Chia Poh Ling*, Lim Chin Chin, Tap Y.W, Michael Tay Ming Kiong
3rd EAFS Conference, Sep 2003, Istanbul, Turkey. (oral presentation)
Currently, standard industry practice requires that bunker oil being supplied to Marine vessels must fulfill the ISO 8217 requirements. ISO 8217 requirements, however, are specification of bulk properties and looks at parameters such as the density, viscosity, flash point as well as the presence of certain elements (carbon residue, sulphur, vanadium, aluminum and silicon). Although ISO 8217 has another criteria which states that it should not contain chemical waste, waste lubricants or any other contaminants which would impair the efficiency of the purification or engine system, such a criteria is difficult to monitor, let allow enforced. At the present moment, the presence of other types of possible contaminants, especially organic contaminants, are not monitored at all. It has surfaced recently that certain bunker tankers’ operators sold contaminated bunker fuel that had been mixed with waste oil to unsuspecting clients. These contaminated bunker oil, however, was still within the ISO 8217 general requirements. Such contaminated bunker oil caused great harm to the vessel’s engine, and clogging of filter as well as high pressure in fuel pumps had been reported.
Our forensic laboratory had analysed samples of bunker oil and waste oil for the presence of common contaminants from the cleaning industries. The bunker oil samples were obtained during the custody transfer sampling when bunker oil was loaded into the marine vessels. The quality of such samples indicate the quality of the bunker fuel that was loaded into the vessels. The presence of any contaminants in the samples would be indicative of an adulteration (whether accidental or intentional) of the bunker oil supply. The waste oil samples were obtained from the different waste tanks of various shipyards.
The bunker oil was heated in the oven at 50 °C for at least 15 minutes and the sample was thoroughly shaken to homogenize the content before a small amount of the bunker oil was sampled. This sample was distilled to a temperature of around 220°C. The distillate collected was injected into Gas chromatography/mass spectrometry for analysis. For waste oil, distillation of some of the samples were not successful due to the mixture of fuel oil with a large amount of aqueous liquid. A novel method of passive headspace sampling using carbon strips with samples heated up to 80°C for 4 hours was used. The carbon strips were subsequently eluted with the solvent hexane and then analysed by Gas chromatography/mass spectrometry. Extracted ion chromatograms/summed ion chromatograms were used to identify the trace amounts of contaminants present.
The common contaminants detected in many of the bunker oil samples were trichloroethylene, tetrachloroethylene, dimethyl adipate (dimethyl ester of hexanedioic acid), dimethyl glutarate (dimethyl ester of pentanedioic acid) and dimethyl succinate (dimethyl ester of butanedioic acid). The common contaminants detected in many of the waste oil samples were trichloroethylene and tetrachloroethylene. Trichloroethylene and tetrachloroethylene are solvents commonly used in dry cleaning, metal degreasing/ desludging, as well as a general purpose electrical solvent cleaner for all electrical and electronic equipment. The dimethyl esters of dioic acids are used as solvents in products such as paint strippers. The contaminated bunker oil were subsequently traced back to fuel supplied by two bunker tankers.