Frequently Asked Questions 2017-11-03T12:50:00+00:00


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 is from 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 80 micron in diameter and fuel filter media elements range all the way from 30 micron for a prefilter down to 2 micron in a fine filter.

Generally – Yes. Even though the process used to lower the sulfur in diesel can also remove some of the components that give the fuel its lubricity. We recommend the use of AFC-705 Fuel Catalyst with lubricity enhancer, as needed, to raise the lubricity to an acceptable level and protect injection systems of the engine.


“Algae” in diesel fuel refers to the organic debris, sometimes called sludge or mud, that naturally forms in the bottom of fuel tanks, representing about 90% of all contaminants found in fuels and oil. This “algae” causes a range of engine problems including:

  • fuel injector damage
  • clogged filters
  • engine shut-down
  • loss of power
  • poor fuel economy
  • excessive smoke
  • toxic fumes
  • loss of reliability

In order to prevent diesel fuel algae from appearing and achieving optimal fuel quality, the contaminants in fuel must be filtered out, water must be separated from the fuel, and the fuel must be conditioned.  This process of filtration, separation, and conditioning is the foundation for achieving the quality of fuel necessary for ultimate reliability.

Good housekeeping and purchasing clean, dry fuel from a reputable supplier are definitely step one.

In applications, such as emergency power generation, we recommend installing a fuel re-circulation/filtration system like the fully automated AXI STS Fuel Conditioning and Filtration System.

These commercial, high capacity systems, typically have the following basic components: a pump, a filter/water separator, a water block or fine filter, a timer, and an electronically controlled monitoring system with alarms.

It is recommended to start a fuel maintenance program with implementing the AXI Fuel Catalyst AFC-705 to stabilize the fuel in the tank. Beneficial features in AFC-705 Fuel Catalyst include corrosion inhibitors and lubricity enhancers to not only preserve fuel integrity, but also to protect your engine equipment.

Traditionally, biocides and filtration were the only treatment available. In many cases, we have seen this regime do more harm than good. The use of an adequate fuel quality management program and service, along with regular fuel testing to monitor fuel integrity, are an absolute necessity and will cut costs. Periodically adding stabilizer is another common practice used, for example, with nuclear power plants, which all have back-up diesel powered generators.

Installing a dedicated AXI Fuel Quality Management system that automatically operates and purifies the fuel is becoming a rapidly accepted standard maintenance for hospitals, data storage, and telecommunications companies.

Also recommended is the practice of removing any water within a storage tank and regularly monitoring for microbial contamination. Since most tanks do not have a water sump or a inclined bottom that can be drained at the lowest point, water must be extracted from within the fuel supply. To remove water from fuel tanks, we recommend the use of either the AXI “Water Eliminator” or an AXI Tank Cleaning / Fuel Conditioning and Filtration System.

The AXI “Water Eliminator” is either a small nylon or a larger stainless steel cylinder, containing a special polymer. The polymer will absorb the water (not the fuel) for easy removal.

While integrating these processes into a fuel maintenance program are a great step into the right direction, optimal fuel quality is achieved by separating water from fuel, filtering fuel, and polishing fuel. The AXI MTC series is a compact mobile fuel polishing system that removes water from the fuel tank while filtering and polishing the fuel in a dialysis fashion.  Click here to learn more about the MTC series.

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

The chemistry behind 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.

The journey fuel has to travel from the refinery to the end user destination is open to opportunities for the introduction and promotion of contamination. It is pumped through pipelines, barged, trucked, and stored intermittently in tank farms throughout this journey. Daily changes in temperature and exposure to the atmosphere will cause condensation and water build up 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, and heaters, causing an increase in asphaltene agglomerations, which negatively impacts combustion efficiency and emissions.

A diesel engine uses only some of the fuel it pulls from the tank. All fuel pulled from the tank goes through the high-pressure fuel pump and the injectors which operate under very high pressure and temperature.

The surplus fuel the engine does not use goes back to the tank. This fuel is continuously re-circulated and exposed to extreme pressure and heat, which results in the agglomeration of asphaltenes, which are high carbon content, heavy end fuel molecules. It leads to the formation of larger and larger clusters and solids, which are very difficult to completely combust. These solids may grow so large that they will not pass through the filter element and become part of the polymer and sludge build up plugging the filter.

In addition, the hot fuel coming back to the tank will raise the fuel temperature in the tank, cause condensation and contribute to microbial contamination, fuel break down, bio fouling and the build up of sludge and acid.

Large fuel droplets and high asphaltene concentrations require more time, more energy and higher temperatures to combust than is available during the combustion cycle.

