No Turning Back: Pipe Welding System Kicks It Up a Notch

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 RMD and Pro-Pulse.

For example, welding 4 in 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,” explains 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. Because of how much metal you can put down with Pro-Pulse and still have 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 upon joint configuration, diameter, schedule, material, etc., general travel speeds for root pass welding are as follows:
• TIG: 2 ipm to 4 ipm
• Stick: 5 ipm to 8 ipm
• RMD: 6 ipm 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 are still able to put a good [second] pass in with less chance of blowing through your initial bead and still maintaining a 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 in to ¼ 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 altogether, which can save 10 minutes to 15 minutes of time on 12 in diameter Schedule 40 pipe.

EARLY ADOPTER
This shop adopted wire welding applications for pipe welding in the mid-1990s because of Mike Shinn’s drive to incorporate new technology. As a result, Sayers has now welded with all of Miller’s pulsed MIG systems, from the earliest to the most recent.