Pump shell for multistage metal working pump

An improved pump shell for a multistage metal working pump, comprising:

• a plurality of pump shell units housed in series within a hollow cylindrical casing and mounting around a shaft, each pump shell unit including:
• an inner shell having a radial inner end, an inner shell side substantially parallel with the shaft, a first curved flow guide bridging the radial inner end and inner shell side, a step and taper holding end extending from the inner shell side, a second curved flow guide bridging the holding end and the inner shell side, a holding ring mounted on an outside surface of the inner end having a holding metal working member which has a top end formed with a sealing flange extending outward, the sealing flange having an outside diameter slightly smaller than an inside diameter of the holding end;
• a diffuser mounted around the shaft having one side attached to an inside wall of the inner end and an outlet;
• an impeller adjacent the diffuser and mounted on the shaft having a front inlet;
• and
• a seal ring held in an annular compartment formed by an inside wall of the casing, outside walls of the holding end, and the inner end for preventing fluid leaking or counter flow;
• wherein the holding end of one pump shell unit may engage with the sealing flange of another pump shell unit to form a precise alignment and sealing for creating a fluid passage to enable pumping fluid flow smoothly from the inlet of one pump shell unit, through the impeller, first and second flow guide and to discharge out through the outlet of another pump shell unit when the shaft is driven to rotate the impeller.