Research On Internal Circumferential Automatic Welding Equipment And Process For Long Distance Pipeline With Big Size

With the rapid development of oil and gas pipeline construction, pipeline welding construction technology, especially the root welding technology developed rapidly. Root welding methods include: uphill welding with low hydrogen electrode, or downhill welding with high cellulose type electrode; downhill technology with STT MIG Semi-automatic (or automatic)welding; automatically downhill MIG welding with pulse characteristics of the power control; external MIG automatic welding for force shaping root bead with copper liners; inner welding machine for root bead etc. Among the current applied root technology, among the fastest within the welding root welding, the inner welding machine can get fast root welding speed, best weld forming and weld quality. The topic study systematically the mechanical structure, Pneumatic Principles and automatic control theory of internal welding machine, and propose set of research programs and prototype.For all-position welding process of inner circumferential weld, this topic analyze the control objects and control tasks, research control system function, composition and working principle of 1219mm IWM welding process, finally achieved a stable & reliable alignment and automatic welding process.Through research and study of welding process control and the auxiliary function of IWM, which including implementation control of welding parameter, realization of internal repair functions and so on, the adaptability and flexibility of IWM in welding construction site can be strengthened.The construction environment and process of pipeline welding present this topic in higher requirement, such as Strong anti-interference ability, good safety, reliable action directive, strict interlocking, self-locking relationship and so on. In response to these requests, according to character of programmable logic controllers (PLC), this topic use a programmable logic controller (PLC) as the core and in first time control operating parameters of long-distance pipeline Internal Welding Machine by the external signal module. Using this control method, can get clear logic, reliable action, low failure rate and strong anti-interference ability.The subject successfully developed IWM-dia.1219mm with eight torches, which is domestic first. The eight torches are distributed uniformly on rotating disc with rational design and novel structure. Each welding torch takes 1 / 8 circumference girth welding work, which resulting in improved welding productivity. The research was the first time to be applied in first spread of second West-East project in 2008, a total of more than 800 joints to be welded and received passing rate of 96%. This research is currently being applied in the other spreads of second West-East Gas pipeline project. The project application result show that weld appearance and weld quality is perfect.