“We haven’t had a wire reject in well over a year,” reports Shinn Mechanical pipefitter/welder Steve Sayers. The advanced MIG welding outputs of Miller’s PipeWorx™ Welding System — RMD™ and Pro-Pulse™ — enable Sayers to make code-quality root, fill and cap welds while completing them three to four times faster than TIG or Stick welding. Other benefits include:
- “Two second” process changeover — just with the touch of a button —helps achieve 200 weld inches per day per operator objective.
- Multiprocess capabilities, including HF DC TIG arc starts for code work.
- Flatter bead profiles and good sidewall tie-in for 30 percent less grinding.
- Operator-friendly controls, superior weld puddle control.
“It’s always better to have the right tools,” says Mike Shinn, president of Shinn Mechanical, Inc., Kent. Wash. “My philosophy is that even if you can save 2 or 3 percent on every job, and you do that over time, it’s a big percentage at the end of the year.” Considering that the overhead rate for pipefitter/welders in the Pacific Northwest exceeds $1/minute, savings add up quickly.
Founded in 1994, Shinn Mechanical serves the industrial piping, processing, HVAC, refrigeration and plumbing markets, welding everything from 1/2-in. diameter 316L stainless steel to A106 double-containment pipe to 34-in. diameter A53 black pipe. It also fabricates complete platforms or skids. Based minutes from Seattle’s Sea-Tac airport, customers include those in the aerospace and military industries, as well as in healthcare construction.
Among its recent money-saving accomplishments, Shinn Mechanical reduced material handling time by at least 10 percent — and increased safety — by building and designing “the ultimate welding boom” (learn more about the boom).
On the welding side of operations, Shinn Mechanical has increased MIG weld quality to the point where operators can’t remember their last rejected weld, reduced grinding time by 30 percent and reduced process changeover time to “two seconds.” Further, its operators complete joints three to four times faster than shops that rely solely on Stick and TIG technology by using the new PipeWorx™ Welding System, a pipe-specific multiprocess welding system from Miller Electric Mfg. Co. and recommended by Jim Hedberg, a representative from Pacific Welding Supply.
PipeWorx features the Pro-Pulse™ pulsed MIG and RMD™ (Regulated Metal Deposition) processes, as well as Stick, TIG and Flux Cored processes that have been optimized specifically for pipe fabrication. It also provides traditional MIG processes. Switching between processes requires pushing one button with no need to manually switch polarity, cables or hoses, thus increasing productivity and eliminating a potential source of errors.
Fast and Good
While some code requirements and weld procedure specifications require TIG and/or Stick welding, Shinn Mechanical has worked with its customers to qualify as many applications as possible for the RMD and Pro-Pulse.
For example, welding 4- and 6-in. diameter pipe generally requires two passes. “We would run an RMD root with a Pro-Pulse cap. We go to Pro-Pulse on every size that requires more than two passes whenever codes and procedures allow,” says Steve Sayers, a pipefitter/welder with UA Local 32 who has worked at Shinn Mechanical since 2005.
“It would be a minimum of double, if not three times faster, to put in an RMD root as opposed to a standard TIG or Stick weld,” he continues. “With the Pro-Pulse capabilities, because of how much metal you can put down with still having an X-ray-quality weld, your production times [are] three to four times faster [with] the same quality of work you could [do] with a TIG or Stick procedure. We haven’t had a wire [welding] reject in well over a year.”
Miller engineers have confirmed Sayers’ estimates for RMD. While productivity rates vary depending on joint configuration, diameter, schedule, material, etc., general travel speeds for root pass welding are as follows:
- TIG: 2 to 4 inches per minute (ipm)
- Stick: 5 to 8 ipm
- RMD: 6 to 12 ipm
Sayers notes that RMD puts in a “heavier deposit of metal than you do with short arc. When you grind your bead out, you’re still able to put a good [second] pass in with less chance of blowing through your initial bead and still maintaining quality bead on the inside without distorting it with too much heat from your secondary pass.”
On average, the RMD process creates a root pass weld with a 1/8- to 1/4-in. throat. In many instances, the amount of root pass metal deposited can support the heat input requirements of a pulsed MIG fill pass. In many applications, Shinn Mechanical eliminates the traditional hot pass, which can save 10 to 15 minutes of time on 12-in. diameter, Schedule 40 pipe.
