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Ship repair & maintenance

Stern tube seal repairs

Hydrex has carried out stern tube seal repairs and replacements underwater and in situ for a number of years now. Together with Aegir Marine, Hydrex has developed the technology that enables stern tube seal replacements to be done on site and underwater. Prior to this technology it was usually necessary to go into drydock for this kind of operation, along with all the attendant loss of time and money.

1.Underwater research, development and progress

In 1998 our divers followed a seal repair training course lead by seal manufacturer Wärtsila, who also worked together with Hydrex in the testing of new developments. At the end of 1999 we successfully started working on injections with lip type stern tube seals.

The next year Blohm & Voss gave our divers a training course to repair their Simplex seals and in the same year we started doing tests for wet bonding on lip type seals. These tests showed us that wet bonding could only give us a 80 % result compared to dry bonding and so we started working on a method to avoid wet bonding and still do the seal repairs underwater. This led to the development of our unique flexible mobdock technique in 2002, which took us an important step forward. For the first time it became possible to entirely replace stern tube seals underwater. This technique has since been refined and used on numerous stern tube seal repairs around the world.

Once the flexible mobdock was developed, a special training course run by Kobelco technical staff, was given to our divers at Hydrex's headquarters in Antwerp. After this successful cooperation, a contract was signed between Kobelco and Hydrex in 2003, stating that Hydrex is the only company that has the authority to perform underwater repairs on Kobelco seals.

In 2006 Hydrex entered into partnership with Aegir-Marine, providing us with the technical knowledge to repair or replace all the major seal types. We continue to develop our stern tube seal repair technique to adapt it to all possible situations.

2.Underwater stern tube seal repair

We use the mobdock (mobile drydock) method to replace stern tube seals underwater. This technology has been approved by all classification societies and can be adapted to most kinds of stern tubes to create a dry underwater environment around the seals. Seal repairs and replacements are carried out in cooperation with top seal specialist companies.

Flexible mobdocks can easily be transported anywhere in the world by plane. They do not require the construction of expensive metal mobdocks, making it a simple matter for us to arrive almost anywhere in just the time it takes to fly there, armed with all the equipment we need and ready to work immediately. Our technical diving team creates a dry environment inside the mobdock and then can disassemble the seal and bond a new one in place. All this can be done while the ship is carrying out its usual cargo or other commercial operations in port. By bringing drydock conditions to the ship rather than having to take the ship to drydock, we save a considerable amount of time and money.

Click on this link for an animation of the procedure.

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