Offshore friction stir welding robot passes design milestone

The world’s first underwater robot to repair ships hulls with friction stir welding has reached a milestone with the finalising of the system’s concept design.

friction stir welding
The concept design of the RESURGAM system devised by a team of engineering experts at Forth (Image: Forth)

The RESURGAM (Robotic Survey, Repair and Agile Manufacture) Project, funded by the European Commission and being developed by 13 partners, will eventually allow a ship’s hull be repaired at sea, removing the requirement for it to head for dry dock.

RESURGAM will allow responsive repair to be carried out remotely from anywhere in the world, and is expected to save industry time and money as well as making it safer by removing the need for specialist divers.

Engineers from Cumbria-based Forth have been appointed as the technical managers of the project. To date, the team has completed a Functional Means Analysis to establish all functions of the new tool, and carried out a full optioneering process to decide on the concept model. A first concept design for the welding head and frame mechanics has also been completed and will be developed in the coming months.

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In a statement, Chris Downham, Forth’s operations manager, said: “The RESURGAM Project is such an exciting initiative to be involved with and having so much input from companies from across Europe shows the true power of collaboration, with each representative bringing a unique set of skills to the project.”

Forth is tasked with designing a bespoke, underwater friction stir welding tool that can be mounted to the side of a ship’s hull and conduct a friction stir weld in a vertical plane between a repair patch and the defective area of the hull.

To secure the machine to the hull, the team has designed a circular track frame to hold the weld head that will be secured to the hull via a frame using four R1000 electromagnets, which each need to produce 7.5 tonnes of force and enable the weld head the required Z-axis force to continue to weld.

The system will be tested in the company’s Deep Test Pond, one of the largest facilities of its kind in the UK.

Forth’s engineers will now begin a detailed design programme using analysis from the design risk assessment to explore the functions the robot requires and identify early design and functional complications.

Once complete, the design will receive a final review before progressing to the final stages of the project and the manufacturing of the system.

RESURGAM Project partners include The Welding Institute; Lancaster University’s Joining 4 Innovation Centre; Element Six (all UK); ACLUNAGA (Spain); AISTER (Spain); European Welding Federation (Portugal); University of Limerick (Ireland); TU Delft (The Netherlands): STIRWELD (France); Engitec Systems International (Cyprus); and GISBIR (Turkey).