Composite protection subdues impact damage on subsea structures

Compolite impact protection and access panels used on the Emden gas and Teesside oil pipelines

With subsea solutions increasingly being recognized as the most suitable method of developing marginal fields, there is a growing need to protect sub sea installations such as wellheads and valves from accidental damage caused by dropped equipment.

To date, protection has been provided by large steel constructions, but Norwegian Applied Technology (NAT) has embarked on an intensive development program to investigate the use of composite materials for subsea impact structures. The company won its first contract for this application from Fabricom at the beginning of the year to supply protection for pipeline connection points on the Phillips-operated Emden gas and Teesside oil pipelines.

NAT provided 240 sq meters of composite impact protection, which surrounds the pipeline junctions, and 216 sq meters of composite access products - panels which sit inside the main protection frame to provide diver access. The completed frames were installed at a water depth of 70 meters in June.

Both the impact protection and access panels are made of Compolite, a glass-reinforced polyester manufactured by the pultrusion method. "Compolite was chosen for the project because of its ability to resist corrosion, as well as providing impact protection to the pipeline connections," explains Compolite department manager, John Drury. In this respect, Compolite satisfies Norsok test procedures for subsea structures and piping systems up to a 5.0 kJ impact load.

In addition, NAT believes the project clearly demonstrates clear advantages over conventional materials by minimizing weight and maintenance, and by reducing the need for cathodic protection. NAT's core business has traditionally been to supply flooring and access products for onshore and topsides structures. "Following the success of this project, we are hoping to increase our business in subsea frames using composite materials," says Drury.

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