When designing instrumentation device, design institute should determine purposes and performances of pump and then choose pump type. Such choice should start from choosing kind and form of pump, so what principle should be used for choosing pump? And what are the references?
        Ⅰ Principle of pump type-choice: 1. Model and performance of the pump chosen should accord with the requirements of device flow, lift, pressure, temperature, cavitation flow, suction lift and other technological parameters. 2. Must satisfy the requirements of medium characteristics. For pumps used to transport flammable, explosive, poisonous or valuable mediums, it is required that shaft gland should be dependable or adopt leak-free pumps, such as magnetic force driving pump, diaphragm pump and shield pump; for pumps used to transport corrosive mediums, corrosive materials are required to adopt for stream unit, such as AFB stainless steel corrosion-resistant pump and CQF engineering plastic magnetic force driving pump; for pumps used to transport solid particle mediums, abrasive resistant materials are required to adopt for stream unit, and if necessary, shaft gland should be washed with cleaning solution. 3. Machinery should be high in dependability, low in noises and small in vibration. 4. In aspect of economy, equipment cost, operation cost, maintenance cost and management cost should be calculated comprehensively to make total cost minimum. 5. Centrifugal pump has characteristics of high rotation speed, small volume, light weight, high efficiency, large flow, simple structure, non pulsation in transfusion, stable performance, easy operation and convenient maintenance, etc. Therefore, except flowing conditions, centrifugal pump should be chosen and used as far as possible: if measuring is required, please choose metering pump. In conditions that lift requirement is very high, flow is very small, and there is not adequate centrifugal pump with small flow and high lift for option, reciprocating pump can be chosen and used, if cavitation requirement is not so high, vortex pump also can be chosen. When the lift is very low and flow is very large, axial-flow pump and mixed-flow pump can be chosen. When medium viscosity is much larger (more than 650~1000mm2/s), rotor pump or reciprocating pump (gear pump and screw pump) can be calculated to choose. When medium contains 75% of air flow, flow is very small and viscosity is less than 37.4mm2/s, vortex pump can be chosen. For occasions with frequent starting or inconvenient pump priming, pumps with self-priming performance should be chosen, such as self-priming centrifugal pump, self-priming vortex pump and pneumatic (electric) diaphragm pump.
        Ⅱ Reference of pump type-choice: the reference should be considered from five aspects, namely liquid conveying capacity, device lift, liquid property, pipeline layout and conditions of operation and running according to technological flow and requirements of water supply and draining. 1. As one of the important performance data for choosing pump, flow directly relates to production capacity and conveying capacity of the whole device. If design institute can figure out normal, minimum and maximum flows in design technique, please choose pump according to the maximum flow and taking account of normal flow at the same time, if there is no maximum flow, generally can take the figure which is 1.1 times of normal flow as maximum flow. 2. Lift needed by device system is another important data for choosing pump, so generally adopt the lift having been magnified 5%-10% of allowances to choose type. 3. Liquid properties include liquid medium name, physical property, chemical property and other properties, in details, physical property includes temperature of c, density of d and viscosity of u , diameter of solid particle in medium and air content, etc relate to system lift, account of effective NPSH and adequate type of pump; chemical property mainly refers to chemical corrosiveness and toxicity of liquid medium, being an important reference for choosing pump material and shaft gland model. 4. Conditions of pipeline layout of device system refers to data of liquid-delivering height, distance and direction, lowest liquid level in suction side and highest liquid level in discharging side, etc as well as pipeline specification, length, material, pipe fitting specification, quantity, etc in the effect that count system lift and check NPSH. 5. There are more operation conditions, for example, liquid operation of T, saturated steam force of P, pressure in suction side of PS (absolute), pressure of container in discharging side of PZ, altitude, whether operation of environmental temperature is interstitial or continuous, and pump position is fixed or movable.
         Above references should be put forward by design institute or consumers under assistance of sales and technical personnel of Yunnan pump valve network, in addition, they should carefully fill in centrifugal pump data chart or pump order consultation list.