Bundles and towed installation

Bundles and towed installation

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SURFACE TOW

ƒ Not normally used in open sea conditions ƒ Dependent upon environmental conditions ƒ Fatigue in heavy seas ƒ Careful control needed whilst lowering bundle to the seabed at the end of the tow ƒ Release of buoys by ROV or divers ƒ Safety issue

Tug

Surface tow: The bundle is towed on the surface of the water with or without additional temporary buoyancy tanks; This is not normally used in open sea conditions; It is very dependent upon the environmental conditions; Assessment of fatigue is required in the tail end of the pipeline for long tows through waves; Careful survey/tug control is involved in lowering the bundle to the seabed at the end of the tow. This system was used in West Africa to load out a rigid steel W riser to an SPM.

CONTROLLED-DEPTHSURFACE ORNEAR-SURFACETOW

CONTROLLED-DEPTH SURFACE OR NEAR-SURFACE TOW

Tow direction

Tubular buoyancy attached to lines

DSV tug

Riser top assembly (buoyant unit)

Riser bottom assembly