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

Research Question

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.

Contributing Partners

Contact the Principal Investigator for information about partners.

Research Products

Bureau of Reclamation Review

The following documents were reviewed by experts in fields relating to this project's study and findings. The results were determined to be achieved using valid means.

Detecting Cavitation to Protect and Maintain Hydraulic Turbines (final, PDF, 546KB)
By John Germann
Publication completed on September 30, 2014

This bulletin summarizes the research results and potential application to Reclamation's mission.

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Last Updated: 4/4/17