Fire broke out in a low-pressure hydrogenation unit at a chemical plant. The unit’s fire detectors sounded the alarm while the 1st process phase (hydrogenation of phenylacetylcarbinol with benzylamine in an isopropyl alcohol solution using a catalyst) was ongoing. An explosion was heard immediately thereafter. The employee supervising the unit threw the emergency shutoff switch and attempted in vain to put out the fire with a halon extinguisher. He sustained severe burns and later died as a result. The plant’s fire-fighting team brought the blaze under control in 40 min, once the intake lines of both hydrogen and phenylacetylcarbinol, which had been fuelling the fire, could be cut. Three fire-fighters suffered smoke inhalation and required hospitalisation; all were released to return home that evening. Property damage was extensive (in the millions of marks) and the plant was totally destroyed. Though the investigation was slowed due to burning of the primary physical elements and the absence of any direct witnesses, the most likely accident scenario was as follows: the isopropanol pipe had been fitted with a bypass featuring steel/glass discontinuity with a double enclosure to protect the glass portion of the pipe. Despite the operating procedure notification, the steel side of the valve had never been closed, triggering a 3.5-bar pressure surge on the glass/metal discontinuity each time the pump started. Rupture of the glass device caused an isopropanol leak, eventually forming an explosive atmosphere and resulting in an ignition (whose source remained unidentified). The adjacent hydrogen pipeline, exposed to strong heat, wound up breaking, thus producing the hydrogen leak and ensuing explosion. Moreover, the fire led to a short-circuit, cited as the reason for a malfunctioning phenylacetylcarbinol pump, which in turn helped feed the blaze. During plant reconstruction, the unit was modified in various ways, including: elimination of glass pipes to the greatest extent possible, installation of an emergency shutoff switch placing the facility in safe mode, placement of an automatic locking mechanism on selected valves, and improved safety training for employees
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