Inspection and repair on FLENDER DMG2 25.4 gearbox

This client from VIETNAM came to us with this FLENDER DMG2 25.4. We inspected the gearbox and performed a repair. After a succesful testrun we shipped the gearbox back to the client.

We got invited for inspection of two mill drive gearboxes to evaluate the condition of the gearboxes.

For the inspection of the bearings, a videoscope was used. With a videoscope, clear images can be viewed and recorded at locations with limited accessibility.

By means of a vibration analysis, gear and bearing damages can be detected, that could not have been noticed otherwise. The vibration analysis can be seen as a useful supplement to a visual inspection.

GBS emphasizes that not all gear and bearing damages can be detected by means of a vibration analysis. Particularly at the slower turning bearings, the vibration levels are often too low to reliably detect damage patterns.

Oil leakages were observed under the input shaft (both ends) and intermediate shaft bearing cover, inching drive side.

As far as visible the forced oil lubrication system was working correctly.

We concluded that the condition of the gearbox was not suitable for long term operation.

Action should be taken to correct the input shaft bearing problem.

Short term action

- Order new input shaft bearings. One QJ axial bearing and two double row spherical bearings.
- Order a complete set of gearbox bearings if the bearing life is close to or exceeding 80.000 running hours.
- Take vibration data on a weekly base.

Long term action

- Prepare all the parts, necessary tools, lifting arrangements, workshop and man power for a full overhaul. Expect a repair period of 2 to 3 weeks, depending on available man power and agreed working hours (single shift or double shift).
- Check if it is feasible to only remove the input shaft for bearing replacement via the vertically split input shaft casing. This will reduce the overhaul time significantly to less then 5 days.
- Check historical vibration data. High overall vibration levels might always have been present around the input shaft bearing casings.