SuitCase® Wire Feeder, Portable Inverters Beat HVAC Challenges as Soldier Field

Executive Summary

Hill Mechanical Group relies on engine drives, inverters and SuitCase® wire feeders from Miller Electric Mfg. Co. to meet tough HVAC demands on the renovation of Soldier Field in Chicago.

Hill Mechanical reported the following advantages:

• Portability of SuitCase® 12VS wire feeder helped complete HVAC work in every reach of the stadium.
• Tough design withstood harsh cold and heavy winds of the Chicago lakefront.
• SuitCase® solved duty cycle issues encountered with older technology.   
• Lightweight XMT® 304 inverter allowed fabricators to carry their welding machine to their work.
• Bobcat 250 D NT engine-driven welding generators stationed throughout stadium provided excellent MIG and Flux Cored capabilities.  

Soldier Field's HVAC System Construction Required Use of Highly Portable and Reliable Miller Equipment

To busy Chicagoans motoring along Lake Shore Drive, venerable Soldier Field looks like it's become a landing pad for a huge spaceship. Climbing out of the historic monument to Illinois war heroes is a gleaming glass and steel structure that looks otherworldly.

Patrick Kelly, a fabricator with Hill Mechanical Group, checks the settings on a Miller Electric Bobcat® 250 D NT engine driven welding generator during construction of the new Soldier Field sports facility in Chicago. Five Bobcat generators strategically placed throughout the stadium provided reliable welding power for Hill's fabricators.

Officially, the project is called "The Adaptive Re-use of Soldier Field." In reality, it is a masterstroke by the Chicago Bears National Football League club, city of Chicago, and state of Illinois to keep the team in the city and on Lake Michigan. "When this project was conceived; there was no way Mayor (Richard) Daley was going to allow the Bears to leave Chicago," said John Principe, sheet metal foreman for Hill Mechanical Group, Chicago, the contractor for all HVAC systems in the new stadium. "Once that was decided, re-using Soldier Field was the most doable alternative."

Hill Mechanical's sheet metal workers - at the peak of construction the crews included 50 sheet metal workers and 30 pipe fitters - turned more than 1 million lbs. of metal into the ductwork that runs throughout the stadium. That meant welding and fabricating the complete heating, air conditioning and ventilating system, from the lower levels of Soldier Field that contain the team locker rooms and offices, through the 144 luxury suites and 70 concession stands on three seating levels.

Hill Mechanical fabricator Patrick Kelly welds a connecting ring for exhaust pipe from the concession stands at the new Soldier Field stadium in Chicago. Workers used Miller Electric XMT® 304 CC/CV inverters to weld the 14 gauge steel ductwork

According to Principe, the welding demands of the project were enormous. Fabricators had to be literally everywhere at the same time to maintain the project's ambitious construction schedule. "It was common to have guys welding exposed stainless steel duct work for the concessions on the upper level, while other fabricators were welding the structural steel of the HVAC system down in the stadium's lowest levels," he said.

With those demands on his fabricators, Principe said it was critical that Hill Mechanical use welding equipment that was highly portable and very reliable. "Soldier Field is one of those high-profile jobs where everything has to perfect," he said. "Millions of people are going to see our work, so we want it done right."

Stadium '100% Blue'

The welding equipment used by Hill Mechanical on the Soldier Field project - inverters, wire feeders and engine drives - is all manufactured by Miller Electric Mfg. Co., supplied and serviced by Miller's Chicago distributor, Welding - Industrial Supply Co (WISCO). "We are 100 percent Miller Electric on this job," Principe said.

Roy Kuzmin, Hill Mechanical sheet metal worker, welds 20-inch round ductwork for the HVAC system in the new Soldier Field stadium in Chicago. In the background is the Miller Electric SuitCase® 12VS wire feeder, which Kuzmin carries with him from job to job throughout the stadium.

The equipment includes Miller XMT® 304 CC/CV multiprocess inverters placed strategically in the stadium to give Hill's fabricators the voltage they need at all times. "We placed three XMTs at mid-stadium on either side, and one in the north end zone," said Principe. "The most important aspect of this job is being flexible, getting welders from one spot to another quickly and knowing they'll have adequate power when they go to work."

