• November 18, 2020
  • Tim Wolstencroft
  • Blog

If ensuring long-term performance of your pumping system is important to you, it is a must for you to be able to read pump curves. In case of new applications, pump curves help us select the pump that will met our exact requirements in terms of performance. It is also important for troubleshooting applications as engineers and operators often solve performance problems by reading these curves.

If you are new to the field of fluid processing and pumps, reading a centrifugal pump curve can be quite a difficult task.  Please remember that different type of pumps have different types of curves.

Imparting energy on a liquid, all centrifugal pumps have their own flow and head characteristics based on the system. How much flow it produces and the performance point on the curve are determined by the pressure the pump is required to overcome. As pressure increases, the performance point moves towards the left of the curve because the flow decreases. On the contrary, the flow increases with decreasing pressure, moving a performance point to the curves’ right side.

There are numerous factors to consider while looking at curves for a new application. In most instances, however, the selection is made as close as possible to the BEP or Best Efficiency Point. For any specific impeller diameter of a pumping system, this is the operating point along the performance curve where the highest efficiency point is shown.

In ideal circumstances, pumps run at this point throughout their life cycles. However, in real-world applications, pumps often operate outside ideal conditions because of fluctuating demand and system upsets.

Whenever a pump operates off its BEP, some common terms are used to describe it.

  • Operating to the left of BEP: Lower flow rate compared to the BEP
  • Operating to the right of BEP: Greater flow rate compared to the BEP
  • Operating away from BEP: Lower or greater flow rate than the BEP

Running pumps off their BEP matters to the pumping systems because it can add energy costs significantly. Most importantly, one of its biggest consequences is an increased chance of pump failure.

Mentioned below is some of the information available on the performance curve of centrifugal pumps.

  • Title Box: It provides information related to the pump’s model, speed, size, and other specific identifying criteria.
  • Flow: Identify the flow amount required by the pump to start your selection. Flow is indicated by the curve’s horizontal axis.
  • Head: It is also important to find out the total head at the specified flow that the pump needs to overcome. The head is indicated by the vertical axis of the curve.
  • Impeller Trim: In some instances, maximum impeller sizes can’t meet the performance points and this is why trimmed impellers are allowed in centrifugal pumps.  The impeller diameters are found on the curve’s left side and a bold line represents the performance for each trim.
  • NPSHR: To ensure proper pump operation, NPSHR or Net Positive Suction Head Required plays an important role. On the suction side of the pump, this is the minimum amount of pressure for overcoming pump entrance losses.
  • Horsepower: Horsepower is seen across the pump performance curve as a dotted line.
  • Efficiency: This is represented as the ratio between the energy that the pump delivers and the energy supplied to the pump.
  • Minimum Flow: Minimum flow is indicated on the left side of the curve, by a vertical bold line.

Hope all of you enjoyed reading this brief article. If you still have questions about reading centrifugal pump curves, please contact us at Tru-Flow Pumps.