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Monday, 04 May 2020 09:00

Understanding How to Measure a Pump’s Performance

Pumps operate mainly through converting electrical power into motion. The performance of a pump can be measured using 3 main analytical models; flow rate (Q), head (h), and efficiency (n). These 3 models allow users to gain an overall sense of how the pump is performing during operation.

Related Blog: General Maintenance Test Questions For Pumps, Motors, and More

What is "Flow rate, Q"

Flow rate is a measure of the speed and velocity of fluid that is passing through the pump. Depending on the use of the pump, flow rate can be measured as a volumetric flow rate (in the case of pumps that move liquids) and mass flow rate (for pumps that operate on other types of fluids).
  • For volumetric flow rate: Q=vA
    Where v=fluid velocity
    And A= cross-sectional area of the apparatus holding the fluid
  • For Mass flow rate: m= pQ= pvA
    Where p= fluid density
    And m= mass


The mass and fluid velocity are related according to the following formula: v=m/pA Head, H

The pump head is a measure of how high fluid can be pushed by the pump. This model allows users to establish how powerful their pump is. If the effect of friction on the inlet and outlet tubes of a pump can be ignored, then the head of the pump would be equal to h, the height of the free end of a hose above the surface of the supply reservoir.

There is a noticeable relationship between head and flow rate for every pump: An increase in head causes a decrease in flow rate.

The head can get to a maximum value at which the flow rate will be zero. When the head= zero, the flow rate is maximum

industrial pumps

Efficiency, n

The pump efficiency is the point at which the flow rate, Q, and the head, h, operate at maximum efficiency.

Maximum efficiency is achieved upon perfect balance between Q and h, particularly at the point between where Q=0 and h=0.

Efficiency is measured by n= output/input; where output is the power delivered by the fluid, and input is the power consumed by the motor.

Efficiency for electric pumps can also be measured by:

Input=VI

  • Where V=voltage supplied to the motor
  • I=current supplied to the motor
Note: All the units used to measure efficiency should be the same so they can cancel out and render the efficiency unit as dimensionless.



By analyzing these 3 analytical models, you can determine how well your pump is performing within its application.

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