Abstract
A propane gas cloud was released into the atmosphere during the loop rector dumping procedure in a process plant. After reactor inertization, the bottom valve of the dump tank was opened to collect spent powder and remove it. Unexpectedly, the powder on the floor started evaporating hydrocarbons. A propane cloud drifted very fast through the plant and ignited at the pump station area: even if the flash fire was extinguished immediately, there were several people injured and one fatality. The fire of the powdered material was extinguished later, by sprinkler system and fire brigade intervention. A detailed investigation was carried out and a multi-step methodology was applied to define the sequences and identify the most likely causes of the accident. It was adopted a complete fault tree, trying to find out without a structured scheme any critical causal factor in each relevant branch. Then, starting from the immediate cause, different sub-steps were identified as possible underlying cause, allowing to evidence in a sort of causal chain possible deficiencies in the safety management system, or in the safety culture of the company. Conclusions are drawn about practical recommendations to improve safety in dumping activities within a polymerization plant, adopting as well possible leading indicators for potential major incidents. The presented case study clearly shows how an effective HSE management system and a corresponding organization could have prevented or minimized the occurrence of such an unwanted event.
