KEVOS® MAKEOS · Hydraulics
Pumping System Design (Head, Power and NPSH)
What head and power does this pumping duty need, and will the pump have enough suction head?
Design of a simple pumping system: pipe velocity, Reynolds number and Darcy friction factor (Colebrook–White), friction and fitting losses, total head from static lift, pressure difference and losses, hydraulic, shaft and motor power, and net positive suction head available from the suction conditions compared with the pump’s requirement.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Duty | ||
| Flow | L/min | Flow rate at the duty point. |
| Static lift (outlet level − suction level) | m | Height difference between the delivery and suction liquid levels. |
| Outlet pressure − suction pressure | bar | Pressure on the delivery surface minus pressure on the suction surface. |
| Discharge and suction pipe | ||
| Pipe bore | mm | Internal diameter of the pipe (suction pipe assumed the same size). |
| Total pipe length | m | Total length of pipe including suction. |
| Total fitting loss coefficient | Sum of fitting and valve loss coefficients, including entry and exit. | |
| Pipe roughness | mm | Absolute roughness of the pipe (0.045 mm commercial steel). |
| Fluid | ||
| Density | kg/m³ | Liquid density. |
| Kinematic viscosity | mm²/s | Kinematic viscosity (1 mm²/s for water at 20 °C). |
| Suction | ||
| Absolute pressure on the suction surface | bar | Absolute pressure on the suction liquid surface (atmospheric for an open tank). |
| Vapour pressure at the pumping temperature | bar | Vapour pressure of the liquid at the pumping temperature. |
| Suction surface above the pump (negative if below) | m | Height of the suction surface above the pump centre line. |
| Suction pipe length | m | Length of the suction line. |
| Suction fitting loss coefficient | Fitting losses in the suction line. | |
| NPSH required by the pump | m | NPSH the pump needs at this flow (from its curve). |
| Machine | ||
| Pump efficiency | % | Pump efficiency at the duty point. |
| Motor margin | % | Margin above shaft power for the motor. |
Method and formulas
- v = Q ÷ A; Re = v d ÷ ν; f from Colebrook–White (64 ÷ Re if laminar).
- Losses h_f = (f L ÷ d + ΣK) v² ÷ 2g; total head H = Δz + Δp ÷ ρg + h_f.
- Hydraulic power = ρ g Q H; shaft power = hydraulic ÷ η; motor = shaft × (1 + margin).
- NPSH_a = (p_s − p_v) ÷ ρg + z_s − suction losses.
- Example: 300 L/min through 80 m of 50 mm pipe needs 28.936 m of head and a 2.331 kW motor.
Limitations
- Single pipe size and steady flow; branched systems need a network calculation.
- Pump efficiency and NPSH required come from the pump curve at the duty flow.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Specify a pump duty point and motor size
- Check whether a suction arrangement will cavitate
- Choose a pipe size by velocity and running cost
Who it is for
- Process engineers
- Maintenance engineers
- Hydraulic engineers
What you get
- Velocity, friction factor and losses
- Total head, power and motor size
- NPSH available against required
Interpreting the result
- If NPSH margin is short, raise the suction level, shorten the suction line or enlarge its bore.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 3021–3026, 3036. Topic reference; no source tables or recommended settings are reproduced.
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