Design and implementation of orbital welding system for large-diameter pipes

This study presents an orbital automatic welding system and an arc-sensing seam-tracking algorithm for medium- and large-diameter pipe applications. The modular carriage integrates a central control module, DC/stepper motor modules, and a welding control module, and supports V-groove, fillet, and diagonal welding. A real-time algorithm estimates seam deviation from arc voltage/current signals and applies synchronized two-axis weaving with lateral and vertical offset correction. A database-management platform segments the pipe circumference into seven angular zones and updates voltage, current, travel speed, weaving cycle, and wire feed in real time to compensate for gravity-induced molten-pool behavior. Field trials on large-diameter water pipes confirmed stable arc behavior and uniform bead formation in both inside and outside fillet welding. Quantitatively, the tracking error remained within ± 0.2 mm under a 0.3 mm offset and within ± 0.3 mm when the offset was increased to 0.5 mm to test robustness. Compared with manual welding by skilled operators, the proposed system reduced variability, improved seam alignment and bead uniformity, and lowered defect occurrence, demonstrating reliable and repeatable performance for repetitive orbital tasks. Synchronized signal analysis further verified the system’s real-time response and tracking accuracy. These results demonstrate practical applicability to pipeline construction by improving weld quality, productivity, and operator safety in spatter-intensive, variable-lighting environments where vision systems are less effective. Future work will integrate vision-based AI for real-time quality assessment and adaptive parameter optimization, and extend validation through metallographic/mechanical testing and long-term durability evaluations using dedicated specimens.