ANSI Pump Performance Curve Guide
Read flow, head, efficiency, power, NPSH3, impeller diameter, and operating-point information before selecting an ANSI process pump.
What a pump performance curve shows
A published centrifugal pump curve maps expected performance at stated test conditions. Read every value at the same flow rate and confirm the curve basis before comparing models or impeller trims.
Energy per unit weight of liquid, commonly shown in feet or metres. For a typical centrifugal pump at constant speed, developed head generally decreases as flow increases.
Ratio of hydraulic output power to pump input power. The highest point on the efficiency contour identifies the BEP for that curve.
Shaft input requirement over the flow range. Motor selection must consider the applicable power curve, service factor, operating range, and fluid properties.
Net positive suction head required at the published three-percent head-drop criterion. Compare it with system NPSH available and the required margin for the application.
Flow, head, and the operating point
The pump curve describes what the pump can produce. The system curve describes the head the piping system requires at each flow rate, including static head and flow-dependent losses.
Their intersection is the expected operating point for that pump and system configuration. A valve position, pipe change, liquid property, or speed change can move the system curve, pump curve, or both.
Does the required duty point fall on a suitable impeller curve and within the manufacturer-defined operating region, with acceptable efficiency, power, and suction margin?
Best Efficiency Point: the flow and head where pump efficiency is highest for the stated speed and impeller diameter.
Why BEP matters
Operation near BEP generally supports better hydraulic efficiency and more favorable internal flow conditions. Operation farther from BEP can increase hydraulic loads, recirculation, vibration, noise, heat, or cavitation risk depending on the pump and system.
- Use the manufacturer curve to locate BEP for the exact configuration.
- Review the Preferred Operating Region and Allowable Operating Region when provided.
- Do not apply a generic percentage range without the relevant pump data and engineering basis.
- Evaluate normal, minimum, maximum, and upset duty points, not only the rated point.
Pump selection example
This teaching example shows the review sequence. The values are a duty-point input, not a recommendation for a specific pump.
| Step | Example input or action | Engineering check |
|---|---|---|
| 01 | Required duty: 500 US gpm at 120 ft total dynamic head. | Confirm normal, rated, minimum, and maximum flow and head values. |
| 02 | Plot the duty point on the manufacturer family chart, then open the candidate published curve. | Verify pump size, speed, impeller range, units, and curve revision. |
| 03 | Select an impeller curve that passes through the required point near the suitable operating region. | Read BEP, efficiency, shaft power, and NPSH3 at the same flow. |
| 04 | Compare the selected curve with liquid and system data. | Correct for viscosity or density when required; verify NPSH margin, motor, material, seal, and nozzle constraints. |
| 05 | Document the proposed pump configuration and curve basis. | Resolve exceptions before quotation and request a certified curve when the project requires it. |
Download and related resources
Existing technical files
These files are served from the current ANSI Pumps Pro production media library.
Performance Curves PDF PDFANSI Pumps Brochure PDFSend the duty point for curve review
Include flow, total dynamic head, fluid, temperature, specific gravity, viscosity, solids, NPSH available, speed, motor details, material, and flange requirements.
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