Welding Contractor Relies on Portable, High-Performance Welding Technology from Miller to Weld World's Largest Tunnel Boring Machine | MillerWelds

Welding Contractor Relies on Portable, High-Performance Welding Technology from Miller to Weld World's Largest Tunnel Boring Machine

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National Welding Corp. has had the distinct privilege of working on some of the largest construction projects across the country — from tunnel work 450 feet underground to bridge work 120 feet aboveground — not to mention welding on specialized equipment like tunnel boring machines (TBMs), penstock and water-treatment plant projects, and more.

Welding Contractor Relies on Portable, High-Performance Welding Technology from Miller to Weld World's Largest Tunnel Boring Machine

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National Welding Corp. has had the distinct privilege of working on some of the largest construction projects across the country — from tunnel work 450 feet underground to bridge work 120 feet aboveground — not to mention welding on specialized equipment like tunnel boring machines (TBMs), penstock and water-treatment plant projects, and more.


That privilege, however, isn’t a matter of luck. It’s the result of careful welding operator training and certification, a deep knowledge of welding codes and the offer of a unique proposition to the main contractors who are responsible for these projects:  As a full-service, high-production welding company, National Welding Corp. allows contractors to focus on the overall project while National Welding Corp. handles the challenges of field welding. To help ease the contractors’ jobs further, the company also focuses its efforts on managing welding operators, as well as designing custom welding trucks, trailers and rigging equipment that can address the needs on any job site.


It was for these reasons that the company was selected in May 2013 to tackle one of its biggest projects ever — welding Bertha, the world’s largest TBM — for the Alaskan Way Viaduct Replacement Program in Seattle. With the shear size of the project, the company needed the right equipment for the job — in this case, XMT® Series multiprocess power sources and SuitCase® X-Treme 12VS wire feeders from Miller Electric Mfg. Co.


About Bertha: the world’s largest tunnel boring machine

Bertha, a SR 99 TBM affectionately named after Bertha Knight Landes, the first female mayor of Seattle (1926 to 1928) will be responsible for boring a 2-mile-long tunnel underneath the city of Seattle — from the southern edge of downtown Seattle under the city to the northern South Lake district. The underground tunnel will provide a thruway for State Route 99 and replace the double-decker Alaskan Way Viaduct that currently runs along the city’s waterfront.


Weighing in at 7,000 tons and measuring 326 feet long and 57.5 feet in diameter Bertha is certainly cut out for the job.


The overall project and the reassembly of Bertha involved many partners beyond National Welding Corp., whose primary objective was the welding of the TBM.


Seattle Tunnel Partners, Bertha’s owners and the contractor hired by the Washington State Department of Transportation, purchased the equipment from Hitachi Zosen in Osaka, Japan. There, the $80 million TBM was tested, dismantled into 41 pieces and shipped across the ocean to its current location in an 80-foot-deep pit that the Tutor Perini Corporation excavated near the waterfront of Seattle. Tutor Perini also excavated the nearby launch ramp and the access pit at the end of the tunnel. It’s within this pit where partner Dragados USA reassembled the pieces, some of which weigh up to 900 tons, and National Welding Corp. completed the necessary welds.


The bulk of welding consisted of weld joints ranging from 1/2 inch to 3-1/2 inch V-groove bevels.


Welding Bertha: improving productivity, quality and costs with inverter technology

The reassembly of Bertha began in Seattle on April 27, 2013, with National Welding Corp.’s welding responsibilities commencing shortly after on May 16, 2013.


According to Vice President of Operations Bryan Hansen, the welding needed to be completed by July 1, 2013, which gave them only a short time frame to lay down a lot of weld metal — 5,000 pounds of weld metal, in fact.


“It was a tight deadline for us to accomplish this within four and a half weeks,” said Hansen. “It had us welding around the clock.”


Hansen, himself a mechanical engineer, knew that careful welding equipment and filler metal selection would be critical in meeting production and quality demands.


“We had 10 welding operators on site for the Alaskan Way Viaduct project, working two shifts throughout the day. And they’re all certified to American Welding Society (AWS D1.1), so with the right equipment, they could handle a job like this one.”


To help them reach their production goals, Hansen relied on the Miller XMT Series multiprocess power sources and SuitCase X-Treme 12VS wire feeders. The majority of the steel on this project was A516, Grade 70 and National Welding Corp. selected Hobart® gas-shielded flux-cored wire with AWS classification E71T-1C/-1M H8 for the job.


Relying on the XMT 350 multiprocess power sources and the Hobart wire, Hansen said that his welding operators were able to meet the challenges of the job with ease and noted productivity advantages by way of several key features: high weld quality; consistent power; portability and good operator appeal.


