Magnetic patches used for stopping leak and welding hull plate

Magnetic patches used for stopping leak and welding hull plate

BW Offshore has successfully used Miko magnetic patches in a pioneering new repair technique that creates significant time and cost savings. The patches were used both for immediately stopping a leak under the water line and for welding the hull from inside for permanent repair.

When some cracks appeared in hull plating in the engine room of the FPSO Abo operating off the Nigerian coast, the BW Offshore’s engineering project team chose magnetic patches from a Miko Tanker Kit to quickly seal the leak and make the vessel safe and secure. At that point conventional repair techniques would have required the vessel to either enter dry dock for repair or for a costly and time consuming exterior habitat to be built over the work location so the leak could be repaired permanently with the vessel in situ. After careful analysis and planning it was realised that it would be possible to weld the cracks from inside the engine room and achieve the same result while leaving the Miko patches in place.

Watertight seal during welding operation
The magnetic patches, called Miko Plaster due to their simplicity of application, are manufactured by a process that mixes rare earth particles with an exceptionally strong blend of nitrile rubber. A finished patch will weigh 10 kg per square metre so an additional layer of buoyancy material is also laminated to the patch so that it can be easily handled under water by divers. These two layers are then laminated onto an external fabric manufactured from high strength PVC. Working closely with Miko technical staff it was calculated that with the cooling effect of seawater against the outside layer of the patch it was possible to weld the hull plating with the patch still fixed to the outside of the hull. The magnetic patch was able to maintain a watertight seal throughout the operation without suffering from any damage created by the heat of the weld.

The patches were kept in place on the hull for over six months during which time a range of structural engineering tasks were completed in the engine room area without difficulty. When the cracks had been welded and the patches removed they showed evidence on the inside of the extreme temperatures they had experienced while the fabric outer surface was unmarked. By demonstrating their ability to withstand welding temperatures, Miko believes that its magnetic patches are now all that is needed to quickly seal a leak and also to carry out a permanent repair. This can now be achieved in one operation without the need for dry docking or the expense of complicated habitats being constructed on the outside of the hull.

Manufactured in Norway
Miko magnetic patches are manufactured in Norway in a range of sizes up to 50 metres by 10 metres. They are most frequently supplied as Tanker Kits which contain a variety of the most practical sizes with some powerful permanent magnets that can be used to provide additional adhesion if necessary. Tanker Kits are now carried aboard a wide variety of vessels around the world including all those of the Norwegian Coastal Administration and those of the French Navy.