Hydrex is able to perform a wide variety of operations with their flexible mobdocks. These enable them to create a dry environment underwater for divers to work in. There is no need to send the vessel to drydock. Hydrex brings the drydock to you and all operations can be carried out alongside or at anchorage with-out interruption. The lightweight mobdocks allow for a fast mobilization and the necessary adaptability.
Hydrex was the first company ever to use a prefabricated cofferdam for hull repairs, introduced as early as 1979. It was used to carry out repairs to the m/v Lunar Venture. By 1983 the technology was in use to perform insert repairs on double bottom tanks from the inside. They have advanced this concept extensively since then to ensure that fast, professional and class approved work can be done while the vessel stays afloat and even while continuing normal commercial activities. Initially these techniques were applied mainly to the repair and re-placement of bow thrusters. Using steel cofferdams as a mobdock to seal off the thruster tunnel, with an access shaft protruding above the water, work teams accessed the tunnel and from there could work on the thruster in complete safety.
They have since then developed this technology further using lightweight flexible mobdocks (mobile mini drydocks). These were first used in 2002 and have been further developed by the in-house R&D department ever since. Hydrex constantly invests in the research necessary to evolve repair techniques and procedures. It is now possible for their diver/technicians to perform permanent repairs on seals, thrusters and any other part of the underwater vessel without the need to go to drydock.
For many of these operations they work together with OEMs. The most common type of mobdock operations are seal and thruster repairs or replacements. Mobdocks needed for underwater repairs on the standard sizes of seal assemblies and thruster tunnels are available in Hydrex’ fast response centers for immediate transportation. Tailor-made mobdocks can also be designed be their R&D department.
Case study: Two assemblies, twelve seals, one Hydrex team
A team of Hydrex divers traveled to Veracruz, Mexico for a stern tube seal repair. The operation consisted of the underwater replacement of the damaged seals on both assemblies of a semi-submersible offshore platform.
The unit left the field after its project was finished and was berthed alongside to have repair and maintenance work carried out without docking. The company was asked to perform the stern tube seal repairs during the available window of opportunity.
After the diving team removed the rope guard of the portside stern tube seal assembly, they performed a thorough underwater inspection of the assembly. Next they installed the flexible mobdock. They then removed the four damaged aft seals one by one and replaced them with new ones. The two forward seals were also replaced during the repair.
All parts of the assembly were then reinstalled and secured. Leakage tests were carried out with positive results, after which the divers removed the flexible mobdock. This part of the operation ended with the reinstallation of the rope guard.
All six seals of the starboard side assembly were then given the same treatment. At the request of the customer part of the diver/technician team remained on standby for a short time to make sure everything was in order. When this was the case, they left the platform together with the rest of the equipment.
Case study: Replacement in stages keeps cruise vessel on schedule
A 208-meter cruise vessel sailing in the Caribbean suffered steering problems after one of its two bow thrusters malfunctioned. Having to depend on a tug every time the ship berthed would quickly become very expensive. Going off-schedule, however, to have the bow thruster replaced would cost the owner both money and reputation.
A solution was therefore needed that could be carried out on-site without interrupting the vessel’s schedule. Enter the tried and tested flexible mobdock technique and Hydrex experienced diver/technicians.
There was only a time frame of eight hour at each port of call during the ship’s cruise in the Caribbean. It was therefore important that the operation was split up in parts that could be finished before the vessel had to leave again. A perfect planning and constant communication between the Hydrex technical department in the office and the team on location was essential in achieving this.
