Bechtel National, Inc. relies on hundreds of Maxstar® 200 TIG/Stick Inverters from Miller Electric Mfg. Co. to weld nearly 187 miles of pipe at the world’s largest nuclear waste treatment plant. Benefits include:
- Portable, lightweight inverter that meets nuclear quality level no. 1 standards.
- Saved thousands of dollars in weld lead cost.
- Reduces chances of lost-time accidents related to lower back strain or tripping.
- Inverter accessibility improves weld quality.
- HF start function provides consistent, positive and inclusion-free arc starts.
Cutting Cable Clutter
Nuclear warfare and the development of ultra-destructive weapons played a major role in World War II and The Cold War. Although over, the legacy left by the specter of nuclear war still threatens American citizens. Millions of gallons of radioactive waste remain buried beneath the ground at the Hanford Nuclear Reservation near the “Tri-Cities” area of south-central Washington state. Nearly one-third of the underground tanks containing this waste have leaked, threatening the ecosystem of the mighty Columbia River and hampering this region’s effort to grow out of the shadow of its nuclear past.
In July 2002, Bechtel National, Inc., one of the world’s premier engineering, construction and project management companies, and Washington Group International began major construction on the Department of Energy’s (DOE) Office of River Protection Waste Treatment Plant Project (WTP Project). This is the world’s largest nuclear waste treatment plant. Before it’s finished, more than 985,000 ft., nearly 187 miles, of pipe will be welded using hundreds of Maxstar® 200 TIG/Stick welders from Miller Electric Mfg. Co.
During the nuclear power plant work of the 1960s and ‘70s, the preferred welders were eight-arc multi-operator welding systems that weighed about 4,500 lbs. While very rugged (which is why the system remains popular today), such a heavy system is relatively immobile. To reach worksites hundreds of feet away, up to 4,000 feet of welding lead (cable) per system would be strung out over the floor, on the ground or hung overhead. This increased safety hazards related to tripping, as well as increased the potential for stress and strain injuries from carrying thousands of pounds of cable. It also increased upfront purchase costs, and it may have hampered productivity.
|Ivan Newcomb, a journeyman pipe welder with UA Local 598, TIG welds with the Maxstar 200 in a work site about 10 feet below ground. “We just brought the inverter down and started welding right away. There was no pulling lead or need to change machines if we switched processes.”
To combat these challenges, Bechtel prefers to supply its workforce with lightweight inverter-based welders that offer premium arc performance, remote amperage control and lightweight portability that brings the welder right next to the work. In fact, portable inverter-based welders fulfill a primary Bechtel value: safety.
“Bechtel believes that every accident, and therefore every injury, is preventable, and we embed that philosophy into every Bechtel project through a combination of technical field procedures and ongoing training programs,” says Terry George, WTP Project Labor Relations manager for Bechtel National. “Our dedication to safety helps keep workers safe, and it also pays off for our customers.”
Inverters significantly reduce cable use, weight and cost, typically from hundreds of feet to 50 or less. To Bechtel, eliminating weight that improves worker safety is priceless.
Bechtel has earned an industry-leading record of achieving zero lost-time incidents on 90 percent of its projects worldwide, representing more than 100 million work hours per year. Year after year, its safety performance is right at the top of its industry. In 2004, Bechtel U.S. had 0.16 lost workday incidents per 100 workers, compared to a U.S. industry average that is historically near 4.0 incidents.
Bechtel’s commitment to zero accidents extends to every aspect of a project, from planning to completion, and from the boardroom to the field crew—and to the type of welder they select. After consulting with UA Local 598, the Plumbers and Pipefitters Local from Pasco, Wash. (who supplied the pipefitter labor for the WTP Project), Bechtel selected Maxstar 200 TIG/Stick welding inverters. Miller Electric developed this machine to produce code-quality welds and for extreme portability through its lightweight design—just 37-lbs.—and Auto-Line™ primary power management capabilities.
Waste to Glass
The purpose of the WTP Project is to solidify nuclear waste through a process known as vitrification. This mixes nuclear material with molten glass and creates a solid glass product that, when placed in stainless steel canisters and containers, isolates the waste from the environment (visit www.waste2glass.com for more details).
