Following its participation in the initial pilot phase of the Skills for Stroud Work Experience Charter, Eastington based weld overlay cladding specialist Arc Energy Resources has achieved the Full Recognition of the standard of the Charter.
The Charter, which is developed as a set of standards aligned with national good practice guidelines, is used as a basis to review the support that companies provide to individuals undertaking work experience activities within their organisations.
Commenting for Arc Energy Resources, director Rosemary Robinson says: “This is an important external endorsement for our organisation and reflects the commitment to, and importance we place, on ensuring a meaningful work experience programme is in place to enable our staff to achieve their potential; and broaden their knowledge of the employment opportunities available to them.” For further information on the Skills for Stroud Work Experience Charter see the resource pack on their website at: www.stroud.gov.uk/workexp.
Weld overlay cladding specialist Arc Energy Resources has successfully completed a contract for supply of two riser joints for Aquaterra Energy, the provider of world-class and award-winning offshore solutions.
The components are part of two low pressure risers for an oil platform. The finished risers were destined for a set of twenty wells being drilled in the North Sea off the coast of Norway. It is a brand new development for a low pressure section of pipes to deal with any drill fluids and shallow gas that they may encounter while drilling the first top-hole section of a well.
Commenting for Arc Energy Resources, director Andrew Robinson says: “This project played well to our core strengths, a full supply contract for which we secured the material for both components (a flange and pipe for each), applied the weld overlay cladding, welded the flanges to the pipes, organised the pressure testing, completed radiographic testing requirements and arranged final coating of both items all within a very tight delivery schedule.”
The project is a DNV class rig, designed to the DNV0SE101 code and was signed off by Det Norske Veritas as suitably manufactured and designed for the task. Aquaterra Energy Project Engineer Matt Hugo comments: “DNV is one of the oil & gas industry’s largest verification bodies, which confirms calculations that pipe wall thickness and flanges are sufficient for the pressure. For this project they also undertook a review of the overall design of this section of pipe.”
The component acts as a conduit for drilling fluids and equipment during the top hole section and ensures that in the event of gas passing up through the well it can be contained and routed to the rig diverter where it can be vented to atmosphere.
The risers need to have a sealing ring groove in the end of the flange, which is inlaid with an extremely hard, corrosion resistant Inconel 625 alloy.
As Aquaterra Energy has previously used Arc Energy Resources for specialist welding requirements, it approached the company again with a view to provide full supply of materials, carry out all required welding, inlaying of the flange, testing and coating.
Arc Energy Resources sourced the machined flanges and clad with Inconel 625, before completing the welding requirements for the project using Submerged Arc Welding – a process that provides a high quality finish.
Once welded, the parts were pressure tested. Domed end caps were welded onto the straight pipe lengths and then both joints were sealed together through adjoining flange faces to form a complete vessel. For the first stage of pressure testing, the riser was filled with water to a test pressure of 750psi, which provided a safe 500psi working pressure. After being held at this pressure for 5 minutes it was pressured down and pumped back up, then held for a further 15 minutes before being drained-down. When the pressure test was complete, radiographic testing was carried out to confirm that the welds hadn’t cracked or been damaged. The end caps were removed with pipe free ends being finish machined as required. The parts were then sent to be coated.
Says Matt Hugo: “We were at Arc Energy Resources’ site when the testing was carried out and were very impressed with the way they conducted the demanding procedures, whilst maintaining their high levels of health & safety.”
The final checks for the unit were carried out by a team that included an inspector from Aquaterra Energy’s customer and their own inspector accompanied by an inspector from DNV. Following the riser’s final check the unit was ready for use. It was delivered offshore and installed in position on-time where it has since operated very successfully.
Summing up, Matt Hugo says: “This project was quite a straightforward concept. But, as with many straightforward concepts, there is potential for things to go wrong. Fortunately, Arc Energy Resources’ knowledge and experience ensured that nothing did, and they kept us up-to-date every step of the way and the whole project went very smoothly. Arc Energy Resources did a sterling job, delivered an excellent project, with exceptional performance throughout the manufacture of the unit. They did everything we have asked of them.”
Eastington-based Arc Energy Resources – one of the UK's leading specialists in weld overlay cladding and quality assured fabrication services – will once again be supporting this year's Stroud Festival of Manufacturing & Engineering and hopes to encourage pupils from the county's local schools and colleges to choose a career in engineering.
Director Rosemary Robinson is proud of the skilled engineers the company has assembled, a team that is qualified to internationally recognised standards and specifications, and capable of delivering quality products from enquiry to delivery and the service beyond.