Weighing just 76 lbs., the XMT 304 CC/VC is lightweight and portable enough to allow fabricators to carry the machine to their work. Each XMT 304 includes a 22A wire feeder for MIG welding with both .035-inch wire for all inside work and self-shielded .045-inch flux cored wire for outside welding.

The XMT 304 features Miller Electric's Auto-Link® circuit, which automatically links the power source to the primary voltage being applied, either 230/460 or 460/575 VAC, single- or three-phase. That ensures Hill's fabricators have the power they need no matter where they are in the stadium.

Roy Kuzmin, a sheet metal worker with Hill, is putting the finishing touches on the exhaust network stretching upward from the concession stand grills. Using an XMT 304, he MIG welds with .035-inch wire along a seam to connect 20-inch round ductwork. "We've had to weld on our backs, on our knees, even upside down and inside some of the ductwork," he said. "I can't say enough positive things about the Miller machines; whether we are welding with gas - such as now with all of our work inside - or with self-shielded flux cored wire, when we were outside battling high winds."

Bringing a 'SuitCase' to the Job

For the portability and flexibility critical to the Hill Mechanical fabricators, Kuzmin called the Miller Electric SuitCase 12VS wire feeders "the ideal tool for this project. We get called from job to job, anywhere in the stadium, and you can just disconnect from the Bobcat and take the wire feeder with you (it weighs only 28.5 lbs.) to the next job. The second most important part of the job for us, after the quality of the welds, is flexibility. Those wire feeders are as flexible as you can get."

Five Miller Bobcat 250 D NT engine driven welding generators are placed strategically throughout the stadium to provide reliable power. A sixth is mounted to the back of a John Deere utility truck for even more flexibility. "We run everything off the Bobcats, especially the 12VS wire feeders," said Principe. "You can set the engine drive for either MIG or flux cored welding and be assured of a rated output of 250 amps at 28 volts, the highest in its class."

Another Hill Mechanical fabricator, Patrick Kelly, said the Miller SuitCase 12VS impressed him for another reason - its ability to operate under the most adverse conditions: Chicago in the dead of winter. Kelly was one of the fabricators who did the final welding on the stainless steel exhaust pipes that extend out from the top of the new stadium.

"That work took place last January, and it was cold - 12 degrees below zero, with wind chills to 30 below on some days," Kelly recalled. "We worked in a 150-foot Condor crane that had to fit in the tight space between the columns of the actual monument and the top of the stadium."

The stadium rises at a 31-degree angle, so Kelly and his partner - only two welders could fit in the gondola with the Miller XMT 304 and SuitCase 12VS -devised a brace which allowed them to lift the sections of pipe at precisely the same angle. "In those conditions you could not lift and hold the pipe for very long, trying to get the fit right," Kelly said. "We could fit the section into the brace on the ground and lift it right into place for the weld."

Still, welding in those conditions - 10-15 mph winds and numbing cold - will test even the most accomplished fabricator. Principe said he was amazed at what Kelly and the other Hill fabricators accomplished. "Every one of them credited the Miller SuitCase 12VS," he said. "It operated flawlessly in one of the most difficult applications you could imagine."

Much of the HVAC ductwork in Chicago's new Soldier Field is exposed to the public, which put a high premium on quality welds. Hill Mechanical fabricators used Miller Electric welding inverters on the project.

Dan Olah, Hill Mechanical's support manager, pointed out that the Miller SuitCase 12VS machines, which became the 'most valuable player' for the fabricators - to borrow a term from the Soldier Field gridiron - were not part of Hill's equipment when the HVAC installation began.

"The SuitCase 12VS' were recommended to us by Darrin Bax, our representative from WISCO, the Miller Electric distributor," recalled Olah. "We were using a different machine at first and the duty cycle was just too small; the guys were constantly stopping to wait for the machine to reset."

Olah said he told Bax of the situation. "Darrin went down to the job site, talked to the fabricators, observed their work, and told John that he might have a machine that would solve the problem," Olah said. "The 12VS was brand new at the time and Darrin brought one out and gave it to John to demo. Well, everyone loved it and now that's all the on-site fabricators will use - not only at Soldier Field but every other project Hill Mechanical is involved in."

Chicago's famous skyline rises above construction of the new Soldier Field stadium. The $632 million project was completed in time for the 2003 NFL football season.

"That's the kind of support we've come to expect from WISCO and Miller Electric," he continued. "That is why Hill Mechanical is all blue."