API PUBL 4018
AN EVALUATION OF METHODS FOR DETERMINING SULFUR IN FUEL OILS
|Publication Date:||27 August 1969|
The imposition of maximum sulfur specifications on fuel oil through clean air legislation results in higher costs(I) for fuel oil suppliers. Thus, there is a clear-cut, economic incentive to the petroleum industry to minimize unnecessary giveaway on fuel oil sulfur content so that low sulfur fuel oil can be supplied at minimum cost to the consumer. Enforcement officials, recognizing an obligation to administer laws so that they do not impose more of a burden on suppliers and consumers than was intended participated in this project.
Prime factors in minimizing giveaway while assuring compliance with the law are the precision and accuracy of the test method used for determining sulfur content. Clearly, the ideal situation would be one where the petroleum industry, governmental agencies and major consumers could each determine true sulfur content with absolute certainty. If this were so, fuel oil could be supplied with sulfur content close to the specified maximum and have no worry at all that governmental agencies would conclude that the sulfur was over the legal limit due to test variability.
Unfortunately, the true sulfur content of a fuel oil sample cannot be determined exactly. Individual test results on the same sample will always exhibit some variation whose range will depend upon the inherent precision of the test method used as well as the care and proficiency of the analyst running the tests. Giveaway allowances are commonly provided to take care of a large percentage of the range of test variability. Thus, sulfur giveaway costs as well as disparity of results between suppliers, consumers and government agencies will be reduced if test variability is reduced. This situation places special emphasis on the petroleum industry to optimize its giveaway through use of trained analysts on accepted test methods of known precision, to maintain the testing process in statistical control and to use the average of multiple tests for release decisions. Governmental agencies recognize that, in addition to these considerations, special care must be exercised in establishing enforcement guidelines that enable them to be highly confident that laws are being met while permitting industry to minimize giveaway costs to the extent practical with current test methods.
The petroleum industry, realizing the importance of the air pollution problem, is endeavoring to obtain factual information to aid both government and industry. Part of this effort is aimed at obtaining quantified measures of inherent test method precision, as well as identifying and measuring other sources of test result variability that are encountered in any practical acceptance testing procedure.
(1) See Bibliography at end of report. Based on figures from the Bechtel report, each additional 0.1% sulfur giveaway costs Caribbean Petroleum Companies about $20 million per year to supply United States East Coast demand.