LIFE EXTENSION OF POWER TURBINE DISKS EXPOSED TO IN-SERVICE CORROSION DAMAGE

摘要

Siemens Energy has a large fleet of aero derivative gas turbines installed in oil & gas and power generation applications globally. Over the past several years, several incidents of disk corrosion damage have been observed during the power turbine overhauls especially for the units fielded in marine environment. Most of the corrosion attack has been observed at disk firtree (blade attachment features), gas washed disk faces and torque transmission features. In all of these cases the mechanism for corrosion has been identified as Low Temperature Hot Corrosion (LTHC) also known as Type-II sulphidation. Siemens has explored a number of potential operating and/or design options e.g. utilization of more corrosion resistant alloys and coatings to mitigate the effects of the corrosive attack on these disks. However, many of these proposals are either intermediate or long term solutions and are addressed more towards new power turbine disks rather than those that are already in service In the short term, Siemens technical solution has focused on development of proprietary repair processes to effectively remove the corrosion damage and extend the operational life of in-service disks as well as salvage some of the previously scraped disks. This Paper discusses the methodology and findings from the development and characterization of the repair of the power turbine disks when exposed to corrosion and other operational damage.