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Note the X-axis is consecutive chronological data points and not a time scale, in order to more easily assess the configuration effect on tube flow rate. To put the data into a more manageable format, the data is separated into four categories and plotted. These categories are forward flow, each having three pumps running with either Pump7A off, Pump7B off, Pump8A off or Pump8B off.
The plots indicate that the CWFF sensors 3 and 4 see lower velocities than CWFF sensors 1 and 2. This might have been due to the water boxes not being totally full. The station uses service water for the waterbox priming eductors. The priming eductors remove the trapped air from the top of the waterbox and thereby help maintain a full waterbox. To remove larger debris, the strainers were installed in the service water piping. The strainers were found to be plugged with debris and Asiatic clams. Therefore the water box level might not have been drawn up as high as designed, causing lower flows through the top tubes.
The plots also indicate that the velocities are much lower with either
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One additional point to be made is that the flow monitors detected issues before they resulted in a significant back pressure increase. In all of these cases, the back pressure increased no more than 0.30″ above design pressure. Therefore, the meters might be used as a proactive tool to help determine a back pressure issue before it becomes significant.
Conclusion
This case study has shown that the CWFF technology is accurate and reliable, having performed well for more than a year. The meters have provided information that identified new performance impacting issues and traced down root causes for chronic maintenance problems. Real-time frequent macrofouling of the tubesheet, water box level issues, circulating water pump capacity performance and associated flow configuration impacts, and reversal flow for the purposes of debris flushing, are among the practical issues that were studied. The data history from the flow meters provided the following benefits:
- Helped determine when macrofouling was becoming significant and helped evaluate the effectiveness of reversing the flow to flush away the debris.
- Indicated a flow discrepancy as various circulating water pumps were operated, which led to the diagnosis of the root cause of MIC.
- Indicated significant flow stratification that was due to water box eductor plugging.
Acknowledgement
The authors wish to acknowledge the assistance of Michael Horn of Plastocor for his assistance with routing the wiring for the sensors in the water box by encasing them in epoxy coating to ensure they do not interfere with water flow or become damaged.
Editor's note: This paper, PWR2008-60172, was printed with permission from ASME and was edited from its original format. To purchase this paper in its original format or find more information, visit the ASME Digital Store at www.asme.org.
Dr. Timothy Harpster is the director of Engineering at Intek Inc., where he leads the engineering team in the application of novel sensor technologies for Intek's instrumentation and applying Intek's condenser technology for engineered condenser retrofits to deliver performance improvements. He received his B.S. in Electrical Engineering from the University of Michigan, specializing in MEMS technologies.
Dr. Joseph Harpster is co-founder of Intek Inc. and has more than 50 years of industrial experience. He has several patents for his inventions in the fields of flow measurement and condenser technology and is a member of the ASME Heat Exchanger committee as well as the chair of the Education subcommittee. He has a B.S. and M.S. in Physics and a Ph.D. in nuclear engineering from The Ohio State University. He also was schooled by the U.S. Navy in steam turbine main propulsion and auxiliary power generation.
Gerald Weber is manager of Operations Support for Midwest Generation, EME, LLC. He has a MSME from the University of Illinois and has worked in the power industry for more than 25 years.
Sunish Shah is the engineering manager at Crawford and Fisk Generating Station, Midwest Generation, EME, LLC. He has a MSChE from the Illinois Institute of Technology, Chicago, and has worked in the power industry for 17 years.
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