According to Hansen, the professional grade arc offered by the XMT multiprocess power source allowed the National Welding Corp. welding operators to maintain high arc quality for long periods of time. When combined with high-grade craftsmen, National Welding Corp. effectively eliminated poor welds and any rework that could lead to downtime and adversely affect productivity. The XMT 350 machines also delivered consistent power, allowing the team to weld for 10 to 12 hour shifts with no trouble.


Adding to the productivity-enhancing features of the XMT 350s is the fact that they are very lightweight (80 pounds) and compact — Hansen’s favorite things about the equipment.


“This is a very tight job site and we don’t have a lot of room to put welding machines. With the XMTs, we can run a long set of leads — up to 500 feet — to where our SuitCase feeders are,” said Hansen. “It’s a huge advantage that the guys can be that great of a distance away from the machine. They can go from location to location on this project to weld and not have to move the machines.”


The small footprint of the XMTs minimized clutter and increased safety, since the welding operators didn’t have to navigate the job site every time they relocated to a new area to weld.


The XMT 350 machines also feature large, dual digital meters that are easy for the welding operators to view, and are able to be pre-set amperage or voltage, which helped simplify training so National Welding Corp.’s welding operators could spend more time welding. 

Withstanding the elements of a Seattle construction site

Combined with the XMT 350 machines, Hansen and the National Welding Corp. welding operators relied on the Miller SuitCase X-Treme 12VS wire feeders to gain access to the surprisingly tight quarters found throughout the mammoth Bertha TBM.


To access many of the joints, welding operators needed to suspend themselves from five-point safety harnesses to reach high, overhead welds in congested areas. This was particularly difficult when welding on the inside of the drill head, or deep inside of the structure. The SuitCase X-Treme feeder easily traveled with them into these tight quarters and withstood the abuse along the way.


“One of the biggest challenges on this project is that Bertha is obviously a huge piece of equipment. We have to be able to climb on top of this machine that’s over 57 feet in diameter. It’s basically like welding a 57-foot-diameter pipe,” explains Hansen. “Plus, there are a lot of internal workings inside this TBM. There are hydraulic lines and electrical equipment we have to work around and protect from the welding, while still gaining the access we need.”


The SuitCase X-Treme VS feeder allowed the National Welding Corp. welding operators to address each of those challenges, and also provided consistent weld quality in the process. The feeder weighs only 35 pounds (without wire), making it easy to carry from location to location on this large job site yet was also small enough to fit into tight spaces inside the drill head.


Plus, the feeder provides accurate and consistent wire feed speeds, ensuring the welding operators gained the best quality and achieved the high deposition rates needed to complete the job in time.


“Really, our productivity here is measured by how long the guys are pulling the trigger,” says Hansen. “The longer a guy can sit and pull the trigger — and this wire feeder will do that —the more productive we are. They are simply depositing more metal.”


Hansen adds, that on a project like this one, using the Miller SuitCase X-Treme VS feeder greatly improves our deposited metal rate from seasoned welding operators.


The wire feeder also provided the consistent arc starts and arc performance using the constant current, Flux-Cored welding process National Welding Corp. used for this project.


According to Hansen, the durability of the SuitCase feeder is just as important on this job site.


“We love the robustness of the feeder and its case,” Hansen says. “We can beat it up so to speak and really use it in the field the way Miller intended it to be used. It can hold up and withstand the abuse.”


The typical Seattle weather made it even clearer why Hansen and the welding operators at National Welding Corp. like that durability.


“We’re dealing with a lot of elements out here, a lot of moisture being in Seattle and from it raining so often,” explains Hansen. “Still, with all of that and the general abuse that the feeders go through, everything has held up really well.


The greater access provided by the feeder, along with the robustness to withstand the unpredictable Seattle weather and job site abuse again increased productivity for the company. They could quickly and easily get into the areas needing welding and there was no downtime to address maintenance, repair or other wire feeder issues.


Boring toward the future of Seattle

With its welds carefully completed and all components otherwise assembled, Bertha began drilling the Alaskan Way Viaduct replacement tunnel in late summer of 2013, moving approximately 30 feet a day. At that rate, it will take approximately 14 months to complete the boring of the 2-mile-long tunnel. The project is slated to be complete and the tunnel open to public traffic in 2015.


As for National Welding Corp., Hansen says that the company and the 10 welding operators on site were pleased to be part of such a historic project — and to have the welding equipment they needed to meet the strict production deadlines.


“The XMT and Miller SuitCase X-Treme feeder allowed the men to be more productive,” says Hansen. “We really got a great amount of productivity because they could move around and work remotely, and we didn’t have to waste time moving equipment.”