The first step: according to the nature of liquid being transported and operating conditions to determine the type; at present, the centrifugal pump on the market by the nature of the liquid can be divided into the following categories: ①water pump: used to transport water and physical and chemical properties similar Clean liquid in water. ② corrosion-resistant pump: used to transport acid, alkali and other corrosive liquids. Step 3: Determine the type of pump (selected from the catalog or catalog) based on the flow rate (usually determined by the production task) and the required pressure in the pipeline. Check the performance table or characteristic curve, flow and pressure required to adapt to the needs of the pipeline. ② If there is a change in production flow, the maximum flow to find, H should also be the maximum flow to find the corresponding value. ③ If H and Q do not match with the requirements, you should find H and Q in the adjacent models are slightly larger. ④ If several models are satisfied, choose the one with the best efficiency under operating conditions. ⑤ For insurance, the selected pump can be slightly larger; however, if it is too large and the operating point is too far away from the highest efficiency, the energy utilization is low. ⑥ If the nature of the fluid being transported and the standard fluid is quite different, then the characteristics of the selected pump curve and parameters should be corrected to see if it can meet the requirements. The third step: If the viscosity and density of the liquid being transported and the difference between the larger water, should be calculated pump characteristics parameters: flow, pressure head and shaft power.