Types of Contamination
There are three broad forms of contamination: gas, liquid
and particulate. Each of these offer
varying degrees of potential damage to fuel and fuel systems.
Most do not see air as a
contaminant, but it is. As a fuel system
breaths, air brings with it a host of contaminants including bacteria,
moisture, dust and particulates. Liquid contamination consists primarily of
three types: water, fuel cross-contamination and acidic byproducts from
microbes. The third form of contamination, particulates, include foreign
particles like rust, scale and sand. It can also include components of the fuel
itself that separate and drop out due to the aging and decomposition process of
The most problematic liquid contaminant
is water. Unfortunately, all fuel
contains water. The allowable limit is
0.05%. This is equivalent to 2.5 gallons water in 5,000 gallons of fuel. Because most fuels contain biofuel additives
or blends, water presents more problems. Cross contamination is also an issue. There
are few dedicated delivery systems meaning all types of fuels are carried
back-to-back. The practice of switch-loading is common. Switch-loading takes
place when one product is carried in the same container prior to another
without cleaning the prior product. The
most common cross-contamination is ethanol enriched fuel (E-10) in diesel fuel.
Acidic byproducts from microbial contamination and fuel aging are also a major
There are numerous types of
particulate contamination. Everything
from rust to microbes. The types of potential particulate contamination are too
many to list. A majority include rust, sand, microorganisms and hydrocarbon components
that have separated during the aging process. As a hydrocarbon ages, it breaks
down. There are several forms of
contaminants that separate as a result:
Asphaltines are asphalt like particles found in
crude oil. When fuel ages it oxidizes
creating byproducts like Asphaltenes.
They are generally thought to be harmless because of their tiny size –
0.5 to 2.0 µm size. During the fuel aging process the substance can stick
together and on equipment or filter surfaces causing damage to both the fuel
system and engine. Water will speed up the formation of Asphaltines.
Wax crystals form in diesel fuel as a result of
low temperature. During the winter months, additives are often added to fuel to
change its low temperature characteristic. Without the additive, waxes can form
and separate, clouding the fuel and clogging filters. Engine and fuel system
damage can occur.
Each type of contaminant has the
capacity to damage a fuel system or engine. Depending on the type and amount,
damage can range from minor to severe. As fuel ages and is left unchecked
equipment damage is almost certain. The shelf life of fuel is 3-6 months
without some level of maintenance. If
water is present, fuel will degrade faster. Both water and heat speed the
process allowing for accelerated biological growth.