Simplicity in Plasma Arc Welding

Linde's latest welding wonder, the ARCLINE® PAW is more than just a redesign of a plasma arc welding system; it might just be the revival of a dying art.

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Some people have always known what they want to do as a profession - for Michael Pfreuntner, it was more than that: “I need to become an industrial mechanic” is what he told himself as a child. And so, that’s exactly what he did.

Michael is now an expert in Welding & Heating Equipment at Linde’s Unterschleißheim location near Munich, Germany. He is also a member of the Research and Development team behind the game-changing ARCLINE PAW® end-to-end welding solution - the latest addition to Linde’s ARCLINE family. Speaking of families, Michael’s not the first Pfreuntner to work at Linde in Unterschleißheim: “My father was a foreman here,” he explains. And as it turns out, the man who sparked Michael’s passion for welding.

Welding Takes Weeks to Learn, Years to Master

“My dad put the first torch in my hands when I was twelve years old,” Michael recounts. “I helped him repair some railings at home and remember being mesmerized by the arc for the first time”. While this special moment could be seen as the beginning of Michael’s informal training, he did go on to formally train as an Industrial Mechanic at the Schweißtechnische Lehr- und Versuchsanstalt München (SLV). Having successfully completed his training and apprenticeship, it was straight to Linde where he spent his first eight years honing his welding skills on hydrogen filling station hardware amongst many other things.

A plasma arc welding system setup in a welding lab. Weling torch in fioreground, gas supply cylinders in background.

“During my studies, I spent a few weeks learning the basics of different types of welding - but TIG welding seemed to come easiest to me”. The words of a natural born welder, because tungsten inert gas (TIG) welding is by no means considered “easy”. It is a craft that requires high levels of precision, skill and experience. “When I weld, I’m welding with my eyes, my ears and my hands,” Michael explains, “You need a feeling for the materials.” As for plasma arc welding (PAW) - even more so.

The Plasma Arc is Pretty Hot Stuff

PAW bears many similarities to TIG welding: both form an arc of highly ionized gas (plasma) between a pointed tungsten electrode and the workpiece. But in PAW, the electrode is positioned within the body of the torch, which means plasma can then be fed through a nozzle. This constricts the arc and forces the plasma out at a much higher speed and temperature - upwards of 28,000 °C (50,000 °F). The end result: faster welding with total and uniform penetration. Perfect for quality-critical applications in the chemical, petroleum, and aircraft industries to name a few. Simple. In theory at least.

In practice, PAW is its own worst enemy. Fast welds, yes. Fast set up? Not quite. “With conventional plasma torches which haven’t changed much since the 60s and 70s, the preparation and assembly is very complicated, time-consuming and error prone,” Michael explains. “The welder has to align and adjust the electrode to a very specific height, grind the electrode, orient the nozzle correctly and ensure the right mixture and flow of gases.” With such complexity, comes a high chance of variation and with that, reduced reliability and repeatability. Too big a chance to take for many manufacturers.

A machine mounted welding torch in action while welding a metal cylinder. The welding torch is producing a bright plasma arc at the metal surface.
A New Age for Plasma Arc Welding

In saying this, while the task is inherently labour intensive, highly skilled and specialized welders are perfectly capable of reducing the variation in their setup. The problem is, such welders are becoming more and more difficult to find.

“I have the feeling that not as many young people are attracted to this sort of trade - doing the same welds day in day out,” says Michael. The stats back up his intuition. The American Welding Society predicts that the industry is expected to face a shortage of about 400,000 welders by 2024. The problem is, in the US anyway, that infrastructure (bridges, highways, buildings) is ageing - but so are the welders that might be best placed to repair it when the day comes. With an average age of 55, the workforce is well on its way to retirement, with a risk of taking the tricks of the trade with it.

This is why Linde’s latest welding innovation is so significant. The company can’t lower the average age of welders in the lab, but it can - and has - lowered the barriers to entry when it comes to PAW.

Blazing a Trail in Welding Design

It was 2018 when Michael Pfreuntner brought all of his practical knowledge and experience into Linde’s lab setting - offering a true “welder’s view” on the project. Since then, the ARCLINE PAW® team has essentially developed a whole new plasma arc welding system from the ground up. At its centre is the Plug & Play torch - easy to implement and use even for less experienced welders thanks to the “Poka-yoke” concept (fail-safe design). Rather than minutes, the pre-configured, water-cooled torch assembly with its one-click bayonet for the few consumables takes just seconds. It’s unofficial but Michael claims that the lab record for changing an electrode currently stands at 4s!

A welder in helmet supervises a machine mounted welding torch in action while welding a metal cylinder. The welding torch is producing a bright plasma arc at the metal surface.

While he, admittedly, may not be the holder, there’s one part of the new solution that he certainly holds close to his heart. “The trail is my baby,” he says proudly. He’s referring to the aluminium module that attaches to the torch and ejects an inert gas to protect the weld from atmospheric contamination. “I was heavily involved in the design and testing of the trail. It was so much fun for me to develop what I think turned out to be a pretty perfect solution.” And he’s not the only one to think so. “I was in Sweden for our pilot customer testing with Swedish process equipment manufacturer ÖMV and they also loved the new technology,” he says.

With experts like Michael at hand to support and advise, it seems that for many more customers, the best welds are yet to come.

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