Large rotating pieces of equipment such as turbogenerators, compressors, boiler feedpumps, etc. undergo thermal growth and thermal movements when they operate.
To accurately determine the accurate xyz thermal movements of the bearing housing has been an extremely difficult task in the past. Typically, thermal movements are guessed at, assumed by very simplistic formulas or measured with outdated technologies that can not be proven to be accurate.
Even manufacturers' recommended thermal growth values often don't apply because of unique setup conditions.
Benefits:
- Accurate and provable xyz values to .001" - .002".
- Many measurements of same point are taken at different angles which provide a redundant and statistical sample of data which will assure the accuracy of the measurement.
- All 3 directions are measured (i.e. not just vertical).
- Not only can data be statistically proven to be accurate but the shaft centerline analysis of the machine's train on a runup will conclusively prove the normal shaft position in the bearing.
Left figure shows shaft centerline plot of a 30MW turbo machine without thermal growth considerations. Machine often tripped due to rotor instability.
Right figure is the shaft centerline plot of the same machine after thermal growth measurements and alignment correction. Machine now operates in a more stable condition and has never experienced rotor dynamics instability again.
