The water contamination in fuel aviation and their solutions – Edition 2007

CONTAMINATION AND CLEANUP

Contamination    On its journey from refinery to aircraft fuel tank, aviation fuel will spend time in storage tanks and also be transferred one or more times. Each time a transfer occurs, there is a potential for contamination of the fuel to occur.

Particulate matter and water are the most common fuel contaminants. Other sources of contamination include: other petroleum products, surfactants, microbes, and dye. This section will describe each type of contamination briefly, and also the procedures and equipment used to remove contaminants from aviation fuel.

Particulate Matter   The dominant source of particulate matter is the solid corrosion products that slough off steel pipes and tanks (rust and scale). While protective coatings are being applied to the interior surfaces of more and more tanks, particularly those in critical service, the predominance of steel in industry facilities and the universality of water as a contaminant ensure that almost any distribution process will result in some rust contamination.

Other sources of particulate matter are: refinery processing materials (catalyst fines and salts); airborne solids that enter through tank vents or slip past the seals of floating roof tanks (dust and pollen); solids from damaged hoses and filters (rubber particles and fibers); and solids from microbial infestation (cellular debris and microbial by-products).

Water   Water in aviation fuels comes from a number of sources. Many refining processes employ water or steam, either directly or as heat exchanger coolant. Any free water picked up during processing is removed before the fuel leaves the refinery.

Because most pipelines are buried, tenders tend to be cooled during transmission. Cooling will cause droplets of free water to form if the jet fuel was close to being saturated with water when it was injected into the pipeline. Even if the jet fuel was dry on injection, it may pick up free water deposited in low spots in the pipeline by the tenders of other products.

Rain water may leak by the seals in floating-roof tanks. Water in moist air may condense in fixed-roof storage tanks, which must be vented. Air flows in and out of a fixed-roof tank as product is added or removed and as the air above the product expands or contracts in response to changes in ambient temperature. When warm, moist air enters during the day and is cooled at night, water may condense and "rain" into the fuel. The amount of water generated by the process depends on the relative humidity of the air and the difference between day and night temperatures; it can be significant for tanks where the climate is humid.

Other Petroleum Products   If a batch of aviation fuel is contaminated with enough of another petroleum product to move one or more of the specification requirements off-test, there is no remedy. The batch must be returned to a refinery for reprocessing. So, aviation fuel lines and tanks are rigorously segregated from lines and tanks containing other products in the refinery and in the distribution chain.

There are situations in which small amounts of product mixing may occur:

• At the interface separating two products in a pipeline.
• When aviation fuel is loaded into a compartment of a vessel or truck that previously contained a different product.