Piping System Fundamentals: Net Positive Suction Head

Our world as we know it could not exist without piping systems. A critical part of our architecture, not to mention infrastructure as a whole, piping systems harness the elements for any use we can imagine. Understandably, they require some incredibly complex engineering.

In this Piping System Fundamentals series, we provide an in-depth look at the most important elements of piping, ranging from specific pieces of equipment to specific fluid mechanic concepts. In this edition, we explore the net positive suction head, a critical parameter in fluid mechanics for understanding pump performance. Read on to learn why it’s so important and how to calculate it in your operation.

What Is A Net Positive Suction Head?

One of the most important fluid mechanic concepts involved in piping systems is net positive suction head (NPSH), a measure of the available pressure on the suction side of a pump. This pressure is required to prevent cavitation (the formation of vapor bubbles in a fluid) from occurring. It is necessary to determine whether a given pump will operate effectively without experiencing cavitation. Another way of understanding NPSH is that it’s the amount of fluid energy at the pump suction in reference to absolute zero energy.

It’s also important to understand the net positive suction head required (NPSHr) for centrifugal pumps. This metric represents the amount of fluid energy required by the pump to operate without cavitation. Pump manufacturers test their pumps to determine the NPSHr over a range of operating flow rates.

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