Inspection and repair on RENK SHH 11 1135,1/760 gearbox

This client from Norway came to us with this RENK SHH 11 1135,1/760. We inspected the gearbox and performed a repair. After a succesful testrun we shipped the gearbox back to the client.

Upon arrival on the vessel in Rotterdam, preparations were made to disassemble the gearbox. Only upon arrival at anchorage in Scheveningen the disassembly could be started.

The gearbox showed no signs of serious damage or wear, beside normal wear on bearings and impact marks on the gears, from running without load. The intermediate shaft driven-end bearing however was found heavily damaged, most likely caused by slipping of the rollers/bearing.

It is suspected that the damage was caused by an undersized/damaged shaft journal on which the bearing was seated, resulting in additional internal bearing-clearance.

GBS advised to recondition the shaft, in order to obtain the correct shrink-fit of the bearing and prevent future damage. However Knutsen OAS Shipping decided to postpone reconditioning of the shaft until the vessel’s next docking. The new bearing was therefore fitted with Loctite, as before disassembly.

After reassembling the gearbox, the gearbox was flushed overnight, prior to performing a test-run.

During the test-run, temperatures and pressures were monitored and recorded. The gearbox reached an acceptable and stable operating temperature.

Our recommendations:
- It is essential to recondition the shaft journal of the intermediate shaft, in order to help prevent future damage to the bearing(s) and gearbox as a whole.
- Carry out a visual inspection of the gearbox annually.
- Carry out an oil sample analysis bi-annually.