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sustaining life—oxygen and water—are
exactly those that are entirely unwanted
and non-essential when considering the life
of stored oil and tanks.
To understand why, let’s start at the
refinery. Immediately after crude is refined
into fractions such as ULSD and heating
oil, these distillates should be free of con-
taminants such as water, sludge, and bio-
organisms. However, even
before
exiting the
refinery, distillates already possess the innate
conditions that can later cause significant
storage problems – and this is where oxygen
and water come into the picture.
Very basically, petroleum is a hydro-
carbon fuel consisting of a connected series
of hydrogen and carbon atoms bonded
together in a variety of individual long
chain lengths. During refining, the fuel is
subjected to extreme heat and pressure in
order to “crack” these chains into shorter
lengths. The advantage of cracking is that
many fuel types can be simultaneously
produced from one crude oil source.
The disadvantage, however, is that
cracking creates a fuel with unstable and
incomplete hydrogen and carbon bonds, to
which oxygen atoms can become attached.
When oxygen joins the hydrocarbon chain,
it tends to create an oil-insoluble compound
that forms a very finely dispersed sediment
of gums, resins, and other organics. These
compounds agglomerate, thicken, and
precipitate to the tank bottom in the form
of sludge. In addition to likely sludge prob-
lems, oxidation also tends to degrade and
destabilize overall fuel quality.
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There probably will never come a time
when we can eliminate oxygen from the
oil system, but there are fuel-compatible
antioxidant components that are available
to replace the oxygen at the bonding sites
and thereby minimize the adverse effects of
oxidation.
Previously the presence of sulfur,
a naturally occurring antioxidant, was often
sufficient to slow the oxidation process.
However, with negligible sulfur content,
the use of antioxidants is increasingly more
important. Of course, antioxidants alone
will not stop sludge deposition, since other
variables invite sludge formations
and this is where the presence o
water comes into play.
Water in storage tanks
creates a myriad of problems,
starting with its ability to form
new oil-insoluble compounds
in combination with oil.
Eventually, these compounds
agglomerate, fall out and
adhere to any sludge at tank
bottom. And that is not all the
havoc that water can promote.
In large quantities, water
can become entrapped and give
the oil a hazy, cloudy appearance.
At sub-freezing temperatures, th
entrapped water can form ice crys
that will clog filters and shut down the
flow of fully liquified fuel oil.
If the fuel should also become supersat-
urated with water content, a separate water
layer will collect at the tank bottom. If close
to the suction level, the water may combine
with the fuel and degrade fuel economy and
performance.
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Another area of concern is generalized
corrosion of tanks due to oxidation. This
is a gradual process, but the presence of a
water layer heightens the likelihood for
rapid tank corrosion and metal degrada-
tion. Acidic organic compounds inherent in
the fuel may leach into the water layer and
accelerate localized pitting of tank floors
and walls. But that’s not all.
The presence of water creates a perfect
environment for the culture and growth
of bacterial organisms. Fuels contain
latent cells of algae, ready to thrive in the
right environment, which can form at the
oil/water interface, where organisms can
breathe oxygen and feed on hydrocarbons.
In the field, these active cells will col-
lect on filters and strainers, another perfect
locale for accelerated growth. Eventually
residues are formed that combine with
sediment to form a slimy, impenetrable
obstruction to oil flow.
So, how can we minimize the damage?
The first line of defense has been, and always
will be, good housekeeping practices.
Inspecting tanks for loose caps and manholes,
the
outside of the
tanks for any structural
flaws, sampling the fuel at various levels
to determine uniformity, and periodically
sampling the bottom of the tank to iden-
tify and, where practical, to remove any
contamination buildup. All these measures
would serve as the start of an effective
maintenance program.
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The second important line of defense
is to be proactive and establish a chemical
treatment program that can meet these
challenges. This means consistently using
a multifunctional fuel conditioner, such
as C&S Scientific’s Treat Now, that is for-
mulated with specific components proven
to minimize the severity of oil storage
problems.
Vital components for multi-function
treatment include: antioxidants to slow
down the impact of oxidation; stabilizers
to prevent co-mingled fuels from stratifying
and to stop sludge deposits, neutralizers
and passivating agents and prevent corro-
sion in the tank and line; wetting agents and
penetrants to remove existing sludge; water
inhibitors to keep fuel clean and moisture
free; and anti-foulants to create an environ-
ment non-conducive to bioorganic growth.
The results of following these two
steps—good housekeeping and consistent
use of an effective chemical program—will
be the preservation of clean oil tanks and
trouble-free, long-term oil storage.
–
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By Jerome P. Sava, C&S Scientific
Fuel Quality
