Canada – Tank Cleaning
Canadian Oil Company puts microbiological to the Test – Tank Bottom Cleaning
DESCRIPTION OF SITE:
A Canadian oil company’s naphtha storage tank had several inches of solidified ferrous oxide and a quantity of residual free product. The tank was 220 feet in diameter and 60 feet in height. The objective was to clean the tank bottom in a cost-effective manner (removing hydrocarbons and oxide), eliminate hazardous confined space entry by maintenance personnel, and prevent the escape of vapors from the tank.
The tank was first flushed with fresh water, leaving 200 to 300 gallons of visible floating product, plus substantial additional product left in the sludge. A rotating liquid delivery system was installed and M-1000H* microbes were introduced. The mechanism was operated for 10 hours per day.
After 13 days, the company reported that where corrosion had been covered by the water, it had dissolved to a liquid and could be pumped out. This was done, and the majority of the material that had covered the tank floor was removed.
It was also observed that near the center of the tank, where the water had not covered the oxide during the treatment, oxide material remained attached to the floor. This material covered an area about 35 feet in diameter and was 1 to 2 inches thick. Since this material had not received a microbial treatment, it was removed in the conventional manner and required 4 more days. It is estimated that it would have taken more than 50 days to complete the cleaning manually.
After all material had been removed from the tank, it was observed that in the areas where M-1000H* came in contact with the floor of the tank, it was clean and appeared to have been “sand blasted”.
LEL vapor readings were also taken every 2 hours of the work day. By day #5 they had dropped to 65% of LEL. By day #10 they had dropped to 30% of the LEL. On day #13, LEL readings had dropped to 0%.
It was estimated that the cleaning would have cost $200,000 or more using the manual method. Utilizing M-1000H* reduced this amount to less than 30% of this figure.