A rulemaking issued by the United States Department of Transportation (USDOT) revises Hazardous Materials Regulations (HMR) to replace the hydrostatic pressure test with appropriate nondestructive evaluation (NDE) methods. The rule change is contained in Federal Register 49 CFR Part 180.509, “Requirements for inspection and test of specification tank cars”, paragraph (e) “Structural integrity inspection tests” (1). The CFR authorizes liquid penetrant (PT), magnetic particle (MT), radiography (RT), ultrasonic (UT), and optically aided visual testing (VT) as allowable NDE methods for structural integrity inspections and tests. Also, included under the requirements of 49 CFR Part 179.7 is the need to qualify not only NDE personnel but the procedures used to perform NDE reliably. To be effective, Federal regulations require that the NDE methods have a proven sensitivity and reliability for finding the type and size of flaws likely to cause a tank car failure. In the early 1970s an internationally accepted quantitative approach that determines the probability of detection (POD) was developed for the National Aeronautics and Space Administration (NASA) and was published in NASA CR-2369, February 1974 (2). NDE PODs have been performed on tank car circumferential butt welds, longitudinal fillet welds and leak test samples requiring inspection under the CFR. The POD effort addresses the sensitivity requirement issued under the CFR and provides quantification of the NDE methods allowed by the rulemaking.

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