Case Study: Oil Carbonization: Causes, Detection, and Impacts on Turbomachinery

Edward Michel, Principal Engineer, GE Power


In April 2019, a customer reported vibration spikes on their steam turbine occurring every one or two days, reaching almost 6 mils. They reviewed operational data and were not able to correlate the vibration spikes to load swings, differential expansion, gland steam temperature, etc.  Following each of the vibration spikes, vibration levels returned to normal. Closer review of long term data by GE Product Service indicated that vibration spikes had been occurring for at least six months and were gradually increasing in magnitude and frequency. There was also some correlation with changes in load, which looked characteristic of rubs due to oil carbonizing on a shaft. Bently Nevada ADRE data was reviewed and further suggested that the location of rubbing was at the end of the rotor, in the vicinity of oil seals. The site followed the short-term recommendation to position a cooling fan near the hot-end bearing to reduce temperatures and minimize oil carbonization, which did reduce the frequency of vibration spikes.Two weeks later the site inspected oil deflectors and found oil and dirt buildup at three bearings, with the worst buildup at the hot end of the turbine. Field engineers also noted that insulation was not in good condition near the ends of the turbine shell and a significant amount of dusting was present in the vicinity of the oil deflectors.


– how to recognize and diagnose oil carbonizing in seals on large turbines
– short-term corrective actions to allow continued operation
– the importance of maintaining a clean plant and proper shell insulation


Edward Michel has 20 years of experience in GE Power Atlanta since graduating as a Mechanical Engineer from the Georgia Institute of Technology. In his current role he diagnoses rotordynamic issues on Gas and Steam turbines and Generators and lead root cause analyses. Edward’s first four years at GE were in the Monitoring and Diagnostics Center, monitoring the GE fleet and diagnosing trips. He also spent two years as a Six Sigma Black Belt, improving processes and enhancing technical depth. Two of his years at GE were also spent as a Machinery Diagnostics Engineer in the US for Bently Nevada.