For this application the tool needed to descend down within a foundation caisson of 30-in. to 20-in. to 13⅜-in. in order to access the inner 9⅞-in. API 5CT Q125 section.
At 30-in. diameter the foundation caisson protruded 8 m (26 ft) vertically above the seabed in a water depth of around 90 m (295 ft) and contained three inner caissons of reducing diameters.
Recovering the inner caisson required a simplified rigging methodology to overcome the shackle geometry constraints that prevented access to the inner 9⅞-in. caisson. The shackle could only accommodate the 20-in. casing section, so a 2.5-m (8.2-ft) modular extension was added to the tool extending its reach to access the inner 9⅞-in. (8.625-in. ID) caisson.
The Ballgrab tool was lowered into the caisson and then remotely activated topsides through a 120-m (393-ft) twin Siamese hose on a reeler, equipped with a hydraulic power unit.
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