In a further expansion of its range of pumps suitable for handling untreated waste water, the KSB Group has developed a new radial multi-vane impeller in open design. The D-max impeller serves to handle fluids containing solid substances and long fibres, coarse solids as well as entrapped gas or air.

It is therefore very suitable for handling untreated waste water, combined sewage, recirculated and heating sludge as well as activated, raw and digested sludge with a solids content of up to 8 percent. This impeller type is also suitable for transporting fluids with a high viscosity.

At approximately 84 percent, the new impeller's best efficiency can be compared with the performance of closed multi-channel impellers. The free passage is at least 76 mm, which meets the requirements of many local plant operators. KSB's hydraulic experts employed the computational fluid dynamics (CFD) method to obtain detailed knowledge about the complex flow processes inside the pumps via computer-aided simulations. In addition to the computer-aided development of impellers, the pump manufacturer also conducted waste water tests in the laboratory as well as intensive field tests around the world, the results of which were then incorporated into the intensive development work.

Each customer receives an impeller trimmed to match the specified operating point. This is also common practice for multi-channel impellers. The D-max impellers are used in the Sewatec and Amarex KRT pump type series. They are suitable for both 50 Hz and 60 Hz electric motors. The maximum head is approximately 90 metres and the maximum flow rate is approximately 2,800 cubic metres per hour. Depending on the composition of the waste water, an operator can choose between the materials EN-GJS-400-15 and 1.4517 as well as EN-GJN-HB555.