An hydrocarbon leak (heavy distillates) occurred at around 1.25 pm when a pump has been removed for maintenance in the vacuum distillation unit in a refinery. The preventive sprinkling caused a release of white smoke visible from outside of the site. The site’s internal safety services mobilised 2 trucks equipped with foam guns and isolation beaconing was set up around the unit. The staff contained the leak without intervention from emergency services by emptying the extraction platform using the second pump located at the bottom of the column. The lower part of this column was then nitrogen inerted. The polluted effluents consisting of hydrocarbons, water and foam (approximately 50 m³) were collected and sent to a tank in unit 401 for treatment.

According to the operator, the leak was caused by faulty sealing of the isolation valve placed on the suction line of the pump that was being removed, and this problem had not been detected during the checks carried out on the pump before its dismantling (possible formation of a “plug” of distillate residues which would then be reabsorbed). The quantity of heavy distillates spread was estimated at 13 m³. Shutdown of the vacuumed distillation unit caused pressure drops and disruptions in the operating conditions of other units in the refinery as well as the flaring of 0.43 t of acid gas for 30 minutes. The inspection authorities for classified facilities, informed by the operator, went to the site. The production plant was sitting up during the night of 10 to 11 July, after the installation of a locking plate pending dismantling and examining of the leaking valve.