In a cooking oil refining and packaging plant, an explosion occurred around 9:30 a.m. in an oil refining condensate discharge line while work was being carried out nearby. A sewer outlet, located about ten metres from the dryer’s water discharge point, was blown more than a metre into the air, tearing off a rainwater downspout. The site personnel were able to intervene immediately after the explosion, using fire extinguishers and a hose reel. The fire brigade evacuated the affected area and measured the hexane concentration at various points on the network. The portion of the network in question was purged with steam, and new hexane measurements were conducted. No anomalies were detected, so the refining unit was returned to service at around 4:45 p.m. The operator has installed a sign directly next to the point where the dryer releases water into the network, identifying this zone as likely to have an explosive atmosphere. No casualties and no environmental impact were reported. However, a firefighter injured his foot while lifting a manhole cover during reconnaissance operations after the explosion.

The Inspection authorities for classified facilities compiled a report the same day and requested that the operator use an explosimeter to regularly check the hexane content in the network at various points. At the time of the explosion, an external company was cutting a metal plate covering a manhole accessing the network used to drain off water from the dryer (water + fraction of hexane extracted from crude oils). According to the facility operator, these operations generated sparks that ignited a pocket of hexane in the pipe. The explosion area had been identified as likely to present an explosive atmosphere, but no specific information or instructions relating to this risk had been indicated in the fire permit issued before the start of the cutting operations.

As a temporary measure and following an increase in the hexane content in the network, the operator replaced the “solid” plate covering the discharge point with an open-work plate, and shortened the release pipe to 20 cm from the ground. The operator also plans to double the measurement intervals to confirm the decrease in hexane content, to inject steam into the network if measurement results exceed 30% of the hexane’s LEL, to shut down the installations and to prohibit work in this area if the measured concentration exceeds 50% of the LEL, until the hexane concentration falls below 30% of the LEL. The Inspection authorities requested that the operator conducts a study to examine what the oil refining installation is doing to reduce the risk at the source.