<p>With the growing demands of onshore oil and gas pipelines that require larger diameters, thicker walls, higher pressure and higher-grade steel, manual and semi-automatic welding methods fall short due to poor welding quality, low efficiency, and high labor intensity. In response, this paper proposes a novel double-torch automatic pipeline welding system that is capable of welding oil and gas pipeline ring weld seams automatically. To accommodate the limited workspace within windproof sheds, the mechanical and control systems for automated welding have been integrated and designed to be lightweight. In addition, a seam tracking system based on arc signals has been developed to reduce deviation between the welding torch and the weld centre line. This system calculates the difference in current integration within 1/4 cycle to the left and right of the torch oscillation centre to determine the torch deviation, reducing computation and providing real-time seam tracking. Furthermore, a fuzzy Proportion Integration Differentiation (PID) control method has been employed to the weld seam tracking system to enhance its anti-interference capability and control precision. This paper details the mechanical structure, control system, and seam tracking algorithm of the developed automatic welding system. Finally, welding experiments have been conducted, demonstrating that the automated pipeline welding system based on arc weld tracking technology achieves a tracking accuracy of 0.35&#xa0;mm, producing aesthetically pleasing weld formations. These designs can now be applied in welding onshore oil and gas pipelines, leading to higher welding efficiency and improved quality.</p>