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

Repair Scope

• Workshop repairs in Denmark: Shaft line, including bearings and hydraulic coupling, was shipped to our workshop. The propeller shaft and two intermediate shafts were cold straightened to within class tolerance, and bearing journals were restored. The intermediate shaft flanges bolt holes were reconditioned, and 20 new bolts were manufactured to fit the repaired flange bolt holes.
• Stern tube and bearings: The stern tube bearings were repaired by removing damaged white metal, re-casting of white metal and re-machining the stern tube bearings with internal offsets to rectify the misalignment in the stern tube housings. Intermediate bearing housings were refurbished with new shells, and the worn seal surfaces were re-machined.
• On-site offset alignment: To eliminate the misalignment in the stern tube housings, our service engineers performed precise laser measurements of the existing stern tube bearing housings misalignment and these measurements were adapted to the final machining of the re-casted existing stern tube bearings. This unique capability allowed us to restore shaft line correctness without the need to replace the stern tube bearings with new ones.
• Installation & alignment: Finally, our team installed and aligned the repaired shaft line equipment, mounted the hydraulic coupling, and assembled the propeller. A final jack-up test, witnessed by the class, confirmed that the shaft line was restored within required tolerances.

Result
MarineShaft carried out a full-scope repair solution combining our workshop expertise with specialized on-site laser measurements. By restoring the shaft line to correct alignment, the vessel could return to service safely and efficiently. MarineShaft thanked all parties involved for their cooperation in making this repair a success.