UA Local 67 Gains Pipe Welding Durability, Control and Space Savings with CST 280 Inverter
UA Local 67 of Hamilton, Ontario is opening a new school in late 2010 to train a new generation of pressure welders for work in nuclear facilities and co-generation plants. Previous generations learned on massive old rectifiers, whereas today's generation is learning on a machine no larger than a piece of carry-on luggage: Miller Electric Mfg. Co.'s CST 280
The United Association of Journeyman and Apprentices of the Plumbing and Pipe Fitting Industry (UA) has mandated its Locals to train qualified pressure welders to fill the void left by retiring members. Local 67 of Hamilton, Ontario, Canada started a school in 2004, achieved Teaching Delivery Agent (TDA) status and now graduates apprentices up to journeyman status and Red Seal certification (interprovincial standards for the trades in Canada).
The issue of skilled welders retiring is compounded by the fact that the nuclear industry in Canada is growing. In Ontario, where energy demands have continued to climb, the refurbishment and construction of new nuclear facilities has created further demand for highly skilled welders. Local 67 trains its welders in proper Stick, TIG and MIG pipe welding technique—ninety percent of what journeymen encounter in the field is Stick.
In late 2010, Local 67 will open a new training facility in Branford, Ontario, with 40 new welding booths. In addition to its own members, staff will train other tradesmen and union members to Red Seal certification in order to help meet this shortage. Whereas the retiring generations learned pipe welding on behemoth “rectifier” and “magnetic amplifier” technology welders, the newe st generation will train on welders no larger than a carry-on suitcase, and about as light: the CST™ 280 Stick/TIG welder from Miller Electric Mfg. Co.
|2nd year welding apprentice Shaun Goulbourne welds a root pass at UA Local 67’s training center in Hamilton, Ontario.
The Education of a Nuclear Pipe Welder
Apprentices spend eight hours a day in the Local 67 classroom. The first half of the day is spent on welding theory, while the second half of the day is spent on practical welding. The object at the end of the term is to do a bend test and obtain a ticket (certification that welder is proficient in a specific process/application) corresponding to the type and position of the pipe weld completed. Each year gets harder as the pipe diameters get smaller. Instructors start incorporating other processes after the third year, but for the first two and a half years are strictly focused on Stick welding with 6010 and 7018 electrodes. 6010 is the industry standard for root passes on carbon steel pipe, and 7018 is the standard for fill and cap passes. Journeymen must have their F3 and F4 tickets to get out of the Local 67 dispatch hall and on to the jobs most in demand.
“It takes us three to four years to build someone up to be a decent journeyman,” says Brian Morrissey, weld test manager, Local 67. “There seems to be a perception in welding that anyone can do it. I know a lot of people who can put two things together, but that doesn’t make them qualified to work in a nuclear power plant. Weld quality has to be top notch because you’re working on high-pressure components, and if anything ever goes wrong, the weld quality will be highly scrutinized. We push weld quality because the industry is changing. We’re not just doing steel mills anymore. We’re getting into higher technology again.”
|Miller’s CST 280 is 1/6th the size of old rectifiers and provides apprentices and journeymen with a lightweight, portable inverter that is much simpler to set and operate.
The CST 280 is designed for construction applications with varying input power considerations, perfect for welders performing plant construction and maintenance. Welders can flip between high (465-570) and low (208-230) primary input voltage ranges with a simple switch on the back of the machine. It is specifically designed for Stick welding pipe and features process settings for EXX10 and EXX18 electrodes. The entire machine is controlled by two knobs: one to set amperage and one to specify arc characteristics by electrode type, which breaks down as follows:
* Stick EXX18 Soft: This setting provides a lower dig/arc force setting for smooth weld performance. A stable weld puddle with little arc “snap” gives excellent weld bead appearance with minimal spatter.
* Stick EXX18 Stiff: This setting provides a higher dig/arc force that gives a slightly more fluid weld puddle, more arc “snap,” and reduces the potential for electrode sticking at shorter arc lengths.
* Stick EXX10 Soft: This setting provides lower dig/arc force for open root vertical up joints or joints that do not require additional current for fit up inconsistencies.
* Stick EXX10 Stiff: This setting provides a higher dig/arc force for open root vertical down joints where additional current is needed to compensate for tight joint fit up without the need to increase overall welding current.
