European oil traders recently have reported so many examples of diesel fuel cargoes contaminated by bacteria that fears of an epidemic are growing.
Some have unwittingly put contaminated cargoes onto the market, so users have complained too.
Independent traders and trading arms of major oil companies alike have been hit by claims, particularly from ship charterers and tank farm managers, for damages caused by contamination.
But loads are rarely analyzed at the time of delivery, so there is no way to trace who caused the fouling.
Most of the contaminated loads seem to have originated in the C.I.S. Strategic fuel stocks are being drawn down following the disarmament program and are being marketed. During storage some have been invaded by microorganisms that feed on the oil.
PROBLEMS
A variety of bacteria and fungi can live in oil. They can produce corrosive chemicals as by-products of digestion. As they accumulate, their bulk can lead to equipment failures. Typical problems include tank and pipeline corrosion, blocked filters, and engine wear. Worst of all are sulphate reducing bacteria, which produce not only corrosive waste liquids but poisonous gas as well.
There are a number of ways to deal with the bacteria and fungi: heating, filtering, and centrifuging. Biocides also are available, but they contain chlorine compounds and so have environmental implications. After a number of biocide treatments the fuel would be a cocktail of pollutants.
The drawback with all those solutions is cost. If every load were treated at each delivery, the bill would be too large. Most of the cargoes, in any case, are clean. At the same time, the problem will not go away if it is ignored.
BENCHMARK
SGS Redwood Ltd., Liverpool, is an independent testing house that has been swamped with samples of contaminated fuel. It has taken the line that prevention is better than cure. Because there is no international standard to guide the industry, it has developed a benchmark.
Redwood recommends sam pling before, during, and after custody transfer. Besides midcargo samples, pump inlet and dead bottom samples need to be taken. Among other things, a good quality diesel fuel will show no trace of sulphate reducing bacteria.
The drawback with thorough monitoring is its time penalty. A laboratory will take at least 5 days before results are available.
A new test kit, like those pregnancy test packs that yield results within minutes, may be the solution. This looks like an ideal opportunity for an enterprising chemist. Any volunteers?
Copyright 1992 Oil & Gas Journal. All Rights Reserved.
