- RMD provides better appearance and quality compared to TIG welding
- Faster travel speeds and dramatically reduced operator training time
- Extremely tolerant of high-low fit up -- RMD can bridge gaps up to 3/16-in.
“It almost welds itself,” says John Silla, co-owner Stainless Piping Systems (SPS), talking about RMD™ (Regulated Metal Deposition), the new modified short circuit MIG process his company just adopted for root pass welding. “On schedule 40 stainless steel, we save about 30 percent of our welding time and eliminate the need for a hot pass. On schedule 10, we save about 20 percent.” At today’s labor rates, this can save SPS about $25,000 a year compared to using the TIG process.
Yet, as impressive as these savings are, they are of secondary importance to Silla, whose main concern is quality. That’s why clients come to SPS and what sets SPS apart from its competitors. To achieve high quality, SPS used to TIG weld all of its pipe root passes. Other processes couldn’t rival TIG for quality and appearance, according to Silla, but the new process changed his opinion. “RMD gives us a nicer root pass than TIG,” he says. “The cost saving is an added benefit since it allows me to not only provide the same or better quality than before, but also to compete on price with the non-union shops in the area.”
Silla is one-fourth owner of Stainless Piping Systems, Inc. of Toronto, Ontario. SPS specializes in the engineering, fabrication and installation of complete process piping systems for the industrial process, pharmaceutical, water treatment, food & beverage, automotive, semi-conductor and medical industries.
|John Silla, co-owner of Stainless Piping Systems, shows some of the detailed documentation for which the company is known.
With a customer list that reads like a who’s who of the most demanding customers (see www.stainlesspiping.com), SPS maintains the highest quality standards. Its quality control manual has been certified by Technical Standards and Safety Authority (TSSA) in accordance with the Ontario Boiler and Pressure Vessels Act, and its welding procedures and operators are registered and certified to comply with ASME Section IX. SPS can conduct non-destructive testing, such as radiographic examination, boroscoping, and hydrotesting, in its shop.
“We’re very precise in our work; all of our welds are cleaned in a bath, and when we say we’re going to do something, we come through,” Silla says. “We’re leading edge when it comes to our documentation. Pharmaceutical companies, especially, want the accountability. We can produce complete documentation packages that trace all of the materials and welds.”
When raw material comes in, workers cut it to size and may prep the material by beveling the ends or cutting holes. From there it goes to the fitters and then to the welders. Finally, it’s cleaned, inspected and sent for installation.
SPS is a union shop, its welders members of United Association Local 46, which until recently didn’t have a welder apprentice program. When it started one, SPS got the first apprentice. SPS doesn’t hire many welders; the company has little turnover, but when it does, the first thing Silla does is get them to put aside any bad habits they may have picked up by training them himself.
The Trick With Stainless Is…
“A welder may be good at welding mild steel, but stainless is a different animal,” observes Silla, who has been welding since he was 13 years old. Silla, whose father also was a TIG welder, started by welding coffee trucks, and later became a pipe fitter. “I know stainless like the back of my hand,” he says.
He sees two main issues with new welders. The first, he says, is “They can be sloppy. If you take pride in your work, you’ll be a good welder. Secondly, they put too much heat into the weld. Stainless doesn’t need a lot of heat. Too much heat will cause it to crystallize and lose its properties.”
When teaching a new welder to TIG weld, Silla stresses learning to read the puddle. “I look for consistency,” he explains. “If the puddle is too big, it’s going to fall through. If it’s too small, you won’t get the penetration you need.” It could take a new welder months to learn to read the puddle and achieve the SPS-quality TIG welds, Silla says. And TIG welding does still have a place in SPS, especially on smaller diameter (less than 8 inches) schedule 10 pipe and tubing, but on larger diameter schedule 10 or on schedule 40 pipe, the new modified short circuit MIG process is changing the way things are done.
Easy to Learn. Easy to Use.
With standard MIG, it takes a great deal of skill to produce code-quality root welds; many fabricators shun the process, and many end users do not include it in their list of approved procedures. A new technology has now made MIG a practical, if not a first, choice. Faster travel speeds and greatly reduced operator training times are just some of the RMD™ process’ benefits.
RMD™ (Regulated Metal Deposition) technology, is a modified short circuit MIG process that anticipates and controls each short circuit, then reduces available welding current to create a consistent metal transfer. By comparison, standard short circuit MIG presents a more unpredictable, more violent short circuit and a more turbulent puddle that is difficult to control and ill suited for root pass welding.
