Repair of damaged surfaces at the vital section of the regulatory mechanism of the hydro turbine guide vane apparatus

Abstract

Vertical Kaplan turbines were installed in 6 hydroelectric generating sets at "Djerdap 1", nominal power 178 MW, that were made in Russia. During the refurbishment of the hydroelectric generating set Al at the hydro power plant Djerdap 1, experimental non-destructive tests on all of its components were performed in order to determine the state of the turbine as a whole. During the testing the damages and cracks were detected on internal surfaces of cranks and sleeves of guide vane apparatus vanes, which were caused by turbine shaft vibrations. Cranks and sleeves were made of cast steel 25L, in accordance with the standard GOST 977. The repair methodology for damaged internal surfaces of cranks of guide vane apparatus vanes is presented in this paper. It was necessary, due to the structural solution used for the design of cranks and sleeves and their function during exploitation, to define a large number of details, carefully reconsider them and carry out all activities with extreme care in order to enable the safe operation and continuous use of cranks. Overlooking, underestimation or incorrect perception of important details could cause significant problems during turbine operation.