Pump Affinity Laws

Q1 / Q2                =             N1 / N2

Flow Changes directly to the change in Speed

H1 / H2                =             (N1 / N2)²

Head Changes directly proportional to the Square of the change in Speed

BHP1 / BHP2    =             (N1/ N2)³

Brake Horse Power Changes directly proportional to the Cube of the change in Speed

For a fixed speed and varying impeller diameter pump affinity laws are as follows:

Q1 / Q2                   =            D1 / D2

H1 / H2                  =           (D1 / D2)²

BHP1 / BHP2       =           (D1 / D2)³    

Nomenclature:

Q1, Q2 – Volumetric Flow rate in m³/hr

H1, H2 – Head  in m

D1, D2 – Diameter of the impeller in mm

N1, N2 – Speed in rpm

BHP – Brake Horse Power in kW

The above two cost reduction techniques in Centrifugal pump may be analyzed using the Pump Affinity Laws before implementation of the project.

Pump Affinity Laws Calculator in Excel

To help the process engineers in Chemical Processing Industry, Pump Affinity laws are incorporated in Excel file and uploaded. You may download this template and use it for Pump Affinity law Calculations.

Excel Calculation File Available Here

Application of Pump Affinity Laws

The practical application of Centrifugal Pump Affinity laws is helpful in implementing energy savings in oversized pumps. In an industry process related pumps may be over sized because of various reasons or it may be underutilized based on the required operating conditions. This results in waste of energy. Pump affinity laws are helpful in implementing “VFD” and “Impeller Trim”.

Variable Frequency Drives are installed for the motor to vary the pump speed according to the requirement and it reduced power requirement.

“Impeller Trim” operation is carried out to reduce the impeller diameter of the pump to reduce the power consumption.

Centrifugal Pump Affinity Law Online Calculator

Simplify Pump Performance Calculations with Our Free Centrifugal Pump Affinity Law Calculator!

Are you a process or chemical engineer looking to quickly estimate pump performance changes with speed or impeller diameter variations?

Check out our easy-to-use online Pump Affinity Law Calculator! It helps you calculate new flow rate, head, and power based on the affinity laws — saving time and improving accuracy for pump scaling and selection.

Key Features:

Input mode for speed or diameter change

Instant calculation of new Q (flow), H (head), and P (power)

Export live formulas to Excel for further analysis

Supports a variety of units: m³/h, m, kW, and more

Perfect for energy savings, pump optimization, and troubleshooting

Try it now and streamline your pump performance calculations:

https://chemicalengineeringsite.in/centrifugal-pump-affinity-law-calculator/

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