DISPLACEMENT SLURRY PUMP

The present invention provides a displacement slurry pump comprising a cylinder having, in coaxial arrangement, a slurry section and an auxiliary liquid section with a diameter greater than that of said slurry section, a reciprocable piston rod in said cylinder carrying a slurry piston in the slurry section with a diameter such that an aperture remains between the periphery of the piston and the wall of the slurry section, and an auxiliary liquid piston with a diameter providing a sealed fitting in the auxiliary liquid section of said cylinder, said slurry piston and said auxiliary liquid piston being separated on said piston rod by at least one stroke length, said slurry section being closed at its end farthest from said auxiliary liquid section and provided adjacent said end with valved slurry inlet means and valved slurry outlet means, said auxiliary liquid section being provided adjacent the slurry section with valved means for introducing auxiliary liquid at a pressure greater than the pressure, at said slurry inlet means, said slurry section being closed at its end farthest from said piston rod passing through packing gland means in said closed end of said slurry section, flange means attached to the inner wall of said closed end of said slurry section, thereby forming an auxiliary liquid compartment in said slurry section, said flange means being provided with an aperture larger than the crosssection of said piston rod through which said piston rod passes relatively loosely, and external valved duct means connecting said auxiliary liquid compartment with said auxiliary liquid section at a locus adjacent the slurry section.