Author(s): Sorin-Ioan Lupa; R Negru; M Gagnon; G Abdul-Nour; L Marsavina; S Muntean

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Abstract: The hydraulic transients associated with flexible operation network balancing tend to induce cyclic overpressure loads on the hydraulic components of the passages. Stresses generated by these have a direct impact on the asset durability and can even lead to catastrophic structural failures. The objective of this study is to analyze the cyclic loads for different hydroelectric generator operating scenarios and to assess their impact on the service life of the spiral casing. First, we look at three different operating sequences: (1) load rejection; (2) start/stop sequence; (3) regulation in transient zones. Experimental data were used to define the parameters for each type of cyclic load. The analytical relationship between cyclic stresses and the durability of a Francis spiral casing was studied using the ASME S-N methodology to assess the impact of cyclic loading on service life reduction. Second, for three representative operating modes: (1) normal operation; (2) intensive operation; (3) peaking, the overall impact of the generated loads on the durability of the spiral casing was established and a comparative analysis was performed. We observe that the most damaging loads are induced by regulation in transient zones, followed by start/stop sequences. Regarding the operating modes, our results reveal that the peaking has the greatest impact on service lifetime, followed by intensive operation. Given these, we propose solutions to improve operating policies and maintenance strategies, based on the initial unit design and the operating mode considered.

DOI: https://doi.org/10.1088/1755-1315/1561/1/012037

Year: 2025