The welder training process will increasingly be dovetailed with on-the-job experience and learning to use smarter tools. This article examines how the newest welding equipment is meeting the challenges.
Article by James Chater.
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Outlook
In September 2017 Sandvik reported strong sales of its welding products, materials and solutions (up 25%). This is part of a global surge in demand for welding expertise, especially from China and NAFTA. This growth in demand has added to a skills shortage that has existed for a number of years. According to Daniel Groves, Director of Construction Labor Market Analyzer, certain crafts such as welding are projected to have a shortage of 200,000 over the next few years for all non-residential construction in the USA, as older workers retire and there are not enough younger people to take their place (1).
Mega-projects in high-growth areas such as the Middle East and Asia are likely to be the most affected by these shortages. This skills shortage, together with the time and expense of training welders, is driving innovation in welding tools in order to make them smarter, bigger, faster and safer. Software and automation can make it easier to use a welding tool once the user has mastered the settings. Instead of relying exclusively on previous training in their work, welders are now more likely to build up experience on the job, improving their skill by learning to exploit the capabilities of the innovative machines they are using.
Faster
Manual or automated? In general the industrial consensus is that mechanized or automated welding is preferable, even if this means a greater upfront outlay for equipment. Speed is one consideration, but elimination of human error, quality control and increased productivity are also factors that favour automation. With this in mind, Polysoude has come up with automated GTAW procedures for welds on oil and gas pipelines. These procedures increase resistance to stress and corrosion and absorption of high dynamic loads. This automated procedure was used on the Shah Deniz 2 Project, where CRA line pipes, flanges and bends were welded using a hotwire GTAW station.
Manufacturers are responding to customers’ demands for more machines that allow more efficient welding procedures. A case in point is the new welding line developed by Seuthe, which allows stainless steel tubes of OD 6mm or greater and wall thicknesses of 0.5 or greater to be manufactured on a single line in rapid sequence. The Coldwater Machine Company has developed a new modular laser welding system for the stainless steel drums of washing machines, dryer drums, baskets and other round sheet metal wrappers. The process eliminates double handling of the part, reducing production time and improving quality. Another criteria for efficiency is portability. As well as becoming larger (see below), welding machines are becoming more compact, packing a large punch into a smaller space. Compactness and a favourable powerto- weight ratio (24-26kg; 235 to 320- amp rated output at 40% duty cycle) characterize ESAB’s Rebel™ machines. This allows greater flexibility when moving a welding machine around the shop or working in the field. This light weight and reduced footprint is shared by the same company’s Aristo Mig 4004i Pulse.
In recent years there has been a marked improvement in welding rates thanks to new pulsed welding technology. New pulsed MIG and TIG technology can improve first-pass yield rates, lower cycle times and reduce piece costs. TIG welding can improve welding of thin stainless steel, but conventional TIG technology is limited to 10 or 20 pulses per second. This is why H.L. Lyons Company, a Kentucky manufacturer of stainless steel appliance components, switched from conventional TIG welders to TIG inverters provided by Miller Electric, thereby increasing pulsing rates from 10 PPS up to 175 PPS and cutting welding time by up to 50%. The high pulse rate increases puddle agitation, which produces a better grain structure and so promotes greater strength. Another alternative to TIG is MIG welding with RMD (Regulated Metal Deposition). Stainless Piping Systems was able to save considerable welding time on stainless steel root passes and also noticed an improvement in quality.
In welding as in other manufacturing fields, speed often equates to automation, and automation means an increased role for robots. Robots have been around since the 1960s, entering the welding industry in the 1980s. Recently, their use in welding has been growing more rapidly. Robotic welding offers greater consistency, accuracy and repeatability and also improved energy efficiency. It is possible, though not obligatory, to pre-programme them. The benefits of robotization can be seen in the case of Van Lierop, a Dutch steel and stainless-steel maker. By installing three work stations operated by a Panasonic TA-1900 welding robot, parts which are welded on the outer stations and then assembled on the middle station are completely welded by robot, eliminating several stages in the procedure. The robot was supplied by Valk Welding, which supplies XYZ systems that are characterized by a welding robot in hanging position from a gantry which can move over the X,Y and Z axes. This allows greater freedom of manoeuvre useful for making large welds.