Explaining the company's approach to people management, Rosemary says that if Arc Energy Resources is to maintain its standards and plan for the future, it is essential to continue to recruit and train skilled staff. "Recruiting and training has proved a major challenge recently. A decade ago there was a pool of skilled staff who moved between companies, many of them having served apprenticeships in large organisations." says Rosemary. "Today this resource no longer exists. Manufacturing became unfashionable with government and education and was allowed to decline. Fewer apprenticeships were served, fewer students entered engineering and, as experienced engineers retired there were fewer, new engineers trained to replace them."
Since last year, Gloucestershire Engineering Training has begun to offer welding and fabrication apprenticeships in Gloucester, which, thanks to its accessibility, they have been very happy to take advantage of by sponsoring their latest apprentice, Tyron Cleaver who has started his first year there.
A recent success for Arc Energy Resources is Charlie Fryer who, at just 14, enjoyed a week's work experience with the company in 2005. Encouraged by the 'experience', Charlie applied for and was accepted for an apprenticeship at Arc Energy Resources on leaving school. And in July 2013, having undergone extensive on- and off-site training and an often intensive course at Gloucester College, Charlie completed his apprenticeship and is now employed by the company as a Project Engineer. And the story doesn't end there because Charlie, now 23, has completed an HND in Mechanical Engineering and is now working towards a degree. Lee Crosbee (22) and Kieran Kellett (24) have continued with their apprenticeships in Fabrication and Welding.
Summarising, Rosemary Robinson explains that the skills and experience the Arc Energy Resources team brings to the company is invaluable in ensuring that it remains the partner of choice for the supply of weld overlay cladding and complex weld fabrications.
If you're considering a career in engineering, Arc Energy Resources will be exhibiting at the Stroud Festival of Manufacturing & Engineering on 24th November at Stroud Leisure Centre and will be on hand to offer advice.
Gloucestershire based weld overlay cladding and fabrication specialist Arc Energy Resources is proud to announce it has recently obtained an ASME U2 Stamp. The company is now the only weld overlay cladding specialist in the UK with ISO 3834-2 certification from the European Federation for Welding, Joining and Cutting (EWF) and certified for welding and fabrication to ASME VIII Division 2.
ASME is the leading international developer of Codes and Standards for mechanical engineering, issuing its first Boiler & Pressure Vessel Code in 1914. The association's Codes and Standards have since grown to nearly 600. The new certification complements Arc Energy’s long standing ASME VIII Division 1 Stamp for the manufacture of unfired pressure vessels and components.
Arc Energy Resources’ ASME U2 Stamp neatly supports the companies specialised weld overlay cladding service, as the company can offer a comprehensive service which incorporates all aspects of welding and fabrication to code. Arc Energy is now one of only seven companies in the UK with the certification, and of the six other companies approved to ASME VIII Division 2 four are existing clients of Arc Energy Resources, and this approval will help to nurture the good working relationships between the various organisations.
ASME U and U2 Stamp holders who require welded or clad components for inclusion into their vessels or equipment can only obtain such items from other companies with the relevant stamp. Because of this, in the short period since obtaining certification, Arc Energy has produced a number of U2 parts for items such as pig launching and retrieval systems, enclosures and doors, blind flanges and nozzles. Arc Energy is also capable of producing complete vessels.
The more stringent Division 2 code is required for vessels where systems are running at higher pressures. Division 1 vessels are usually designed to work at pressures up to 3,000 psi, where as the additional demands of Division 2 allow for design to pressures as high as 10,000psi. Typically, both types are being used by Arc Energy Resources’ customers in the oil and gas and related industries.
When producing Division 2 vessels, Arc Energy becomes responsible for verifying the customers design brief and responsibility extends to verification of all potential load cases including seismic, wind, snow and other issues, as well as the effect of thermal stress and cyclic loading.
Explaining the work involved in gaining the certification, Technical & Quality Director Neil Cook says that during months of preparation, authorised inspectors from Arc Energy’s chosen authorisation inspection agency visited the factory to ensure that the company’s procedures and processes were strictly to code. The audit itself took six ‘man-days’, with three auditors at the Arc Energy site in Eastington for two days. During the audit, Arc Energy successfully demonstrated design and production of a complete test pressure vessel.
Arc Energy’s other accreditations include ISO 9001: Quality Management System; ISO 3834-2: Welding Management System; ISO 14001: Environment Management System; OHSAS 18001: Occupational Health and Management System and Investors in People Bronze.
