Water is always present. Fuel accumulates water during
refining, transportation and storage. No matter how carefully it is handled,
water will find its way into fuel. The question is, “How much water is too
much?” The answer will vary depending on the type of product. Free water is the
most damaging. Once saturation is reached – 100% RH – water will begin to drop
out of suspension and settle to the bottom of the tank. In reality,
conventional fuels should be kept below 200 ppm. Aviation fuels have a more
stringent requirement, below 30 ppm. Ethanol enriched gasoline can hold around
.398% water to fuel volume before full phase separation occurs. While there are
many different specifications limiting water in fuel, the ideal is to reduce
water down to the lowest possible amount.
Removing water from fuel depends on the type of water and
the type of fuel. Ethanol enriched fuels require a different remediation
process than other fuels due to the chemical composition of ethanol. It
does not take much water to cause fuel to phase separate. Less than 20 gallons of water in 5,000
gallons of fuel will result in phase separation. Tank monitoring systems may not be able to
detect that small amount and water finding paste can be difficult to read if
this is the method used for identifying water in fuel. The only sure way of determining water in
fuel is to take a sample of the fuel.
Bottom sampling is the first line of defense against phase separation.
The use of a water detection field test kit can help to quantify the amount of
water in suspension. System inspections are important to minimizing water
issues and can often catch a problem before it becomes unmanageable.
phase separated fuel be remediated? The
simple answer is yes. Most phase
separation can be corrected, although if there is a catastrophic event that
causes large volumes of water to enter the fuel, the alternative may be
disposal. There are a few simple steps to correcting phase separation.
- Determine the volume of
phase at the bottom of the tank.
This can be accomplished by using a fuel sampler. First take a sample on the very bottom
of the tank, then at 1 inch increments until you determine where the phase
ends and the fuel begins. There is a definite difference in the phase layer
and the fuel layer on top (see photo). After determining how many inches
of phase you have in your tank, you will know how much needs to be pumped
out. Once the ethanol drops out of the fuel and forms a layer on the
bottom of the tank, it cannot be reintroduced into the fuel. It must be
properly disposed of with the water and contaminants.
- Pump off the water/ethanol
phase and properly dispose of the waste.
Take bottom samples from the lowest accessible point in the tank to
verify you have removed all of the phase before moving on to the next
step. Keep in mind that it may be necessary
to remove the STP for proper access to the lowest point in the tank. It is
also important to refrain from stirring the fuel too much. Stirring can
- Use a filtration system
that has coalescing and water separation capability to remove any
remaining dissolved water. It is
likely that some water remains and needs to be removed. Remember not to stir the fuel during
filtration. The suction hose should
be placed on the bottom of the slowest access point in the tank and the
return should be above the fuel level in order to minimize any unnecessary
agitation. Speed is not your friend
when removing water from ethanol enriched fuel. Moving the fuel across the
filters at a slower velocity will allow for improved water removal. Once
the water has been adequately removed, the fuel octane level will need to
- If phase separated fuel
was 87 octane E10, it is possible to blend 93 octane E10 fuel at a ratio
of 1:1 to correct the octane level in the fuel. For example, if you have 3,000 gallons
of regular remaining in the tank, blending 3,000 gallons of 93 octane
premium fuel should correct the octane deficiency. Always verify octane through testing
once blending is complete. If the
phase separated fuel was 93 octane E10, then the fuel should be usable as
87 octane fuel. Again, octane
testing should be completed to verify results.
A second problem attributed to water and ethanol is
corrosion – specifically microbial influenced corrosion or MIC. Fuel
deterioration has been documented since 1895 and accelerated deterioration
since 1994. So what has changed and why is corrosion such an issue today? Since the mandated use of ethanol, MIC has
increased and become a serious problem.
MIC costs the United States an estimated $50 billion per year in
damage. Oil production, transportation
and storage are all affected. In the most recent research, accelerated
corrosion has been associated with the presence of ethanol in fuel.
Water must be present for there to be microbial growth. Because ethanol is both hydrophilic and
hygroscopic, ethanol blended fuels are more water soluble. In other words, water is more easily
dispersed in fuel. Condensation is more
easily absorbed. It is also thought that
ethanol serves as a food source for microbial growth.
The combination of water and ethanol serve as the perfect
breeding ground for microbes. These
hydrocarbon utilizing microbes produce acids.
The most prevalent, Acetobacter, produces acetic acid. Once the colony gains control of a fuel
system, corrosive growth accelerates.
Unlike typical corrosion that can take years to seriously damage a fuel
system, MIC can form overnight and severely damage a system within months. Costly damage has been seen in fuel systems
less than six months old.
How does the damage occur?
A microbial colony begins to grow when water is present and feeds on the
hydrocarbon producing an acidic byproduct.
This acid will lay on the bottom of the tank and remain suspended in the
fuel with any water that may be present.
The combination of water, microbes, acids and deteriorating fuel form a
biomass. “At the fuel-water-tank interface, all of the
necessities of life are present: a carbon source, water, an electron donor (the
hydrocarbon/ethanol blend and/or metals in the tank), and an electron acceptor
such as O2 or previously oxidized metal (e.g., rusted steel).” Even cathodically protected stainless is susceptible to
corrosion. Carbon steel definitely
proves no match.
As the biomass grows and accumulates on the tank bottom, an
acidic off-gassing is common. The vapor fills the tank and enters the dry
spaces within the fuel system. Corrosion
in submerged turbine pump (STP) sumps is often a result of MIC.
While ethanol is the catalyst to an abundance of problems,
there are some simple answers. No doubt
phase separation and corrosion present challenges to the industry but neither
are insurmountable. For both of these
problems the common denominator is water.
Neither phase separation nor MIC are an issue without water. If you can keep your fuel dry, then you can
minimize the problems. All it takes is a
Biodiesel presents several maintenance challenges especially
as it pertains to water removal. Because biodiesel is more hygroscopic than
ULSD, more suspended water is likely. Dissolved water in biodiesel promotes the
breakdown of fuel molecules resulting in surfactancy increase and lower IFT. Because
most biodiesel already has lower IFT, the problems are exacerbated. The more
biodiesel in a fuel, the more water and particulate holding potential. A
combination of filtration media may be necessary to remove water from
biodiesel. Monitoring the quality of the fuel and the water content while
filtering will help determine the need. Using Dixon cleaning and filtration
equipment and filters will mean CleanFuel!
Conventional fuels have similar problems with water
contamination. While not as challenging to clean, the problems are still
present. The most efficient way to
remove water from conventional fuels is through coalescing and water
separation. Dixon’s two stage filter housings provide the desired results –
capable of removing water down to as low as 50 ppm. Absorption filters are another option for
removing water, especially when the fuel is highly emulsified. With the right
filter element, water content can be brought down below 30 ppm. Knowing the
application and the cleanliness requirement helps determine the type of filter