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XMT Multiprocess Inverters from Miller Allow Expansion without Updating Incoming Power Service; Improve Welding Processes

Executive Summary:

New XMT® 304 inverters from Miller Electric Mfg. cut the primary power draw per machine in half. This allowed J.W. Williams, Inc. to add production without having to update its incoming power service – a major savings. New inverters also increased productivity and improved quality:

Fabricator Overcomes Power Limitations and Expands Operations with Efficient XMT Inverters

Losing a leg was the last straw. It happened when nearly 22 welding operators struck an arc simultaneously. Their antiquated, power-hungry welding machines reached out for power all at once. The building's incoming service, already pushed to its limit through the addition of other new equipment, couldn't handle the load and dropped one leg of the three-phase power.

Kelly McGowan, the shop manager then, did not have a good day. Fortunately, energy-efficient, inverter-based welding machines would soon solve his power problems. Inverters would also reduce welding time by more than 25 percent and help improve the number of welds passing x-ray tests by six percentage points.

McGowan works for J.W. Williams Inc., which is part of Flint Energy Services Ltd. Based in Casper, Wyo., J.W. Williams is an engineering, fabrication, modular construction and field service company working on projects in the natural gas and crude oil processing industries. The shop McGowan managed fabricates two- and three-phase separators, indirect heaters, shell and tube heat exchangers, tanks and pressure vessels. These components become parts of systems for wellhead heating and separation, glycol dehydration, mechanical refrigeration, crude oil stabilization, amine gas sweetening, gas liquids fractionation and vapor recovery.

Keeping Up with Demand

With the rapidly increased demand for natural gas, J.W. Williams's business is booming. Natural Gas E&P companies want to bring new capacity on-line quickly, and they turn to J.W. Williams for quality craftsmanship and on-time delivery. To satisfy this demand, J.W. Williams decided to add eight manual welding stations and a mechanized submerged arc welding station. However, the local electric utility informed McGowan that the shop already teetered on the edge of its capacity, as the lost leg of three-phase power indicated.

"We initially thought we could not add more welding machines without major changes to our incoming service," says McGowan. Altering primary service would have included adding a transformer with greater capacity. This, in turn, would have required replacing the old wiring, breaker box and junction boxes with new wiring capable of carrying the increased load. Changes of this magnitude could have cost tens of thousands of dollars, and the company would have to rely upon 15-year-old welding machines. Fortunately, McGowan's welding supply distributor, Dan Petumenos of Air Gas Intermountain in Casper, provided a solution with energy-efficient XMT 304 inverters from Miller Electric.

Out with the Old

Like many other fabrication and mechanical contracting companies, J.W. Williams "had antiquated welding equipment," explains McGowan. "A lot of stations had a Stick machine that was just a Stick machine and wire machine that was just a wire machine. Even though the operator didn't weld with both machines at the same time, they both drew a lot of power and took up space. Plus there was the cost of machines sitting idle and being non-productive, and that's even with sharing equipment between stations. When we needed to upgrade, it didn't make sense to buy 'new' equipment if it featured the same antiquated technology."

J.W. Williams' old welding machines each placed a load of 30 to more than 40 amps on the incoming service. "Conversely," says Petumenos, "state-of-the-art inverters like the XMT incorporate power factor correction. On 460 volt service, power factor correction lowers the XMT's primary power draw to just 18.9 amps at rated output. That's about half the draw of the old units. I explained that J.W. Williams could build its new welding stations simply by replacing four old machines with eight efficient inverters."

In with the Efficient

McGowan didn't need more convincing - "there's no way we could have expanded without inverters," he says - so he asked Petumenos to provide machines for evaluation. Petumenos brought in the XMT and another leading brand, both with a 300 amp/60 percent duty cycle output rating. The XMT was paired with Miller's D-60 dual wire feeder; one reel held ER70S-3 .045 in. solid wire and the other held E71T-1 .045 in. flux cored wire.

McGowan says, "I liked the fact that the XMT had Stick and wire welding capabilities rolled into one machine. As our shop expanded, Dan was also helping us shift from primarily a '5P' Stick mentality to relying mostly on wire welding."

