Issue:Find a multiprocess, energy efficient, operation and maintenance friendly power source.

Solution: XMT® 304 inverter-based power source.

Results:Lower electricity bill, less maintenance and a $7,434 rebate check from utility company.

Whose advice on boosting energy efficiency can be more trustworthy than that of the local power utility? When Kaukauna Utilities suggested that Team Industries, Inc. evaluate its equipment's energy efficiency to save money, the Kaukauna, Wis.-based piping and tank fabricator complied. Starting in March 2001, Team began replacing aging, power-hungry welding machines with efficient inverter-based welding power sources from Miller Electric Mfg. Co.

Team's investment will result in a $303 annual electricity savings per power source and a $413 rebate per power source from Kaukauna Utilities. Team also stands to save thousands of dollars per year in maintenance costs through improved reliability. Perhaps most importantly, Team has invested in its own future by guaranteeing a consistently superior product.

Energy Efficiency

“After considering Kaukauna Utilities' recommendations, we made a commitment to look at our equipment needs and what would be required to sustain us over the next 15 years. Obviously, energy cost was a high priority issue,” says Donald J. Murphy, president of Team Industries. “We knew that welding machine technology had changed greatly, so we wanted to invest in this technology, particularly the newer energy-efficient power sources. But we also wanted machines that were operator- and maintenance-friendly, along with multi-process capability. The bottom line was how to perform the same amount of work using less energy.”

Kaukauna Utilities seeks to foster this mind-set among its customers. “Our philosophy is to work with customers to ensure they use energy as efficiently as possible,” says James J. Brown, Kaukauna Utilities' customer service representative and a consultant to Team and other industrial customers. “When Team indicated that it wanted to improve energy efficiency and power factor, we knew that we could help,” Brown says.

When high-use utility customers such as factories improve efficiencies, the benefits flow both ways. Kaukauna Utilities generates a certain amount of its power through seven hydroelectric facilities, but buys the rest on the open market, which incurs penalties to the utility.

“If our customers can reduce their energy demand, we can reduce the amount of electricity we have to purchase on the market. We save costs and pass on less cost to the end user,” Brown says. “Additionally, reduced demand enables us to generate fewer kilowatt hours to meet that demand. Our ‘avoided cost’ is converted into rebates for customers that use energy efficiently.”

Rebates

With energy efficiency in mind, Team tested the Miller Electric XMT 304 inverter-based power source in-house for a year before selecting it. The XMT is a CC/CV, multiple process welding unit with a 5 to 400 amp output (300 amps at 60 percent duty cycle). It features an average energy efficiency of 85 percent and good power factor (see sidebar for more information about power factor). Team installed 18 XMT 304s in March and April of 2001 and will eventually purchase up to 52 units.

Versus Team's old 250 amp multiple process power sources, the XMT inverter saves Team Industries $303 per machine per year in electricity costs, an average figure Team and Kaukauna Utilities derived from test meters and other power consumption calculations. In addition, because Team's power factor improved by using more energy-efficient machines, Kaukauna now returns a $413 rebate per inverter, up to a total rebate of $7,434.

“At our plant, welding machines are among the most common electrical devices — 52 welding units are in use here daily,” notes John Panetti, Team's executive vice president of manufacturing. “That makes them one of the highest users of electrical power, so we definitely needed the most energy-efficient welding machine we could find to replace our older units.”

Obviously, Team officials also critically evaluated the XMT 304's arc characteristics. “Our testing proved that the Miller power sources would be able to deliver a smooth and stable arc consistently and in all welding modes,” Panetti says. “This was key for us, because our work demands high-quality, multi-process welding capabilities.”

Maintenance Efficiency

The second major force driving change at Team Industries was rising maintenance costs associated with the company's aging welding units. “We could have gotten by with our existing machines,” says Jason Sturn, Team's maintenance supervisor, “but it's not always the right thing to do. You have to weigh how much downtime and repair bills you're accumulating using older equipment that starts to break or wear out.”

Team's first 18 inverter units have replaced the older generation machines that had the highest maintenance record and/or those getting the most arc time. Team anticipates that the XMT 304's design should significantly increase maintenance efficiency.

Welding Quality

Since 1987, Team Industries has provided piping, tank and modular fabrication for the brewery, chemical, pulp and paper, power, refinery, petrochemical and industrial gas industries, to name a few. In the last 14 years, its manufacturing capabilities have expanded to include pipe spools, skid-mounted equipment modules and manifold assemblies, structural modular framing, rack-mounted process piping, ASME tanks and pressure vessels, and tanks, hoppers and fittings of all varieties. The company also manufacturers its own line of welding positioners and grippers, which it designed especially for pipe fabrication.

