Synthetical NDT And Image Processing For Weld Joint Of Pipeline

Natural gas is the one of major energy sources in 21st century. The trunkline is a complicated power system that is buried under the ground with gigantic transportation volume, less field areas, less impact by terrain and climate, linking field gas-collecting system and city gate stations, is considered as the most effective and the largest scales delivering system at present. The long distance of natural gas pipeline is determined by market economy for achieving maximum economic profits and social interests. Nevertheless, the natural gas is not identical to ordinary product oil, because the natural gas pipeline is to provide the residents with fuel, related to everyday life of families and social stability. With flammable combustible gas, the trunkline of natural gas is featured with high transporting pressure, vulnerable to crack and tear-down due to damage. The sabotaged pipeline can not be repaired in very short time so that the defects such as crack shall be prevented for better quality which requires meticulous operation during the construction and establishment of impeccable quality-assuring system for pipeline.As fast development of new energy industry, a good number of long-distance pipelines at home and broad will be put into service based on the primary safety and reliability to be required by pipeline construction and storage & transportation. The welding technology in close connection with quality of project, efficiency, cost, safety, reliability and profits, has been working as key part of construction. Susceptible to fracture, failure and leakage, the gas pipeline has become significant issue on society and end users in terms of safety, because any accident will bring about great losses and negative influence. The higher requirement will be proposed for field welding service and working staff in urgent hope of comprehensive and scientific standard for welding quality control. In addition, the thesis describes rudimentary theory and relative merits of laser welding technology. In the meanwhile, the preliminary probe is done to laser welding on thick wall pipeline according to progress and tendency of laser welding.Detection & evaluation of welding structure for potential defection is a key procedure shaped continuously. With the updating of information technology, regular detecting methods have had more breakthrough and creation, such as TOFD, THz NDT and infrared imaging NDT, which safeguard the welding quality and other industrial activities.The paper detailed the process of forming of weld beads, types of defects and reasons and consequences to be occurred, describing fatigues and damages by the mentioned defects and importance of NDT of pipeline welding beads. The key attention has paid to TOFD and infrared NDT technology for manifesting high successful findings and expansive prospect due to simplicity and amenity. The high successful finds will help NDT staff with prompt assessment and decision for repairing, moreover, with predict running of pipeline and life span of service according to statement of defects and welding quality.Digital image technology has found their versatile roles in many fields. Image processing and image understanding speed up production and guarantee quality in industrial testing, industrial detecting, CAM etc. The paper has introduced a large number of intelligent imaging and photoelectric imaging contents, particularly had discussion in terms of infrared bead image processing and application. In the synthetic application of multiple NDT technology, the most reasonable method has been applied to separate defects from images of the beads on the basis of characteristics of infrared images for increasing successful rates and make sure high quality of pipeline welding.