|Pumps at a wastewater treatment plant.|
The unattributed paper begins, "One of the most common questions from water and wastewater utilities when they are asked about their maintenance practices in lift stations is 'What do other organizations do?'....Maintenance practices for utilities include run to fail, preventive maintenance on a schedule of time or time in service, and predictive maintenance by monitoring leading indicators of pump and motor problems."
As the title suggests, the study discards at its outset the long-cherished concept of preventive maintenance, using the critique in Thompson and Granger's monograph What Price Preventive Maintenance?, published in 2004:
"For years companies have been performing the preventive maintenance recommended by manufacturers without question...reasoning...that manufacturers have done all the research needed to ensure their equipment will operate properly in any environment. Most companies also want to ensure that equipment warranties are maintained during the initial install period. Once these maintenance actions are entered into the CMMS [computerized maintenance management system] or work routine, no one challenges their validity or periodicity because 'that is the way we have always done it.' This can be a very costly way of doing business."The Multitrode study found that "across the majority of utilities in the U.S. and Australia the most common methodology was run to fail. Manpower shortages and/or lack of a budget for better monitoring and control were by far the most common explanation for this choice..."
"The major problem with run to fail is that it is a choice to fly blind as to the state of the assets. While there are many reasons why pumps and motors can deteriorate faster than historical data shows, there isn't space in this article to detail them all. However, an excellent example is given in article in Pumps & Systems ["Unbalanced Voltages and Electric Motors," July 2008] by Thomas H. Bishop."
Bishop looked at the effects of slight voltage imbalances--"around 10 percent below nominal"--on the life expectancy of pumps in the United Kingdom "at a large regional municipal utility that introduced a predictive maintenance into the lift stations..."
"[B]ecause the 3-phase supply wasn't remotely monitored, no one was aware of it. The supply reduction was causing higher running currents, but not enough to trip any panel components or the pump thermistor. Still, the pumps were running too hot, causing a big reduction in lifetime." Pumps that should have lasted 25 years were burned out after less than a third of that--only seven to eight years--because of a seemingly trivial voltage shortfall.
Not only can miscalculations like the preceding make "run to fail" extremely costly, but at the same time, predictive maintenance has become much more affordable, practical, and easy to install and operate; that is, cost-effective. Once regarded skeptically as a cross between sorcery and algebra, predictive maintenance is now making a home where pumps, motors, compressors, fans, and any other rotating machinery is in operation.
Photo by Christopher Shannon/KCF Technologies. All rights reserved.