Lincoln Electric’s Patented Surface Tension Transfer® Welding Process Simplifies Six-Month
Industrial Air Separation Plant Process Pipeline Expansion
For example, while TIG welding produces good pipe welds, travel speeds are slow, and the heat input required for successful welds is high.
And stick welding with cellulose electrodes provides good fusion characteristics but leaves deep wagon tracks, which requires more labor for grinding. Also common are highly convex root welds and a high-hydrogen deposit which can lead to weld cracking.
In comparison, the STT® process produces a low-hydrogen weld metal deposit in open-root joints with easier operation, better back beads and sidewall fusion, and less spatter and fumes than other processes. It is a viable option for welding in any position and is effective for welding mild and high-strength steels, as well as stainless steel and related alloys.
The original job estimate factored in welding time using TIG root and stick fill and cap for welds on 30-inch pipe at 12 hours for one 30-inch weld. Using the STT® process onsite, with .045 inch diameter wire and 100% CO2 shielding gas on the root pass and .035 inch diameter wire and a 90% Ar / 10% CO2 shielding gas mix on the fill and cap pass, McKee said he and the welding team could complete two 30 inch, x-ray-quality pipe welds in less than six hours. The complete project had more than 200 circumferential weld joints on 30 inch pipe and 500 other joints on 6 inch to 24 inch pipe.
“It really does save time,” McKee says. “That’s the biggest benefit.” Another benefit, he shared, is the STT® process capability to easily fill larger gaps on the root pass weld.
“It can fill root gaps up to ¼” to ⅜” inches wide, x-ray quality welds,” he notes. “You couldn’t do that with stick welding. It would be a mess.”
While the STT® equipment is traditionally used in the shop, Jameson knew it would be the perfect solution out in the field. The Lincoln Electric and AGWS teams worked with him to take a bench model wire feeder designed for stationary use and make it more portable. Using longer than typical power and control cables (roughly 30 to 50 feet), the wire feeder could be positioned close to the work with a scissor lift while leaving the power source on the ground.
“It makes it a much smaller component and got the job done - on schedule and with quality welds,” Jameson says. “We really credit Lincoln Electric and AGWS for helping us come up with such a workable solution.”
McKee says it was almost effortless for the Ayrshire team to certify on the STT® process thanks to the user-friendly characteristics of STT® and the intensive training program provided by Lincoln and AGWS.
“It only took me about one or two days in the shop to get up to speed before I took and passed the certification test,” he said. “Obviously, welding experience helps, but even guys who had no experience picked it up quickly. While it’s an entirely different machine, it is easier than stick and faster than TIG. Plus, it’s self-correcting and takes a whole lot of error out of welding. That saves time on the job, too.”
The result: Ayrshire finished the project on time and on budget and has firmly established itself as the bidder to consider in future pipe welding opportunities.
“The construction industry is a competitive field to say the least, so we’re always looking for an edge” Jameson says. “When we’re putting out bids, if we can say we can finish the job by using the STT® process in one-third of the time that it takes someone using TIG and stick welding, we’ve given ourselves an advantage. If we can weld a single 30 inch pipe in three to four hours, like we did on this job, and the other guys are doing it in 12 hours, then obviously we can prove we can be the most efficient choice.”