A fire broke out on at 5 p.m. in the deodorising column of an oil manufacturing plant. A significant amount of smoke was seen billowing from the upper manhole of this 8-stage 10 m³ column. At the start of the intervention, two explosions occurred at the manhole. The column had been under maintenance for 5 days, the start of its annual technical shutdown period.
The deodorising system was shut down and cooled to allow for cleaning of its compartments where polymerised oil forms on the coils and internal surfaces. On the morning of 17/06, after the manholes were opened, a crew began manually cleaning the surfaces. During the night, cleaning operations were suspended, and the manholes were closed with 2 bolts. Cleaning operations resumed the following morning and were stopped at 1 p.m. The manholes were simply closed, as the deodoriser was considered without danger after having been shut down for 5 days already. Four of 5 stages of the columns had been cleaned and only the last stage remained to be cleaned. This mechanical cleaning phase is a traditional practice at the site and in the company since it was the 10th time that the process had been carried out (10th shutdown of the tower). The cleaning procedure had been the same for roughly 10 years.
The fire was discovered at 5:14 p.m. and was initially contained, but then resumed an hour later. The plant’s internal contingency plan was initiated. The facility operator closed off the various openings in the installation to limit the supply of fuel (oxygen) in an attempt to smother the fire. The external and internal firemen set up several hoses on the various levels of the tower and put out the fire by filling up the tank 2/3 with water. The internal contingency plan was lifted around 5:40 p.m.
According to the operator, 200 m³ of water was used to extinguish the fire; 100 m³ for fighting the fire and 100 m³ for filling up the column. The column was emptied in the morning of 22/06, and the 200 m³ of water was confined to a retaining basin provided for that purpose.
According to the operator, the probable cause of the incomplete combustion (presence of CO and thick smoke) inside the column came from a hot spot which, despite the 5 days of cooling, eventually ignited polymerised oil residues with the air supplied through the poorly closed manholes (bolts not in place). However, further analysis must be conducted. On 28/06, the manufacturer was to analyse the damage inflicted on the column during the fire. Based on the conclusions, a production stoppage could be required.