Des Moines Water Works: Pump Polymer Coating Application Improves Efficiency

DMWW first used polymer coatings to repair a 1923 era, two-stage diesel-powered pump that could generate up to 2,000-horse power (HP) and 30 million gallons per day (MGD). This diesel pump was used as a back-up pump and it had had severe tuberculation damage to both volutes that reduced its hydraulic capacity. Upon completion, the pump capacity increased by 3.4% over the original factory specifications. The improvement was attributed to the glass-smooth finish as opposed to the rough finish of a normal cast-iron volute. Since the diesel pump’s use was reserved for emergencies, the decision was then made to coat a 1,000-HP electric pump that was used daily to see if the polymer coating would improve the wire-to-water efficiency for that unit. The seconds pump is one of two identical pumps side-by-side, pumping water into the same header, so comparative analysis of energy consumption and capacity would be easy to do. Additionally, the pump had been scheduled for rebuild, and disassembly had already begun. The polymer manufacturer recommended coating the impeller along with the volute and indicated that doing so would yield even better results than with the diesel pump. After a side-by-side comparison, the net improvement in wire-to-water efficiency was 7.2%, combined with a 3.2% increase in pump capacity compared to factory pump performance curves.