Size the drive for a pump or fan. Enter the flow and either head or pressure rise, plus the pump or fan efficiency and motor efficiency, and the calculator returns hydraulic power, absorbed shaft power, motor input power and an installed rating with a service factor applied.
What it gives you
- Hydraulic power from flow, head and density
- Shaft power from pump or fan efficiency
- Motor input power and installed rating with service factor
- Equivalent head from pressure rise for fans
- Power versus efficiency curve at the current duty
Method and standards
Hydraulic power is density times gravity times flow times head. Dividing by the pump or fan efficiency gives the shaft power the driver must supply, and dividing by motor efficiency gives the electrical input. The installed rating applies a service factor so the motor is not selected at its limit. Confirm against the manufacturer's pump or fan curve before ordering.
How to use it
- Enter flow and head (pumps) or flow and pressure rise (fans).
- Set the pump or fan efficiency and the motor efficiency.
- Read the shaft power and installed rating, then pick the next standard motor size.
Questions engineers ask
- What service factor should I use?
- 1.1 to 1.25 is common for general duty. Use the higher end for fans with uncertain system resistance or pumps that may run off their best efficiency point.
- Does it handle non-water fluids?
- Yes. Set the density for the fluid being pumped.
- Why is the fan result in head as well as pressure?
- Fan duties are usually stated as a pressure rise; the calculator converts to an equivalent head for the power calculation and shows both.
Need this calculation done properly, with a signed-off calculation pack or FEA behind it? Forgepoint provides mechanical design, analysis and pressure equipment engineering from Manchester, UK-wide.
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