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Weld overlay cladding and fabrication specialist Arc Energy has completed a complex on-site repair of a set of expansion bellows for an alumina refinery.

The heat-exchanger expansion bellow is fitted to an 8ft-diameter heater, one of two live steam heaters in a run of seven mounted horizontally on an elevated process area one storey up.

The location meant that all equipment and materials had to be lifted into position.

The work area also needed to be scaffolded and clad with plastic sheeting to protect the welders from the elements for the duration of the repair.

The outer shell of the heat exchangers expands and contracts owing to the high operating temperatures, so bellows are fitted to compensate for the movement and to protect the internal tubes from distortion.

One of the two sets of bellows, which have been operating for around 30 years, was suffering from pin-hole leaks caused by cracking at the point where the stainless steel bellows is welded to the carbon steel vessel.

As steam was escaping, the heat exchanger was shut down and the standby unit brought into service.

At the time, there was a three-week window of opportunity to repair the bellows and, as the customer’s own welders were not qualified to undertake the repair, nor were there suitable qualified welding procedures, Arc Energy Resources was contacted.

A two-man team was despatched – both welders and one acting as site supervisor – equipped with all the necessary equipment and materials.

The bellows were heavily encased in 16 25mm-thick carbon steel retaining straps that were installed when the heat exchangers were built, in order to prevent the bellows from flexing during transport.

To gain access to the vessel, these had to be cut and removed together with some of the side plates of the supporting structure.

This left very little space underneath the vessel to excavate the old weld and reinstate it with the new one.

The new weld was created using a two-pass procedure with 309L alloy, designed to weld stainless steel base metal to carbon steel and to ensure a leak-free joint.

On completion, the bellows were hydro-tested to a pressure of 13bar and the welds passed first time.

The customer has since purchased Arc Energy spools and has replaced a complete line of electroplated spools with weld overlay spools.

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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