Marine Repair Facility Completes 7,044 Feet of Welds, Achieves Zero Defect Rate with New Pipe Welding Technology
April 12, 2010
RMD and Pro-Pulse pipe welding processes from Miller also help Sause Bros. save six to eight man-hours and $500 per pipe by eliminating the need for a chill ring.
Russ Gleason, yard superintendent, Southern Oregon Marine
Southern Oregon Marine, Coos Bay, Oregon, is the marine construction and repair division of Sause Bros., whose services also include ocean towing, cargo handling and ship assist. In November 2008, TITAN Salvage asked if we could weld 12 jack-up barge pipes to API-2B specifications. The pipes had a finished length of approximately 145 ft., an outside diameter of 5 ft. 11 in. and were 1-1/2-in. thick. The average single pass weld was 18 ft. 4 in. long, and each joint required approximately 32 passes for a total of 587 ft. of welding per joint.
Using new welding equipment and pipe welding technology from Miller Electric Mfg. Co., coupled with an internal training program, Southern Oregon Marine welded a total of 7,044 ft. of weld and achieved a zero defect and repair rate. Compared to our previous process, we save six to eight man-hours and $500 per pipe by eliminating the need for a chill ring.
Extending the Piping
TITAN Salvage, a Crowley company, completed a difficult and well-publicized job with its removal of the New Carissa wreck (read about that here) in 2008. TITAN used our Coos Bay facility as a staging area for its equipment at the end of the job, including the jack-up barges Karlissa A and Karlissa B, which have a combined clear deck space of 1,880 square meters. Before moving these barges to their next work site, TITAN requested that we extend the length of the 12 jack-up pipes from their current 110- to 113-ft. lengths to approximately 145 ft. by welding on additional pipe sections, which TITAN supplied.
|The jack-up barge Karlissa A, positioned at sea for wreck recovery. The Karlissa A and Karlissa B have a combined clear deck space of 1,880 square meters.
Previously, we had never welded pipe with a diameter larger than 42-in., and we did not have mechanized or submerged arc welding equipment. However, we had recently modernized our welding equipment fleet with the addition of 450-amp multiprocess inverters and two systems with processes designed specifically for pipe welding. These processes, developed by Miller, are called RMD™ (Regulated Metal Deposition), which is a modified short circuit MIG process used for welding the root pass, and Pro-Pulse™, a pulsed MIG process designed specifically for welding the second and subsequent passes on pipe (learn more).
We explained the benefits of these new technologies to TITAN, showed them what our procedure would be and assured them that the work would be done to API-2B specifications, which included ultrasonic testing.
|TITAN requested that we extend the length of the 12 jack-up pipes from their current 110- to 113-ft. lengths to approximately 145 ft.
The beveling was accomplished using a wrap-around, track-mounted cutting torch using acetylene gas and a #1 cutting tip. The pipe was beveled at an angle of 30 degrees with a root face of 1/16 in. The finished root opening after fit up was 1/8-in. and tacked and welded using the RMD and Pro-Pulse processes and a SuitCase™ 12RC feeder.
Pipe cutting and beveling tolerances had to be held to within 1/16 in. per foot of diameter, with a maximum allowable deviation of 1/4 in., measured with a square and straight edge across the end of the pipe.
The extension pipes varied in length, allowing us to match longest existing jack-up pipe with the shortest extension pipe and vice versa to achieve the desired length the customer requested. Each extension pipe was placed on the rollers and aligned to achieve the proper face-to-face fit up for match burning, as well as rolled to position the existing longitudinal welds so that they were no less than 5 ft. apart. After set-up, the pipes would be marked, cut and re-aligned and verified for straightness and fit-up before welding.
Additional work included removing lifting eyes and 4 in. blow-down pipes for displacing sand or mud while driving pipes into the sea floor. We installed lifting eyes and new watertight plates in the extension pipes and we sealed the holes where the blow-down pipes existed.
Using the RMD process allowed us to bridge the 1/8-in. root gap, as well as any deviation in the bridge height without the need for a backer plate or ring, greatly speeding up the weld process and minimizing interior cleanup or re-work. We estimate eliminating this task saved six to eight hours in time, plus materials costs. Total savings on the root pass alone is estimated at $500 per joint compared to welding the root pass with conventional short circuit MIG or Stick.
|Using the RMD process allowed us to bridge the 1/8-in. root gap, as well as any deviation in the bridge height without the need for a backer plate or ring, greatly speeding up the weld process and minimizing interior cleanup or re-work.
Because the RMD and Pro-Pulse processes use the same filler wire and shielding gas (in this case ER70S-6- .035 wire and C-10 gas), we could continue welding the next two passes using Pro-Pulse without any changes, saving an estimated 15 minutes of time compared to our old methods (which required changing consumables and polarity or changing machines).
We dedicated a two-man crew to welding with the RMD and Pro-Pulse processes, each welding half of the pipe from the bottom up. After three weld passes, this crew moved to the next pipe and a second two-man crew performed the fill and cover welds using Miller’s XMT 456 inverters paired with SuitCase X-TREME™ 12VS-suitcases’ running .052-in. diameter Hobart Brothers’ Excel Arc™ 71 flux cored wire with 100 percent CO2 shielding gas.
|We dedicated a two-man crew to welding with the RMD and Pro-Pulse processes, each welding half of the pipe from the bottom up.
The average single pass weld was 18 ft. 4 in. long, and each pipe required approximately 32 passes for a total of 587 ft. of welding that took two days to complete. All welding was done in position without use of pipe rollers. Using four two-man crews, welding continued 24-hours-a-day to keep the pipe at temperature to reduce concerns related to hydrogen cracking.
Ready for Testing
Each weld was ground flush with no undercut or cupping allowed in preparation of non-destructive testing to satisfy API-2B specifications. The first and second completed pipes were subject to 100 percent testing of each girth weld. As no defects were found, the remaining welds were subject to 45 percent testing in locations randomly chosen by the inspector. The inspector found zero defects and zero causes for repair on all 12 pipes, and he commented on how unusual it was for a job to have no rework at all. We believe that without the use of the Miller equipment it would have been a lot more challenging. However, the RMD process worked as promised, easily overcoming gap or alignment variations and making a weld with a smooth transition.
Completed pipes were moved to a pier side area using our 4000 and 4100 Manitowoc 200 ton cranes, with 1-1/2-in. thick pad eyes welded to pipes. Each pipe was transferred from pier side to the deck of the Karlissa A by the use of TITAN’s 300-ton R ing Crane and stacked six per side in a pyramid shape anchored by three 16-in.-wide A-frames. Steel dogs were welded on one end of the pipes to tie them all together.
The teamwork of Sause Bros., TITAN Salvage and Miller welding equipment made this job seamless and produced a satisfied customer ready to take on its next job anywhere in the world.