viable and attractive option for onshore pipeline welding, especially when consid- ering trade-offs in deposition rates and mechanical properties. In comparison with all passes being completed using SMAW electrodes, the hybrid option presents several advantages, including: improved productivity due to higher travel speeds and deposition rates; reduced downtime due to the continuous workflow associated with using the a pre- programmed bug-and-band system for the more time consuming fill and capping runs; high consistency, quality and repeatability; and much lower repair rates due to porosity or lack of fusion indications. To fully realize the potential benefits, however, it is imperative to use flux-cored wires specifically designed for pipeline applications for the fill and capping runs. These provide proper support to the weld bead, especially in the critical positions between 6:00 and 4:00 o’clock. Typical consumables include: diamondspark 52 RC or one of the diamondspark X60 to X80 pipe range of consumables, depending on the base metal pipe specifications. Another essential component of this Hybrid solution is a bug and band system that is fully programmable, digitally con- trolled, and offers high precision welding arc manipulation. Productivity evaluation To evaluate the productivity gains, trial welds were conducted on Grade API 5L X 70 pipe with a diameter of 910 mm and a wall thickness of 15.0 mm. The trial involved the described method and a fully manual SMAW process on comparative weld joint. The root consumable for both methods was FOX CEL (AWS A5.1: E6010), a cellu- lose electrode designed for vertical-down welding of pipelines. The hot pass was completed using SMAW with FOX CEL 80-P (AWS A5.5: E8010-P1).
Böhler Welding’s hybrid girth welding methodology uses the pipeRunner®️ bug and band system for fill and cap welding, with uphill progression using a conventional V-bevel joint preparation and rutile flux-cored wires.
Charpy CTOD test results (J)
Weld Area
Position Temp (°C)
1
2
3
AVG
-30 -60 -30 -60 -30 -60 -30 -60
60 29 43 36 82 40 80 43
60 41 51 38 84 42 77 54
54 29 45 31 88 48 84 52
58 33 46 35 85 43 80
12 o’clock
Root
6 o’clock
12 o’clock
Cap
6 o’clock
50 Table 1: Charpy V-notch test results in a girth weld of a Grade API 5L X 70 pipe welded using the hybrid approach. Tensile test Result Yield strength (MPa) 537 Tensile strength (MPa) 613 Elongation (%) 27,8 Table 2: ASTM E8 Tensile Test results from a longitudinal sample taken at 3 o’clock.
For the mechanised fill and capping passes, the Böhler Welding pipeRunner® bug and band system with the TERRA 400 PRM welding power source and the diamondspark X70 RC-Pipe (AWS A5.29: E91T1-K2M-JH4) flux-cored wire specifically designed for pipelines were used, moving vertically up from the 6:00 o’clock to 12:00 o’clock positions. This approach resulted in a defect-free, high-quality joint with an excellent bead appearance, which was completed with
five mechanised FCAW fill and cap passes in addition to the SMAW root and hot passes – seven weld passes in total. In comparison, the manual root, fill and cap passes with FOX CEL and FOX CEL 80-P required a total
A comparison between the fill sequences for a pipe girth welding trial: Left: Pipe welded using a fully manual SMAW process. Right: Welded using a hybrid process with the fill and cap passes completed using the pipeRunner® bug and band systems with a rutile flux-cored wire.
19
July-August 2024
AFRICAN FUSION
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