Short-circuit transfer GMAW speeds pipeline project (2024)

Editor’s Note: This article appeared in the May 2024 issue of Canadian Fabricating & Welding.

In late 2022, Miramichi, New Brunswick-based Sunny Corner Enterprises (SCEI) took on the task of constructing a pipeline to transport paper pulp across the U.S.-Canada border. Pulp and paper manufacturing in North America, like industry anywhere, relies heavily on the timely and efficient transport of raw materials and the ability to put those materials together effectively.

SCEI looked inward at its various assembly processes and found an opportunity to upgrade. While the company had relied on gas tungsten arc welding (GTAW, or TIG) to lay a root pass on pipe, it set its sights on a technology that was faster, less labor-intensive, and more cost-effective.

International Partnership

SCEI is a multitrade construction and maintenance contractor. Founded in 1965, it does turnkey projects for a variety of industrial customers—mostly in eastern Canada, with additional operations that reach into the northern U.S.

Among SCEI’s customers is a paper mill based in northern Maine, with operations on both sides of the U.S.-Canada border. The mill produces paper pulp at its Edmundston, N.B., location and transports it across the St. John River to the company’s Madawaska, Maine, operation via four separate sections of stainless steel pipe—each 900 ft. long—spanning the Edmundston-Madawaska Bridge.

Welding of the pipeline is performed in two places. The initial assembly takes place at SCEI’s fabrication shop about 155 miles from the bridge, on the other side of New Brunswick. The pipe lengths are then transported by truck to the bridge, where the final assembly takes place. “We’re running four stainless steel lines,” said Bill Schenkels, vice president of business development at SCEI. “Three are 20-in. lines and one is 24 in. So they’re big welds. We’re prefabricating those in our shop into 60-ft. lengths, and then we’re shipping them to the site and doing the connecting welds in the field on that bridge.”

Rethinking the Status Quo

Manual GTAW worked well for SCEI in both the fab shop and in the field, Schenkels explained, but technical challenges and labor demands often slowed the process.

“In the field, you had to keep the wind off the welder,” he says. “You also had to do an argon purge, and you needed skilled welders who understood that purge process.”

Finding those skilled welders was—and continues to be—a challenge, said Schenkels, who is continually looking for ways to navigate current and future shortages of skilled labor in the welding and fabrication industries.

“Anything we can do to be innovative—any way we can do more with less—is something we would want to explore,” he said. “We don’t want to shoot ourselves in the foot, because we make money by putting people to work. But we also make money by being able to meet a deadline and get a job done. We’re looking for ways to be proactive rather than reactive.”

Part of that proactive approach involves looking beyond standard procedures. “It’s easy to say, ‘This is the way it’s always been done, and this is the personnel we have to do it. We know we can get the job done using TIG and using an old process that may be a little more painful,’” said Schenkels. “But knowing that labor shortages are coming, we chose to really get in front of them and try to avoid them.”

Surface Tension Transfer Process

Because of its longstanding partnership with Lincoln Electric, SCEI met with the welding technology company to explore options to build efficiencies into its existing pipeline manufacturing process and reduce costs. The solution came in the form of STT Field, a newer field welding technology developed by Lincoln Electric.

Surface Tension Transfer (STT) has several benefits, one being proven performance for pipe root welding. This controlled short-circuit transfer GMAW process produces a low-hydrogen weld deposit, making it easier to achieve a high-quality root weld in all positions. It differs from traditional GMAW short-arc processes because the arc current is precisely controlled independently of the wire feed speed.

“It was the large quantity of welds that we needed to do at this site that prompted us to say, ‘Here’s a really good opportunity to have a big impact from a change toward the STT process,’” Schenkels said. “If we were doing one weld here or there, it would really come down to our capacity in the fab shop. But there’s more to it than that. There’s the welding that gets done on the field side, which is a little different. I think that’s what really drove us to look for an alternative approach.”

The STT Field system includes Lincoln Electric’s Flextec 350X Power Connect power source paired with the Activ8X Pipe wire feeder and Lincoln Red Max stainless steel wire. In the shop, the Lincoln Electric PIPEFAB system uses the same STT process. This allows the welders to simplify transition between shop fabrication and field fabrication of similar pipe joints.

