Displacement pump suitable for pumping suspensions

A hydraulically-driven pump of the displacement type intended particularly for pumping various suspensions of liquids and solid particles (slurry) and/or for high pumping pressures comprises a pump housing with a pump chamber (4) with an inlet pipe and an outlet pipe, and associated inlet, and outlet valve, respectively, and a pump piston, disc (16) or corresponding provided in the pump chamber. The pump housing, which is vertically arranged, also comprises an oil section (6) arranged above the pump chamber and having connection (7) to a high pressure hydraulic unit for producing a working pressure on a working piston or piston disc (17) connected with the pump piston through at least one mechanical connecting member (23), and a clean water section (5) arranged between the oil section (6) and the pump chamber (4), said clean water section extending between the working piston and pump piston so that the same water pressure (Pv), which is of approximately the same magnitude as the pressures in the oil section and in the pump chamber, is exerted on the front side of the working piston as on the rear side of the pump piston.