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Dry Shaft Seal Renewal Underwater in Australia
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Dry Shaft Seal Renewal Underwater in Australia

In May a Hydrex diver/technician team carried out underwater stern tube seal repairs on a 200-meter roro vessel in Port Kembla, Australia. The ship was suffering from an oil leak, making an on-site repair necessary. Taking advantage of the Hydrex flexible mobdock technique the team was able to carry out the entire operation on-site and underwater.

A leaking seal is always an unpleasant experience for a ship owner. It will force him to go off-hire, costing him time and money. To avoid going to drydock and keep the loss of time to the absolute minimum, Hydrex has developed the technology that enables repairs or replacement of all types of shaft seals to be carried out afloat. The ship can keep its schedule as seal repairs can be performed during cargo operations. By creating a dry underwater working environment around the shaft, work on the seal assembly can be performed in dry conditions. This is done by using our flexible mobdocks which are designed specifically for this type of repairs.  They fit all sizes of seal assembly.

The following case study gives an account of a recent underwater stern tube seal repair performed by Hydrex.

Leaking stern tube repaired on-site

Immediately after the operation was confirmed our technical department arranged for a rapid mobilization of a team of Hydrex diver/technicians to the roro vessel’s location in Australia, together with all the needed equipment.

The diving team first set up a monitoring station. The operation then started with a thorough underwater inspection of the stern tube seal assembly.

After the inspection, the team detached the vessel’s rope guard. Next the divers installed the flexible mobdock around the stern tube seal assembly creating a dry underwater environment so that they could work in drydock-like conditions. The split ring was then disconnected and brought to the surface to be cleaned. After cleaning the entire assembly, the team removed the damaged seals one by one and replaced them with new ones.

All parts of the stern tube seal assembly were then reinstalled and secured. Leakage tests were carried out with positive results, after which the divers removed the flexible mobdock. The operation ended with the reinstallation of the rope guard.

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Fast worldwide response

Every Hydrex office has a fast response center equipped with all the latest facilities, equipment and tools. These centers were designed specifically to increase speed of service. The lightweight flexible mobdocks packed in flight containers allow for a very fast mobilization and a timely arrival of Hydrex teams on any location around the world with everything they need to successfully complete the job.


Damaged stern tube seals will cause an increasing amount of oil leaking or water ingress as the damage worsens. By replacing the seals when the damage is first discovered Hydrex keeps the down time low.

The team worked in shifts to perform the stern tube seal repairs within the shortest possible time frame. This allowed the owner to let the ship continue its schedule without unnecessary delay, saving him precious time and money.

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