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The Journey To Predictive Maintenance With the digital age fully upon us, it's time for treatment plants to evolve beyond preventative maintenance and embrace predictive maintenance. By Paul Brake E ffective and efficient maintenance is at the heart of any treatment plant. It doesn't matter how well a process was designed, how expertly it was installed and commissioned, or how expensive the components are; if maintenance fails, the whole system fails. There is an old saying, "Stay out in front, but stay behind the plow." The Costs Of Standing By Traditionally, maintenance was based on failure. We fired up our sys- tems, and when something broke, we rushed in and fixed it. This has proven to be costly — very costly. The first big cost is for parts. Either we have to warehouse a spare for every critical piece of equipment, or we have to expedite delivery from a vendor. Both are cost-prohibitive. The second major cost comes with the process downtime. If you lose a pump, everything downstream of that pump goes out of commission. Don't make the mistake of thinking this applies only to major feed pumps. If a chemical injection pump fails, the entire line then can go out of com- pliance, and you have to shut it down for repair. There is a fourth cost to the "run to failure" mode that most do not stop to consider. If you wait until a bearing fails completely in a pump, think about how much collateral damage that can cause. What if it allows your impellers to contact the housing? What if it allows a significant leak? What if it takes the drive motor out with it? The cost of "run to failure" is so high that almost nobody does it anymore. The Preventative Paradigm Today, and for quite some time, a paradigm of "preventative main- tenance" has prevailed in most facilities. This is definitely a step forward. Historically, it has reduced maintenance costs by about one-third. Preventative maintenance relies on equipment history and statistical techniques to determine a theoretical mean time to failure. Using this calculated result, a company will order replace- ment parts, schedule turnarounds and area shutdowns, and prepare staff or hire outside contractors for scheduled maintenance. This sounds like a good plan, and before modern computers and sensors were in play, it certainly was. We do that with the cars we drive. A manufacturer will tell you, for example, to change your oil every 3,000 miles and your transmission oil every 50,000 miles. But these numbers ignore operating conditions. One car may be doing highway driving in dry, cool air, while the next will be city driving in highly polluted, wet, hot air. One car may be driving on flat prairies near sea level, and the other could be in the mountains. Therefore, any experienced operator or tradesman will tell you that the mainte- nance requirements must be different. There is no way that the oil in these cars will be in the exact same condition at 3,000 miles of travel; yet, they all change out at that distance. In fact, there may be some driving conditions that would allow change out at 6,000 miles and others that require service at only 2,000 miles. This is the critical flaw of preventative maintenance. We base our maintenance on statistical time intervals and ignore the specific operating conditions of the equipment. The two typical results are that we either perform unnecessary maintenance, or we don't get to the equipment in time, and we have a full failure. In the first situation, we create unnecessary shutdowns that cost us process and production losses. We employ maintenance staff that could be otherwise better employed. We bring in outside contractors that we really don't need to hire and pay. We throw out bearings that are perfectly serviceable. And our maintenance budgets are bulg- ing at the seams. In the second case, we are actually operating in a run-to-failure mode and do not realize it. We then face all the problems and costs of that methodology; yet, we are completely unprepared for it, and thus it costs us even more. If our processes are subject to changes, then no preventative maintenance system is appropriate. Our inflow in summer could be 10 or 20 degrees higher than in winter, as could be our operating conditions of motors and pumps. That alone will render a preven- tative maintenance schedule ineffective. A New Era We are in a new era of maintenance. It has snuck up on us slowly as a happy byproduct of a completely different technology advancement. The growth and developments in the computer industry have spawned an entire product line that allows the next generation of maintenance methodology. These computer advances have created smart sensors, information pathways, and computational equipment and software that allow for modern predictive maintenance techniques. One side of the road was run to failure, the other side was preventative maintenance. Think of predictive maintenance as a happy, middle-of-the-road approach that takes advantage of the benefits of both, while eliminating the liabilities. In the water and wastewater industries, like many others, we have moved progressively into automating our processes and equip- ment. Automation involves condition-monitoring of specific pro- cess measurements as well as equipment setpoints. And automation 16 wateronline.com n Water Innovations The growth and developments in the computer industry have spawned an entire product line that allows the next generation of maintenance methodology.