Abstract: There is disclosed a valve assembly for a pump such as a dual-piston reciprocating pump, and to such a pump incorporating a valve assembly. In one embodiment, a valve assembly (10) is disclosed which includes a valve main body (98); a valve member (100) mounted for movement within the valve main body, to control the supply of an actuating fluid to a pump (10); a main valve inlet (81) formed in the valve main body, through which actuating fluid is supplied to the valve main body; and an inlet valve (83) for controlling the flow of actuating fluid through the main valve inlet into the valve main body. Providing a valve assembly with such an inlet valve facilitates accurate control of the flow of actuating fluid into the valve assembly. This in turn facilitates control of the flow of actuating fluid to a pump, thereby permitting one or more operating characteristics of the pump to be varied.

Abstract: There is disclosed a pump, in particular a reciprocating pump. In one embodiment, a reciprocating pump (10) is disclosed which comprises an actuating cylinder (12); an actuating piston (16) mounted for reciprocating movement within the actuating cylinder; a discharge cylinder (52); a sleeve (40) releasably mounted within the discharge cylinder, to thereby define an operating diameter of the discharge cylinder; and a discharge piston (30) coupled to the actuating piston and mounted for reciprocating movement within the sleeve to successively draw fluid into and discharge fluid from the discharge cylinder. There is also disclosed a sleeve for such a pump, and a method of changing output flow from such a pump.