New impeller combines reliability and efficiency

The newly developed free-flow impeller for waste water pumps will be the trade fair highlight showcased by KSB Aktiengesellschaft, Germany, at this year’s IFAT in Munich. The F-max impeller now incorporates different distances between its blades, which are arranged in groups with two small and two large distances. Thanks to this asymmetrical blade arrangement, the F-max offers impressively wide free passages ensuring that even larger rigid solids pass easily and are reliably handled by the pump.

A further focus for KSB’s engineers when designing the blades was their ability to create a swirl in the hub area. This swirling effect shifts fibres away from the impeller hub and transports them to the outside. Based on decades of experience in free-flow impeller design, the pump manufacturer’s hydraulic experts employed the CFD method (Computational Fluid Dynamics) to gain detailed knowledge about the complex flow processes inside the pump via computer-aided simulations. This led to the design of the F-max impellers which are capable of achieving efficiencies that have previously only been reached by single-channel impellers.

Subsequent balancing is no longer required with the new impeller type. Since the radial forces and vibrations created by the new impeller are usually lower than those of single-channel impellers, the service life of shaft seals and rolling element bearings is increased. Pumps with F-max impellers thus require only minimal maintenance. Replacing the impeller itself is also straightforward. When they rotate, free-flow impellers develop a strong swirl which keeps the solids in the pump casing suspended and, in combination with the inclined suction area, generates an additional flushing action.

This significantly reduces the risk of clogging in the impeller’s centre caused by long fibres, in particular by wet wipes. These have become a major problem in waste water transport as their use has markedly increased in the last few years.

As a result of the trend towards conserving drinking water and separating stormwater and waste water, the waste water to be handled has become “thicker”. This is why operators now demand non-clogging impellers which offer reliable operation without sacrificing high efficiencies, even for small waste water pumps.

For transporting acid waste water, too, KSB also supplies impellers made from stainless and acid-resistant duplex steel. It provides protection against pitting and stress corrosion. Stainless steel waste water pumps are primarily used in industrial waste water treatment. White cast iron variants for particularly abrasive media are also available. 

F-max impeller Thanks to the asymmetrical blade arrangement, solids of different sizes can easily pass the new F-max impeller. © KSB Aktiengesellschaft, Frankenthal

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