This report marks the fourth quarter of the third phase of the centrifugal slurry pump improvement program. The program was begun in 1982 to improve the operating life of centrifugal slurry pumps for coal liquefaction service. The first phase reviewed pilot plant experience with centrifugal slurry pumps and identified, with the help of a literature search, the critical design parameters and materials required for such improvement. The second phase encompassed extensive small-scale testing of several hydraulic design concepts and materials testing and selection - the results being incorporated in a prototype slurry pump design. This third phase of the work has included i) prototype slurry pump testing against a state-of-the-art coal liquefaction slurry pump, wherein substantial reduction of wear was obtained at 60% higher speed at the same head and flow rate therefore at 60% higher specific speed - and ii) an investigation as to whether still higher specific speed is possible. The prototype pump tested in (i) had a specific speed of 600. Another pump of this same design was re-fitted for investigation (ii) with a smaller impeller and associated liners so as to operate at a specific speed of 1000. Both the 600 and the 1000 impellers for this latter investigation (ii) were made of mild carbon steel to accelerate the testing time. The two pumps were run in series in the slurry test loop using AS (number sign)110 sand ((approximately) 110 mesh) at a concentration of 30% by weight in water at 80(degrees)F. As previously reported, 24 hours of test time revealed a slightly lower overall wear rate for the 1000-specific-speed pump; however, excessive local wear occurred in the impeller eye area of that pump. This was attributed to too large a clearance between the pump-out vanes and the suction side of the volute liner. Wear elsewhere in the pump was uniform and comparable to that of the 600-specific-speed prototype pump. 3 figs., 2 tabs.
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