The vitrification process requires miles of pipe that must safely contain hazardous materials. To weld to very stringent “nuclear quality level No. 1 standards,” Local 598 intensified its training program so that it could provide hundreds of qualified journeymen and apprentices (see related story in the Education section of MillerWelds.com).
“Local 598 personnel weld stainless steel pipe, Hastalloy pipe, coaxial pipe and Inconel pipe to standards that, outside of pipefitters and the building trades, are nearly impossible to duplicate,” says George. “These guys come out here as qualified welders and put their employment on the line everyday. If they can’t weld successfully, they’re not going to be around. If we [Bechtel] don’t deliver quality welds, then we’re not going to be around. Local 598 has made considerable efforts to make sure that they come with the skills and qualifications that meet our very, very high expectations. We also make sure that we buy high quality equipment and put the right equipment in their hands to be successful.”
The Maxstar 200 weighs 37 lbs., produces 1 to 200 amps of DC welding power (175 amps at 60 percent duty cycle) and features a built-in high-frequency (HF) TIG arc starting function and Adaptive Hot Start™ Stick for arc starts (see side bar story on HF arc starts).
|Steve Davis, a UA Local 598 journeyman welder on the WTP Project, only needs a 15-ft. TIG torch and work clamp¾and no additional cable¾when welding with the portable Maxstar 200.
While several inverters offer lightweight portability, the Maxstar 200 is the only inverter in its class to feature Auto-Line. This technology enables the inverter to automatically connect to single- or three-phase, 50 or 60 Hz, 120 through 460 V primary power. Auto-Line also enables the Maxstar to ride through voltage spikes and dips that cause other machines to shutdown for self-protection, and it lowers primary amperage draw to a mere 5.2 amps on a 460 V, three-phase line.
In short, no matter what type of power is available throughout the WTP Project site—and almost any location in the world where Bechtel works—the Maxstar 200 can plug in and go to work. As a result of Auto-Line input power flexibility, coupled with lightweight inverter portability, the Maxstar 200 eliminates the need to purchase, transport and manage tens of thousands of feet of welding lead.
Reducing the Need for Lead
Less mobile welding systems often need 300 to 600 ft. of welding cable per arc (round-trip distance) to guarantee accessibility to distant work locations. For a heavy, eight-arc system, this could easily add up to 4,000 ft. of cable. As shown in Figure 2, 4,000 ft. of cable could weigh more than 3,200 lbs. and cost more than $8,000 to purchase.
“On job sites without inverters, we sometimes have to drag lead 200 or 300 ft., and you have to drag lead for both the welding and the work clamp. It’s really heavy and time consuming,” says Ivan Newcomb, a journeyman pipe welder with UA Local 598 working on the WTP Project. “Fortunately, inverter technology is taking over the industry, as it has with Bechtel. Inverters are so portable, we can just bring the welding machine right to the point of use, even when we’re working on scaffolds or below ground. We don’t have a bunch of leads strung all over the job. Inverters are really quite a convenience.”
Ed Enloe, a senior welding engineer with Bechtel National, agrees. “Inverters add to the economy and efficiency of the WTP Project because we don’t have to string out a lot of lead,” he says. “In fact, the Maxstars pretty much stay with the person [pipe welder]. All they do is unplug it and it just goes with them.”
A typical inverter system at the WTP Project includes a heavy-duty extension cord, Stick electrode holder and work cable (2/0 diameter) that are each 15 or 50 ft. long, plus a TIG torch with a 12 or 25-ft. cable. Supplemental lengths of welding lead are rarely needed (see Figure 3).
“Running lead is non-productive. We want welders making welds, not running lead,” says Labor relations manager George. “And welding lead is heavy. Any time you are dragging, pulling or pushing extra welding lead, you increase the opportunity to strain, sprain and twist the body.”
In fact, back pain is one of the most common musculoskeletal injuries experienced in the American workforce today, according to OSHA's Advisory Committee on Construction Occupational Safety and Health. Many of these injuries are caused by improperly lifting heavy objects and can lead to costly downtime and worker’s compensation claims (visit http://www.cdc.gov/niosh/elcosh.html for an electronic library of construction occupational safety and health resources).
As with any system, removing complexity eliminates potential sources of error, and the same is true with cable clutter. To keep cable off walkways as much as possible, operators put up hangers just for that purpose. In the course of a couple of weeks, hundreds or thousands of feet of unused lead gets left on the hangers, and the company ends up ordering even more lead.
