What normally happens in dry dock, SKF and the underwater repair specialist Trident Group recently dared to do in the “wet element”: For the first time, this team of experts installed a swiveling fin stabilizer of the “Type S” on a floating ship. Thanks to the successful action, the affected crusader was able to continue his journey through the Atlantic as planned.

In addition to the staff and luxurious equipment, aboard cruise ships provides a lot of "hidden" technology for the comfort of passengers. These include, for example, hydraulically operated fin stabilizers on many modern ships, which are swung out below the waterline when the sea gets a bit rougher. While driving, these fins then counteract unpleasant ship movements. In calm waters, however, the stabilizers are folded back into their "parking positions" in the hull to minimize flow resistance. Many of these fins are manufactured and maintained by SKF.

Unwelcome surprise on port

In the routine inspection of a cruise ship in 2014, the technicians noticed damage to its port stabilizer fin. Presumably, the damage was due to a collision with flotsam. In order to avoid consequential damage, it was decided to temporarily decommission the stabilizer until the next scheduled overhaul of the ship in dry dock.

In March 2017 it was time: In a German shipyard, a team of SKF engineers from Hamburg on the disassembly and repair of the stabilizer plant. However, they found that the fin stabilizer had suffered much more serious damage than originally thought: The impact had several vital components of the fin mechanism bent or even broken.

Whilst the complete replacement of a marine-damaged stabilizer is routine for SKF's marine experts, in this case they were on the back burner: the team calculated that the required work would require at least 150 h. However, since the ship only had a five-day dry dock stay, even with "24 hours shifts" it would have been impossible to get the job done on time. And an extension of the stay was out of the question, because the next tourists wanted to board.

Exceptional measure

In order not to disturb the ship's operations and the passengers under the given circumstances, the shipping company and SKF decided to take an extraordinary measure: underwater installation. For this purpose, the defective stabilizer was dismantled in dry dock and his "parking bay" in the hull temporarily closed with two steel plates. So the ship was able to set sail as planned. The removed stabilizer was meanwhile shipped to the halls of SKF Marine GmbH in Hamburg, where the experts carried out the necessary repairs.

After the fin stabilizer had been repaired and tested here, the base of the stabilizer was sent by container ship to a port in the Canary Islands. Smaller components - such as the control systems - landed as part of a European stopover in the belly of the Crusader. The schipperte now also in the direction of the Canary Islands to accommodate the first passengers of the winter season.

No diving holiday in the Canary Islands

Unlike the tourists, the SKF and Trident Group specialists in the Canary Islands did not think about vacation: they were already preparing the stabilizer that had arrived in the meantime for its underwater installation. To this end, they have, inter alia, all parts of the stabilizer Mechanismusseses that do not normally come into contact with the sea water, protected or sealed accordingly.

At the beginning of November 2017 also made the passenger ship in the harbor: 58 h long it would be there at anchor. This started the crucial countdown for the SKF experts as well as the Trident team's diving missions. With clear water and mild temperatures, the professionals first mounted a kind of "watertight bell" over the fin box. Thus, the steel plates, which had previously closed the "parking bay" of the stabilizer, could be safely removed. Then the stabilizer fin was carefully lowered by a crane next to the hull and maneuvered slowly into position by the divers. Shortly after, they managed to mount the stabilizer properly. After that, they were also able to reduce the provisional air chamber again.

After completing the mechanical installation work on schedule, SKF's engineers stayed aboard. On the way to the Caribbean, among other things, they connected the control technology and checked the proper operation of the system. The fact that the associated tasks were already completed within a day, should not have been in this case quite to the taste of the technical "short crusaders".