A Hydrex diver/technician team carried out underwater stern tube seal repairs on a 157-meter dredger in Montevideo, Uruguay in April. The ship was suffering from an oil leak, making an on-site repair necessary. Using a Hydrex flexible mobdock the team was able to carry out the entire operation on-site and underwater, saving the owner an expensive and time-consuming trip to drydock.
Hydrex has carried out on-site, underwater repairs and replacements on all types of seals for a number of years now. A dry environment is created underwater in which the divers can work. Several major classification societies have also awarded Hydrex certificates that accept the Hydrex revolutionary flexible mobdock technique to perform permanent underwater seal repairs which previously would have had to be done in drydock.
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.
The following case study gives an account of a recent underwater stern tube seal repairs performed by Hydrex.
Oil was leaking from the stern tube seal assembly of a 157-meter dredger. A team of Hydrex diver/technicians therefore mobilized to the vessel’s location in Uruguay, together with all the needed equipment.
After the diving team had set up a monitoring station they removed the rope guard and performed a thorough underwater inspection of the stern tube seal assembly. This revealed that the entire housing of the assembly was severely corroded and needed to be replaced. Because the housing consisted of split shells, this could easily be done by the Hydrex team.
Next they installed the flexible mobdock. By doing this, the divers created a dry working environment around the stern tube assembly. This is needed for any permanent stern tube seals repair. The team then removed the three damaged seals one by one and replaced them with new ones.
Because the existing running area was worn out, the diver/technicians installed a spacer ring to create a new running area for the seals. Thanks to a newly developed method, this could also be done inside the flexible mobdock, saving precious time and avoiding water ingress during the installation of the spacer ring .
Leakage tests were then carried out with positive results, after which the divers removed the flexible mobdock. The operation ended with the installation of a new rope guard. This was necessary because the old rope guard had suffered severe cavitation damage and could not be used again.
The stern tube seal repair was carried out in less than optimum conditions. There was almost no inwater visibility at Montevideo at the time of the repair. It made the diving operations a lot more challenging than expected. However, our divers are trained to be flexible and adapt to constantly changing working conditions making it possible for Hydrex to perform the stern tube seal repairs under the strictest safety regulations, to the highest quality standards and without any unnecessary delay. The dredger was able to leave Montevideo in time to sail to its next operation.