After testing both machines, J.W. Williams easily selected the XMT over the competitive unit. Welding Operator Sam Waddy explains that "the boards on the other machines went bad, and sometimes the wire would 'jolt' instead of feed smoothly. I wouldn't even put one of them in my garage. The XMT blows away that machine. I haven't had any problems with it. The wire feeds consistently, and I love the Stick arc. It's a great machine that's always there; I had other machines up and die on me."

The XMT offers the best reliability of any inverter in its class. It features a more robust design and fewer components. Its Wind Tunnel Technology shields sensitive parts from grinding dust and dirt by directing cooling air through a 'tunnel' in the center of the machine. The unit's Fan-On-Demand function turns on the cooling fan only when needed. This reduces the amount of particles pulled into the machine, prolongs life, reduces maintenance and lowers noise.

After evaluating the XMT for three months, Waddy says "the maintenance manager asked me if he could take my machine and move it to another station. I told him if he did that he'd have one heck of a fight on his hands." Other operators shared Waddy's sentiment. McGowan ordered four XMT/D-60 systems in November 2000, another four in February 2001 and a total of 46 by May 2002.

Saving Labor with Wire

While the shift from Stick to wire began a few years earlier, the acquisition of the Miller inverters allowed more operators to wire weld. Petumenos explains the history, saying "J.W. Williams mostly ran a stringer bead with a 1/8 in. 5P rod and a hot pass with a 1/8 or 5/32 in. rod. I showed them how to put in a MIG stringer bead and use flux cored wire for the remaining passes."

McGowan notes that "once an operator is trained to weld a MIG stringer, he'll learn it's more forgiving than a 6010 rod. I ran the first MIG welding test, and the weld passed x-ray."

Welding Operator Archie Crichton says "running flux cored wire is like welding with a low hydrogen electrode on a roll. The clean-up is easier, too, and you don't get as much spatter." Crichton also reports that the wire process reduced welding time by 25 percent on simple products like a three-phase heated separator. This vessel has a 30 in. diameter, a 1/4 in. wall thickness and four exterior fittings.

Petumenos notes that "switching to the MIG process cuts production time on this vessel from 35 minutes to 10 minutes on the stringer bead alone." McGowan says that "our crude time savings analysis - having Waddy and Crichton weld the same type of products but with different processes - showed us that wire welding reduced labor by 25 to 28 percent. As our operators become more proficient and comfortable with it, we expect the shop to average at least a 35 percent time savings."

He emphasizes that the impact of the wire process varies significantly by application. "A vessel with four exterior fittings isn't as time-consuming to weld as one that looks like a porcupine. Vessels with many fittings give us more places where we can use the flux cored process," McGowan states. "Eventually, we'll weld everything with wire. It's faster, more productive and better for the operator because he spends less time under the hood."

Petumenos also adds "as a national average, 50 percent of a Stick rod ends up as slag or a stub thrown in the trash. Flux cored wires deposit more than 85 percent of the weight into the finished product, so it's more time and cost efficient. For further improvements, I plan to introduce J.W. Williams to metal cored wire. That has deposition efficiency of around 96 percent, and it saves time because there's no slag to chip."

99 Percent Passing Rate

Although J.W. Williams purchased inverters because of their low primary power draw, the new machines also helped the company improve weld consistency.

Woodie Ridley, quality control manager at J.W. Williams, adds, "The XMT's are user friendly, and the welding process has come a long way to increase productivity and quality."

Since adding the XMTs and welding with the wire processes, 98 to 99 percent of all welds pass x-ray tests the first time.

"We increased our x-ray quality by about six percentage points," says McGowan. "I think the process change is a big part of this, and the other part relates to the fact that we had 15-year-old machines."

Old welding machines often produce an erratic output and do not have line voltage compensation. This technology, incorporated in the XMT and other new machines, maintains weld output within 1 – 2% of the set amperage, even though primary voltage may vary by +/- 10% of nominal. This helps ensure that weld output remains consistent, improving weld quality.

McGowan says that even before he witnessed its efficiency and savings "I had no qualms about investing in the XMT. Too many fab shops are stuck with 1950's technology. That's kind of ridiculous. The rest of the world has evolved, and the welding fabrication business is lagging. Anywhere we can improve our processes and equipment, I believe that's money well spent. The return on investment is extremely short."<-->

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