Pump Duty Workbench: calculator

Example data loaded. A small foul pumping station, one duty and one standby. Replace it with your project's data. Inputs save in this browser.

Setup

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Project and fluid

Project / station Calc reference Prepared by Checked by Approved by Revision Fluid Water temperature °C

Notes and assumptions

Duty requirement

Required flow l/s Duty pumps running Pump speed %

Speed below 100% applies the affinity laws to the pump curve, for VSD-controlled stations.

Levels and wet well

Discharge level m AOD Start TWL m AOD Stop BWL m AOD Impeller eye m AOD Wet well area m² Main high point m AOD Pumps alternating Dwellings served Average inflow l/s Emergency storage m³

Leave average inflow blank to estimate it from dwellings (2.35 persons × 125 L/head/day + 25% infiltration). The design duty is taken at BWL, where static head is highest. If the rising main crosses a summit above the discharge level, enter it as the high point; static head is then measured to the summit.

Rising main

Material Roughness k_s mm Internal diameter mm Length m Pressure rating PN bar Wave speed m/s

Fitting	K	Qty

Typical K values for bends, valves and the outlet are included. Tick “Detailed fittings losses” in Setup to edit them.

Pump branch, each pump

Internal dia. mm Length m k_s mm

Fitting	K	Qty

Branch pipework and valves carry one pump's flow; the rising main carries the whole station flow.

Pump curve, one pump at 100%

Pump / model Solids passage mm

Q l/s	H m	η %	NPSHr m

Read 4–8 points off the manufacturer's curve, including shut-off (zero flow). Efficiency and NPSHr are optional but enable the operating range, motor and NPSH checks.

Suction conditions

Atmospheric pressure kPa Suction losses m

Suction static head is BWL minus impeller eye level, flooded positive.

Design criteria

Criteria set

Min. main velocity m/s Max. main velocity m/s Max. starts / hour Op. range low % BEP Op. range high % BEP Motor margin % NPSH margin m Min. solids passage mm Max. branch velocity m/s Max. retention h Curve fit tolerance % Min. main bore mm Min. run time min Surge study over m Storage L/dwelling Storage h at DWF Pump rate × DWF Max. over-pumping %

Pump and system curves

Station pump curve System at BWL System at TWL Efficiency Preferred operating range

Design checks

Station section

levels to scale

Hydraulic breakdown

at design duty, BWL

Friction losses use Darcy–Weisbach with the Colebrook–White friction factor and water properties at the stated temperature. Wet well volume uses V = Σ T·ΔQ/(4·n) for each pump stage, with n the number of pumps alternating. Surge uses the Joukowsky upper bound a·V/g. The pump curve is a least-squares quadratic fit through the points entered. Results support design and must be checked before issue.