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Report of the 14th technical Seminar - 'Innovations in Flash Butt Welding' |
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The seminar provided a valuable update on the state of flash welding in the industry, and prospects for the future. It focused mainly on the equipment available for on-site welding of rail, and nicely illustrated present capability with a number of video reports. It was very well attended and almost 30 organisations were represented from the UK and overseas, including rail authorities, major rail contractors and suppliers to the industry. 
The scene was set by Brian Whitney of Network Rail, who described his company's strategy and how flash butt welding (FBW) can contribute to its achievement. The vision was of a 24/7 railway - modern, reliable, affordable and easy to maintain, as one would expect. There are major projects to be delivered to make this possible and meanwhile, maintenance must go on too. Brian set down a number of specific challenges.
Jay Jaiswal of Corus Rail, like many later speakers, set out to provide some answers to Brian's challenges. His talk covered developments in rail metallurgy and factory FBW, with the aim of reducing rail degradation despite increases in rail traffic and freight loading. The effect of rail material on resistance to degradation was described and the benefits of the various premium rail steel grades highlighted. These steels presented challenges for welding and Jay described their work to refine FBW procedures to optimise the width of the weld zone and hardness changes associated with the weld. Corus has patented this narrow heat affected zone process. Jay also emphasised the importance of geometry, noting the need to avoid stress raisers at steps in the rail foot and the possible benefits of improved rail head profiling after welding to avoid running band deviation. The Swiss company H G Schlatter AG was represented by Jurg Wahrenberger, who described the range of FBW machines they produce. Their stationary DC welders produce LWR or switches and turnouts. MFBW machines include the recently introduced AMS100 which can handle heavier rails (up to 75kg/m) and grooved tramway rails. Both mobile welders are available in containerised or truck mounted form and incorporate full programming and weld quality monitoring functions. Plasser & Theurer has been making FB welders since their K355PT in 1973. Rainer Wenty described how their machines have developed into the latest APT600 series welders incorporating the 'Superstretch' pulling unit, which can weld rail of up to 15,000mm cross-section. They are micro-processor controlled, use the distance controlled upset method, and monitor each weld, automatically checking for compliance with set tolerances. Plasser's welders are available as rail borne machines, lorry mounted in road/rail form or containerised. Charles (Chuck) Battisti described the MFBW machines produced by Kansas City, MO based Chemetron Railway Products Inc., a wholly owned subsidiary of Progress Rail Services Corporation (a Caterpillar Inc. company). Their latest machines are DC welders, whose heads are 35% smaller and 300lb lighter than their AC predecessors. The advanced control systems of these machines sounded extremely impressive, offering tight control of the welding process and very advanced data logging. Exceptionally advanced diagnostic and instruction systems for operator assistance are included in the system software. The machines have a 180t pulling capacity with a 12 inch stroke, for closure weld capability. Further information may be found in the article on page 3. The installation of new track for the Stirling-Alloa-Kincardine rail project, a 16km single line with passing loops, was described by John Oates of Babcock Rail (formerly First Engineering). 18m rails had to be delivered by road to three stockpile locations and welded into 198m LWR strings welded using a Plasser & Theurer APT500L truck mounted FB welder. It made almost 2,500 production welds and 103 bend test welds in 96 shifts at an average of 25 welds per shift. Closure welds were aluminothermic. John suggested there was a need for further development/enhancement of specifications and methodologies. Bob Hervey from GrantWeld described the development of their 'Super Puller Lite' equipment, used with their MFBW machine to stress rail and to allow restoration of stress during the installation of closure rails. Bob showed their technique that overcomes the limitation of rail temperature differential. The rail one side of the final weld is unclipped and displaced to the side to draw back the rail end. This provides the distance needed for the temperature differential, to close the weld gap and allow for the 30mm of rail consumed in welding. As the weld is made, the displaced rail is drawn up and moves back into the rail seats. For a closure rail installation, the process can take as little as 30 minutes from the first cut into the rail.
Martin Benkler presented SERSA Group experience on five recent high speed rail projects in Europe, using MFBW to install hundreds of kilometres of CWR involving thousands of FB welds. Martin noted significant variations in the specifications of geometrical tolerances and in acceptance procedures between countries, and believed this requires resolution. SERSA also discovered that two well known, calibrated electronic rail measuring devices gave different results on the same welds and Martin recommended defining the measuring equipment to be used at the contract stage. Malcolm Richardson described how Future Welding Ltd, had taken a slightly different approach to MFBW, perceiving competitive advantage in an all-terrain MFBW. As a result, Philmor Rail produce a self contained unit by modifying a standard Doosan machine. The welding head is a K922 with Paton patented pulse flashing, and again incorporates weld management and recording capability. An incorporated stressing system can pull up to five inches, so the machine can install closure rails and restore stress. The machine can access track anywhere that a normal 3600 road/rail excavator can, and welds on track or from its road wheels. Altogether the seminar made a very interesting and educational day. It was clear that FBW was a reliable method and choice of equipment was likely to depend on the features and capabilities of the various systems. The Chairman for the day, Tim Jessop thanked BOC Ltd for their kindness in hosting the event and for their warm hospitality. The above is an extract of an article by Chris Parker in the rail engineer, Jan 09 issue. The rail engineer can be obtained free for engineers who work in rail. |
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