We received a service request for a high vibration issue on a 4706 kW, 11 kV, 1000 RPM Hydro Generator coupled with a Pelton turbine. The customer reported elevated vibration levels during operation, affecting machine stability and reliability.

Our team visited the site and started with comprehensive vibration data collection across all measurement points. During initial analysis, we observed vibration levels reaching 4.83 mm/sec RMS, with a dominant 1X running speed component, indicating a probable unbalance condition.

To confirm the root cause, we carried out detailed checks including mechanical looseness, structural integrity, and coupling condition. All parameters were found to be normal, with no indications of looseness or external mechanical issues influencing the vibration.

Based on the vibration signature and phase analysis, we proceeded with field in-situ dynamic balancing using a single-plane correction method, considering the rotor behaved as a rigid body at operating speed.

As part of the balancing procedure, a 600-gram trial weight was applied, and the response in amplitude and phase was carefully monitored. The initial phase was observed around 88°, clearly indicating the unbalance location. Using influence coefficient calculations, the exact correction weight and angle were determined.

After applying the calculated correction weight on the rotor, a significant improvement was achieved. The vibration levels reduced from 4.83 mm/sec RMS to approximately 1.46 mm/sec RMS, and the phase shifted to around 341°, confirming proper correction and stable rotor behavior.

The machine was then operated under normal conditions, and smooth performance was observed with no abnormal vibration. The customer was highly satisfied with the outcome.

The key takeaway from this case is that accurate phase analysis, proper trial weight selection, and controlled balancing execution are essential for successful field balancing. Additionally, understanding rotor behavior is critical—since rigid rotors can often be effectively balanced using a single-plane approach.

For professional vibration analysis, field in-situ balancing, and rotating equipment troubleshooting, please contact:
📧 info@rasetechservices.com