Root pass welding change
Change can be hard, but leaders in the pipe welding industry are upping their game by changing from the status quo.
Meeting stringent quality requirements and demanding project timelines are critical in pipe welding, both in the field and the shop. Having the capabilities for advanced welding processes when customers call for them means contractors can capitalize on those opportunities and bid on more jobs.
Approximately 80% of the costs associated with welding are related to labor. Giving welders technology and equipment that improves their productivity can save significant time and money.
Here are five benefits a switch to the Regulated Metal Deposition (RMD®) process for open root pipe welding in shop and field applications can deliver.
5 benefits of converting to wire welding
- Faster process changeover
Using advanced wire processes like RMD (a modified short-circuit MIG process) and pulsed MIG welding allows for simple process changeover between weld passes with the push of a button.
This greatly reducing switch-over time compared to using TIG and stick welding, which requires changing polarity between each process switch. With PipeWorx 400 and XMT® 350 FieldPro™ with Polarity Reversing systems, operators can change polarity with the push of a button — without moving the electrical connection. In addition, RMD and pulsed MIG can provide a one wire, one gas solution that reduces time spent on changeover.
In the shop, a welding system with a dual feeder option allows flexibility to set up each side with any gas or filler metal combination required. This delivers even more time savings in setup and switch over. Operators can just pick up the desired welding gun and weld.
- Improved productivity
RMD and advanced wire processes are much more productive than TIG and stick welding for several reasons.
The wire-fed processes offer travel speeds that are three to four times those of TIG or stick welding. Wire processes are typically easier for new welders to learn than TIG and stick welding, which saves time in training. In the PipeWorx 400 system and the ArcReach® Smart Feeder, RMD is also fine-tuned for open root pipe and vessel welding. This makes the process more efficient for producing code-quality welds.
Pipe fabricator Dixie Mechanical doubled welding productivity — completing twice as many welds in the same amount of time — with a process switch. The company had been welding stainless steel pipe with a TIG root pass and argon back purge followed by flux-cored fill and cap passes. They switched to an RMD root pass and eliminated the time-consuming and costly back purge.
Kiewit Power Constructors also increased productivity when they switched to RMD and flux-cored welding for several power plant projects. In some instances where Kiewit previously TIG welded the root pass for P11 and P91 pipe, they used RMD without a purge. For the remaining passes, they used flux-cored welding instead of stick.
- Optimized arc performance
The RMD process is engineered with a high-quality arc specifically tailored for open root/joint pipe and vessel welding.
Early prediction of the short clearing enables the power source to quickly reduce the available current. This minimizes the excessive arc force on the puddle and results in a calm, controllable puddle.
The smooth arc and bead profile wets out nicely — helping welders of all skill levels produce high-quality welds.
RMD and advanced wire processes aren’t limited to shop welding applications, either. With the ArcReach Smart Feeder, you get consistent arc performance on the jobsite for multiple weld processes — even when weld cables are hundreds of feet long.
- Eliminate back purge
Using RMD instead of TIG for the root pass on stainless steel and chrome pipe welds may allow operations to eliminate the back-purge process. Back purging provides gas shielding on the back side of the joint while welding, but it adds significant time and money to the process.
It can require 20 to 30 minutes each time, depending on pipe size, to set up the argon shielding gas and tape the pipe ends for purging. In addition, the argon gas used for back purging adds to consumable costs. Back purging can also introduce safety hazards to operators who can be overcome by the argon gas and suffer inert gas asphyxia. Eliminating back purge saves time and money and reduces the risks involved with the process.
With RMD, welders can more easily control the weld puddle, welding speeds and heat input. A lower heat input allows the weld puddle to freeze faster. All of these factors combine to result in a less turbulent weld puddle and smoother shielding gas flow. This allows the gas to push through the open root and protect the weld's back side from sugaring, or contamination. Because the puddle freezes so quickly in the RMD process, such gas coverage is only needed for a short time — eliminating the need for back purging.
- Train new welders faster
As the industry faces a continued shortage of skilled welders, contractors are looking for ways to train new welders faster. This may be especially critical on large plant construction projects that span two to three years and require dozens of full-time welders.
Compared to stick and TIG welding, wire-fed processes like RMD are generally easier to learn and use, reducing training time.