“Sunny Corner was already familiar with the STT process in the shop utilizing the PIPEFAB shop welding solution,” said Wayne Chuko, product manager for Activ8X Pipe at Lincoln Electric. “With the implementation of the portable Activ8X Pipe/Flextec 350X PowerConnect solution, the same STT process could now be easily applied in the field with minimal equipment, a quick and easy setup, and a manageable learning curve.”

“We had four positioners set up in the shop – three lengths of pipe laying on rollers and two operators doing the STT process,” Schenkels added. “And then we had two other crews capping out with a separate machine. We moved all that work through the shop in a couple months.”

By summer 2023, most of the fabricated material had been moved outside the shop and was shipped to the bridge site. To date, X-rays of weld joints have yielded favorable data and shown consistently high-quality welds.

Cost Reduction, Efficiency, Mobility

Within months after the STT process was implemented in the field welding portion of the project, the construction and maintenance of the pipeline across the Edmundston-Madawaska Bridge was more streamlined and cost-efficient.

The process was field-ready, and with the transition to an STT root pass operation, the argon purge in the field was no longer necessary. Root passes passed X-ray inspection with full side wall fusion and a smooth back bead on the inside of the pipe.

This not only reduced costs but saved time by enabling SCEI operators to weld more pipeline joints per day. The ability to do more with fewer workers helps to alleviate the effects of the labor shortage.

“Without the need to purge, we’re not lugging gas bottles around every day,” said Schenkels. “As far as our labor force, we have our key welders, and they’re welding twice as fast with this process. This increase in speed, especially on the shop side, makes us more competitive with other pipe fabricators in the region.”

Another primary concern was field mobility.

“The shop environment is no problem; you’re bringing the work to the machine,” Schenkels explained. “But at the site, you’re bringing the machine to the work. The power source can stay stationary, and the wire feeder can move from one spot to the other.”

This is the ideal application for Lincoln Electric’s small and portable Activ8X Pipe wire feeder.

The ability to weld more in a single day improves the overall quality of the welds themselves. “If you can get through filler welds and capping in a day, you’re not leaving open roots,” said Schenkels. “You’re not leaving the possibility of cracking. It works better in relation to the shift schedule. You don’t have situations where the operators are saying, ‘It’s late in the day. I shouldn’t start.’ You can gain an extra weld or two in a day’s time that you might not have been able to do otherwise.”

The pipeline construction is a long-term project for SCEI and its pulp mill customer, as the bridge itself is scheduled for a rebuild. This STT process is an ongoing contractor-customer partnership as much as an immediate solution.

“The customer is putting a lot of trust in us to use the right procedures and take a proactive approach to the job,” said Schenkels. “They’re relying on our expertise to be productive, innovative, efficient, all those things. They aren’t doing this just because they want to do it. They’re doing it because there’s a new highway bridge in the works, and the structure where the pipes run now isn’t going to be there in a year. So in a sense, they were forced into a certain course of action. It’s not a moneymaker for them. It’s a must-do.”

Long-Term Commitment, Long-Term Success

A truly successful business partnership is one that benefits both sides. The STT process has helped achieve that success.

“STT was invented by Lincoln Electric engineers, then further developed into an applicable welding solution with assistance from our clients and partners,” said Chuko. “This application with SCEI and stainless pipe welding without backing gas really highlights how powerful the partnership can be when both sides fully understand the prevailing challenges and give the proposed solution a chance to succeed.”

For all of SCEI’s success with the U.S.-Canada pulp mill pipeline, its implementation of the STT process doesn’t end here.

“This isn’t a one-off solution,” said Schenkels. “We’re trying to persuade other customers to accept this procedure, and we’re making good headway on that. Our goal is to use this for all of our stainless pipe welding, hopefully to avoid purging at all.

“This particular operation includes a lot of pipe, so there are a lot of welds required on a fairly tight schedule,” he added. We knew it would be a job that required a lot of repeatability, so it was an opportunity to try a different approach. If we discovered early on that it wasn’t working, we still had time to correct and go back to the old method. So it was a bit of a leap of faith but a good place to try out a new process without too much risk and a high potential for gain.”

In the end, there was never a need to course-correct or circle back, says Schenkels. The STT welding solution was a leap of faith that paid off for everyone.