Abstract: A pump, for example, a centrifugal slurry pump, has a casing (10) with an inlet (12) and an outlet (14). The casing (10) and a separate backliner (28) define a chamber (16) in which an impeller (18) is arranged to be rotated by way of a drive shaft (20) which extends axially with respect to the casing (10). Fine running clearances are defined between the front and rear surfaces of the impeller (18) and the adjacent surfaces of the casing (10) and the backliner (28). In order to compensate for increases of the running clearances, for example, due to erosion, the backliner (28) may be moved axially relative to the casing (10). The backliner (28) is connected to an annular flange (38) which is bolted to an annular flange (36) connected to the casing (10) and the spacing between the flanges (36, 38) may be adjusted by removing one or more shims (40) provided therebetween.