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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 hydrocarbon.

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 concern.

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.

  • Carbonaceous particles

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.