Pump Curve • System Curve • Operating Point • NPSH • Cavitation Margin • Efficiency • Power • VFD / Affinity • Parallel & Series Pumps

Marine Centrifugal Pump Performance, NPSH, Cavitation & System Curve Tool

Find where the pump actually operates against the ship's piping system, then screen suction margin, cavitation exposure, motor loading and off-design operation. Simple mode uses a fast quadratic pump/system approximation. Advanced uses entered OEM curve points, Darcy-Weisbach system losses, pressure/elevation terms, NPSHr, speed changes and multiple-pump arrangements.

Figures represent
↑
Fast pump/system intersection with nine inputs.Use OEM or test data where possible. NPSHr is a pump-specific curve value. A positive NPSHa − NPSHr difference is not automatically a complete cavitation margin; use the entered project/OEM margin requirement.
Operating PointPump curve × system curve
SuctionNPSH margin screen
Off-designFlow vs reference/BEP

Pump Curve Approximation

m³/h. Use BEP if known; otherwise rated/reference flow.
m liquid.
m liquid at zero flow.

System & NPSH

m³/h used for the entered friction loss.
m. May be negative for static assistance.
m at the system reference flow.
m at the expected operating condition.
m at the expected operating condition.
m. User-entered project/OEM target.

Pump Arrangement & Operating Limits

rpm for entered curve points.
rpm. Affinity-law scaling is applied.
Identical units represented by the entered curve.
m³/h at OEM curve speed.
% of entered head curve for wear/fouling scenario.
% of entered efficiency curve.
kW. Enter 0 to disable motor loading check.
% of motor nameplate.
m above entered OEM NPSHr.
% of entered BEP flow.
% of entered BEP flow.
% of entered BEP flow.
% of entered BEP flow.

Fluid, Source & Destination

kg/m³.
cSt.
kPa absolute at liquid temperature.
kPa absolute.
kPa absolute.
m relative to pump centerline. Positive = flooded suction.
m relative to pump centerline.
m³/h. Enter 0 to disable measured-point diagnostic.
m at measured flow.

OEM Pump Curve Register

Enter pump flow, head, efficiency and NPSHr at the OEM curve speed. The operating point is solved only within the entered curve range. For speed changes, affinity-law scaling is used as an engineering estimate and should be checked against manufacturer limits.

UseFlow m³/hHead mEfficiency %NPSHr m

System Loss Register

Pipe losses use Darcy-Weisbach. K represents valves/fittings on that row. A fixed component ΔP can represent a strainer, cooler, filter or other item and is scaled with flow squared from its reference flow.

UseSideComponentLength mID mmRoughness mmKFixed ΔP kPaΔP ref flow m³/h

Operating Scenario Register

Stress the same pump/system with different speed, tank levels, resistance and pump count. Scenarios do not alter the baseline inputs above.

UseScenarioSpeed % of OEMSource level ΔmDestination level ΔmSystem resistance %PumpsArrangement

Engineering Checks

Engineering boundary: this tool is a planning and diagnostic model, not a pump acceptance test or cavitation certification. Use the actual OEM curve, project-specific POR/AOR and NPSH margin, and verify shipboard measurements, fluid condition, suction geometry, minimum submergence, air ingress, vortexing, transient operation and manufacturer limits.
Technical basis: centrifugal-pump operation is determined by the intersection of the pump Q-H curve and system curve. Advanced piping losses use Darcy-Weisbach and entered component losses. NPSHa is calculated from source absolute pressure head, source elevation, vapor-pressure head and suction losses. OEM NPSHr remains pump-specific. Speed changes use standard centrifugal-pump affinity relationships as an engineering estimate. ISO 9906:2012 remains the published ISO hydraulic performance acceptance-test standard for rotodynamic pumps and is under review; the Hydraulic Institute treats POR/AOR and NPSH margin as pump/application-specific considerations.
Generated by ShipUniverse.com
By the ShipUniverse Editorial Team — About Us | Contact