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A single-stage pump is defined as having one impeller and its related discharge collector that together produce fluid flow when powered by a driver, but due to having just one impeller, there are limits to the performance of a single-stage pump. On the other hand, a multistage pump is one where fluid flows through multiple impellers that are in series, which increases the total head (pressure) generated by the pump. Single volutes, double volutes and diffuser casing designs can all be configured into multistage pumps.

As the fluid flows through each stage, pressure becomes higher than it was in the previous stage. In multistage pumps, the impellers sometimes differ in design but should always be designed to have nearly identical flow characteristics. An example where the impellers will differ is to avoid significant cavitation in low net positive suction head (NPSH) systems. In this case, or others requiring a pressure boost prior to the subsequent stages, the first stage will be designed for low NPSH operation (such as double suction impeller) and effectively operate while increasing the pressure, prior to entering the subsequent stages.

Industrial applications of multistage centrifugal pumps

Multistage centrifugal pumps are used for a wide variety of industrial applications thanks to their increased efficiency and ability to pump fluids at higher pressures.

• boiler feed water Pumps feed water into a steam boiler.
• firefighting Used to pressurize water to help extinguish fires.
• high-pressure cleaning Creates a powerful stream of water used to clean an object.
• irrigation Used to pump water throughout an irrigation system.
• reverse osmosis Used to remove impurities from water.
• snowmaking Pressurizes water to make snow for use in sports and resorts.
• water circulation Adds pressure to the system to continuously circulate water.
• water supply boosting Increases pressure for water usage.