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What Price Preventive Maintenance?

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Every manufacturer of the equipment used in water and wastewater facilities recommends periodic maintenance to assure that their equipment continues to deliver top performance for many years. The trouble is: each manufacturer is ultra conservative, advocating far more frequent inspections and tear downs than are really necessary for most operating conditions. This overwhelms maintenance departments with limited human resources and budgets. These days, that includes most maintenance organizations. Unable to begin to comply with the recommendations for maintaining hundreds of pieces of equipment, they lose ground and eventually end up spending far more time trying to correct malfunctions than in preventing them.

After spending untold dollars compiling all of the recommended maintenance procedures for its equipment, one major metropolitan water and sewerage district could not even get all the tasks into its computerized maintenance management system (CMMS). There were just too many. City workers were spending 90 percent of their time “putting out fires” on reactive maintenance (the most expensive kind of maintenance) and only 10 percent on preventive tasks (the second most expensive kind). As a result, equipment availability – that is the amount of time the equipment is actually available to perform the functions for which it was purchased, was only 60 to 70 percent. In order to keep operating with almost 40 percent of its equipment down at any one time, either being fixed or waiting for a crew to arrive and try to figure out what went wrong, the city was forced to spend still more money installing redundant systems at critical locations.

There has to be a better way; and there is! By applying advanced diagnostic technologies to the issue of equipment maintenance, the probability of any one piece of equipment continuing to operate effectively can be accurately determined. When matched with machine histories, this information often points directly to equipment showing signs of wear or fatigue and in need of service. Repair crews can check on advance warnings, not the calendar, before going out to inspect, tear down (if necessary), and repair a piece of machinery. This is the essence of predictive maintenance, and it's far less expensive than the old fashioned preventive maintenance so many of us grew up believing in.

The water and wastewater treatment district mentioned earlier is now taking this concept a step further – to reliability centered maintenance. A Streamlined Reliability Centered Maintenance assessment was performed at one pumping station to prioritize the station's equipment. This involved identifying equipment that is most important to the mission of the station and making sure it receives the attention needed to keep it running. Each preventive maintenance task was reviewed for applicability and a technology matrix was developed to pinpoint areas that predictive technologies could be effectively applied. At the same time, many routine tasks on non-essential equipment were identified for elimination or greatly decreased frequency.

Following the priorities established at this station, an asset optimization program was implemented there and at 30 other pumping stations within the district. This included conditionbased vibration monitoring of key equipment and allowed decreased preventive maintenance of less-important equipment. As a result of this program at all 30 stations, the man hours that would be needed to perform all the manufactures recommended maintenance were slashed by nearly two-thirds, resulting in a calculated avoided cost of more than 4.3 million dollars. At the same time, worker productivity has increased because time spent chasing “fires” has been greatly reduced.

Numerous other cases exist where predictive maintenance based on accurate vibration analysis, infrared surveys, and oil analysis has replaced tear down inspections. Total maintenance time needed for large pumps and motors in those stations has been greatly reduced.

This paper will examine how various advanced technologies retrieve and utilize essential diagnostic information from various types of equipment to impact maintenance costs in the water and wastewater industry beyond pumps and motors. In the end, we will show that the price of original preventive maintenance is far higher than most people realize and too high for most facilities to bear.
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Document Type: Research Article

Publication date: 01 January 2004

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