Roller box lifting

Situation

One of the most eye-catching features of a pipe-laying vessel is its ‘stinger’; a long, protruding frame structure that guides the pipeline to the sea bottom. The largest offshore pipe-laying vessel in the world, the ‘Solitaire’ of Allseas, features an automatic welding system in which the pipes are assembled, welded, tested and provided with a protective layer. The stinger, attached to the rear of the ship, is an integral part of this horizontal production line. The stinger can be raised 40 meters above sea level to avoid contact with the water during extreme weather conditions.

The entire stinger is lowered, raised and fixed with the aid of a hydraulic skid mechanism. The frame construction consists of a maximum of 4 components which allow for a laying radius of between 100 up to 300 meters. These components and the rear portion of the production line are therefore rotatable, as well as the roller boxes, over which the pipeline can be ultimately transported back to the sea bed.

Challenge

Roller boxes are designed to carry the welded pipeline on the stinger and support it into the water. For this reason, they have to be adjustable in different height positions, according to the calculated permissible bending curve of the stinger. Standard steel pulling cylinders turned out to be too heavy for the crew to handle, since they have to be quite often repositioned.

Solution

Holmatro and Allseas designed an aluminum pulling cylinder with a 24 ton capacity. Based on the concept of its standard range of aluminium cylinders, due to its considerably lower weight, it proved much easer to handle. Setting the height of the roller boxes is now more user-friendly and safer.

Would you like to know more about this project? Contact us via e-mail industry@holmatro.com or call +31 (0)162 751500.