Abstract: This study was motivated by a cargo tank explosion incident involving No. 6 fuel oil at a temperature well below its flash point. The overall objective of the study has been to evaluate the general fire and explosion hazards of high flash point liquid cargo, i.e., Grade E cargo. A review of Coast Guard and National Transportation Safety Board incident reports identified several other explosion incidents involving high flash point liquids at temperatures below their flash points. Three other incidents involved residual oil, two involved oily waste water, and one involved asphalt. The flammable atmosphere in the cargo tank in these incidents (and in other reported cases where there was no explosion) is due in some cases to cargo contamination by more volatile liquids, and in other cases to vapor evolution from the Grade E cargo itself, particularly when it is heated and/or transferred to other tanks. Laboratory tests have been conducted to determine the effect of small concentrations of contaminants on the closed cup flash point of representative Grade E cargo. Results show the addition of only 0.7% heptane by liquid volume to a sample of No. 6 fuel oil reduces its flash point from 95 deg C to 72 deg C, which is a typical temperature during No. 6 fuel oil transfer operations. Data for other Grade E cargo show similar qualitative effects, with the magnitude depending on both the cargo and contaminant flash points. These results, as well as a review of previous studies and current practices in the shipboard use of combustible gas detectors, are combined to provide an overall assessment of Grade E cargo hazards and possible protection measures.
| Limitations: |
 APPROVED FOR PUBLIC RELEASE |
| Description: |
Interim rept. Jul 93-Aug 94 |
| Pages: |
64 |
| Report Date: |
OCT 95 |
| Contract Number: |
DTCG39-93-F-E00571 |
| Report Number: |
A917203 |
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