Welding large-bore pipe
With a global footprint and an aim to be the number one energy infrastructure company in North America, TC Energy is constantly tracking methods to help improve quality and efficiency.
The company owns and operates 57,500 miles of pipeline and natural gas storage, 3,000 miles of oil and liquids pipelines, and 650 billion cubic feet of natural gas storage in Canada, the U.S. and Mexico. Quality and safety are top priorities, but efficiency is also critical for keeping projects running smoothly and on schedule.
TC Energy recently tested a welding and preheating process change for large-bore pipe on several construction projects and realized numerous benefits for quality and efficiency — including productivity increases of up to 52%.
More contractors and companies are making the move from traditional shielded metal arc welding (SMAW) to wire welding processes GMAW and FCAW for pipeline construction. Learn more about how TC Energy made the change and the benefits the company uncovered.
Pipe welding trends
In the Province of Alberta in Canada, the welding labor shortage is a significant issue affecting future pipeline construction and maintenance projects. The average age of certified pressure welders in Alberta is 59. Both the Federal and provincial government, labor unions, pipeline owners and contractors are all working to find more efficient ways of welding compared to traditional processes in an effort to address the skills shortage.
The province’s largest welding union, UA 488, is teaching wire-fed welding processes, and the apprenticeship program in Alberta has revised their training program to implement a greater concentration toward the wire welding processes. More contractors are moving toward wire welding thanks in large part to the efficiency and productivity improvements the wire processes can deliver without affecting safety.
As a pipeline owner, TC Energy works with contractors that complete pipe maintenance and construction to determine the best welding methods for each project. With 65 years of experience in the industry, TC Energy has established welding procedures in place, but the company encourages contractors to bring forward alternative methods for review.
“There’s a special balance you have to achieve. The newest thing may not get you the best results, so we have to weigh out the risk and the reward before implementing a change to a critical path function such as welding,” says Jason Althouse, manager–Welding and Materials, TC Energy.
After discussion with contractor partners and appropriate vetting through laboratory testing, TC Energy recently trialed several wire welding processes on jobsites in the field. For large-bore pipes on several projects in Alberta, TC Energy switched from the SMAW/SMAW processes to waveform-controlled gas metal arc welding (GMAW-WFC) and flux-cored arc welding (FCAW) processes. The company also trialed induction heating for welding preheat on those large-bore pipes, comparing it to the traditional open flame preheating method.
Traditional processes vs. wire welding
On pipe welding projects in the field, contractors for TC Energy had previously preheated the weld with a torch and used an F3 (E6010) root pass followed by F4 (E*018) SMAW for the remaining passes on thicker P1 pipe material.
For the trial of wire welding processes on some projects, TC Energy utilized Regulated Metal Deposition (RMD®) — a type of waveform-controlled GMAW process from Miller Electric Mfg. LLC — for the root pass followed by FCAW for the fill and cap passes on any pipe greater than 16 inches in diameter. They also trialed induction heating for welding preheat in conjunction with the welding process change. For pipes less than 16 inches, contractors had the option to continue using traditional thermo heating processes.
The company wanted to trial the processes with larger-bore pipes first since those projects are where any efficiency gains would deliver the most advantages. Larger pipes require more weld time, meaning productivity benefits can produce big savings.
Delivering results for quality and efficiency
TC Energy deemed the trial of wire processes a great success. Once welders became accustomed to the RMD and flux-cored processes, the quality of welds was very high and consistent, with less than 1% repair rate.
They liked the profile and bead shape created with the RMD process, finding that it didn’t create a vortex due to the weld profile. Also, because RMD is an easier and more forgiving process, less experienced welders were able to grasp it more quickly and produce great welds by following established parameters.
The profile and thickness of the RMD root pass also allowed them to eliminate the hot pass that they previously had to use with the F3/F4 processes.
The company saw significant gains with the switch. Previously, welding a 48-inch pipe approximately 1 inch thick with F3/F4 weld passes took about 11 and a half hours to complete (including flame preheating). With the change to wire processes and induction heating rather than open flame, that same weld takes five and a half hours to complete — a 52% increase in productivity.
“We saw very good results. There were numerous benefits,” says Terry Mueller, senior welding engineer with TC Energy. “The RMD and flux-cored processes are very forgiving. The workmanship rejection rate is very low.”
The results easily met the benchmarks established for the test. The ability to complete two large-bore pipe welds in one day — compared to the previous one weld a day — helps TC Energy improve efficiency and keep projects on schedule and budget without affecting safety of the piping system.
“If we can get welders to weld up two joints when usually they would take one day to do one joint, that’s just basic economics,” Mueller says.