Release Risk Model to Evaluate Highway Cargo Tank Component- Specific Safety Performance in Transporting Hazardous Materials

摘要

This paper introduces a release metric as the expected value of the quantity lost from a highwaybulk package given that it is involved in an accident. The associated release risk model isdeveloped in terms of potential releases from tank head/shell components and tankappurtenances, such as top and bottom fittings, valves and larger openings. The model definesconditional probabilities of release for release size, failure mode, and failure source. Theseverity measure used in the model is the percentage of packaged lading released.The use of the risk model is illustrated in estimating the severity levels of releasesnormalized with respect to the conditional probability of release given that an accident hasoccurred. The normalized release risk model is used to evaluate the performance of tankhead/shell components and tank appurtenances in accidents reported to the U.S. Department ofTransportation Pipeline and Hazardous Materials Safety Administration over a five year period.The analysis showed that given a release event involving a cargo tank, the expected releaseseverity for the head or shell is higher than for tank appurtenances. Furthermore, “burst orruptured”, “ripped or torn” and “gouged or cut” failure modes correspond to the greatest severitygiven a head/shell failure.