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Inspection and repair on CMD JC62 JUMBOREX gearbox

Inspection and repair on CMD JC62 JUMBOREX gearbox

  • CMD gearbox
  • Input=___ rpm / ____ KW
  • UAE

Scope of work:

We performed an inspection and repair on a gearbox CMD JC62 JUMBOREX.

This client from SAUDI ARABIA came to us with this CMD JC62 JUMBOREX. We inspected the gearbox and performed a repair. After a succesful testrun we shipped the gearbox back to the client.

After the disassembly of the shafts and the bearings, a recommendation has been provided of what was necessary to replace in order to get the gearbox running. In addition, we investigated what was causing the damages. The mechanics and engineers were able to provide sufficient information on what has occurred after which the situation was clear.

In the control room it was noticed that there was a small vibration in the bearing of the third shaft. We were ascertain that the mechanics had replaced the bearing as the disassembly had left its marks on the shaft. The original bearing of the third shaft was replaced with counterfeits (fake). We were not able to determine the validity of the bearing of the second shaft, thus remaining unknown. After the mechanics replaced the bearing, the was shaft was placed in the gearbox. Nobody was aware that the bearing houses are eccentric, resulting that the angle of the shafts were not aligned to each other.

The first problems were:

- No good alignment of the shafts
- Fake bearings with a different clearance and quality than the original bearings.

After the repair conducted by the mechanics, the gearbox was up and running for a month after which the tooth of the second stage gear was heavily damaged. The company decided to swap the gears from their good gearbox with the gears from the broken ones. A Chinese company was hired to take care of the clearance and the fine tuning. After this repair, more problems occurred up until the point that the gears from the second stage broke, causing a lot of damage.

This type of gearbox requires perfect alignment of the input shaft in comparison to both second stage gear wheels (double helical input shaft). In the current situation the input shaft was more than 20 mm incorrectly positioned in the gearbox (towards the electrical motor). Consequently, the electric motor could not fit in its original position on the foundation. Therefore we most likely suspect that the mechanics have cut out the foundation holes, thus enabling the electric motor to fit.

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Location - date:

SAUDI ARABIA - April 2018

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