Three-tier, adaptable system for flexible pipeline installations

A modular system for installing flexible flowlines, risers and umbilicals is being designed, fabricated and tested by Rotterdam-based Huisman-Itrec on behalf of Rockwater. The structure comprises three main components - a replaceable tower structure with tensioners, A&R winch, sheaves and chutes, a multiple reel drive unit and a power and control system. Each element can also be used individually. They were designed, however, as parts of the integrated system. Modularization allows the system

A modular system for installing flexible flowlines, risers and umbilicals is being designed, fabricated and tested by Rotterdam-based Huisman-Itrec on behalf of Rockwater.

The structure comprises three main components - a replaceable tower structure with tensioners, A&R winch, sheaves and chutes, a multiple reel drive unit and a power and control system.

Each element can also be used individually. They were designed, however, as parts of the integrated system. Modularization allows the system to be reconfigured in different ways.

The pipelay ramp has a tower structure and is connected to the vessel by two steel pins. It can be removed at any time and used on another vessel. The ramp is equipped with two modular tensioners which can be removed for standalone use. Four-track tensioners are standard, but three or two-track tensioners can also be incorporated, if a different frame is employed.

Huisman-Itrec also developed the modular pipeline tensioner, which can be used for both rigid and flexible pipelines. Tensioner functions are incorporated in track units. The tensioner is assembled by combining various track units in a frame. Conceivably the geometry of the tensioner - more precisely the use of the tracks - could be altered for a particular pipelay project.

In addition to modularity and mobility, easy transportation is another feature of the new system. Most components have been adapted to ISO container formats and can be transported by container vessels. The reel drive units, for example, are foldable to dimensions that permit transport on a 40ft flatbed. The A&R winch fits in a 20ft container. The track units can be removed from the frame and transported in containers, and the power packs have been built inside a 20ft ISO container.

Rockwater's flexible pipelay system carries on Huisman's extensive experience in designing and fabricating pipelay installation equipment. Examples include the stinger handling system for Allseas' Solitaire, the world's biggest pipelay installation vessel, and the pipelay ramp for the Seaway Falcon, owned by Stolt Comex Seaway.

The latter system comprises a lightweight structure which was placed on the Seaway Falcon in a single lift. The pipelay ramp can be tilted between 20 and 90 degrees, and can thus be viewed as a combination of J-lay and a horizontal firing line. Self-leveling platforms and stairs adjust automatically to the ramp's angle.

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