| Flow | Head | Density | Pump eff. | Motor eff. | Safety | Required power | hp | Energy/day |
|---|---|---|---|---|---|---|---|---|
| 50 m3/h | 30 m | 998 kg/m3 | 75% | 90% | 10% | 6.646 kW | 8.91 hp | 53.164 kWh |
The calculator uses standard hydraulic power and efficiency relationships.
- Q → m³/s
- H → m (or compute from pressure)
- ρ → kg/m³
- Select Total head or Pressure rise.
- Enter the flow rate and choose its unit.
- Provide head or pressure rise based on your selection.
- Enter density or specific gravity for the pumped fluid.
- Set pump efficiency, motor efficiency, and safety margin.
- Optionally add hours/day and tariff for cost estimates.
- Click Calculate and review results above the form.
- Use realistic efficiencies from datasheets or test data.
- Apply safety margin when data is uncertain.
- Verify motor selection against available nameplate ratings.
Power components reported by the calculator
The calculation separates hydraulic power, pump shaft power, electrical input, and required motor power. Hydraulic power is energy transferred to the fluid; shaft power includes pump hydraulic and mechanical losses. Electrical input adds motor losses, and required motor power applies the safety margin for selection. Results are reported in kW with an hp equivalent, plus computed head and equivalent pressure rise for cross-checking.
Why unit normalization improves engineering accuracy
Mixed-unit projects often combine flow in gpm, head in feet, and density in lb/ft³. This tool converts every input to SI units internally and then reports results consistently. For reference, 1 ft equals 0.3048 m, and 1 psi equals 6.89476 kPa. It also standardizes gravity at 9.80665 m/s², aligning pressure and head conversions across fluids consistently in calculations. That workflow reduces scaling mistakes that can shift motor sizing and energy targets.
Efficiency sensitivity and selection impact
Efficiencies dominate real-world power requirements because they act as divisors. If pump efficiency drops from 75% to 60%, required motor power increases by about 25% at the same duty point. Likewise, selecting a higher-efficiency motor reduces electrical input for the same shaft requirement. In the built-in example (50 m³/h, 30 m, water-like density), hydraulic power is about 4.078 kW. With 75% pump efficiency, 90% motor efficiency, and 10% safety margin, the required motor power becomes about 6.646 kW.
Energy and cost estimates tied to operating hours
When hours per day and tariff are provided, the tool estimates daily energy in kWh and extends it to 30-day and 365-day costs. For example, a 10.000 kW requirement running 8 hours per day consumes 80.000 kWh/day. At a rate of 0.12 per kWh, that equals 9.60 per day and roughly 288.00 per month.
Engineering checks and practical limitations
The model assumes steady, incompressible flow and a single duty point. It does not replace pump curve verification, NPSH checks, viscosity corrections, or transient analysis. Total head should include static lift, friction losses, minor losses, and any control valve differential. Always confirm the selected motor against nameplate ratings, service factor, and site power quality. Validate results using measured head, flow, and electrical input readings.
FAQs
1) Should I enter head or pressure rise?
Use head when TDH is known from system calculations. Use pressure rise when your data comes from a pump curve or differential pressure measurement. The calculator converts between them using density and gravity.
2) What flow, head, and pressure units are supported?
Flow supports m³/s, m³/h, L/s, L/min, gpm, and cfm. Head supports meters and feet. Pressure supports Pa, kPa, bar, and psi. All are converted internally for consistent results.
3) How do I choose pump efficiency?
Use efficiency at the expected operating point, preferably near the best efficiency region. If you only have a range, choose a conservative value. Avoid using peak efficiency if the duty point is off-curve.
4) Does the result include a safety margin?
Yes. The required motor power multiplies electrical input by (1 + safety%). Typical margins are 5–20% depending on uncertainty, fouling, and future expansion. Use project standards when available.
5) Does this replace pump curve verification?
No. It estimates power from duty inputs and efficiencies. Always confirm the duty point lies on the selected pump curve, check allowable operating region, and verify NPSH requirements for cavitation risk.
6) How should I handle viscous or solids-laden fluids?
Viscosity and solids can reduce efficiency and increase required power. Apply vendor viscosity corrections or test data, then enter adjusted efficiencies. If uncertainty is high, increase the safety margin and validate with field measurements.