Hydraulics in use
Roller box lifting aboard the Solitaire - Allseas
One of the main characteristic features of a pipe-laying vessel is its ‘stinger’: a long protruding outboard structure that guides the pipeline to the sea bottom. Allseas ‘Solitaire’, with 300 meters the largest offshore pipe-laying vessel in the world, accommodates an automatic welding system where the pipes are assembled, welded, tested and coated. This horizontal firing line leads to the stinger, attached astern the Solitaire, which is adjustable in angle and radius. The stinger tip can be lifted to a height of 40 meters above sea level to avoid impact with the water in extreme weather conditions.
The entire stinger is lowered, raised and fixed with a hydraulic skid mechanism. The stinger structure consists of up to 4 sections allowing a laying radius of 80-350 meters. These sections and the aft part of the firing line can be rotated and adjusted relative to each other, as can the various individual roller boxes, giving support to the pipeline bend.
The roller boxes are designed to carry the welded pipeline on the stinger and they support it into the water. For this reason they have to be adjustable in different height positions, according the calculated allowable bending curve. Standard steel pulling cylinders turned out to be too heavy for the crew to handle, since they have to be moved around quite often. Based on the concept of its standard range of aluminium cylinders, Holmatro and Allseas designed an aluminium pulling cylinder, which can easily be handled due to its considerably lower weight. The height setting of the roller boxes is now executed more conveniently and safely.