Bigger
Companies regularly invest in expanded capacity and increased range. These expansions occasionally call for larger machines, especially in the aerospace industry. In 2015, what was thought to be the world’s largest welding machine was transported from Michigan to Connecticut on a 200-foot flatbed truck. The welder has doubled Pratt and Whitney’s capacity to make the fan blades at the front of jet engines. Moog and Thompson Friction Welding have developed the world’s largest linear friction welding machine. Two-and-a-half metres tall and weighing 100 tonnes, the E100 can weld a surface of 10,000 square mm and apply 100 tonnes of pressure to a welding point. It opens up new possibilities for welded fabrication of parts that previously needed to be machined from solid metal.
It will transform manufacture of jet engines by cutting production times and reducing waste of materials such as titanium. More dramatic still is the world’s largest spacecraft welding tool. The friction stir welding tool at the Michoud Assembly Facility in New Orleans stands 170 feet tall and 78 feet wide. NASA is using it to assemble the heavy-lift Space Launch System (SLS), part of the Orion rocket that will take a four-person crew to Mars. The tool will be used to friction-stir weld sections made of lithiumaluminium. It will store cryogenic liquid hydrogen and liquid oxygen that will feed the rocket’s four RS-25 engines.
Safer
Welding machinery that improves quality and reduces human error is also contributing to safety, both for the welder and the end users. One significant advance in safety consists of robots that can carry out inspection. ABB’s IRB 2600 inspects the quality of the weld, using the latest 3D vision inspection technology. It is equipped with SafeMove2, software that enables people to safely work alongside robots without compromising productivity. Other software has been created to guide welders through the whole welding procedure so as to avoid incidents and mistakes. Not all accidents, however, are the result faulty welding procedures, as some recent horrific accidents have demonstrated.
Conclusion
The objectives of smartness, speed and safety are inseparable. Together with the greater versatility achieved in both larger-scale projects and in more compact tools, the mechanization and automation of welding is accelerating. The welder of the future will not only need a steady hand and a clear eye; he or she will also need to be at ease with ever more sophisticated software.
Reference
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Welding projects
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K-TIG welding technology will be used for the construction of the Acueducto Gran San Juan, a 31-mile pipeline that will transport drinking water to San Juan, Argentina. About nine miles of the pipeline will be fabricated by Industrias Metalúrgicas Jaime using keyhole TIG welding technology, a high-energy-density variant of GTAW, on stainless steel. Both the longitudinal and circumferential weld seams in the pipeline are being welded in a single, full-penetration pass.
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In September 2017 welding of the main circulation pipeline (MCP) was completed on reactor 1 of the Belarus nuclear power plant. PJSC Energospetsmontazh completed overlaying austenitic stainless steel on the inner welds of the MCP which protect the pipeline from corrosion.
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The ITER fusion reactor project in Caradache, France, includes some highly complex welding operations. Among these was the welding of the vacuum vessel sectors. The doughnut-shaped reactor vessel (“torus”) consists of a double-walled container in the form of an austenitic stainless steel vacuum chamber with a height of 12 metres and a diameter of 18 m. In 2012 Equipos Nucleares S.A. (ENSA) won a four-year contract to weld the nine vacuum vessel sectors and 54 port structures. Its shape requires the massive stainless steel pieces to be joined together by welding challenging geometrical forms. The contract includes development of specialized welding and testing tools and involves 150 contract workers. Special narrow welding torches had to be made to allow access to very tight spaces, and robots had to be used in areas where human access was impossible.
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The US DOE’s Argonne National Laboratory has developed a way to weld components made of high temperature superconductors. The new welding process bonds pieces of yttrium-doped barium-copper-oxide (YBCO) using layers of thulium-doped barium-copper-oxide (TmBCO). It is thought this innovation will allow widespread use of high-temperature superconductors in the electric-power industry.
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Accidents
It has been estimated that 1 in 250 welders will fall victim to an accident during their career. Burns are most common and obvious type of injury, but less obvious ones can include exposure to UV or IR radiation or exposure to intense light. Other hazards include exposure to fumes or fluid, electrocution, fires and explosions. Even robotic welders can be dangerous, especially during nonroutine operations such as programming, maintenance, testing, setup, or adjustment, when an unforeseen movement of the robot can cause traumatic injury.
Explosions occur when welding sparks come into contact with inflammable fluid, often during work on gas or petroleum storage tanks. The sites most often concerned are oilfields, oil refineries and (petro)chemical plants. In Norwich, UK, two men were killed in 2015 as they were working inside a paint-spraying booth; welding sparks seen in the vicinity may have been to blame. In Ohio, in 2008, two welders were killed when sparks ignited hydrocarbon vapours. In 2006 three workers died at a Mississippi oilfield when welding sparks ignited flammable vapor venting from a storage tank.
