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160MW Skoda Steam Turbine On-Site Balancing Work
Problem Identification:
- The customer requested support from the Resonance Institute technical team due to high vibration problems experienced in the steam turbine.
- Measurement and on-site balancing were performed on a 160MW Skoda turbine.
- Fixed 3000 RPM, variable load
- The equipment trips before reaching full speed due to high shaft vibration in the LP rotor bearings.
Diagnosis:
- The data collected during the initial acceleration phase was examined, and it was determined that the shaft sensors in the LP bearings were causing the trip condition.
- The condition causing high vibration in the data obtained from these sensors has been diagnosed as an ‘imbalance’ problem in the LP rotor. The imbalance causes the LP rotor to reach its first critical speed, resulting in high vibration values.
- It has been decided to implement the on-site balancing procedure (modal balancing at the first critical speed).
Diagnosis:
- The balancing weights are distributed equally between plane #1 and plane #2 (the front and rear planes of the rotor).
- The correction weights are distributed proportionally around the 0° hole (hole no. 1) and the surrounding holes.
- A total of 2-3kg of trim weights have been added to both planes.
Result:
- Following the removal of the correction weights, an acceleration test revealed that the vibration levels decreased from a Pk-Pk value of 200 microns to a Pk-Pk value of approximately 80 microns.
- As the current vibration levels are acceptable to the customer, the on-site balancing work has been terminated at this point.