A partially completed root pass on carbon steel pipe.
A capping pass with the CST 280 on carbon steel pipe.
“On 6010, we set the machine on a stiff setting so that we get good pounding and we get that root,” says Steve Knapp, certified welding instructor, Local 67. “We’ve got separation with root landings, preparation, gaps, and we’ve got to get that weld all the way throughout the interior side of the pipe. We’re fighting gravity from the bottom up. On an X-ray or a bend test, 6010 penetration has to be on the inside diameter of the pipe, and if it’s not, you fail. With the stiff settings on the CST 280, we work way less to get what we need inside there.”
“The wetting out with the new inverters gives you good stability and good arc control, especially when you have a key hole,” adds Morrissey. “Old rectifiers tended to come on with about 50 amps as a hot start, which just blew everything up. With the Miller technology it’s very passive. When you’re doing a root pass it gives you more dig and you’ve got great control with it. We find that it makes it far easier to weld.”
When switching to the fill and/or cap passes, a simple flip of the knob to the soft setting for XX18 series rods and an increase in voltage (depending on pipe size) is all a welder needs to start.
“We set the machine on its soft setting when we go to the 7018 series for the fill and cap passes,” says Knapp. “We find that we get a lot more buttering. A lot of our stuff is done in the 6G position, which is on a 45 degree angle and we run a lot of stringer, so there’s a lot of blending of welds.”
“The soft xx18 setting when using low hydrogen electrodes is perfect for capping,” says Morrissey. “You get very smooth, very fine ripples.”
Simplifying the control settings of the machine makes training easier in that it allows apprentices to focus on technique rather than worrying about settings. Taking that variable out of the hand of the welder ensures consistency and confidence in one of the trickiest welding specialties in the industry. While the rest of the industry catches up to inverter technology, however, many of the apprentices will still encounter the old rectifiers out in the field.
“They’re kind of spoiled being here in the shop with the new inverters,” says Knapp. “When they go out to jobsites, our big steel mills and co-generation plants, they never get these types of machines. The CST 280 helps a welder a lot. If you know how to use the machine and the proper settings, that machine will help a welder be better. When they get out into the field and don’t have that, they really have to draw back to the core of what we’re teaching them.”
Big Power in a Small Package
Weighing in at only 41 lb., the CST 280 provides pipe welders with industrial-strength welding performance in a very portable design. The welder provides 5 to 200 amps of Stick/TIG welding output using single-phase power and 5 to 280 amps running off three-phase power. Knapp reports that it is about 1/6th of the size of their old rectifiers, and Morrissey explains what that means to the layout of a training booth and to a journeyman in the field, especially in nuclear facilities and refineries where space is tight:
“We chose them because we actually put them in our booth,” says Morrissey. “They’re small, compact. In the construction industry, if you’re out in the field, you don’t need a crane to move them around. A man could pick them up just like a suitcase and bring it right up into his welding area wherever he’s working. So they’re very portable.”
Having a machine close to you versus stringing out dozens of feet of welding lead and cable not only reduces hassle, it makes it easier to make adjustments to the machine as you work. It also features remote amperage control provided through a 14-pin receptacle on the front of the machine. This permits the use of standard remote amperage control devices.
Having the machine in the booth with the apprentices, and next to the action in the field, exposes it to more grinding dust and weld particulate than if the machine was kept away from the work, but neither Knapp or Morrissey report that to be a problem. The only maintenance Knapp reports having done on the machine is blowing the dust out and it hasn’t missed a beat.
“The machines that we have in our shop right now, we’ve had them two years,” says Morrissey. “They run everyday, eight hours a day, and I’ve never had any breakdowns yet. I would unequivocally recommend it to any UA Local or pressure vessel/pipe fabricator.”
And, in the grand scheme of things, Morrissey believes it’s absolutely the right tool to train the next generation of UA journeymen:
“When you give someone something really difficult to do, they lose interest fast. With the new inverters, once you get the confidence up and get them going and let them understand the process, now you can take them to something that is ancient—the old rectifiers—and they’ll have an easier understanding. It’s easier to go back than it is to go forward.”
Steve Knapp, certified welding instructor, UA Local 67, and 2nd year welding apprentices Alicia Komejan, Shaun Goulbourne, Nathan Guthrie and Devon Wilson.