Effective Cavitation Detection Techniques for Hydraulic Turbines
Project ID: 9933
Principal Investigator: John Germann
Research Topic: Improved Power Generation
Priority Area Assignments: 2011 (Climate Adaptation), 2012 (Climate Adaptation)
Funded Fiscal Years: 2011, 2012 and 2013
Can the Bureau of Reclamation (Reclamation) effectively reduce scheduled outages, improve machine performance, and reduce repair time and maintenance costs on its generating units and still maintain its reputation as a technical leader in the hydropower industry?
Need and Benefit
Cavitation damage is costly to the hydropower industry in several ways. Turbine outages to inspect for cavitation damage result in lost revenue during unit downtime. Cavitation repairs can extend outages 2 to 6 weeks and include extensive manpower, equipment, and material costs. For example, the Grand Coulee Power Office at Grand Coulee Dam spends an estimated $400,000 per year per unit for cavitation repairs on the third powerplant unit. Production losses for these extended outages are very expensive, with additional cost of lost power revenue due to repair outages running up to and over $350,000 per day for these units.
Current industry practice is to extend unit production and availability and to minimize maintenance downtime. Because of this, turbine draft tube and runner inspections are often omitted, allowing cavitation damage to go unnoticed for long periods of time between maintenance inspections. During this time, erosive cavitation can increase exponentially, resulting in severe damage. In certain cases, damage can be so severe that the equipment is destroyed. This occurred at Fremont Canyon Powerplant. The estimated base cost for the design, manufacture, and delivery of two new turbine runners to replace the cavitation damaged on Fremont Canyon Powerplant runners is $4,000,000. Installation and testing will further increase these costs.
The integration of wind power into the power system is increasing the need for research work in this area. In the past, to help minimize cavitation damage, a wide range of a generator output was prohibited because cavitation may occur within this "cavitation zone." As more wind power is added to the system, hydropower will be required to provide additional regulation, and large "cavitation zones" that prohibited operations will become very costly and will limit hydropower's ability to support wind power. The ability to detect the onset of cavitation in real time would allow operators to dynamically adjust the size of the "cavitation zone" depending on actual conditions, allowing a hydrogenerator to provide increased regulation.
In October 2004, the Hydroelectric Research and Technical Services Group entered into a partnership with the Wyoming Area Office with the intent to conduct machine condition monitoring and cavitation detection research at Fremont Canyon Powerplant. The runners at this facility have a long history of cavitation erosion on the runner blades. New runners are scheduled for installation in 2012 to replace the severely damaged ones. Research at the facility determined the cause of the cavitation and set operating conditions to reduce further cavitation.
Reclamation has a unique opportunity to build upon past research accomplishments by conducting cavitation research on the existing runners at the Fremont Canyon facility prior to the installation of new runners. The units are an excellent research platform for these studies because they already exhibit severe erosive cavitation, and the operating conditions that lead to it are already known. Rarely in the worldwide hydroelectric community are large hydroelectric units available for research and testing that exhibit these conditions.
As to date, cavitation and machine condition work conducted on the two units at Fremont Canyon Powerplant have been very productive. Continued research would be highly beneficial to the overall knowledge base in this arena.
Contact the Principal Investigator for information about partners.
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,
By John Germann
Publication completed on September 30, 2013