Centrifugal slurry pump impeller shroud with lip

A centrifugal slurry pump assembly including:

• an outer casing, an inner liner arranged within the outer casing, the inner liner including a main liner and two side liners which form a pumping chamber, an impeller mounted for rotation within the pumping chamber, the impeller including:
• a back shroud and a front shroud each with opposed inner and outer faces and an outer peripheral edge, a central axis, a plurality of pumping vanes extending between the inner faces of the back and front shrouds, the pumping vanes being disposed in spaced apart relation, each pumping vane including opposed main side faces, a leading edge in a region of the central axis and a trailing edge in a region of the outer peripheral edge of the back and front shrouds with passageways between adjacent pumping vanes, wherein the inner faces of the back and front shrouds along a length of the passageways, leading from the leading edges to the trailing edges, includes a planar inner region beginning adjacent the leading edges of the plurality of pumping vanes and an outer region ending at the outer peripheral edge of the back shroud, wherein the outer region of the inner face of the back shroud includes a lip formation with an apex including a convex surface, and the outer region of the inner face of the front shroud is substantially planar and is in a plane that is substantially perpendicular to the central axis, and wherein the pumping chamber includes a void between the outer peripheral edge of the back and front shrouds and an inner peripheral surface of the inner liner to provide for the circulation of fluid in the pumping chamber when in use.