Application of 12%Cr Steel for Geothermal Turbine Rotor

Abstract

Since the first geothermal turbine was installed at Larderello in Italy, many geothermal power plants have been developed. Due to corrosive gas, impurities and high wetness in geothermal steam, geothermal turbines suffer damage such as high stress part of turbine rotor including moving blades, eroded part of turbine sealing part and last stage long blade and so on. In these a hundred years, so many technologies on material selection, steam cleaning system, low stress designs to prevent the damages have been developed. Today, the reliability of geothermal turbine has been significantly improved and the availability has reached to the level of 90% which is very close to thermal units. Recently, in order to increase the stress corrosion cracking (SCC) resistance of geothermal turbine rotor materials and improve the reliability of geothermal turbine further, 12%Cr steel has been developed and actually applied for both rotor forging and welding material for refurbishment. In this paper, the result of verification study of 12%Cr steel and the weld repair by 12%Cr steel as welding material for geothermal turbine rotor are introduced.