“Job sites end up looking like a plate of spaghetti,” says Local 598 training coordinator Pete Nicacio, who began welding in 1978. He explains that welders can understandably disconnect the wrong lead when moving locations, or they adjust the wrong control back at the welding machine. Further, different shifts and crafts [e.g., pipe fitters and ironworkers] may be using the same lead, which also compounds the potential for error and subsequent downtime. Finally, when the supervisor calls for a roll back, where all the strung out cable gets reorganized, one-half to a full day of welding time is lost.
“It costs a lot of money to string welding lead, plus it’s one of the jobs welders hate the most because it takes them from their work,” says Local 598 business manager Rick Berglund.
Fortunately, none of this is a problem on the WTP site. By lifting the burden of carrying excess cable off the shoulders and backs of operators, Bechtel further reduces the chances of lost-time accidents related lower back strain or tripping. Any action taken to reduce work-related injuries increases productivity and lowers operating costs. Bechtel has also been able to save thousands of dollars in lead cost by relying on portable machines with shorter leads.
“We have a simple philosophy here on the project,” says George. “It stretches from the person with the tools in their hand to anyone designing the job or anyone associated with the work, including our tools and equipment. If you have safety, then you have quality built in, and then you’re going to have success. And that’s what we’re looking for—safety, quality and success.”
Proximity Promotes Quality
Welding codes in critical applications demand that every single weld pass visual and ultrasonic (UT) or x-ray inspection (see Figure 4). Historically, reject and rework rates may have been higher than necessary. With the heavy, immobile welders, operators sometimes made do with one weld parameter setting rather than walking back to the machine to fine tune the arc. That’s not the case with a 37-lb. inverter.
|James Hughes, a QC/Welding Engineer with Bechtel, visually inspects a coaxial pipe for weld flaws.
“I make a better weld—we all make better welds—with an inverter like the Maxstar 200 at arm’s length,” says Roy Saltz, a journeyman pipe welder with UA Local 598 working on the WTP Project(Figure 5). “With the Maxstar inverter so accessible, I always take the time to adjust my amperage. For example, when Stick welding, most welders like to run slightly different amperages on the bottom, top and sides of a pipe. Being able to adjust my amperage means I don’t have to deal with a less than optimum arc or shutdown and walk back to a distant welder which could be on another floor to change amperage.”
|Having the Maxstar inverter just arm’s length away lets Roy Saltz, a journeyman pipe welder with UA Local 598 working on the WTP Project, quickly adjust the amperages for welding on the bottom, top and sides of a pipe.
“If you have to go back and forth to a machine, you can get tired of it and settle for the settings you have,” says Steve Davis, another journeyman welder on the WTP Project who also teaches welding. “You risk having operators welding to a minimum standard. But, when you have the availability of the machine right where you can switch leads back and forth from TIG to Stick, or you can fine tune it, you’re going to have a better quality product every time.”
When TIG welding, operators use a foot pedal to control the Maxstar inverter’s amperage when the position allows, or a welder’s helper uses a remote hand control (refer to Figure 1). The welder will yell, “coming out” and the helper will begin lowering the amperage, which in turn lets the weld puddle “dry up” easily.
“If you come off the puddle too quickly, it forms an inverted dimple that could promote crater cracking,” says Davis. “The QC inspector will bust you for a crater crack every time at a nuclear facility.”
Labor relations manager Terry George sums up Bechtel’s philosophy behind using lightweight inverters on large job sites: “Inverters put our pipe welders and fitters closer to the machine controls, so they can control their own destiny. Inverters make the workplace safer, easier and more productive.”
Inclusion Free Arc Starts
Many nuclear-related welding codes require a “non-contact” TIG arc starting method to help prevent tungsten or material contamination. During an HF start, the welding power source uses a few millisecond burst of high frequency, low voltage current that helps welding current jump the gap between the tungsten and the workpiece during the arc start.
With its built-in HF start function, the Maxstar 200 inverter provides consistent, positive and “inclusion free” arc starts. The programmable HF start function also allows the operator to independently set HF starting conditions based on process or application. Many older TIG welding machines require a separate “HF arc starter and stabilizer."