Contract Code : 81/011

101-J turbine with superheat steam (38-40 bar and 380-400c ) and with 7000- 7300 RPM is a plant process air compressor motive. It has been in service in a quiet normal conditions for 2.5 years. After some problems in LP air compressor and condenser vacuum system, turbine was shut down in normal condition and after remedying the vacuum problem, the compressor ( water leakage of side coolers ) was restarted. But in rotations higher than   4000 RPM it was shut down compulsorily because of high abnormal voice and vibrations and after reinvestigating and bearings change ( there were some scratches on them ) it was restarted. But it was shut down for second time on vibration and abnormal conditions in the rotation less than 2000RPM and after the third investigation it was started. In the process conditions the evidences showed that just the outlet steam pressure (vacuum condenser ) was low and the mechanical investigations showed that the damping wire was broken, three blades of the final row were broken and caused damages on the case, nine blades had cracks and finally the rotor was unbalanced. This researching project is designed and performed by cooperating of industry and university in order to investigate the reasons of the failure scientifically.