Commenting, Neil says: “The ASME U2 Stamp reflects the company’s commitment to developing its service for our clients in every aspect of the business and reinforces our capability to support clients with highly qualified and knowledgeable welding staff.”
As offshore drilling technology advances and wells become ever deeper, the problem of corrosion increases proportionately. The presence of hydrogen sulphide, carbon dioxide and chlorides creates a potentially catastrophic corrosive mixture. Add to this the extremely high product temperatures from deep wells and there are significant problems that need to be overcome.
When assessing the corrosion protection of any production system, piping and process engineers have a number of options to consider. The effectiveness of each will vary dependent on a number of factors including: the aggressive nature the product; pressure and temperature; size and complexity of the system; well-life expectancy; available development period and the budget.
A production pipeline, from wellhead to topside processing, will typically include pipe, various types of connectors, fittings (tees, elbows etc.), complex valve blocks, pig launcher/receivers, etc., all of which will be subject to corrosive and possibly erosive attacks on their internal wetted surfaces. So how do engineers design a system to resist these attacks?
Protection methods where risk of attack is low and life-cycle short, may be as simple as an injected inhibitor used with conventional high-strength carbon or low alloy steel.
Where greater protection is needed corrosion resistant alloys (CRAs) such as austenitic (300 series); ferritic/martensitic (400 series); and duplex stainless steels or the more complex high nickel chromium alloys, must be considered.
With apologies to the manufacturers of austenitic stainless steels, it is unlikely they would have the resistance required for the very worst conditions. They would have to be used in very heavy wall section to match the pressure retention achieved by the carbon steels in common use (API 5L X60 or X65 for instance).
Duplex steels and nickel based alloys, such as alloy 625, are the only materials in general production which, when welded, will achieve the strength to match carbon steels. However, there are constraints to their use in solid form – namely cost, availability and the need for very rigid fabrication procedures.
Cost is particularly relevant where large quantities of pipe and fittings or large forgings or castings are needed. Wellhead valve systems and pipe bundle bulkheads are typical examples.
The use of carbon and low alloy steels clad with a corrosion resistant alloy has been common practice for some years and is a proven, economical and technical alternative to solid alloys.
The term ‘cladding’ covers a wide range of processes including: hot roll bonding, explosive bonding, diffusion bonding, centricast pipe, co-extruded pipe and weld overlay cladding.
Each has particular merits, so the processes are not necessarily competing for the same market. For example, whilst hot roll bonded plate, rolled and welded into pipe, may be economical for a 12m length, co-extruded or centricast would offer savings if 12km are required. Also, in periods of high demand, the lead times for some of these techniques may preclude them from use in a fast track or refurbishment project.
Weld overlay cladding
Weld overlay cladding technology presents the materials engineer with a wide choice of welding processes and immense flexibility. An almost infinite range of component shapes and sizes can be protected, with an equally wide range of base material/cladding alloy alternatives.
The combination of high strength low alloy steels (AISI 4130 or 8630 for example) and alloy 625 (Er-NiCrMo-3) is probably the most common for high pressure retaining wellhead equipment.
Weld procedures are normally qualified to ASME IX, as are the welding operators. Additional testing to prove conformity with API 6A and NACE MR01-75 is also completed, along with any contract specific requirements from the end user.
Selection of the most appropriate welding process is largely dependent on factors such as the size of the clad area; access to the area to be clad; alloy type, specified clad thickness; chemical composition limits; welding position; and NDT acceptance standards.
Welding processes in common use internationally include:
Given that the process used must be practical, viable and provide the mechanical and chemical conditions to achieve service requirements, economics dictate that the higher deposition rate processes should prevail. Details are available to optimise processes and deposition rates while taking into account the limitations that may apply.
Automated or mechanised processes generally offer the best deposition rates and provide the most consistent quality of deposit. This enables the finished cladding to closely match the results provided during procedure qualification testing. Mechanised equipment can also be designed to access areas that simply cannot be reached by manual methods – for example through a small-bore pipe.
GTAW processes can be used in bores as small as 15mm, and are ideal for components of varied geometry where the position of the welding head requires frequent adjustment, from a simple flange that needs to be clad through the bore and across the sealing face, to a complex valve body with several interconnecting bores.
Often equipment also needs cladding to RTJ grooves. The control available with the GTAW process means that cladding can follow the profile of the groove rather than filling it completely. This not only saves time and material but also reduces the cost of finish machining.
