The physical and chemical properties of the transport medium directly affect the pump performance, materials and structure, is an important factor to consider when selecting the type. The physical and chemical properties of media include: media name, media characteristics (such as corrosiveness, abrasiveness, toxicity, etc.), solid particle content and particle size, density, viscosity, vapor pressure and so on. When necessary, should also list the gas content of the medium, indicating whether the medium is easy to crystallize. Pump process parameters Process parameters is the pump selection of the most important basis, should be based on process and operation to determine the scope of change. (1) Flow Q Flow refers to the quantity of medium required to be pumped by a process plant, and the process personnel should normally give the normal, minimum, and maximum flow rates. Pump data sheets often give only normal and nominal flow rates. Pump election, the required flow rate of not less than the maximum flow device, or take the normal flow of 1.1 to 1.15 times. (2) Head H refers to the lift required for process equipment, also known as calculating head. General requirements for the pump rated head lift l.05-1.1 times the required device. (3) The inlet pressure P and the outlet pressure Pd refer to the pressure of the pump inlet and outlet flange, the size of the inlet and outlet pressure affect the pressure resistance of the shell and the shaft seal requirements. (4) Temperature T refers to the pump inlet medium temperature, generally should be given during the process of pump inlet medium normal, minimum and maximum temperature. (5) NPSHa, also known as the effective NPSH. (6) Operation status The operation status is divided into continuous operation and intermittent operation. Site conditions Site conditions include the installation location of the pump (indoor and outdoor), ambient temperature, relative humidity, atmospheric pressure, atmospheric corrosion conditions and the classification of hazardous areas and other conditions.
