Around 3:20 pm at a plastics plant, a rapid level rise was recorded in a CDA (cyclododecane) unit reactor. The technician on duty noticed a grey cloud (hydrogen and CDA mix) forming around a valve on the blow line for anti-clogging filters. The H2 supply line was shut off instantly and leak intensity dropped. Shift personnel proceeded to decompress the unit manually. Fifty minutes later, fire broke out in CDA-saturated heat insulation. Despite technicians’ response with powder extinguishers, the blaze spread to the CDA pooled on the floor. Fire-fighters arrived and quickly extinguished the outbreak using powder. The site safety flow chart was immediately checked. The next day, the premises and machinery were inspected by the plant’s inspection office; equipment damage was reported adjacent to: the D906 tank (severely deteriorated heat insulation, manometer and temperature gauge, all rendered inoperable); the D901A hydrogenator (‘blistered’ insulation sheet metal); the structural frame (damage to paint and gratings); and peripheral pipes and accessories (widespread burns, major risk of leaks on the tap stuffing boxes). An extraordinary meeting of the company’s Safety and Hygiene Committee was convened on 9th July. Thanks to this meeting and the battery of ensuing analyses, the causes of this incident could be clearly identified: an off-gas return line installed a few years prior, and then disused and missing on all fluid flow diagrams. The fire subsequent to the leak was not caused by H2 but instead by CDA that had flowed onto the reactor heat insulation in creating a catalyst support medium, thereby lowering the CDA ignition temperature. During this meeting, corrective measures and actions were taken. The plant operator decided to: automate the decompression valve; establish a bottom valve position; update emergency plans; develop a response sheet for cases of major leaks; inventory the injection points on each unit so as to modify those located in high-risk zones; and provide the lead technician with a portable gas detector for hydrogenation.
