Water and Energy Abstracts
Year : 2004, Volume : 14, Issue : 1
First page : ( 10) Last page : ( 11)
Print ISSN : 0021-1672.

16. Efficient Cavitation Detection Technology for Optimizing Hydro Turbine Operation and Maintenance

Mossoba Youssef

(Proceedings, Hydro 2003, Vol. I, Croatia, pp. 93–100).

Abstract

Cavitation damages are the result of repeated collapses of transient vapour cavities. When the micro-jets or shock waves of water vapour implosions hit the metal surface of the runner blades, they leave a signature of vibrations at very high frequencies. By measuring vibrations at strategic points on the hydroelectric unit, important data can be retrieved. These data are then mathematically treated in order to isolate vibrations resulting directly of cavitation erosions from other noises inherent with turbine operation. Hydro-Quebec has spent considerable effort in studying cavitation detection using the vibratory approach. In recent years a technology transfer activity took place from lab and field development to field measurement applications. In this paper we will principally describe recent field results. We will explain how these data are valuable for optimal operation aiming at maximizing availability and minimizing maintenance. We will also explain how transferring the technology from IREQ, Hydro-Quebec's research institute to Hydro-Quebec Generation Group helped adapting the method to the field needs. After developing highly cavitation resistant materials and the Scompi robot for cavitation repairs, Hydro-Quebec has spent considerable effort in cavitation detection by the vibratory method. When this technology reached field implementation, the different applications have emerged into: Measuring relative cavitation aggressiveness; Measuring absolute cavitation aggressiveness; Monitoring cavitation aggressiveness. Many uses could be resulting from these applications: Identification of optimal operating conditions for minimizing cavitation damages; Comparison between two machines, one that has been modified and the other not; or comparison between before and after a modification on a machine; Predicting the time of performing repairs, i.e. optimizing repairs planning; Except for an initial inspection, eliminating future cavitation inspections; Verification of model cavitation predictions; Performing acceptance tests. The cavitation detection technology applied on machines with cavitation problems or on new, upgraded or rehabilitated machines can minimize maintenance costs and operating revenue losses.

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Keywords

Cavitation, Transient vapour, Implosions, Vibrations, Detection.

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