TPT September 2018

T UBE M I L L S & R OL L FORM I NG L I NE S

Cold welding streamlines tube production A CUSTOMISED cold welding system developed by British company PWM (Pressure Welding Machines) in partnership with US manufacturer Virtus Precision Tube (formerly Luvata) has streamlined and improved the process of copper tube production. according to Joe Napier, VPT’s engineering programme manager. “We produce over 40 million pounds of roll-and-weld copper tube each year, in sizes from ¼" to ½",” he said. “The cold welding system we have developed with PWM is part of our continuous improvement programme. It supports our ongoing drive to develop high-performance tubing solutions The system has improved uptime, reduced costs and created a better working environment for operators,

for the HVAC and refrigeration heat exchanger markets. “The new cold welding process is more straightforward than the cross-weld process we used for a decade, and works the first time, every time. It’s faster, easier to standardise and requires less operator input and training. Most advantageous of all, the new weld is stronger and capable of handling the tensions we place on the strip during tube production.” Before approaching PWM, VPT tried alternative methods of joining strip such as brazing, dovetail profiles, lap joints and laser welding. PWM successfully test-welded VPT’s strip using a portable ST40 cold pressure welding machine, capable of joining copper strip as wide as 45mm and as thin as 0.2mm. Precision engineered to create reliable permanent welds stronger than the parent material, the ST40 enabled VPT to reduce scrap by about 1.5 per cent during production trials. PWM has now supplied VPT with three ST40 welders that run full- time in production. Adaptations such as automatic flash trimming and annealing of the weld (to soften it and make it less brittle), and automation of the weld cycle and die opening system, have been developed to streamline the process. VPT will field the new system across all tube mill production lines, and currently has four more ST40 units on order, with more to follow. “Technical assistance from PWM, particularly from its chief design engineer, Ivan Turner, has been incredible throughout,” said Mr Napier. “Any problems we had during the development and early fielding of the units were quickly resolved. For example, we went through four design improvements to arrive at our current tooling.” Steve Mepsted, managing director of PWM, said: “This has been a fascinating bespoke project to work on. VPT shares our commitment to quality and innovation and together we’ve created a customised welding solution that significantly improves business performance. We’re delighted with the outcome.” Pressure Welding Machines Ltd – UK Email: pwm@btinternet.com Website: www.coldpressurewelding.com

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Virtus Precision Tube – USA Website: www.virtustube.com

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SEPTEMBER 2018