Potomac Electric Power Co. (PEPCO) was  experiencing accelerated corrosion and erosion problems with their stainless steel river water pumps at the Morgantown Generating Station. Additionally, the pumps had velocity problems in the suction bell intake area which caused cavitation damage to the metallic impellers and pump casing. According to Ted Fasca, PEPCO maintenance engineer, the pumps needed to be replaced after an average of only 7-14 months of service.

One of the two 3-stage screen wash pumps custom built and designed by SIMS engineers for the  Morgantown Generating Station for Potomac Electric Power Company.

The maintenance group at Morgantown decided initially to try upgrading the impellers of the existing pumps. Sims Pump Valve Co. was chosen to redesign the vane  geometry of the existing metallic impeller and machine a new composite impeller from their Simsite® graphite composite.

River water pump’s stainless steel suction bowl showing the severe effects of corrosion.

  Simsite is a combination-fiber reinforced composite with phenolic resin. The fibers are interwoven in a bi-directional or tri-directional weave. Individual components are machined (rather than cast) from solid blocks of the material, and are lighter in weight and exhibit lower coefficients of friction than their metallic counterparts.
    The new impellers were inspected after three years of service, and showed no signs of corrosion, erosion, electrolysis or cavitation. Using the composite material solved the impeller wear problems, but corrosion and electrolysis were still noted on the stainless steel pumps’ metallic casing.

  Based on the results of the impeller up-grade, the decision was made to design a complete river water service pump, including the suction bell, diffuser bowls, spider bearings and column piping, manufactured completely from Simsite composites.

  The new river water service pumps are rated for 10,000 8pm with a head of 40’ at 1,180 rpm.  In addition to an impeller design that reduces cavitation effects, Sims created a special locking device that keeps the impeller positioned properly inside the diffuser bowl and prevents it from slipping on the shaft. The pump features flanged structural composite spider bearings every 4' along the column pipe. These self-lubricating open guide bearings are designed to be cooled with river water and are machined from Simsite Grade SMS-325 which can handle dry running at startup.

The Simsite Impellers are precision machined and designed to minimize the  effects of cavitation damage  while maximizing the impeller efficiency and performance.

The stuffing box and packing gland at the top of the river water pump are made of Grade SMS-375 and in-corporate a Simsite ring at the top and bottom of the packing, ensuring the packing will be positioned properly inside the stuffing box.