All-position automatic welding: A revolutionary technique for long-distance heat transmission pipelines
All-position automatic welding is a highly efficient and quality-assured welding process that has gained considerable attention in the industry. This technique involves fixing and aligning the pipeline, after which a welding carriage moves the welding gun along the track of the circumferential weld seam around the pipe wall, achieving automatic welding. The primary components of all-position automatic welding equipment include the welding carriage, walking track, welding power source, wire feeding mechanism, and an automatic control system.
All position automatic welding
Despite its high efficiency and superior welding quality, all-position automatic welding is not yet widely used. However, it is poised to become the main promotion direction for the welding process of long-distance heat transmission pipelines. The process requires preliminary assembly and root welding work, which adds to the complexity of the construction procedure.
Types of Automatic Welding Suitable for Long-Distance Pipelines
Single Torch Gas Metal Arc Welding (GMAW)
Compared to self-shielded flux-cored semi-automatic welding, single torch GMAW can improve welding efficiency by more than 30%. It offers aesthetically pleasing welds with good weld seam density, achieving a weld seam pass rate of over 97%. The technique also boasts high weld seam toughness, low labor intensity for welders, and a better welding environment. Consequently, it is set to become the primary method for on-site welding of long-distance heat transmission pipelines.
However, compared to stick arc welding, GMAW systems require a higher initial investment, sophisticated equipment, and skilled personnel for operation and maintenance. Additionally, GMAW has poor wind resistance (typically less than 2 m/s), which needs careful consideration.
Double Torch Gas Metal Arc Welding (GMAW)
Building on the single torch method, double torch GMAW has been developed to be smaller and lighter, significantly reducing welder fatigue. This method allows for the adjustment of single or double torches and features capabilities such as arc tracking, smart card programming, online data acquisition, and touchscreen control. These functions enable interactive control of welding parameters during the welding process, ensuring that each weld seam meets the required standards.
Double torch GMAW features a unique single-sided welding double-sided forming root welding function, capable of completing root welding, hot welding, filling, and capping processes. The two torches can simultaneously perform double-layer overlay welding or row welding, greatly enhancing welding efficiency. The system is compact, highly automated, and easy to operate, with welding efficiency 30-40% higher than single torch systems. Despite its maturity in technology and products, double torch GMAW is expensive and requires a high degree of intelligence and operational skill, limiting its application in engineering practice.
Multi-Torch Internal Welding Machine for Pipe Circumferential Seams
For the welding of long-distance heat transmission pipelines, the efficiency is largely dependent on the completion speed of root welding. For large-diameter pipe installations, a multi-torch internal welding machine for pipe circumferential seams has been developed both domestically and internationally. This is currently the fastest root welding technology, used in the West-East Gas Pipeline Project Phase II. For example, welding the circumferential seam of an X80 pipe with an outer diameter of φ1219mm took only 90 seconds.
SAW offers high production efficiency, excellent weld quality, no arc light or splatter, low labor intensity, and is not affected by wind, enabling complete automation. It is commonly used for factory-based, automated pipeline welding. However, due to its complex equipment and limited mobility, SAW is not suitable for field welding of long-distance heat transmission pipelines. Additionally, the implementation of this method requires the construction site to have conditions suitable for transporting double or triple pipes.
All-position automatic welding, with its various techniques, promises to revolutionize the welding processes of long-distance heat transmission pipelines by enhancing efficiency, improving weld quality, and ensuring better working conditions for welders. As technology and equipment continue to mature and become more accessible, these methods are expected to see broader application in the industry.