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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 – are built by BAE Systems Submarine Solutions at Barrow-in-Furness.

Number four is named Audacious and the other is as yet unnamed.

BAE and the MoD have an on-going programme to achieve significant cost-cutting and productivity gains on Astute.

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.

Alan Brown, sales director for Arc Energy, said: ‘The material is very expensive and extended delivery lead times could have impacted on the vessels’ build schedule.

‘By using readily available high-quality carbon steel, protected by a suitable corrosion-resistant alloy in areas where there is contact with sea water, Arc Energy’s weld overlay cladding process was indeed able to make a contribution on both cost and delivery.’ Eight 2m-long centre tubes and sixteen 1.1m long end sections – all 430mm in diameter – are clad throughout the bore and in the complex sealing areas at each end.

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 (AWS A5.14 ERNiCU-7) – 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.

Included in the ‘source and supply’ contract was the purchase of the carbon steel and the pre-machining of the components to ensure that sufficient material was deposited to achieve the very tight tolerance specified for the final dimensions.

After cladding, final machining and NDT inspection, Arc Energy Resources’ fabrication division produced and welded in place the location bosses, which enable the three sections of each assembly to be fitted together.

Arc Energy then arranged for the external surfaces of the components to be coated with an aluminium spray.

Arc Energy’s weld procedures had been tested and qualified in similar marine and naval contracts, thus providing the customer with documented proof of the successful application of the processes.

Although the size of the components was well within Arc Energy’s scope of manufacture, it was decided to produce special jigs and fixtures due to the precision finish required, particularly for the fabrication and mounting of the location bosses.

Arc Energy Resources

Arc Energy Resources is one of the UK’s leading specialists in weld overlay cladding and quality-assured fabrication services with a turnover approaching £5m, employing 70 staff in work space totalling more than 30,000ft2. The company’s expertise in weld overlay cladding services provides heavy-duty protection against corrosion and wear for process and pipeline equipment destined for use in any hostile environment. It can clad bores up to 4m in diameter and areas of restricted access within bores as small as 20mm in diameter.

The manufacturing infrastructure is qualified to ISO 9001:2008, ISO 3834-2, ISO 14001:2004 and ISO 18001:2007. The company also holds ASME U and R stamp certificates of authorisation, which qualifies it to fabricate and weld on components destined for use on pressure vessels built to ASME standard.

Arc Energy’s welders and fabricators are qualified to internationally recognised standards and specifications. A wide range of base metal/cladding combinations has been qualified to ASME IX, API 6A and NACE. In addition, Arc Energy offers in-house test weld, heat treatment, PMI and NDT facilities.

Arc Energy has recently invested £500,000 in two new rotating-head welding machines to increase productivity and extend the size and scope of work the company can handle. While conventional workstations move components around a fixed welding torch, the new machines use automated controls to manipulate the welding torch around a fixed component, accurately positioning it to apply the overlay while working close to the component’s footprint. The investment expands and enhances Arc Energy’s ability to handle complicated component geometries for the full or partial cladding and fabrication of a huge range of component sizes weighing anywhere up to 15 tonnes.

Managing director Alan Robinson is one of very few UK-registered European welding engineers. He has a Master's degree in welding and is a chartered engineer, a European engineer and a senior member of the Welding Institute. He has assembled a highly skilled team capable of delivering quality service from enquiry to delivery and beyond, which can engineer the perfect solution to the biggest of challenges.

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