| CPC F04D 29/4293 (2013.01) [F04D 7/04 (2013.01); F04D 29/24 (2013.01)] | 10 Claims |

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1. A pump back side part comprising a disk like main body having a main axis the main body including a side wall section which extends laterally with respect to the main axis and has opposite facing first and second sides, an outer peripheral side wall or rim extending between the first and second sides, the second side having an outer edge adjacent the peripheral side wall or rim and an inner edge defining an inner opening sized to receive an impeller hub therethrough in use; a plurality of formations on a surface of the second side including an inner formation and an outer formation in spaced relation to the inner formation, the formations being circular or ring like in configuration when viewed in the direction of the main axis (Y-Y) and arranged concentrically with the main axis (Y-Y), wherein the formations are in the form of channels or recesses in the surface of the second side, and the channels or recesses are generally continuous and arcuate in cross-sectional profile having a sinusoidal-like curved profile with smooth sides and smooth transition between formations.
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