Knowledge Hub

Pump duty calculator

Size the pump from the line conditions, not the catalogue. The nine-field enquiry below is written by the duty you enter.

Last-project duty is a reasonable starting point; the sheet rewrites it against the conditions you enter. No model and no OEM — family shortlist, an estimate, and the enquiry.

Families: industrial pumps. Duty-point cost: small equipment failures.

Worksheet

Line conditions in, enquiry out

Inputs left. Live duty right. The specification beneath is the same document — it is composed from these numbers, not typed afterwards. Switching paths enriches the sheet; it does not wipe it.

Line conditions

Path

Units

Job

Fluid / medium

Flow Q m³/h

Flow must be greater than zero.

Head H m

Head must be greater than zero — or enter suction and discharge pressure in Advanced.

Temperature °C

SG (water = 1) Optional. Default 1.

Viscosity cP · optional

Solids % by volume · optional

Efficiency η Assumption — centrifugal default 0.70. Editable.

Hours / year Used if you switch to the energy path.

Advanced · head from pressure, NPSHa

If you have suction and discharge pressure instead of head, enter both — head is converted. NPSHa is a system number. NPSHr is not invented; it lives on the manufacturer’s curve.

Suction P_s bar g

Discharge P_d bar g

Suction static H_s m · positive flood, negative lift

Vapour pressure P_v bar a

Suction line losses m

Tank pressure (optional) bar g · blank = atmospheric

Size from the line conditions, not the nameplate. Last-project duty is a reasonable starting point — the sheet rewrites it against current conditions. Enquiry is a re-spec, not a like-for-like replacement. Assessment frame: ISO 14414.

Nameplate or measured kW Current draw is assumed to stay near this figure when the pump is throttled — typical of an oversized centrifugal running against a valve.

Rated flow m³/h

Actual flow m³/h · or % of rated below

Actual flow entered as

Hours / year Default 8000. Overwrite for the real calendar.

Tariff KES/kWh. 25 is a 2026 industrial-order-of-magnitude example — overwrite it. Not an EPRA published tariff.

Hydraulics, materials and seals selected for the fluid, not just the flow rate. This path writes questions into the enquiry — it does not name a certified steel grade.

Fluid family

Concentration (optional)

Temperature °C · same duty temperature; edits feed the sheet

Solids / abrasives

Duty hygiene

Example is illustrative only — not a named plant.

Result · live

Enter valid line conditions. Q > 0 and a head (or suction and discharge pressure).

— kW

Family —

Job: —
Approx. motor kW: —
η (assumption): —
Standards: —

No BEP from this sheet — a BEP is a curve figure we do not have.

— KES / yr

USD — · 2026 conditions, ~130 KES/USD

This pump, these hours: —
Article band (context): USD 4–23k / KES 0.5–3M
Shaft power at actual flow (if H known): —
Q actual / rated: —

Family hint

Standards —

First-pass filter for the enquiry — the language already on the pumps page. Confirm with manufacturer compatibility data. Grade not named until the medium data sheet is attached.

Estimate for enquiry, not a certified OEM sizing. It does not name a steel grade and it is not a pump curve. Confirm with manufacturer software and the duty on site before a purchase order. Related: small equipment failures (duty-point cost).

Auto-composed from the duty above

These nine fields are not a blank form. They rewrite as you size. Edit a line if you need to; otherwise send it as composed.

1 Job
2 Hydraulic duty
3 Process medium
4 Family shortlist
5 Hydraulics / BEP / off-duty
6 Connections / seal
7 Materials
8 Certification / standards
9 Maintenance

Email this spec to yourself Send a copy to our team

ISO 2858 · ISO 5199 · ANSI/ASME B73.1 · API 675 · API 676 · ISO 9906 · ISO 14414

Shaft power: P_kW = Q_m³/h · H_m · SG / (367 · η) — η is an editable assumption (centrifugal 0.70 · PD 0.60 · metering 0.90). No motor-efficiency overlay, no BEP claim.
NPSHa: NPSHa ≈ H_static + 10.197·(P_surf − P_v)/SG − H_loss (bar a, metres). NPSHr is a curve figure — not invented here.
Annual energy cost: Cost = kW · hours · tariff. Tariff is an editable 2026 industrial order-of-magnitude example, not an EPRA fact.

Published off-duty envelope, mid-sized East African plant, 2026, ~130 KES/USD: USD 4–23k / KES 0.5–3M · Not OEM-certified sizing · No model is selected.