Abstract: A centrifugal pump for pumping slurries and other abrasive liquids having an axial inlet and a circumferential outlet, an impeller rotating within a housing and a suction liner secured to the housing wherein the impeller has a radial nose projecting toward the suction liner, a wear ring providing a complementary confronting surface axially spaced from said impeller and positioned as a part of a spool piece within the suction liner. The spool piece also includes a control means connected to the wear ring to move the wear ring surface axially toward and away from the impeller nose to maintain a preselected clearance therebetween to offset the abrasive wear occurring due to the pumping of the slurry.