Critical Aft Propeller Shaft Seal Repairs Performed on Military Vessels

12 June 2012

Military installations find themselves continually on a high level of alert. Even while idle in harbor, these grey hull behemoths are always ready for a good fight. Sometimes even these seemingly invincible vessels are plagued with aft shaft seal issues. While operating in the Indian Ocean a military installation developed a critical situation when one of its main propulsion shaft aft face seals. The face seal, seal seat and bellows became damaged due to the entanglement of a line. In order to mitigate further damage to the propulsion shaft line and to minimize any environmental impacts, the vessel was taken out of service and taken to Korea for emergency repairs. The manufacturer of the seal system contracted the Subsea Solutions Alliance to perform an Original Equipment Manufacturer and class approved repair.

While the vessel steamed toward Korea, the Subsea Solutions Alliance immediately deployed equipment and personnel to the site. By maintaining specialized flexible hyperbaric cofferdams in strategic locations around the world, the Subsea Solutions Alliance is able to deploy personnel and equipment within hour of order to the far-reaching areas of the world. Upon arrival on site, the diver / technicians sprung into action. The rope guard was properly removed using a carbon arc gouging system. By utilizing this process, the rope guard can be quickly and cleanly removed from the stern tube; saved for reinstallation once the repair is completed. Once removed, the diver / technicians were able to confirm that the face, seat and seal bellows were damaged; thus requiring replacement. With the entanglement removed the team move forward with the installation of the Subsea Solutions Alliance’s flexible hyperbaric cofferdam.

With the flexible hyperbaric cofferdam installed, a completely dry repair could be executed to the damaged face, seat and shaft bellows. The seal face and seat were carefully removed. Due to excessive gouging due to the entanglement, these components needed to be replaced. The diver / technicians continued to exchange the damaged seal system bellows.

Managing the complex spring loaded bellows assembly, the system was safely and efficiently exchanged using the same process and tooling as if the work was being done in the dry dock. As the diver / technicians of the Subsea Solutions Alliance are factory trained and certified in the replacement of this type of seal assembly by the Original Equipment Manufacturer, a fully warranted and Class approved repair was performed. Within a few days of its failure, the vessel was deemed "fit for duty” and headed on her way.