Pump head from gauge readings
The actual total head of a running pump from the suction and discharge pressures, the gauge height difference and the pipe velocities — to compare with the rated curve.
H = (p_d − p_s) / (ρ · g) + Δz + (v_d² − v_s²) / (2 · g)v = 4 · Q / (π · d²)Compare H with the rated head at the same flow rate: a clearly lower head points to worn impellers and wear rings or to cavitation. Mount the gauges on straight runs next to the nozzles and read them on the same scale; the velocity heads may be neglected only if the suction and discharge pipes have the same bore.
Source: ISO 9906 — pump total head in acceptance tests
Inputs
You can change a field's unit: the value is converted to the formula's units automatically.
Suction gauge reading (vacuum with a minus sign). Both pressures gauge or both absolute.
Fresh water 1 000, crude oil 800–900, formation water 1 050–1 180 kg/m³.
Negative if the discharge gauge is lower.
Unit converter for this formulaPressure · Density and °API · Length · Liquid rate · Power
- MPa1
- kPa1,000
- bar10
- atm9.86923
- kgf/cm²10.1972
- mmHg7,500.62
- MPa(g)0.898675
- barg8.98675
- psi145.038
- psia145.038
- psig130.342
- ksi0.145038
psi and psia are absolute pressure; gauge units (barg, MPa(g), psig) are above atmospheric (101.325 kPa = 14.696 psi). Pressure differences in the formulas do not depend on this.
- H_p — Head from the pressure difference–
- Δh_v — Velocity head difference–
- P_h — Pump hydraulic power–
More in Pumps
Hydraulic power from the flow rate and head, shaft power from the pump efficiency, power drawn from the supply, and the smallest motor rating with a margin.
Net positive suction head available (NPSHa) for a pump taking liquid from a tank, separator or vessel, and its margin over the NPSH required (NPSHr) from the pump curve.
Flow rate, head and power of a centrifugal pump at another speed — including an ESP or a pump on a variable speed drive — and with a trimmed impeller.
Results are engineering estimates from standard formulas; for design decisions check them against the codes, project documents and specialists' calculations. The formulas carried over from the original set are unchanged, and their errors are described in the notes.