MarineShaft – When One Component Fails – the Entire Shaft Line Is at Risk

A stern tube bearing failure on an offshore supply vessel had caused misalignment and damage to the shaft line. During a scheduled dry docking in Spain, MarineShaft was called in for an inspection that revealed that both bearings and shafts were misaligned and damaged.

After the alignment tests MarineShaft delivered a full-scope repair solution. By combining specialized in-house workshop repairs with precise on-site services, they restored the shaft line alignment – without replacing the existing stern tube bearings.

This case highlights how accurate fault detection, technical expertise, and efficient execution can prevent further damage and ensure a fast return to operation.

Read on to discover how MarineShaft solved this repair case, from inspection to straightening, machining, and final alignment.

Case study:

An offshore supply vessel suffered a stern tube bearing failure, causing shaft line misalignment.During a planned dry docking in Spain, MarineShaft was contracted to carry out an alignment test of the shaft line. The inspection concluded that the stern tube bearings and shafts were misaligned and damaged.

The propeller shafts, including bearings and hydraulic coupling, were sent to MarineShaft’s workshop in Denmark.

In-house Repair Scope

The propeller shaft and two intermediate shafts were cold straightened to within class tolerance using MarineShafts‘ unique cold straightening method.

The bearing journals and the intermediate shaft flanges‘ bolt holes were reconditioned, and 20 new bolts were manufactured to fit the reconditioned flange bolt holes.

Removing the stern tube bearing damage by machining and re-casting it with new white metal.

The intermediate bearing housings were refurbished with new shells, and the worn seal surfaces were re-machined.

On-site Repairs

Two service engineers from MarineShaft went on-site to complete the repair scope. 

To eliminate the misalignment in the stern tube housings, they performed precise laser measurements of the existing stern tube bearing housings misalignment, and these measurements were adapted to the final machining of the re-cast existing stern tube bearings.

Finally, the shaft line equipment was aligned and reinstalled. The hydraulic coupling was mounted and the propeller assembled. A final jack-up test, witnessed by the class, confirmed that the shaft line was restored within required tolerances.