A Chemical Safety & Hazard Investigation Board report and safety video released last week shows that stress corrosion cracking in the wall of a 50-foot-tall, high-pressure crystal production vessel likely led to the 2009 catastrophic accident at NDK Crystal, a manufacturing facility in Belvidere, Ill. The explosion in the 140,000-lb vessel sent structural steel parts and an 8,600-lb fragment flying as far as 650 feet, injuring bystanders and killing a trucker at a nearby gas station. CSB determined that NDK had ignored previous safety recommendations and relied on an acmite coating inside the production vessel to protect the vessel’s low-alloy, high-strength steel from caustic sodium hydroxide used in the manufacturing process. However, NDK did not verify the integrity or effectiveness of this coating, CSB finds. The caustic chemicals promoted stress corrosion cracking that weakened the vessel.