Simulation and reliability evaluation of automated ultrasonic testing technology in semi-automatic welding of oil and gas pipelines

Abstract

The simulations and reliability evaluations were utilized to determine whether the automated ultrasonic testing (AUT) technology was appropriate for evaluating semi-automatically welded oil and gas pipeline joints. The simulations found how the AUT technology was affected by beam coverage at the groove and in the volume channels, the time-of-flight diffraction (TOFD) surface dead zone, the root detection angle, the weld groove angle, and welding line deviations at the weld groove fusion. Detailed analysis of large datasets identified the distribution of defects that resulted from semi-automatic welding. Then, a model was proposed that evaluated the reliability of the AUT technology in examining semi-automatic welding. The corresponding results indicated that the technology could detect most defects in semi-automatically welded joints. The critical heights of the defects in the thermal welding zone and at the groove were less than 1.2 mm at a confidence level of 95% and a percentage of defects (PODs) of 90%. This supported the hypothesis that the AUT technology could identify defects resulting from semi-automatically welded oil and gas pipelines. During actual testing, rationally optimized AUT technology detected all forms of semi-automatic welding defects to meet the reliability requirements. The testing process has certain requirements for the quality of the grooves in the semi-automatically welded joints. Specifically, variation of the groove angle should not exceed ± 2.5°, and the horizontal offset of the groove should be within ± 4 mm. Similarly, for the incomplete root fusion of semi-automatic welding, the root should be covered with an incident angle as small as possible, and wave beams of 60° or greater should be avoided.