Pumping of high viscosity materials

A reciprocating vane pump for thick materials having a viscosity greater than 35,000 poises, comprising:

• a pump body having a material inlet and a material outlet;
• a piston slidably positioned in said pump body;
• a rod fixed to said piston and extending therefrom along the length of said pump body to said material inlet;
• a vane fixed to a distal end of said rod at said material inlet;
• at least two partitions spaced along the length of said pump body to separate the interior of said pump body into a plurality of stages, said partitions having ports for permitting passage of said rod, said ports each having a clearance with respect to said rod large enough to permit free passage of the material therepast;
• and
• check valves associated with at least one of said ports and with said piston for permitting material flow only from said inlet to said outlet, said check valves each providing a clearance, when open, sufficient to permit free passage of the material therepast, whereby material is pumped from said inlet to said outlet by reciprocation of said piston in said pump body,
• wherein said check valve associated with said at least one port comprises a ring shaped valve member surrounding said rod with a diametrical clearance of between 1 and 2.5 mm and having a bronze bearing surface for guiding said rod.