RMD’s preci sely controlled metal transfer provides uniform droplet deposition, creating only small ripples in the weld puddle and producing a consistent tie-in to the sidewall. This, along with its ability to maintain the same arc length regardless of stick-out, makes it much easier for even apprentice welders to control the puddle and quickly and easily learn to create uniform, high-quality welds.
“This is great,” says Silla. “My welders can go right into production. They [Miller] say an experienced welder can learn it in a day or two. It didn’t take us that long. We had one experienced welder learn the process and he was immediately—I’m talking with the first joint—he was immediately productive.
In addition to the short training time, the new process had several immediate benefits for SPS. Enough metal is put down during the root pass that the welder can go right to the fill passes, eliminating the hot pass. No hot pass is required on schedule 10, which is why the time savings are greater on the thicker pipes.
|Vince Peca was immediately productive with the new modified short circuit process, saving about 30% of the time on schedule 40 and 20% of the time on schedule 10 pipe.
The process is also extremely tolerant of high-low fit up. RMD can easily bridge gaps up to 3/16 in. “There’s always a high-low mismatch,” says Silla. “You can’t get rid of it. You just try to minimize it. It takes skill with TIG to bridge the difference. This [RMD] is so much easier.”
The Root Pass that “Almost Welds Itself”
Rather than perform position welds, SPS prefers to rotate the pipes and keep the gun stationary, eliminating the challenge of out-of-position welds. This makes for one, long continuous weld, which saves time as opposed to stopping and starting. Also, stops and starts may require the welder to grind out any porosity, taking additional time. And stops are also good excuses for taking a cigarette break. At union wages that time can quickly add up. SPS is now considering taking the ease of the process one step further.
“We tried one experiment,” Silla recalls. “We mounted the MIG gun on a pipe stand, adjusted the rotation speed and set the trigger lock. We didn’t even hold the torch, and we had awesome results with that. It also lessened operator fatigue. You just have to watch the weld and remove the tape.”
The tape is used to contain the backing gas in the pipe. The new processes can eliminate the need for backing gas in welding stainless steel, but many companies, especially pharmaceutical companies, still require it.
“We’re still experimenting with the stands, but…[RMD] really does almost weld itself.”
|As John Silla watches, Vince Peca makes a root pass with the RMD process. Whenever possible, SPS rotates the pipe and keeps the gun stationary.
Same Quality—Lower Cost
What does this mean for SPS? On schedule 10 (diameters above 6 inches), about 20-percent time savings per weld, Silla notes. On schedule 40, those savings increase to about 30 percent. “On schedule 10, we still need a root and a cap pass, but the root pass is much quicker,” Silla says. “On schedule 40, the root pass is quicker and we’ve eliminated a hot pass.”
RMD can rival TIG for appearance and increase productivity by up to 30 percent. Because the process is so easy to use, SPS is experimenting with using stands to hold the gun while welding, freeing up both of the operator’s hands.
Although, SPS prides itself on the quality it provides—the quality of the work, the services and even the documentation, which may include weld logs that trace each weld—these time savings translates into another competitive advantage for SPS.
“Customers are always concerned with price,” says Silla. “We may have lost a few jobs to non-union shops, only to get the customer back because the quality wasn’t there. But we’re a union shop; we cost more than a non-union shop. And although quality of our work, our services and even our documentation are unrivaled, with some customers the bottom line is always price. This new processes better lets us compete in that area, too. Our quality is the same, if not better, but we’re even faster.”
Typical costs for a union welder around the Toronto area is about C$80 an hour. Silla estimates that half of a welder’s time is spent on the root pass, so if he saves 20 to 30 percent of that that, he’s saving $8 to $12 an hour or potentially $320 to $480 a 40-hour week per welder. That’s $24,960 a year, more than enough to buy two new welders. Or, as importantly to Silla, enough to give SPS’s customers the quality they expect at an even more competitive price.
Silla’s customers are becoming familiar with benefits of the modified short-circuit MIG process. “We had one customer asking for the process,” Silla says. “They know our quality, but they’re always looking for a faster time and a lower price. Fortunately, I was able to tell him, “You know what? I just bought a machine.”
To find out more about RMD, see
"Welding Smarter On Stainless"
"Advancements in Pipe Welding Processes and Techniques"
"New GMAW Options Offer Increased Productivity for Pipe Fab Shops"