Arc Energy Resources has delivered 24 tubular components for the main circulating sea-water system that cools the nuclear reactors on numbers four and five in the Astute submarine series. The submarines – the first three of which are named Astute, Ambush and Artful – were built by BAE Systems Submarine Solutions at Barrow-in-Furness. Number four is named Audacious and the other is as yet unnamed. Because the same components for the first three submarines in the class had been produced from solid billets of an expensive copper nickel alloy, engineering and procurement staff investigated alternatives. Arc Energy recommended the use of ASTM A694 F65 forged steel as the base material as it is used extensively in similar pressure-related environments. Nickel copper alloy 400, noted for its resistance in chloride environments such as seawater, was selected as the welding consumable. An overlay thickness of 5mm was applied to ensure that the surface of the deposit would meet the chemical requirements of the alloy.