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.