Subsea Global Solutions (SGS) supports offshore asset maintenance with in-water technical repairs worldwide and a recent project highlights its capabilities in this field
Following an initial enquiry about a 27,000gt semi-submersible accommodation barge with underwater hull damage, and a requirement to remove its thrusters to facilitate repairs, SGS’ underwater specialists applied what Jonathan Baker, director, business development and marketing, describes as “thinking in the water logic” to deliver the most effective solution for the client.
He says, “Normally this type of situation would require repositioning the unit to an available drydock of suitable capacity, and in this case the demounting of the six large DP3 azimuth thruster systems to access the dock itself, all of which would have needed extra time and of course money for the owner operators. Having successfully completed demountable thruster and underwater welding projects for offshore clients around the world, our Singapore project team was able to propose an alternative approach for the client to consider.”
Diver checking the cofferdam pad eyes
Shell plate repairs underway inside the cofferdam
Once the approach was agreed, an SGS dive team was promptly deployed, and its underwater inspection confirmed the extent of pontoon shell plate damage. The team then took all necessary measurements to plan for a cofferdam to safely encompass the approximately 6.5m by 3 m of damaged shell plating. The project team took time to explain the underwater procedures to secure client and class approval for the plan and technical repair phases.
The substantial cofferdam, weighing over 10tonnes, was fabricated onsite and preparations made for the installation. Diver-technicians completed all the relevant underwater welding work in conformance with the Class A requirements of AWS D3.6 underwater diving code to be able to install the cofferdam safely. Once installed, and dewatered, fabricators and coded welders were then able to cut out and replace the damaged frames and stringers, and ultimately complete shell plate inserts, suitably keyed into the surrounding plating, all safe in the knowledge that the dive team was also monitoring the cofferdam installations. Meanwhile all quality control checks including vacuum and ultrasonic testing were completed to approval of the attending class surveyor.
The cofferdam being hauled out of the water at the conclusion of the repair job
In addition to the repair work, the unit’s future deployment required a full and thorough hull cleaning, including all the thrusters and niche areas to meet rigorous Australian biofouling inspection regulations. This work was completed concurrently, saving the client even more time.
Baker adds, “We currently have over 200 highly skilled commercial diver-technicians positioned around the world. With 14 hub offices spread over five continents, our global footprint puts us in an unparalleled position to provide scheduled or unscheduled underwater maintenance and repair services to a wide range of marine assets.”
