【2026 Pump Selection】Pump selection and pipeline pressure drop calculation
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I. Steps for the design and calculation of pump and piping systems: 1. Estimate the required flow rate of the pump based on the material demand and the time requirements of the process, then add a margin of 15~20% to determine the designed flow rate of the pump.
2. Determine physical properties such as density, viscosity, and saturated vapor pressure of the material to be pumped based on its type；
3. Based on the process conditions, process flow diagrams, and on-site piping diagrams (or pipe layout drawings), determine the location of the equipment as well as the route of the pipes (pipe lengths, valves, fittings, etc.)；
4. Segment the system by using the equipment (suction tank, pump, target tank, etc.) as nodes, determine the names of each pipe segment; if there are branch pipelines, allocate the material flow rates to each branch according to the process conditions (for parallel connections, V = V1 + V2 + V3 + …; for series connections, V = V1 = V2 = …)；
5. First, estimate the required pipe diameter based on the economic flow velocity of the fluid, and then select inlet and outlet pipes of appropriate sizes; generally, the pump suction pipe is one size grade larger than the discharge pipe, and the actual flow velocity is calculated accordingly；
6. Based on the pipeline layout diagram (single-line diagram), calculate the straight pipe length for each section of the pipeline, the number of fittings (elbows, tees, etc.) and valves (including check valves and control valves), as well as the equipment located along the pipeline; additionally, determine the height difference between the starting and ending points of each pipeline section；
7. Calculate the Reynolds number of fluid flow based on the flow velocity of each pipeline, as well as the density and viscosity of the material, to determine whether the flow is laminar or turbulent; then calculate the friction coefficient based on the type of flow and the roughness of the pipeline；
8. Calculate the frictional pressure drop, local pressure drop, static pressure drop, total pressure drop, and pressure drop per 100 meters for each section of pipeline using the pipeline pressure drop formula；
9. Determine the pressure within the pump’s suction side equipment (the pressure must be reduced by this value in the pump’s suction pipe) and the discharge side equipment (the pressure must be increased by this value in the pump’s discharge pipe)；
10. Calculate the effective net positive suction head of the pump piping system based on the pressure drop in the pump inlet pipeline, the pressure drop across the equipment, and the saturated vapor pressure of the material at the conveying temperature；
11. Calculate the head required by the pump based on the total pressure drop of the piping system, and then determine the shaft power of the pump using flow rate, head, and the density of the material；