SUBSEA PIPELINE CONNECTIONS AND REPAIRS USING DRY HABITATS

Abstract

Research on hyperbaric welding was carried out by Comex several years ago.

The first hyperbaric weld on site in 1975 was the result of about twenty hyperbaric tests performed at the Comex hyperbaric centre in Marseilles. These tests took place at simulated depths from 75 m to 155 m and allowed the evaluation of different welding processes such as Tungsten Inert Gas (T.I.G.), Manual Metal Arc (M.M.A.), Metal Inert Gas (M.I.G.).

Divers, welders and pipe fitters follow extensive training programmes before being involved in evaluation tests. Professional welders are first selected for diving courses and qualified for subsea work. They then perform qualification tests on specified welding procedures and are finally assigned to various tie -in operations.

Comex has designed and built four subsea pipeline connection spreads which cope with the range of operational configurations required by the industry. A spread consists of alignment equipment, welding habitat and diving system with the appropriate surface support. The range of sizes vary from a 12-tonne repair habitat to a massive 250 -tonne alignment and welding frame. The field applications of these techniques to this day have been in the North Sea in water depths ranging from 90 to 155 m.