Friction created by rough, rusty casings forces a pump to work harder, which wastes electricity. Photos: MCWA
Treating a pump casing with a ceramic coating creates a smooth surface that reduces friction and boosts pump efficiency.
Looking to extend the life span of ‘' its pumps, the Monroe County Water Authority (MCWA) launched a study looking for ways to get more out of the gear. Among the findings: anti-corrosion, low-friction coatings increase efficiency and slash energy costs.
“The results we got from lining pump casings with ceramic-filled epoxy coatings are encouraging news for water suppliers all across the country,” says MCWA water system analyst Paul Maier. “In addition to lowering electric bills, these coatings extend the service life of pumps.”
The MCWA conducted the tests on five double-suction, cast-iron pumps. Based on the results, the MCWA and the New York State Energy and Research Development Authority (NYSERDA) are moving forward on a jointly funded test project to coat some larger pumps (up to 1700 hp) and collect data over the next three years. The project is part of the state's efforts to encourage adoption of emerging or underused energy-reducing products and technologies.
Some of the pilot study's most dramatic results emerged from the one of the MCWA's booster pumps: a Goulds 75-hp model 3405M with 5-inch suction, 8-inch discharge, and a 13½-inch-diameter impeller. The maintenance department first dismantled and then rebuilt the pump, installing new bearings, sleeves, and wear rings. MCWA contracted with a local contractor to sandblast the pump casing to remove all interior rust and attain a white-metal finish (SSPC-SP5).
Next, two products from Massachusetts-based Devcon—chosen for their surface-friction coefficients, shear strength, cavitation resistance, immersion characteristics, and overall corrosion-prevention properties—were applied to the freshly prepared casing. Devcon's Ceramic Repair Putty, a durable alumina-filled epoxy compound, was troweled on to fill voids and create a uniform surface profile. Then two coats of Devcon's Brushable Ceramic, which is National Science Foundation-certified for potable water applications, were applied for a smooth, long-lasting protective barrier against abrasion, cavitation, and corrosion.
After refurbishment and coating, the booster pump's efficiency jumped 18% (from 64% to 82%). Based on previous experience, the MCWA estimates that at least half of this increase can be attributed to cleaning and coating, while the other half is due to mechanical refurbishment. The flow, head, and efficiency of the pump were all restored to the manufacturer's specifications for a new pump.
Thanks to power monitors installed under a previous grant from NYSERDA, the MCWA can measure the energy usage of individual pumps in real time. Previously, MCWA engineers suspected the kilowatt demands of many pump stations were higher than they should have been, but they couldn't pinpoint how much of the problem could be pinned on poor pump efficiency.
“We never thought roughness of internal pump surfaces could be costing us so much money,” says Maier. “Our engineers were shocked to find that many of our pumps were operating 15% to 25% below the manufacturers' specifications.”
After extensive research, the MCWA has concluded that pump manufacturers and users have largely ignored corrosion-caused decreases in pump performance.
Maier hopes other municipal water suppliers that lack the resources to conduct their own testing will rely on MCWA results and begin coating their pumps.
— David Bongiorni is marketing director for Devcon.