NO TURNING BACK:
PIPE WELDING SYSTEM KICKS IT UP A NOTCH
Using the PipeworxTM Welding System from Miller Electric, Shinn Mechanical has increased its pipe fabrication quality and productivity with flatter bead profiles, good sidewall tie-in for 30 percent less grinding, and superior weld puddle control – with no wire rejects in over a year.
Posted: September 28, 2011
PROGRAM STORAGE
As noted earlier, this shop works to qualify many procedures for the RMD and Pro-Pulse processes. To facilitate quick changeover between these processes, Sayers uses a dual wire feeder that stores four welding programs on each side. He uses the right side to put in the root pass. “I’ve got my RMD setting, MIG settings for different applications and then I’ve also got a pulsed setting for certain applications,” he says. “I can put a bead into anything with any of those four settings. Then I just switch over to my left side gun, and that’s where my Pro-Pulse side is for my fill and my caps. I can generally, off of those four programs, run anywhere from 2 in Schedule 40 pipe up to as large a pipe as there is” just by adjusting wire feed speed.
To switch between programs, Sayers uses the trigger select function that eliminates the need to return to the feeder’s control panel to switch between passes.
ARCS DESIGNED FOR PIPE WELDING
Unlike other multi-process welding systems, PipeWorx utilizes arc characteristics that are specifically designed for pipe welding. For example, the arc characteristics, metal transfer, wet out and puddle control of Pro-Pulse and RMD produce optimum results in the joints and welding positions typical of pipe welding.
“You can get out of position a little easier and it seems to hold a puddle better,” observes Sayers. “RMD also leaves less wagon tracks in your weld in the side walls of the pipe. When you’re doing high quality work, you don’t have to grind out nearly as much of your base metal to get down to clean metal again [before] your second pass.” Sayers estimates that RMD reduces grinding time by 30 percent compared to conventional short circuit MIG.
On 12 in diameter pipe or larger, RMD can save five minutes or more of grinding time per joint, which helps Sayers accomplish his daily goal of 200 weld inches per day. He continues to describe RMD by saying, “It looks closer to a TIG weld. It lays down flatter than short circuit welding does and doesn’t seem to fall in as much. It tends to hug the sides of the walls of the pipe to where it does have the tendency of laying flatter, maybe . . . a little wider and get really good penetration. It doesn’t seem to drop in nearly as easily as short arc does. This way, you don’t have excessive penetration on your root pass.”
OPERATOR FRIENDLY
Pipe fabricators have traditionally refused to adopt conventional MIG processes or, if they did, limited their use to non-critical applications. Fabricators felt that consistently producing code-quality welds with no or little rework required a high degree of skill and significant training.
To address these skill and training issues, Miller designed RMD so that novice welders could learn it in a matter of days and experienced welders could learn it in hours. “RMD runs extremely smooth,” adds Sayers. “It is easy to tell when you do have a problem because it will be noticeable. The machine will let you know to stop because the arc will have a crackle sound that is not familiar. When it’s running consistently, it always has the same sound . . . it does not change.” Further, “if it creates a little bit of a keyhole, you just slow down, and it seems to fill itself right back in.”
One of the biggest challenges in pipe welding occurs when two sections of pipe are misaligned. This is commonly known as a “high/low” situation. Sayers points out that if the misalignment is within 1/8 in, RMD “generally has no problem picking up both of those edges and doing a good tie-in [so] you don’t have to try to go back and grind or try to make a repair. [It] doesn’t thin out your walls too much to where when you try to put your secondary pass in it doesn’t want to blow through.”
RMD provides these benefits by precisely and consistently controlling metal transfer. Uniform droplet deposition produces a stable and more controllable weld puddle (as opposed to the “explosion” of traditional short circuit transfer). RMD enables consistent tie-in to the sidewall, compensates for high-low misalignment, easily bridges gaps of up to 3/16 in and creates more consistent root reinforcement on the inside of the pipe.
POINT OF NO RETURN
Through August 2010, Shinn Mechanical had gained nearly two years of experience with the RMD and Pro-Pulse processes and one year with the PipeWorx Welding System. In that time the fabricator has paid for its PipeWorx system many times over. Its shop has proven that this new welding technology consistently produces X-ray quality results in critical applications for root, fill and cap welding. Add in productivity-enhancing features such as quick process changeover, trigger select, and welding speeds that help accomplish a daily goal of 200 weld inches, and there is no way pipefitter/welders such as Steve Sayers will go back to older welding technology.
“With the PipeWorx setup that we have and all of the things that we brought in with our [new] shop, it’s unbelievably fast,” he says. “The fabrication time you save is just unbelievable. I could not imagine trying to weld pipe any other way.”
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