Team is authorized to use the ASME “PP” and “U” code symbol stamps and is qualified to perform code fabrication to ASME Section I and VIII Division I, ASME B31.1 and B31.3, as well as other National Code Standards. Team's 80 welding operators use SMAW, GMAW, GTAW, SAW and FCAW processes. The company works with a wide range of materials, including 304, 316, 321 and duplex stainless, carbon steel, cast alloys, aluminum, nickel base alloys, titanium and P91 and P22 chromes.

“Basically we sell welding, and welding is our forte,” says Panetti. “We have some of the best operators in the world welding here. The systems we build are subject to pressures as high as 2,500 pounds psi at 1,500 degrees Fahrenheit. We x-ray approximately 1,000 pipe welds per month. We can't afford not to provide the latest technology to our welding operators.”

Use of advanced technology allows Team to claim a rejection rate of less than one-half of one percent for materials that arrive to the field, one of the lowest rates in Team's industry. Consequently, the company avoids expensive rework. For example, a weld that fails Team's x-ray or ultrasonic tests can cost $200 to $300 to repair. The loss of the operator's productivity increases that figure to a $400 to $500 loss.

The new inverter welding power sources have contributed to Team's quality and manufacturing efforts in a number of ways. User-friendliness was the first benefit Team's welding operators experienced. “We brought the units in on Friday, their day off, and on Monday morning the welding operators figured out what to do on their own,” Panetti remembers. “If there were any major questions, a 15-minute explanation solved the problem. The XMT's process selector switch makes switching between processes fast and simple.”

More to Come

The second phase of Team's welding power source replacement project starts next year. From all indications, the transition will continue seamlessly, according to Panetti. “We rely heavily on feedback from the plant floor,” he says. “So far, from everyone the word is 'smooth.' The operators are very pleased with the new power sources, whether the application is TIG or MIG. I have yet to hear even a hint of a negative comment about the XMT 304s or our decision to buy them.”

The increased efficiency that the XMT 304 units have given Team's welding operators has had a ripple effect throughout the plant. “Our pipe fitters are a little concerned that they can't keep pace with the welders,” he notes. “But I think they'll rise to the challenge and adapt to this new production level — with the new Miller power sources, the welding operators aren't going to be working any slower.”

Inverter Power Calculations

Arc-on welding cost:300 amps x 30 volts (welding output) x $0.11* (energy cost per kW-HR) x 2400 hours (annual arc-on time) ÷ .85 weld efficiency) = $2.795.29

Unit idle cost:.028 kW idle power draw x $0.11 x 1600 hours idle time = $4.93

Old Welding Unit Calculations

Arc-on welding cost: 300 amps x 30 volts (welding output) x $0.11 (energy cost per kW-HR) x 2400 hours (annual arc-on time) ÷.71 (weld efficiency) = $3,346.48

Power cost to operate old machine: $3,418.82

Power cost to operate inverter: $2,800.22

Power savings potential with inverter: $ 618.60 per year, per machine

Efficiency and Power Factor

Inverters provide both good electrical efficiency and good power factor. Before 1995, all transformer-based welding power sources did a poor job of converting incoming line power to welding output power. Efficiencies of 60 to 70 percent were typical, with constant current machines being bigger offenders than constant voltage machines. With inefficient units, most of the “lost” primary power ends up heating the transformer (which is why welding machines have cooling fans). All that hot air costs a lot of money in the form of high utility bills. In fact, if someone gave you a free machine, but it used power inefficiently, you could be losing money within two years.

In 1995, Miller improved the way the copper wire wraps around the iron transformer core and added a cooling fan that only ran when needed. This boosted power conversion efficiency to approximately 80 percent for Miller's traditional three-phase input machines and 85 percent for its inverters. An independent laboratory confirmed that the new power sources provided a 10 to nearly 25 percent energy efficiency advantage over units featuring the old transformer design. The calculations in the chart below show the impact of energy efficiency on utility bills.

Power Factor Correction

Power factor is defined as the ratio of real power (or “working” power, the power that produces useful work, such as creating a welding arc) to apparent power (the total power being provided by the utility). Simply put, the current required to operate a piece of equipment having low power factor is quite a bit higher than that required for equipment having high power factor. Many utility companies charge an additional fee if an industrial facility has low power factor.

Low power factor is caused by inductive loads, such as in the transformer of a welding power source. To overcome low power factor, manufacturers like Miller Electric incorporate a feature called power factor correction (PFC) into a welding power source. PFC is optional on some power sources and a standard function on others, including the XMT. As a result of PFC, the XMT 304 draws just 18.9 amps on 460 V, 3-phase primary service to produce a 300 amp/32 VDC welding output. An old CC/CV power source without PFC may draw 30 to more than 40 amps of primary current, or more than double the load of an inverter.