May-June 2019 NPJ

Nuclear Plant Journal, May-June 2019 NuclearPlantJournal.com 45 level comparable with its severity classification. As a result, to replace the Vibration Analysis PM task with continuous on-line monitoring, three monitoring methods are recommended: bearing metal temperatures, electrical signature analysis (for electric motor- driven pumps), and vibration analysis.  Bearing Metal Temperatures are required to address wearout due to fatigue, thrust bearing pad wear, issues concerning the heat exchanger or internal bearing cooler, or any other condition within the integrated lube oil system.  Electrical Signature Analysis is required to address physical changes such as erosion or damage to volutes, diffusers, channel rings, or the impeller.  Vibration analysis through triaxial vibration sensors detect changes in vibration, obviously. Each monitoring method identifies the sensors and the analysis methods required.  Bearing metal temperatures require temperature trend analysis on the inboard, outboard, and thrust bearing sensors. Simple temperature trending is sufficient.  Electrical signature analysis requires time-waveform analysis, spectrum analysis, wavelet, and Park’s transformation analysis using voltage and current transformers. Advanced monitoring beyond simple trend analysis is required to detect changes in air gap, voltage and current anomalies, rotor bar and winding anomalies, discreet pump power changes, etc.  Lastly, vibration analysis requires time waveform, spectrum, frequency band filtering, phase analysis, enveloping, and trend analysis on the inboard and outboard triaxial sensors or proximity probes, as well as a key phasor. These are to perform diagnosis when the anomaly is detected to assist maintenance crews with pinpointing the problem. The Monitoring Result for this example is to replace task with online monitoring. Itmay seemtobeoverkill by replacing manual vibration data with more than vibration sensors, but a probe on a bearing is not the same as human interaction. The human is looking at the equipment, smelling the equipment, listening to the equipment, and touching the equipment A Page From Inside a Quick Guide. to feel for more than vibration. When all degradation mechanisms and failure modes are considered, additional sensing points are required. One easy-to-implement modernization approach that provides true value There is little argument against modernizing the current nuclear fleet. COLM Quick Guides are a part of EPRI’s overall support of plant modernization. The guides apply proven technology based on a sound technical basis. When you apply sensors coupled with accompanying analysis methodology, based on evaluating degradation mechanisms and failure modes, the hardest part of converting to a condition- based monitoring strategy is letting go of yesterday’s processes. “The Wolf Creek Nuclear Operating Corporationhas beenusingEPRI’sCOLM Quick Guides since September 2018 to determine the feasibility of implementing online monitoring for Condition Based Maintenance with acceptable risk and a positive return on our investment,” said Wolf Creek Manager Strategic Projects Matt Hall. EPRI is leading and coordinating a global industry effort for implementing new processes and value-added technologies in plants as part of its plant modernization initiative. Our focus is on deploying technologies that improve plant economics and performance, including guidance to enable a modern digital infrastructure, wireless networks, and data analytics in a cyber secure environment that makes CBM a viable cost-effective solution. Contact: Christine Rivers, Electric Power Research Institute, 1300 West WT Harris Blvd | Charlotte, NC 28262; telephone: (980) 495-7478, email: crivers@epri.com .