NIST analysis helps the US Chemical Safety Board pinpoint root cause of pressure vessel failure
In 2009, a violent rupture of a 50-foot pressure vessel used to produce synthetic crystals at the NDK Crystal facility in Belvidere, Illinois fatally injured a member of the public and caused significant property damage to the plant itself and the surrounding area. In response to the accident, scientists from NIST's Material Measurement Laboratory were approached by the U. S. Chemical and Hazardous Material Safety Board (CSB) to review data and assist in identifying the failure mechanism. The review found strong evidence of stress corrosion cracking (SCC) on and near the inner diameter of the vessel fragment, and a reduction in material toughness during service. This combination likely resulted in a flaw reaching critical size, causing the catastrophic failure. The results were included in CSB's recently published final report on the incident investigation.