Gearbox Rotor Rub Problem
Problem Definition:
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The newly assembled Motor - Gear Box - Pump equipment tripped due to high temperature during the first start-up test phase.
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As a result of examining the data from vibration and temperature sensors, it has been observed that there is an unusual condition in the gearbox output bearing.
Diagnosis:
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When the trend values of the temperature sensor in the gearbox output bearing are examined, it is seen that the equipment exhibits a normal heating trend up to 75 degrees C, but then the temperature value rises to 105 degrees C quickly and therefore the equipment trips.
Run-up
Heating
Rub
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When the "Shaft Center Line (SCL)" graph taken from the X and Y displacement sensors are examined, it is seen that the rotor exhibits a large change in its position during the run-up and warm-up phases. After this position change, which is approximately ~150 micron Pk-Pk, it is seen that the position orientation momentarily changes to the right-upward and continues to change in this direction until the temperature trip.
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This behavior observed in the temperature and shaft center graph points to the "Rotor Rub" problem. It is estimated that the rub problem that occurs as a result of the rotor contacting the inner surface of the pads is caused by a situation such as misalignment/installation problem.
Conclusion:
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After the overhaul of the gear box, it was observed that there was a rub problem in the bearing.
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Improvements on alignment & installation solved the problems and results in reliable operation of the equipment.
