Cavitation Detection Technology for Optimizing Hydraulic Turbine Operation and Maintenance
Project ID: 2386
Principal Investigator: John Germann
Research Topic: Condition Assessment
Priority Area Assignments: 2014 (Renewable Energy and Energy Conservation)
Funded Fiscal Years: 2014
Keywords: cavitation detection, cavitation monitor, hydroelectric, hydraulic turbines, acoustic emissions, vibrations
Can Reclamation develop effective cavitation detection techniques and through this study, develop a cavitation detection monitor that can be used to substantially reduce hydro turbine maintenance costs by accurately predicting erosive cavitation?
Need and Benefit
Turbine cavitation damage is usually the most costly maintenance item on a hydroelectric turbine. At this time there is no effective method or commercial instrumentation available to detect on-going erosive cavitation on an operating turbine. This research is being conducted to develop better techniques and instrumentation for eventual use as a machine condition monitoring tool. The overall goal is that with these techniques and instrumentation in place, better economic models of the costs associated with cavitation damage that is occurring within turbines operating in cavitation prone zones can be better determined.
Detection of cavitation occurring in an operating hydroelectric unit is difficult. Cavitation occurring in a hydroelectric turbine is a very complex phenomenon that is difficult to assess. Cavitation that occurs within the hydraulic turbine can be damaging or non-damaging. Direct access to assess cavitation that is occurring within the water passage of the turbine is not possible. A primary task of past Reclamation research was to explore the best type of sensor to use to pick up cavitation noise, the best location(s) for sensor placement and better signal processing techniques for dissemination of signal data. These researches lead to the development of a shaft-mounted cavitation detector. It was proved that one of the best locations for detecting damaging cavitation that is actually occurring on the turbine runner surface is off of the turbine shaft. Technologically, this is difficult though since high frequency signals must be transmitted off of a high speed rotating platform and there are high safety and reliability concerns with anything spinning at a high speed.
Reclamation has two hydroelectric turbines with new turbine runners at Judge Francis Carr (J. F. Carr) powerplant that exhibit extremely aggressive leading edge cavitation. Cavitating vortex swirl is also seen with these turbines. In 2013, the Technical Service Center, mechanical equipment group, through this research, entered into a partnership with the Northern California Area Office (NCAO) with the intent to conduct machine condition monitoring and cavitation detection research at J. F. Carr powerplant. The only means to limit damage to these runners is to accurately predict cavitation prone operating zones and restrict operation within these zones. To accomplish this, a cavitation detection monitor must be developed, installed and tested. Once this is accomplished, and through long term study, effective algorithms can be developed to predict erosive cavitation so that it is possible to actually quantify dollar loss amounts associated with damage occurring from operating in the cavitation prone areas. Other facilities such as the Hoover and Grand Coulee power stations have expressed interested in this research for applications at their facilities.
Reclamation is the only known entity in the world that is currently conducting research on cavitation in hydraulic turbines. Reclamation has a unique opportunity to build upon past research accomplishments by conducting cavitation research on the existing runners at the J. F. Carr facility. The units are an excellent research platform for these studies since they already exhibit severe erosive cavitation. Without this study, the ultimate destruction of these $7,000,000 runners is inevitable. The findings from this research will be disseminated to other outside organizations through technical papers and conference presentations.
The shaft mounted cavitation detector designed by Reclamation through this research will be continually tested and upgraded. This product will be made available to Reclamation powerplants as requested. Its use for other, non-cavitation related measurements outside of this research, has already been discovered and utilized.
An effective cavitation monitor(s) will be designed, fabricated, installed and tested at J. F. Carr powerplant. This product will be tested and made available to Reclamation powerplants as requested.
New insight will be developed into better cavitation detection methodology, detection techniques and instrumentation, signal analysis and software tools, and measurement of cavitation aggressiveness, relative to damage that is occurring on actual hydroelectric turbines.
These findings will be disseminated throughout Reclamation and the hydroelectric industry through the writing of technical papers and presentation at various conferences