Shinn Mechanical adopted wire welding technology for pipe welding in the mid-1990s because of Mike Shinn’s drive to incorporate new technology. As a result, Sayers has welded with all of Miller’s pulsed MIG systems, from the earliest to the most recent.
“I started out welding with the 60M series feeder with an XMT™ 304 as the power source, to a 64M with a Phoenixä 456,” he says, referring to Miller’s older “M series” wire feeders, which contained the controls necessary for pulsed MIG welding. “Then we moved up to the PipeProä and now we’re on to the PipeWorx. The PipeWorx is really a superior machine for pipe welding compared to everything that’s been in the past. It runs unbelievably smooth. It’s really simple to pick up and learn how to use that machine, and RMD is easy to run.”
Sayers touches on two key features of the PipeWorx — ease-of-use and arc performance — that result from Miller engineers listening to the workflow and quality needs of pipe fabricators.
One for All
On any given day, pipefitter/welders need TIG, Stick, Flux Cored, MIG and pulsed MIG welding capabilities. A traditional pipe shop would equip its welding areas with a TIG/Stick welder and perhaps a multiprocess welder, which typically doesn’t have a high frequency (HF) start function.
“With the PipeWorx, you have the ability to have a high-frequency start, which is huge when you’re doing quality work,” says Sayers. “Now you don’t have a scratch start, which always takes a chance of leaving a tungsten inclusion. [PipeWorx] keeps us from having to buy an additional welding machine just to have the high-frequency capabilities in the start, which is a huge money savings.”
The PipeWorx’s push-button process change capabilities also provide a significant savings. In a matter of seconds, operators can switch between:
- DC TIG, with Lift-Arcä starts or high frequency for non-contact arc starts
- Stick, with arc performance optimized for E6010 or E7018 electrodes in pipe applications
- Flux Cored
- Conventional MIG
- RMD or Pro-Pulse processes
“Let’s say I just did a Pro-Pulse cap and then wanted to switch back to a TIG start,” says Sayers. “It can take me a minute to grab my torch, my foot pedal, set it up and I’m ready to go within a minute’s time between changeovers. And the only reason it takes that long is because my TIG torch and foot pedal are all wrapped up. In order to change between the TIG setup and the wire setup, it takes all of two seconds. Just walk right over to the machine, pull the trigger on either one of the guns and I’m right back into the MIG position.”
With all other multiprocess welding systems, process changeover takes five to 10 minutes. Operators usually need to change the welding lead (TIG torch to Stick electrode holder to wire feeder, etc.) as well as swap the work lead because different processes require different polarities. In pipe fabrication shops, MIG, Stick and Flux Cored use reverse polarity (DCEP) where TIG uses straight polarity (DCEN).
Pipefitter/welders typically change processes an average of eight times per day, which adds up to a total of 40 to 80 minutes of changeover time. Using a conservative overhead rate of $60/hour, changeover costs of old welding systems quickly add up:
- $40 to $80 per day per operator
- $200 to $400 per week
- $10,000 to $20,000 per year
By eliminating unproductive process changeover time to “all of two seconds,” coupled with faster welding speeds, Shinn Mechanical pipefitter/welders can easily achieve their daily goal of 200 weld inches (i.e., completing 20 joints on 10-in. diameter pipe).
As noted earlier, Shinn Mechanical 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 all the way 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, which eliminates the need to return to the feeder’s control panel to switch between passes.
Arcs Designed for Pipe Welding
Unlike other multiprocess welding systems, the PipeWorx features arc characteristics 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 that, “It looks closer to TIG-like. It lays down flatter than short circuit welding does. It 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. That way, you don’t have excessive penetration on your root pass.”
Historically, pipe fabricators refused to adopt conventional MIG processes, or they limited 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 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,” says Sayers. “It’s 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’s not familiar. When it’s running consistently, it has always the same sound; it doesn’t 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, known as a “hi/lo” situation. Sayers states 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 because it precisely and consistently controls 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
As of August 2010, Shinn Mechanical has had nearly two years of experience with the RMD and Pro-Pulse processes and one year with the PipeWorx Welding System. In that time, the company has paid for its PipeWorx Welding System many times over. It 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’s no way pipefitter/welders such as Steve Sayers would go back to older welding technology.
“With the PipeWorx setup that we’ve got and all of the things that we’ve brought in with our [new] shop, it’s unbelievably fast,” he says. “The fabrication time you save is just unbelievable. I couldn’t imagine trying to do it any other way.”