Fluor Corp. has made a major breakthrough in a new application of Ultrasonic Time of Flight Diffraction (UT-TOFD) that enhances ultrasonic examination of thermoplastic, pipeline butt welds. The capability to non-destruc-tively characterize, evaluate weld integrity, and detect defects, including porosity and lack of fusion (LOF) or cold welds of plastic pipe in operation, was needed by industry, but not previously available. Fluor, in conjunction with RTD, developed, calibrated and correlated a novel application of the UT-TOFD technique that proved to be highly reliable at detecting, locating, and characterizing defects in high density polyethylene (HDPE) welds. For pipe wall thicknesses up to 4 inches (100 mm), UT-TOFD detected defects down to 4% of wall thickness. A strong correlation was found between UT-TOFD scans and actual defects in a large sample of shop and field welds. The high-resolution examination of welds is suitable for both shop and on-line field applications. This method has been tested and proven effective in large-scale field pipeline applications. Now, pipeline operators working in a demanding industry have a tool that provides high-quality verification of weld integrity for inspection, engineering evaluation, and comprehensive risk analysis. Avenues are now open for improving pipeline construction and HDPE fusion practices, and for monitoring integrity of operating pipeline systems.
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