The main challenges in developing a composite repair solution for damaged or corroded risers and caissons are to engineer a resin system that can bond and cure underwater and also to devise an application procedure that can undertaken by air divers.
Walker Technical Resources have developed a composite repair system, Technowrap Splashzone, where the resin system is capable of adhering to metallic surfaces and curing in a water environment. To develop an application procedure for this repair system a demonstration test was performed at the National Hyperbaric Centre in Aberdeen.
The challenge of developing an application procedure for underwater application was to simplify standard applications procedures (wet lay-up) to enable them to be used by air divers.
The application procedure consisted of two main elements, application of the wet cloth and then compression of this wetted cloth onto the steel riser/caisson.
The following photographs present the application of the wet cloth on a 36 inch riser followed by the application of stricture which ensures compression of the repair onto the riser . Once the stricture is applied the repair is then left to fully cure which takes approximately 24 to 48 hours depending on water temperature.
The trial of the application procedure was successful as the air divers were able to apply 4 layers of Technowrap Splashzone on a 36 inch diameter riser within a time period of 1 hour.
Based on the successful conclusion of this application trial and other qualification tests (according to ISO/TS 24817), the Technowrap Splashzone repair product is now available for field trial application.