What is the performance curve of a centrifugal pump? 

The performance curve of a centrifugal pump gives you an idea of how this machine works and how it really performs in its daily tasks. That is why it is important to know how it works and what each of the readings we periodically take indicates.

We always recommend paying attention to the performance curve of a centrifugal pump. This is a graph that represents the unique relationship between load and flow that the pump guarantees at a certain rotational speed of its impeller, and whose reading varies depending on the task that the pump is carrying out.

curva de rendimiento de una bomba centrífuga

Why should you consider the performance curve of your centrifugal pump?

curva de rendimiento de una bomba centrífuga

Nowadays, the market makes it possible for the customer to purchase a pump model that allows us as manufacturers to select the characteristic curve of a centrifugal pump, depending on the operating point where this element will be placed.

It is essential to be clear that there are two types of pump curves, those of centrifugal pumps and those of positive displacement pumps.

Thus, centrifugal pumps account for 70% of pumping applications. To read it correctly, the user should be aware that pump curves are generally crescent-shaped. That is, the highest point on the left shows the maximum working pressure, but the lowest flow rate, while the far right of the graph shows the highest flow rate the pump can deliver, but the minimum pressure.

Another aspect to be considered is the duty point, which is normally set by the efficiency indicated as a percentage.

The importance of reading the performance curve of a centrifugal pump

The performance curve of the centrifugal pump shows various duty points that this element can reach. You should be aware that not being clear about this can create many problems for the installation.

It is imperative that you know that if the operating point of a pump is too far to the left on its curve, its capacity cannot be increased if a pressure miscalculation is detected.

On the other hand, if it is too far to the right, there is a risk of cavitation, which in practice could destroy the pump casing and cause the liquid to boil.

For peace of mind, a selection should be made that allows a safety margin of 10% to the left of the operating point, to ensure that the pump can operate under different conditions, as the efficiency can be reduced, but never increased.

There are some basic parameters that must be considered for a correct reading of the performance curve of a centrifugal or Positive Displacement pump:

  • The common indicator of readings is fresh water at 20 °C above sea level, which may not reflect the requirements of your application. In such cases, a study of the representation of results must be made considering other aspects such as fluid viscosity and specific gravity.

  • Viscosity characteristics vary between fluids, so measurement with elements besides water is a vital issue. It should be noted that there are elements that have a viscosity indicated at 20 °C or 60 °C, a range that differs from the actual pumping temperature, which affects the performance and life of the pump.

The value of the motor speed of your centrifugal pump 

The revolutions of the motors in centrifugal pumps vary according to the poles of the motor. The higher the number, the slower it will run.

Increasing them allows the pumps to generate more flow at lower pressures, thus also reducing the NPSH required.

This also serves to use a smaller motor and suffer less wear and tear.  On the other hand, if you are looking for higher pressure, lower flow pumps will run at higher RPMs to achieve the pressures you need.

If you would like us to provide you with personalized advice and answer any questions you may have, all you have to do is contact our sales department. You can do so by filling in the following form, writing to us at inoxmim@inoxmim.com, or calling us on (+34) 972 58 20 40. We will be delighted to help you!