# Advanced Automatic Welding System for Offshore Pipeline System with Seam Tracking Function
## 1 Introduction  
An automatic welding system has the advantages of low labor intensity, good welded joint appearance, and high-speed welding in the offshore pipeline industry [1; 2; 3; 4; 5; 6]. A welding system in pipeline construction must be capable of working in harsh environments with minimal maintenance intervention. The equipment should embrace modern technology, but it should be easy to set up by the operator. From the perspective of offshore pipeline projects, productivity and reliability are the most essential features of an automatic welding system. Pipe welding in many industrial applications, such as oil drilling platforms and chemical factories, must be handled by an automatic welding machine because of the precision needed to avoid a hazardous leak. An automatic welding system should offer high-quality welding performance for a long period of time and not break down. If the water is deep, the pipe can be installed on the seafloor using several methods. The main ways that subsea pipes are laid include the S-lay and J-lay method, as shown in Figure 1. In the S-lay method, the pipe joints are welded together onboard the vessel in a horizontal production line. The seagoing pipe is supported by a stinger to control the radius when the pipe bends towards the seab. Due to the high production rate and the possibility of installing pipes, the S-lay method is extremely suitable for pipe installation in shallow and intermediate waters. The J-lay method is suitable for deep water because the pipe leaves the lay system in the vertical position, and the pipeline is bent while arriving at the seabed. This reduced amount of bending is beneficial for installing pipelines that are sensitive to fatigue. The J-lay method has a relatively low production rate due to thesingle position welding of the pipe. To ensure the competitiveness of offshore pipeline laying, it is necessary to maintain production balance among the welding processes, minimize the work process time, and ensure perfect welding quality. Since the work process is performed on a barge floating on the sea, working conditions are more difficult than those on land. Moreover, it is difficult to accurately obtain the various automated pieces of equipment used in pipeline work due to their high cost. After aligning pipes with an internal clamp and finishing construction work, more time is spent on repetitive work, which separates the welding carriage with loosening a screw in guide track independently in a conventional welding system. There are two different situations where automatic welding machines are used. Semi-automatic welding uses a pre-programmed automatic welding machine, but the parts are loaded onto the welding bench by an operator who arranges them and switches on the welding machine until the weld is completed. The operator then removes the finished workpiece and repeats the process as many times as necessary. Fully automatic welding removes the human element, except as an overall observer to make sure the machines are running properly. In these set-ups, the parts and finished workpieces are moved by other machines, such as conveyor belts, and the welding operation is continuous over a large number of individual pieces. Welding productivity is also greatly influenced by the geometry of the weld joint. In narrow groove, welding time can be minimized by reducing the amount of welding, but the narrow groove can increase the welding defect, such as a lack of fusion on sidewalls [7,8]. To get the most out of narrow groove welding, the welding system incorporates an automatic seam tracking, and an without operator intervention is essential to compensate for the fit-up condition. Since automatic pipe welding systems incorporate tandem welding processes to increase production, but multiple arc behavior  
Figure 1: Integrated pipe lay systems: (**a**) S-lay system and (**b**) J-lay system. makes it difficult to observe the weld centerline, so an automatic seam tracking system is necessarily required [9; 10; 11; 12].