Increasing welding efficiency with mechanized automation

For many industries, like pressure vessels and penstocks, mechanized automation in the form of a welding manipulator can be the most effective approach. Here we see a Lincoln Electric Pantheon™ S submerged arc manipulator with Power Wave® AC/DC 1000® SD being prepared to be put to work.

When people think about welding automation, they typically envision some sort of robotic system: a robotic welding arm attached to a welding power source and a controller, lined up in the hundreds, using GMAW wire to weld automotive parts by the thousands.

While this is certainly accurate in automotive and related industries, when it comes to oil and gas (pressure vessels and process piping), pilings, penstocks, shipbuilding, and some structural steel applications, efficiencies are more likely to be gained using some form of mechanized automation, usually in the form of a welding manipulator (also known as a column and boom), side beam, or gantry system.

In these industries, when we think of a welding manipulator, we think of the submerged arc welding (SAW) process. This involves a heavy-duty manipulator designed for welding the circumferential and long seams in a pressure vessel shop, sporting one or two 1,000-amp power sources, flux recovery, and maybe powered cross slides.

While SAW manipulators make up a large part of the market, we are now seeing a larger number of manipulators set up for open-arc processes such as GMAW, metal-cored, and flux-cored welding. These systems also can have options like advanced inverter power sources, HMI controls, and water-cooled guns.

Some systems have both SAW and open-arc capabilities.

Rigidity and Precision

Maintaining a repeatable process depends on a welding manipulator that has rigidity and precise positioning capability and avoids undesired movements and lash that would affect weld consistency.

For instance, manipulators are available that have linear bearings and variable-frequency drives (VFD) to help keep the weld head stable and welding speed consistent while booming out to weld the long seam. VFD-powered travel carts provide a consistent, repeatable travel speed, which allows welding while the whole manipulator is in motion. A heavy-duty equipment platform can carry the control systems, welding power sources, flux-recovery system, and a single power drop.

Manipulator Options

If a welding manipulator will be dedicated to SAW, decisions have to be made with respect to power source, flux recovery, user interface, powered cross slides, and seam tracking.

Stability in any system is critical for quality welds. Here we see the Lincoln Electric® Pantheon™ manipulator, which has linear bearings and variable frequency drives (VFD) to stabilize the weld head and keep welding speed consistent while booming out to weld the long seam.

An advanced inverter-based power source can offer several advantages over a transformer-based system. The ability to weld with a variable AC square wave mode offers increased welding deposition rates and control over penetration. In addition, data collection abilities on some products, with procedure memory recall and lockout, can help operators choose the correct weld procedure for every application.

Flux recovery is also important. Flux that ends up on the floor without being properly used is wasted, never mind the time required for an operator (and organization) to keep flux supplied to the manipulator.

Fortunately, a variety of flux-recovery systems are available, including electrical and air-powered, hopper-mounted versions. A pressure feed system (from a pressurized flux tank on the equipment platform) allows the weld head to access a smaller opening, which is useful for interior welds on small-diameter applications. When a flux vacuum is added, a closed loop-system is created, offering significant improvements in both time and flux usage efficiencies.

Another major factor in operator efficiency is the user interface. Put simply, how will the system be controlled? One option is a series of control pendants. At minimum, a typical welding manipulator has a control pendant for the manipulator itself, as well as one for the welding power source and perhaps the powered cross slides. In some circumstances, multiple pendants can become unwieldy if the operator is setting up the weld while the manipulator is fully extended.

Another option is a human machine interface (HMI), like the Lincoln Electric MAXsa® HMI. This type of control system combines all the user interfaces into one screen, offering additional control over the welding process. In addition, an HMI can provide greater ease of welding procedure selection and variable monitoring such as heat input calculations.

When paired with a camera system, the HMI controls the system from ground level, while the manipulator is fully extended and up in the air on the top of a penstock or pressure vessel.

The last major decision is about control of cross slides and seam tracking. A manual set of cross slides can be cost-effective and durable, but these can increase the operator’s work. Another option is powered cross slides with a tactile seam tracking probe. These systems help to position the first welding pass precisely on the joint centreline, aiding in complete joint penetration (CJP) and the reduced possibility of lack-of-fusion defects.

To determine which options you need, it’s best to partner with a welding company that can compare the various trade-offs and specify and deliver a system that’s right for your company.

Scott Stanley is the national marketing manager for The Lincoln Electric Company of Canada, www.lincolnelectric.ca.

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