Cruise control

First ever underwater stabilizer fin replacement

With ocean cruise liners transporting thousands of passengers at full capacity, there is no room for delays. SKF and Trident Group recently performed the world’s first underwater stabilizer replacement to keep a luxury cruise ship on schedule.

The global cruise industry is riding a wave of popularity. This year, passenger numbers are expected to exceed 25 million for the first time—over three times higher than at the turn of the millennium. To ensure all these passengers have a comfortable journey, even during stormy weather, there is a hidden technology at work. Most modern cruise liners are equipped with a pair of hydraulically-controlled stabilizer fins to counteract the effects of rough sea conditions on the motion of the vessel. These can be folded away into the ship’s hull to minimize drag and facilitate maneuvering in ports.

Restoring stability

However, when sailing the high seas, there is always a small risk that damage could disrupt a vessel’s operations. During a routine inspection on a luxury cruise vessel in 2014, it was revealed that the port stabilizer fin was damaged. To avoid complications, the stabilizer had to be taken out of use until the ship’s next scheduled overhaul in March 2017.

While the vessel was in the dry dock in Germany, a team of engineers from SKF in Hamburg set about repairing the damaged stabilizer. They discovered that the damage was more serious than anticipated: several critical parts in the stabilizer mechanism were bent or broken. This meant that fixing the unit would require full disassembly, extensive machining, and replacing numerous major components.

A tight schedule for a challenging task

Although this work was nothing new for the SKF engineers, time was against them. The team calculated that the job would take at least 150 hours, making it impossible to complete the work during the five-day dry docking time—even with round-the-clock operation. With a full load of passengers set to board the ship immediately after the docking, the pressure was on.

To minimize disruption for the passengers, SKF and the vessel’s owners decided to undertake a task that had never been done before: replacing the stabilizer while the vessel was afloat. Firstly, the hull was sealed with two steel plates so the vessel could return to service while SKF repaired the stabilizer. Then, once they had reassembled and tested the stabilizer, SKF transported it to the Canary Islands, where the ship was scheduled to pick up its next load of passengers.

Teamwork keeps the cruise on schedule

When the repaired stabilizer arrived in the Canary Islands, a team from specialist marine engineering company Trident Group prepared it for underwater installation. This involved protecting and waterproofing all parts of the mechanisms that are normally exposed to seawater. Fortunately, when the vessel arrived in port for a 58-hour layover at the beginning of November 2017, weather conditions were perfect for the operation.

The Trident team installed a waterproof dome around the fin box so divers could safely remove the steel plates. A crane then lowered the stabilizer fin into position, allowing the team to mount the unit. Once the fin box was secured, they were able to remove the temporary dome.

With this basic installation completed, SKF engineers sailed with the vessel on its journey to the Caribbean. During the first day of this voyage, they performed the finishing touches by connecting the stabilizer control systems and conducting the final testing. Thanks to this collaboration between SKF and Trident Group, the cruise liner could continue on its route without delay: leading to many happy vacationers.

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