the pump 1, the type and performance of the selected pump in line with the device flow, head, pressure, temperature, cavitation flow, suction stroke and other process parameters. 2, must meet the characteristics of the media requirements. Pumps that deliver flammable, explosive toxic or valuable media require dependable shaft seals or leak-free pumps such as magnetically driven pumps, diaphragm pumps, shielded pumps, pumps that deliver aggressive media, convective components require corrosion-resistant materials , Such as AFB stainless steel corrosion pump, CQF plastic magnetic drive pump. Pumps containing solid particulate media are required to have a wear-resistant material for the convection components and flush with a cleaning fluid if necessary. 3, high mechanical reliability, low noise, small vibration. 4, the economic should take into account the equipment costs, operating costs, maintenance costs and management fees the lowest total cost. 5, centrifugal pump with high speed, small size, light weight, high efficiency, large flow, simple structure, infusion without pulsation, stable performance, easy operation and maintenance features such as convenience. Therefore, in addition to the following circumstances, the centrifugal pump should be used as far as possible: When there are measurement requirements, the choice of metering pump head is very demanding, the flow is small and not suitable for small flow High-lift centrifugal pump can be used when optional reciprocating pumps such as cavitation When the requirement is not high, the vortex pump can also be used. The lift is very low. When the flow rate is very high, the axial pump and the mixed flow pump can be used. Medium viscosity (greater than 650 ~ 1000mm2 / s), consider the use of rotor pump or reciprocating pump (gear pump, screw pump) medium 75% gas content, the flow is smaller and the viscosity is less than 37.4mm2 / s, the choice of vortex Pump. On the occasion of frequent or inconvenient irrigation pump should be used with self-priming performance, such as self-priming centrifugal pump, self-priming vortex pump, pneumatic (electric) diaphragm pump. Second, the pump selection based on pump selection basis, should be based on process, water supply and drainage requirements, to be considered from five aspects, both liquid delivery capacity, the device head, liquid properties, piping layout and operating conditions 1, the flow It is one of the important performance data of pump selection, it is directly related to the entire plant's production capacity and delivery capacity. Such as the design process can be calculated in the pump normal, minimum, maximum three kinds of flow. Select the pump, based on the maximum flow, take into account the normal flow, in the absence of the maximum flow, it is usually desirable 1.1 times the normal flow as the maximum flow. 2, the lift system required for installation of the pump is another important performance data, generally to enlarge the 5% -10% head lift to choose. 3, the liquid properties, including the name of the liquid medium, physical properties, chemical properties and other properties, the physical properties of the temperature c density d, viscosity u, medium particle diameter and gas content, etc., which involves the system lift, effective gas Erosion margin calculation and the type of suitable pump: Chemical nature, mainly refers to the liquid medium chemical corrosion and toxicity, is the selection of pump materials and choose an important basis for the type of shaft seal. 4, the installation of piping system conditions refers to the liquid from the height of the liquid into the liquid distance to the suction side such as the lowest level, the highest level of the discharge side of some data and pipe specifications and length, material, pipe specifications, the number , Etc., in order to carry out the Department of combing head calculation and NPSH check. 5, the operating conditions are many, such as the operation of the liquid T saturated steam P, suction side pressure PS (absolute), the discharge side of the tank pressure PZ, altitude, ambient temperature operation is gap or continuous, the pump position is fixed Or removable.