This flexibility also lends itself to cladding irregular shaped components such as pipefittings. Elbows and tees as small as 2” NB can be clad, particularly where specifications do not allow for a mixture of base materials – for example a carbon steel pressure vessel, where fittings in solid alloys are not permitted due to risks from the use of materials with different thermal expansion rates.
Using this process the chemical composition of the welding consumable can be achieved at 2.5mm from the base material/cladding interface (this can be reduced to 1.5mm in the case of 300 series stainless steels, where over alloyed wires are available).
Where plain bores (in pipe or flanges for example) are greater than 250 - 300mm, the faster depositing electroslag and submerged arc processes can be considered. Equipment is available to enable pipe lengths of 12m to be successfully clad.
The electroslag process utilises a large weld pool that requires substantial base metal backing (generally a minimum of 20mm) to prevent burn through and support the edge of the weld pool to avoid collapse of the molten weld/flux covering.
It is ideal for areas of plain, open access. It is not ideal for cladding adjacent to convex or concave edges. The deposit thickness is nominally 5mm with the strip widths discussed here. With 60mm strip, deposition rates of up to 22kg per hour can be achieved.
To enable the chemical composition of the deposit to match that of the consumable specification within the first layer (3mm from the interface), over-alloyed strip and ‘loaded’ metal containing fluxes, are available.
Where a strict limitation is imposed on iron dilution into the cladding, a second layer can be added to give entirely undiluted weld metal. However, the use of a 9 -10mm thickness of cladding may negate the commercial advantage of the high deposition rate process.
In these circumstances additional production test plates have been produced, and corrosion tests carried out on the single layer to prove the acceptability of the material for known service conditions.
Another option is the use of a combination of processes. A recent example required a final layer of alloy 400 over a significant surface area. The first layer was pure nickel, deposited by spray GMAW. The second, with 30mm electroslag strip (to ER NiCu-7) ensured that the chemistry (in particular the low iron requirement) was achieved and a total thickness of 7mm was deposited. A material saving of up to 30% was achieved with only a small increase in production time over the two layers of strip.
Submerged arc welding using a solid wire consumable, while not as fast, is a useful ‘halfway house’ between strip cladding and slower GTAW and pulsed GMAW. The welding heads used are not as large as strip heads, and the consumable delivery method is much more flexible. Hence the ability to use this in smaller bore diameters. Traditionally larger diameter consumables (2.4mm +) have been used for this process, again resulting in the need for fairly thick substrates to accept the high heat and large weld deposits.
Recently, procedures have been developed using 1.2mm wires allowing use on thinner section components, and giving more controlled thickness of deposit while maintaining deposition rates of approximately 5kg per hour. As with strip cladding, consumable/flux combinations are available to make single layer deposits viable, especially with duplex and ferritic/martensitic stainless steels.
When weld overlay cladding was first employed, re-machining after cladding was the norm. However, as techniques and equipment have improved, the ‘as welded’ finish has become much smoother and many areas of clad equipment are now left ‘as clad’. This would not apply to sealing/gasket areas, which have to be produced to the very finest of tolerances.
Without doubt the GTAW (and PTA) processes give the least contoured deposits, so procedures have been developed to use the quicker submerged arc or GMAW processes for the first layer and finish with GTAW – combining the benefits of two processes.
When cladding high strength (and therefore more hardenable) low alloy steels such as AISI 4130, 21/4 Cr 1 Mo and, potentially, martensitic stainless steels such as A182 F6NM or AISI 410; PWHT is invariably adopted. This stress relief ensures that the layer of base material immediately below the weld (heat affected zone) is within the recommended hardness levels for the service conditions (as required by NACE).
Test procedures
The level of NDT will be in accordance with the specification to which the equipment is being produced, plus any client or contract requirements detailed in quality plans and purchase orders.
This will almost invariably include liquid penetrant inspection, usually after any machining has taken place. Ultrasonic inspection is less often required, but is used to confirm sound fusion and the absence of volumetric defects.
Chemical analysis of the clad surface is sometimes requested and can be tested in a number of ways, the most common being by analysis of swarf samples from the component, or by use of an X ray spectrograph (PMI) machine, or similar.
Where austenitic or duplex steels have been used, reporting the phase balance may be an additional requirement. This can be calculated from chemical analysis using one of the internationally recognised formulae, or by use of a suitably calibrated magnetic ferrite detector.
The ability to clad ‘off the shelf’ components of any shape and size with a wide variety of corrosion resistant alloys, has made weld overlay cladding the most adaptable and flexible in use - whether you need a one-off special or a large production run.
