The Fuel We Use And What To Know About

[ToolManTimTaylor]

Good read on the growth and effects

Algae are a life form found in water, similar to algae growing in an aquarium. However, for years, people have been referring to tank sludge and to the jelly, slime and other contaminants found in fuel filters as "algae". The colloquialism "diesel fuel algae" is widely used and understood. However, there is no relationship between the "algae" growing in your aquarium and the sludge "growing" (forming) in your fuel tank and showing up on your filter elements.

There are three basic areas of concern in fuels and oil. They are: 1. water 2. in-organic debris (sand, dust, rust, etc.) and 3. organic debris (fuel breakdown products and waste products of fuel deterioration and re-polymerization). The organic debris represents more than 90% of all the contaminants found in fuels and oil. It is this organic debris, the sludgy, slimy, acidic material that people refer to as "diesel fuel algae". It could also be called polymer, tar or wax and asphalt!

In South America, people refer to the "Algae" as "mud". In gasoline, the organic fuel breakdown products are often referred to as gum, varnish, or lacquer. Taken literally these words could be confusing too


Up until about 15-20 years ago, refineries used only about 50% of a barrel of crude oil to make distillates such as gasoline, jet fuel and diesel. The remainder of the barrel of crude oil went to "residual oil". Today, as a result of different refining techniques and additive packages, the refinery uses 85% or more of the same barrel of crude, which clearly has consequences for fuel stability.

More than 90% of the debris on filter elements and the sludge in our storage tanks is organic material, fuel and oil breakdown residue. In most cases, this debris is acidic and not good for your engine. It causes corrosion in injectors, pumps and storage tanks.

The solids that form as the result of the inherent instability of the fuel and the natural process of degradation will accumulate in the bottom of your tank. The sludge will form a coating or bio-film on the walls and baffles of the tank, plug your filters and impact combustion efficiency. Eventually it will clog fuel lines and ruin your equipment.

*Hydrocarbons are organic compounds composed entirely of carbon and hydrogen divided in four major classes: paraffins, naphthenes, olefins, and aromatics. These classes share common structural features but differ in size, (number of carbon atoms per molecule) and/or geometry. While hydrogen and carbon are the predominant elements in crude oil, small amounts of sulfur, nitrogen and oxygen are also present and referred to as hetero-atoms (other-atoms). Compounds containing hetero-atoms are non-hydrocarbons. Typical non-hydrocarbons found in diesel are dibenzothiophene and carbazole, which play a large role in determining certain fuel properties.


3. What is the "stuff" that clogs my filters?

Filter plugging can have several causes. For example, low temperatures can cause wax crystallization, which can lead to filter plugging. An example would be using summer diesel in cold weather. Wax or paraffin is part of the diesel fuel.

Chemical incompatibility may cause dramatic filter plugging. This may happen when fuels with incompatible additive packages are mixed.

Contaminant build up resulting from excessive microbial growth and bio-degradation of fuel can cause filter plugging. Micro-organisms, bacteria and enzyme activity, fungus, yeast and mold cause fuel degradation and the formation of waste products. The process is similar to milk turning into cottage cheese, a different form of milk. Of all the microbial debris and waste products in the tank only about .01% is bugs. Even though microbes may cause and accelerate the process of fuel degradation, it should be clear that the waste products clogging your filter are not the microbes but fuel components which have formed solids.

Frequently, the application of a biocide aggravates the situation and turns bio-film into solids, creating a real fuel filter nightmare. Bio film develops through out the entire fuel system. It grows in the water fuel interface and on the walls, baffles, and bottoms of storage tanks. An unlucky end user may be filling up his tank and getting this debris delivered as a part of his fuel, for the same price as the fuel.

Poor thermal fuel stability can plug filters. Fuel will form particulates (solids) when exposed to pumps and the hot surfaces and pressure of the fuel injection system. This will result in an increase in asphaltene agglomerations, polymerization and a dramatic loss of combustion efficiency.

Fuel systems, in general, are designed to return a significant proportion of the fuel, not used for combustion, back to the tank. This return fuel is very hot and will promote polymerization and fuel breakdown. Eventually, more and more solids from the tank will reach the filter and over time, plug the filter. These problems continuously occur in commercially operated engines, such as trucks, heavy equipment, shipping, and power generation, but will also appear in recreational boats, RV's and all types of fuel storage tanks.

Truck engines are used continuously and, in most cases, the tanks "appear to be clean". However, a 2-micron filter element does not last very long, in general 15,000 miles or less. It should be 30,000 miles or more. In the marine industry 400 hours is in many instances SOP while filters should easily last 1000 hours or more.

Short filter life is quite remarkable realizing how "thin" diesel fuel actually is and knowing how clean the tanks on most trucks "appear" to be.

Short filter life is symptomatic of polymerization, increase in the size of the fuel droplet, agglomeration of asphaltenes and the formation solids in fuel systems. The consequences are carbon build up in engines and exhaust systems, higher fuel consumption and excessive smoke.


4. Can diesel fuel plug your filters?

Yes, it can. The stuff that clogs your filters is actually fuel in some way, shape or form. In excess of 90% of this organic debris are fuel breakdown products. It is not sand, dust, stones, rust or in-organic matter that blocks your filter.

The inorganic material like sand, dust and other particles will not cause your filters to clog. In fact, a lot of sand in a fuel filter would act as extra filtration. The pores between the sand particles are much larger than the pores in a standard fuel filter element. Sand filters are commonly used to filter water. A hair is approximately 40 micron and fuel filter elements range all the way from 30 micron for a prefilter to 2 micron in a fine filter.


5. How does fuel stability affect the user?

Fuel stability is a serious concern for the diesel fuel user.

The chemistry of diesel fuel instability involves the chemical conversion of precursors to species of higher molecular weight with limited solubility. The conversion process often involves oxidation of the precursors. Fuel solvency plays a role, since the development of insolubles is always a function of both the presence of higher molecular weight species and the fuel capacity to dissolve them.

We all realize that fuel is an unstable, organic liquid that goes "bad". Your vendor will always sell you the highest fuel quality possible. However, due to a variety of circumstances fuel may have "aged", oxidized and/or contain water. It may have been contaminated before it was delivered to you or to your vendor.

Fuel has to travel from the refinery to the end user destination. It is pumped through pipelines, barged, trucked and stored in tank farms. Diurnal changes in temperature and exposure to the atmosphere will cause condensation and water in storage systems. None of this will help improve fuel quality.

When your fuel is finally used, it is exposed to the heat and pressure of engine injection systems, centrifuges, pumps, heaters causing an increase in asphaltene agglomerations, which negatively impacts combustion efficiency and emissions.


6. What is bad fuel?

Fuel is made to certain ASTM specifications. When it does not meet these specs., we could refer to it as "bad fuel". However, we tend to refer to fuel as "bad fuel" when we see symptoms such as: -dark hazy fuel, -filter plugging. -sludge build up in tanks, -poor engine performance, -excessive smoke & emissions, -etc. We refer to fuel as "good fuel", when it is clear and bright. Or rather in that case, no reference is made at all to our fuel. We simply use it and take fuel quality and peak engine performance for granted. Bad fuel is fuel that does not meet ASTM specifications.