| Small-diameter process tubing | 6–60 mm (0.24–2.36 in) | 1–4 mm (0.04–0.16 in) | Austenitic stainless steel, nickel alloys, titanium | Orbital GTAW/TIG with inert-gas shielding | Compact orbital power source with automatic torch rotation, programmable current, and closed-loop travel control | Low-current stability, precise arc control, purge-gas monitoring, and repeatable heat input |
| General utility and fabrication pipe | 60–168 mm (2.36–6.63 in) | 3–12 mm (0.12–0.47 in) | Carbon steel, low-alloy steel, stainless steel | Orbital GTAW for root passes; GMAW or FCAW for fill and cap passes | Modular positioner or rotating-chuck system with multi-process power capability | Workholding range, torch access, wire-feed synchronization, and easy parameter recipe changes |
| Medium-diameter pipeline joints | 168–406 mm (6.63–16 in) | 6–20 mm (0.24–0.79 in) | Carbon steel and low-alloy pipeline steel | Mechanized GMAW, pulsed GMAW, or narrow-gap GTAW/GMAW | Track-mounted or band-mounted welding carriage with automatic seam tracking | Carriage stability, root-gap tolerance, arc-voltage control, interpass-temperature control, and weather protection |
| Large-diameter transmission pipe | 406–1,219 mm (16–48 in) | 8–25 mm (0.31–0.98 in) | High-strength carbon and low-alloy steel | Mechanized pulsed GMAW, tandem GMAW, or hybrid multi-process welding | Multi-head internal and external welding system with synchronized controls | Deposition rate, synchronized travel speed, joint tracking, preheat management, and data logging |
| Heavy-wall pressure pipe | 114–610 mm (4.5–24 in) | 20–60 mm (0.79–2.36 in) | Carbon steel, low-alloy steel, creep-resistant alloy steel | Narrow-gap GTAW for root; GMAW, FCAW, or SAW for subsequent passes | Multi-pass CNC welding system with oscillation, layer control, and pass sequencing | High duty cycle, thermal management, narrow-gap torch geometry, layer alignment, and full weld traceability |
| Stainless and corrosion-resistant pipe | 25–406 mm (1–16 in) | 2–16 mm (0.08–0.63 in) | Austenitic stainless steel, duplex stainless steel, nickel-based alloys | Orbital GTAW, pulsed GTAW, or controlled-pulse GMAW | Precision orbital system with programmable pulse waveform and internal purge control | Heat-input limits, purge quality, interpass temperature, shielding coverage, and corrosion-resistance requirements |
| Aluminum and lightweight alloy pipe | 50–406 mm (2–16 in) | 3–12 mm (0.12–0.47 in) | Wrought aluminum alloys and selected aluminum-magnesium alloys | AC GTAW/TIG or pulsed GMAW with suitable aluminum wire | Rotary positioner with AC-capable power source, high-frequency arc start, and wire-feed control | Oxide cleaning action, thermal distortion control, wire feeding, torch cooling, and cleanliness procedures |
| High-production shop fabrication | 168–914 mm (6.63–36 in) | 6–30 mm (0.24–1.18 in) | Carbon steel, stainless steel, and low-alloy steel | Mechanized GMAW, FCAW, SAW, or combined multi-process welding | Automated welding cell with powered rotator, seam tracking, fume extraction, and production monitoring | Cycle time, duty cycle, loading method, operator safety, fixture repeatability, and compatibility with existing WPS procedures |