As new power plants have become harder to permit, maintaining the performance of plants that some would consider past their prime has become more important than ever. Like a vintage coupe at a car show, an old plant that has been well-maintained doesn’t show its age. Even 40-year-old plants can deliver many more years of profitable and reliable service—if their equipment has a good health care plan.
Over the past two decades, plant owners have increasingly used equipment condition monitoring (CM) to maximize plant availability and revenue and minimize maintenance costs. Among the most popular CM systems and schemes are data historians, digital control, trending of critical operating parameters, vibration and oil analyses, and infrared scans.
However, many of these methods either focus only on whether a system is currently operating within prescribed limits or track only certain measures of performance. In both cases, human analysts must then infer overall equipment health and its direction. Newer CM systems and techniques can extrapolate readings of common plant parameters to evaluations of overall equipment health in real time. By comparing past and present readings, they can predict—fairly accurately—when a system or component will fail or begin causing problems elsewhere.
When a plant’s analytic or interpretive methods fall short, its bottom line suffers. Two scenarios, both undesirable, are possible. If systems are maintained according to strict schedules, with no regard to their actual condition, man-hours and scarce O&M dollars may be spent on repairs that aren’t yet needed. If the maintenance philosophy is too cavalier, incipient problems that should be addressed may not get fixed in time (because they were detected too late) to avert an expensive failure.
Neither too soon nor too late
Implementing predictive maintenance (PM) techniques solves both potential problems. If real-time readings of key parameters indicate that a piece of equipment is continuing to operate normally, a scheduled overhaul can be delayed, along with the cost of performing it. Conversely, slow but sure changes in readings enable analysts to detect impending failures early, before the equipment’s condition worsens to the point of needing urgent attention. Early awareness of a problem makes it possible to schedule repairs at a convenient time (for example, during an upcoming planned outage) and gives the plant’s O&M staff time to line up the team of technicians best qualified to do the work.
Although PM has become commonplace at power plants in the developed world, the technique is more likely to be applied to key million-dollar systems such as boilers, turbines, and generators than to balance-of-plant (BOP) equipment such as motors, fans, pumps, and air heaters. Using case studies, this article argues that PM programs have their greatest positive impact on plant availability and profits when they also include BOP equipment. Comprehensive PM programs can even quantify the financial losses avoided by optimizing maintenance schedules to reflect actual equipment health.
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