The baltic pipe above water tie-in project

Overview

When submarine pipelines are laid from opposite direction (shore to shore, platform to platform, etc.), the two ends of the laid segments need to be welded together. One method is to weld pipeline segments on the seabed (hyperbaric welding in enclosed habitat) generally suitable for water depth >30m; or above water (shallower water depth). The latter is known as the Above Water Tie-in (AWTI) operation.

A specialist laybarge is utilised to lift the two pipeline segments up above the waterline, weld the two ends together and lower the pipeline down on the seabed again. Detailed engineering is required to perform this critical operation in open seas, where the environmental condition need to be carefully analysed. This paper presents the key installation analysis steps to be taken and presents examples of Saipem’s experience in the AWTI operation.

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