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Flexible Impeller Pumps

What is a flexible impeller pump?

A flexible impeller pump is a type of rotary positive displacement pump, which uses a rubber rotor (it is called an impeller, even though it really isn’t) with flexible radially oriented vanes or blades that bend and rub against the eccentrically shaped casing in which they rotate. The main advantages of flexible impeller pumps are that they are self-priming, relatively low in cost, and they can handle all kinds of fluids, including those containing solids, without causing any damage.

How do they work?

In flexible impeller pumps, the rubber impeller has radially oriented blades which are in contact with the inner walls of the eccentrically shaped casing. As the impeller rotates, the blades bend as they pass across the eccentric part of the casing. This creates a vacuum which draws fluid into the pump inlet. The flexible impeller then carries the fluid between the blades of the impeller and the casing, and directs the fluid to the discharge, where it pushes the fluid out the discharge. This type of pump is only capable of generating relatively low pressures (about 60 psi) and relatively low flows (about 150 gpm), so that may limit its applications. The rotation of the pump can be reversed to change the direction of flow in the pump. Since the impeller is rubber, this pump cannot be run dry, as the rubber would be damaged by rubbing against the pump casing.

Where are they used?

The most common application for flexible impeller pumps is in the marine industry, where they are used as ballast and bilge pumps in small and medium sized marine craft. They are ideal for handling fluids that are delicate, usually with relatively low viscosities, and are also used across the pharmaceutical, cosmetic, and food industries. Sanitary versions of this pump are available, with FDA approved rubber materials for the impeller.

Other related Pump Types include: sanitary pump, water pump, marine pump, industrial pump, self priming pump.

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