Any device in the fuel system exposing the fuel to stress (heat and pressure) such as pumps, heaters, or centrifuges will increase the formation of asphaltenes and negatively impact combustion.

This is a question many of us have asked more than once. And what we really want to know is: “Will the stuff damage my engine?” Engines are expensive, and ruining an engine is costly, so operating an engine on “bad fuel” is not wise.

Most engine failures start in the fuel tank. When all mechanical parts are in good operating condition, the cooling and lube systems are working, and the lube oil is clean, a diesel engine or turbine could almost run forever. The only limiting factor is Fuel Quality. Dark fuel is symptomatic of poor quality, and even though it will work in most cases, fuel in this condition will provide poor combustion and add to filtration problems.

“Dark fuel” is, in general, indicative of oxidation and that the process of fuel degradation is in a far advanced stage. Hazy fuel is indicative of water emulsified in the fuel. In general, dark hazy fuel will not cause immediate damage your engine, but will over time if left untreated. It indicates, however, poor fuel quality, which will definitely not provide you with peak engine performance.

Using less than optimal fuel quality negatively impacts engine efficiency and accelerates the process that makes new engines old. Diesel fuel, in its native state, can range from colorless, to amber or light brown color, depending on the crude oil and the refinery process used to produce it. In addition, dyes may be added to change the fuel color for tax identification purposes.

In time, stored fuel will darken due to oxidation, repolymerization, and agglomeration of certain components. The darkening is a result of the formation of sediment that plugs filters and causes poor combustion. Fuel & Oil vendors suggest that if diesel fuel is stored for emergency use, it should be replaced with fresh fuel within a year, unless special precautions or remedial actions are taken.

The University of Idaho conducted tests on the life expectancy of fuels to determine the timeline on degradation of stored #2 diesel. The results indicated 26% degradation after 28 days of storage. Disposing of old fuel and purchasing new fuel is a very expensive proposition. Many larger companies, government institutions, hospitals, etc. have dumping of fuel and the purchasing of new fuel as standard and accepted practice.

The implementation of AXI technology eliminates these costly, wasteful, and environmentally unfriendly dumping practices. AXI will preserve fuel integrity almost indefinitely and can help you put in place good housekeeping measures, along with a quality fuel-monitoring program.

Well, filtration simply cannot, and will not, do that. At best, filters, separators, and centrifuges remove debris suspended in the fuel before it reaches the engine. Stopping, preventing, or reversing the process of fuel breakdown is a completely different matter that can be addressed, and resolved, with AXI Fuel Conditioners. It is not very likely that filtration (either the filter on the engine, or an external filtration system) will remove the sludge coating from the walls and baffles of your storage tank, and the use of biocides will almost always aggravate the situation. Filtration has no effect on fuel break down processes.

Simple in-organic debris, dust, sand, rust, etc. can easily be removed from the fuel stream with a filter.  This in-organic material will be trapped in the filter without clogging it. Most of the debris we see on the filter elements (the stuff that plugs our filters) is the result of the fuel having begun to form solids.

The water separator is designed to remove free-water. However, a separator, filter combination, or centrifuge cannot remove emulsified water. Free water in fuel can simply be removed from the fuel stream with the use of a water separator. Several well-known and very efficient combination filter/water separator devices exist within the market and are essential in any diesel engine application.

Temperature, humidity, and condensation are very important factors to consider in managing fuel quality. The presence of free water provides the medium for microbiological growth, resulting in the formation of slime or acids that can cause corrosion of metal surfaces; such as storage tanks, pumps, injectors, etc.

Other key factors leading to fuel deterioration, polymerization, and stratification within storage tanks are chemical incompatibility and stress caused by heat and pressure from pumps, centrifuges, and heaters. Since most diesel engines return considerable amounts of fuel back to the tank (due to fuel not being completely used during the combustion process), it is easy to see that the engine itself contributes to fuel deterioration.

Optimal Fuel Quality means Peak Engine Performance. New engines will retain maximum engine efficiency much longer using good quality fuel. AXI treated fuel extends the life of both old and new engines.

AXI fuel conditioning technology optimizes fuel quality and eliminates the build up of organic solids, tank sludge, acid formation, and clogged filters. It enhances combustion by reducing the size of the fuel droplet sprayed by the injector, eliminating carbon build up, and reducing harmful exhaust contaminants.

The implementation of AXI technology lowers operating cost and brings equipment in compliance with the Clean Air Act, reducing environmental concerns about smoke, particulate, and oil sheen on the water.

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