Subsea protective structures from Claxton

A major operator asked Claxton to provide technical advice and guidance for design, specification, manufacture and supply of a subsea protective structure to protect subsea distribution and umbilical termination assemblies for the East Davy Field. Claxton completed the project ahead of time, and on-budget.

THE PROBLEM
The design of the structure needed to consider the seabed bearing strata and the need for the structure to be fishing friendly by allowing fishing nets and gravel boards to pass over without snagging.

THE SOLUTION
The subsea protective structure was designed by Claxton to locate and fix to the seabed by means of its own weight. To aid the fixing and to prevent movement of the structure four cruciform spikes were located under the protective structure. These spikes are designed to cut in to the seabed surface thus anchoring the unit in place.

The design also included extending legs which, had the protective structure sat higher than anticipated, would have dropped from the external structure to fill the gap between the unit and the seabed, thus preventing any snagging areas for nets or gravel boards.

The protective structure was primarily fabricated out of rolled whole section structural steel with steel plate grating panels provided internally to allow for access and equipment mounting. A premium quality two-pack epoxy paint system, with a shot blasted surface preparation, was applied to the entire surface of the subsea protective structure and, as the unit could not be tied back to an existing CP system, the structure was fitted with sacrificial anodes to provide cathodic protection for the life cycle of the unit (10 years).

Suitable lift points were provided to allow the subsea structure to be lifted using a single four point lifting bridle. All lifting points were certified and suitable for Offshore/Marine lifts. These lift points were designed to avoid creating a snagging point for nets and gravel boards after installation.

Due to the size of the unit, the structure was fabricated at local facility which had a quayside access. The unit was then loaded on to a vessel and sailed to it’s final delivery point of Hartlepool

THE RESULT
The whole project, from contract award to delivery, was completed in three months and the structure remains in successful operation today. The client commented on the pace Claxton provided and technical merit of our design. 

Find out more about our protective structures.