Project Completion Marks Contractor’s Second Success Using Advanced Weld Method
It was a challenging weld job: An inlet and rack line expansion MarkWest Energy Partners needed built in just five months at one of its gas processing facilities. The project—located at the Sherwood Complex in West Union, West Virginia—involved a series of exterior piping that ranged from 2 to 30 inches in diameter and required more than 300 heavy wall weld joints.
To meet MarkWest’s expectations, Graycor Industrial Constructors, the project’s general contractor, knew the aggressive schedule required streamlining its workflow—particularly, the large number of welds needed. Following the project’s start in February 2017, heavy rains in the spring months presented another challenge as the team dealt with delay impacts that threatened the project’s timetable.
Using the Right Tool for the Job
For years, construction companies have sought a faster, easier welding technique to make single-sided root welds on pipe. Traditional methods include gas tungsten arc welding (GTAW) and shielded metal arc welding (SMAW), better known as ‘TIG’ or ‘stick.’
Graycor’s team chose an advanced weld process, one that enabled them to overcome the challenges and successfully complete the expansion—and welds—within the needed time frame. Prior to this project, the company first proved the method successful in its own fabrication shop and then in the field on a project completed in 2016 for MarkWest in Dallas, West Virginia.
At Sherwood, the operations team used a modified short-circuit gas metal arc welding process (GMAW-MSC). This welding process—whether using Lincoln Electric’s Surface Tension Transfer® (STT) or Miller Electric’s Regulated Metal Disposition™ (RMD)—achieves the time and cost efficiencies required in today’s competitive construction market.
The GMAW-MSC transfer process produces a low-hydrogen weld deposit, making it easier to achieve a high-quality root weld in all positions. Welders can complete a root pass using GMAW-MSC in lieu of more traditional methods, and then switch to a different wire welding process for the fill and cap when using an advanced multi-process welding power source.
MarkWest’s project required welding 20-inch diameter by 0.594-inch wall thickness stainless steel piping—normally welded using a back purge. To increase efficiencies and reduce costs while maintaining a superior weldment, Graycor chose the GMAW-MSC process with no gas backing over a GTAW root and finished with a flux cored arc welding (FCAW) fill and cap.
To support the effort, Lori Kuiper, welding engineer at Graycor, says the company qualified a welding procedure specification allowing stainless steel pipe to be welded without a back purge. “This not only saved considerable money in purge gas, but also time costs associated in welding with the faster processes,” she explains. Site operations estimated back-purging the stainless line would cost approximately $40,000 in gas alone.
The Proof is in the Weld
Graycor trained and qualified four local welders to use the high-efficient processes. To minimize the learning curve and reduce rework, a newly developed weld tech position was added to Graycor’s operations staff which supported the successful welding from initial training to field installation.
The results were better than expected with zero defects and dramatically improved weld times. After the first couple of welds, the welders became comfortable with the processes and were faster at switching over to FCAW. The time to weld the 20-inch stainless (at 0.594-inch wall thickness) improved to a fraction of the initial welding man-hours—significantly improving the man-hours bid for the work.
FCAW fill and cap was also successfully utilized on the 24-inch diameter (at 1.22-inch wall thickness) carbon steel pipe in lieu of the SMAW process. Man-hours were significantly reduced using the wire process compared to the work hours needed using SMAW. While a little extra tenting—or ‘hooching’—was needed with the wire processes, the returns far outweighed the negatives.
“In construction, we’re always looking for an edge above our competition,” says Kuiper, who expects the time saved using GMAW or FCAW processes will give Graycor an advantage over bidders offering conventional welding methods.