The machine also uses Lincoln Electric's Nextweld Waveform Control Technology that is built with electronic regulation circuitry to control and shape the output waveform. Lincoln Electric said that its Waveform Control Technology allows welding parameters to be tailored to the application.

The AC waveform can operate at any frequency between 0 Hz and 200 Hz. The frequency is adjusted by a single knob. Dialing in the frequency helps to stabilize the arc.

In addition, technology allows the amplitude and duration of the positive and negative cycles to be adjustable independently. That delivers greater control of bead shape, higher deposition rates and lower heat inputs. Also, other welding parameters can be controlled and regulated automatically so adjustments can be made by the machine while welding.

The machine can use a variety of operating modes so that desired outcomes — such as high deposition or high travel speeds — can be optimized.

For multiple arc set ups, any phase relationship can be achieved between the output waveforms regardless of the input connection. That helps to reduce arc blow.

Most manufacturers of large tanks use submerged arc welding because it has a very high deposition rate and high travel rates and because it delivers a quality weld.

Southern Tank & Manufacturing Co. Inc. (www.southerntank.net) produces a wide variety of large storage tanks, above and below ground, for fuel, water, chemicals and other applications.

The company was founded in 1937 in Owensboro, Ky., by William E. Kennedy Sr. He learned how to weld in the family business, Kennedy Tank and Manufacturing Co. Inc. of Indianapolis, which was founded in 1898, and still is in business today. Patrick W. Kennedy, the grandson of William E. Kennedy, Sr., is president of Southern Tank today.

Submerged arc welding is one of the company's primary processes in the manufacture of its tanks.

Charlie Mackey, plant manager for Southern Tank, said submerged arc welding is not a new process, but that it's a tried-and-true process for making tanks because of its numerous benefits, including its high deposition rate. Southern Tank has developed a submerged arc welding system that fits its special requirements.

“We have somewhat of an automated system that we've created as we've gained experience in the submerged arc process. We can do the round-about seams — the circumferential seams — but we have a DC drive gear motor to do longitudinal seams as well,” Mackey said.

Southern Tank's submerged arc welding equipment sits on a cart that runs along a track beside the tanks. It runs from circumferential seam-to-seam, and its travel speed can be reduced to allow it to weld the longitudinal seams between the circumferential seams. Southern Tank's submerged arc welding system also has a flux recovery system.

“We don't have any electronic guidance systems. We basically use a laser pointer that shines a red dot on the seam and the operator adjusts the weld head to track that seam,” Mackey explained.

“The tank is turning underneath the operator, whose basic job is to check if the weld puddle is tracking along the seam. With submerged arc welding you rarely ever see a spark, so he doesn't wear a hood. He's basically along for the ride,” Mackey said.

Flagg said Lincoln Electric is seeing a new and growing application for submerged arc welding: The manufacture of wind towers for wind farms, the latest green energy source.

The molten weld and the arc zones in submerged arc welding are protected from atmospheric contamination by being “submerged” under a blanket of granulated flux that consists of lime, silicon, manganese oxide, calcium fluoride, and other compounds.

The thick layer of flux covers the molten metal completely to prevent spatter and sparks as well as to suppress the intense UV radiation and fumes that are a part of the shielded metal arc welding (SMAW) process. Submerged arc welding requires a continuously-fed consumable solid or tubular (flux cored) electrode.

Submerged arc welding normally is operated in the automatic or mechanized mode, but semi-automatic — hand-held — submerged arc welding guns with pressurized or gravity-flux feed delivery also are available.