Where Contaminants Originate
Contaminants come from many sources including product aging,
the environment, microbial infection, transportation error and fuel system
deficiencies. The image below showing the fuel supply chain from refining to
end user demonstrates many places where contamination can occur.
At every point in the transportation of fuel contamination
is a concern, compounded by the growing need for cleaner fuels. Once fuel is
refined, it often goes into temporary storage prior to being conveyed to a
terminal. Delivery might include pipeline, ship, barge, tanker or rail car
before arriving at terminal storage. Fuels may be allowed to settle prior to
being shipped to its next destination. Settling is important as it permits
contaminants to fall out and be pumped off. However, if settling time is not
provided contaminants will to be transferred to the next location. Tankers
transfer fuels from terminals to intermediate storage or end users. This might include additional storage or
directly into equipment.
Many of the components of a fuel distribution center are
made up of low to mild carbon steel. The
tanks, pipes and pumps are very susceptible to corrosion. Rust and metal particulates are often carried
downstream to the end user. Water continues to be a problem. Throughout the
distribution system water can be transferred along with fuel. Even pipeline
cleaning, called pigging can attribute to higher contamination levels. Even
when filtration is a part of the distribution chain, it may not be adequate.
There have been many contamination studies performed and
most agree that particulate and water contamination are continuing problems.
Biofuels tend to test dirtier than non-biofuel samples. On average, a tank that receives 8,000
gallons of fuel a week can gain as much as 35 pounds of particulate
contamination per year. This does not
include the potential for water contamination. Much of the filtering done
through dispensers – especially retail – proves to be inadequate for providing
fuel that meets today’s engine cleanliness requirements.
Water is the most common contaminant found in fuel. It can
enter fuel from refinery to end user. Water is actually used during refining in
the cooling process. It can enter fuel during storage and delivery as rain,
condensation, ship ballast water and fuel system deficiencies. As water finds
its way into fuel it will be dissolved or suspended as tiny droplets. Depending
on the composition of the fuel and temperature, the amount can vary. Biofuels absorb
more water and this can lead to accelerated degradation leading to a breakup of
the fuel at the molecular level.
One of the most neglected
areas is air contamination. As fuel moves in and out of a system, the tank
breaths drawing in air. Air carries with
it contamination in the form of dust, microbes and water vapor. All of these will accumulate in the fuel
system, contaminating the fuel and creating problems over time. The buildup of
contamination over the fuel supply chain is accumulative. By the time the end
user gets the fuel, contamination levels are high.