Selection of steels for vital structures and turbine components of the hydro power plant ’Djerdap 1’

Abstract

Vertical Kaplan turbines, manufactured in Russia and with nominal power of 200 MW, have been installed in 6 hydroelectric generating units at ’Djerdap 1’. During the refurbishment of hydroelectric generating sets A4, A5 and A6, non-destructive and destructive tests were carried out on parent material and weld metal in order to complete the state analysis and assessment of damage level and causes of damage occurrence at vital structures and components, which showed that the selection of suitable material has a crucial role regarding the safe operation of hydroelectric power plants. This paper contains comparative results of mechanical tests performed in order to obtain mechanical properties of materials used for the fabrication of the upper rings of guide vane apparatus installed in 1973 and made of steel St 3 (GOST 977-88) and those recently made through the use of steel S 235 (EN 10025-2), as well as for turbine covers, made of steels S 355 NL (EN 10025-2) and S 355 NL + Z25 + N (EN 10025-3).