Performance testing of inspectors to improve the quality of nondestructive testing

This paper describes the results of performance testing conducted to improve the quality of nondestructive testing (NDT) used to evaluate the structural integrity of welded-steel bridge components. Common NDT technologies, such as magnetic particle testing (MT) and ultrasonic testing (UT), rely on trained inspectors to implement the proper procedures and interpret the responses to identify and assess indications. High variability in test results can occur between qualified inspectors, who may implement the same procedures with differing levels of thoroughness and care and may interpret responses differently. As a result, the reliability of the implementation of the technology cannot be assumed. Performance testing assesses inspectors, who demonstrate their capability to implement procedures through their detection and analysis of known defects. Such performance testing can improve the quality of NDT inspections by ensuring that inspector capability is adequate. This paper describes the results of performance testing of NDT inspectors at work on the Sherman-Minton Bridge, which carries I-64 and US-150 across the Ohio River and connects Louisville, Kentucky, with New Albany, Indiana. Inspectors assigned to conduct UT and MT on the bridge were first assessed through a performance test program that required them to demonstrate their capabilities. The welded-steel specimens used for performance testing in general included fabricated test plates with embedded flaws of various sizes. The results of the performance tests identified inspectors whose performance was substandard and provided quantitative measures of the variations in the NDT results. This paper describes these variations and the overall results of the performance test program.