Underwater repair specialists UMC International recently used its specialist Design and Consultancy Department to develop procedures and specify suitable equipment to assist with the floatation of a transformer rig located in Belfast Dry Dock.
This type of electrical generation design platform has grown from a relatively small simple system over the past 20 years to a large sophisticated unit and was under final assembly. Belfast Docks is a location that is big enough to facilitate the unit and also well placed to float a rig out to the North Sea on completion.
The platform weighs more than 7000 tons and can install itself under its own power. To reach its final destination the platform has to cover a distance of around 900 sea miles. The route leads across the Irish Sea, the English Channel and finally into the German North Sea.
Although the platform has inbuilt natural buoyancy, its overall weight increased substantially during assembly due to additional steel work that was added to the rig during a re-fit. This meant that the rig would not be buoyant enough to float over the sill of the dock out into open sea.
UMC Engineering Director, Dave Richards said: “To solve this issue our marine engineers worked together with BARD Engineering on an arrangement of lift bags that we could effectively position and attach to the rig to keep it level and balanced whilst on its undocking programme.”
He continued “After four weeks of on-site project management and engineering support, we installed a total of 30 air lift bags which provided an additional 600 tons of buoyancy, and reduced the draft of the rig by 1.2m. This solution enabled us to successfully float the rig over the sill and out of the dock where we could remove the additional floatation bags and allow the rig to be towed to its final location.”
The rig was bound for the German Sector in the North Sea where it operates in conjunction with the offshore wind farm “BARD Offshore 1”, enabling renewable energy to be collected and transferred to land-based electrical distribution networks.
Dave Richards added: “UMC has gained experience in solving many unusual offshore rig problems with some unique and novel solutions. For instance, we recently designed and installed man-entry habitats to repair spud cans of a jack up rig severely damaged in Hurricane Katrina.
Penny Sparrowhawk
