AM FLEET STANDARDS
Definitions & Testing Methods
Product Data definitions and explanations:
- Specific Gravity — The density of the product as measured at a specific temperature.
- Weight per Gallon — The number of pounds one (1) U.S. gallon weighs.
- Flash Point, T.C.C. Tag Closed Cup) — A specific test to determine at what temperature the vapors will burn in an enclosed space. The vapors are extremely concentrated and then a flame is introduced. T.C.C. is the name of the test and it is a standard test in the refining industry.
- Viscosity — The actual thickness of a chemical at a specific temperature. Usually this tells how easily a chemical will pour as the temperature gets colder.
- Pour Point — The temperature at which a chemical cannot be easily poured out of a container because it is too cold. The container and content amount are test specific.
- Color — The color of the chemical in its pure form before mixing with the fuel. ASTM D-1500 is a specific test, basically a color chart, that the chemical in glass is compared to. Lighter than 2 is usually the standard that is used for diesel fuel.
Abbreviations and their explanations:
- A.S.T.M. — American Society of Testing and Materials. A.S.T.M. tests are generally used and accepted as testing standards in nearly every refinery in the world. Their procedures cover all facets from metals, water, air, to various grades of fuels, etc. Many governments and refiners may change the pass/fail requirements but the procedures are highly respected. It is not uncommon for foreign entities to increase the pass thresholds for pass. This is especially true for performance and environmental concerns. These increases are why the U.S. is far from being the leader in fuel quality for different fuel types.
- N.A.C.E. — National Association of Corrosion Engineers. N.A.C.E. tests are by a U.S. based association and used mostly for production, crude pipeline, refinery & process, and agricultural products. Some tests are extremely useful in different chemical applications.
- E.M.D. Diesel Fuel Stability Test — Electro Motive Division of General Motors. Very similar to ASTM D-2274 but uses air vs. oxygen. ASTM D-2274 is usually much preferred /reliable.
- Assorted Data — There are many tests that are asked for by clients that are named after various refining companies (mostly foreign), engine manufacturers, generic with no sponsor or authorization agency, etc. Many of these tests have questionable reliability or validity. We question these tests highly but when used in our data we clearly try to identify source(s). EXAMPLE: A.S.T.M. has not developed a committee approved test for injector cleaning or for mileage improvement, nor has the U.S. D.O.T., after many years and extensive testing. Test the fuel yourself to your parameters.
The following is a listing of the A.S.T.M. tests and a brief explanation of each test and how it is performed. All of the tests take special equipment and are conducted according to a very closely followed procedure. Many different laboratories and refineries can run these tests. A.S.T.M. stands for American Society of Testing and Materials. It is a membership group of people from respective industries that devise different ways to test materials to determine that they meet certain standards. The tests that AM Fleet uses most often are the following:
¨ ASTM D-613 — This is the test used to measure the cetane of the fuel. D-613 is the number of the test. Cetane number is to diesel fuel like octane number is to gasoline. Cetane number is a measure of the degree of combustibility of the fuel. It is measured by using a test engine that closely monitors how the fuel burns. Chemicals can be added to a known cetane fuel and measurements can be made to determine how much the chemicals increase the cetane rating. A higher cetane rating is a better fuel. It is very common to see diesel fuels today with a cetane rating of 40. Before 1979 is was common to see fuels with a rating of 50 to 52. The refining methods were changed during 1978-1980 which lowered the cetane ratings to as low of 35 or 36. Generally now most fuels have a rating between 38-42 cetane. That’s in the U.S. Europe and most of Asia fuels are much higher.
¨ ASTM D-97 — This is the test for diesel fuel to determine how the fuel flows at extremely cold temperatures. Straight diesel at the refinery, with no chemicals added, starts to form wax needle crystals at 10 to 15 degrees above zero Fahrenheit. At first it starts to look cloudy, forming a soft white cloud in the middle of the fuel. As the fuel gets colder, usually to about 4-5⁰F, you will see the wax needle crystals form. The larger crystals (6+ microns) plug the filters and the engine will starve (and quit) because of lack of fuel.
The test is conducted by putting the fuel in small bottles, treating the fuel in different concentrations, and putting all the samples in a special freezer and cooling them down very slowly, one (1) degree at a time. The fuel is checked continuously for wax formation and the temperature is recorded when the fuel will no longer flow. There are a number of various tests by other people to test for the same result; AMOCO REFINING and their pumpability test is but one example.
All refineries add chemicals, kerosene, or a combination of both to their winter fuels to stop the wax from forming. Most refineries try to treat their fuel to about – 10/15⁰F below zero. After that, it takes a lot of chemical or kerosene and the cost is prohibitive under their standards. Generally, AM Fleet tries to treat all fuels to -40⁰F below zero (C⁰ and F⁰) with our chemicals designed to treat for lower temperatures. In these commercial formulations, we use the same chemicals that the major refiners use; we just use them at a stronger concentration.
The important thing to remember is that wax needle crystals will form unless you add chemicals to inhibit and modify their formation. Large wax needle crystals will form at very low temperatures below -0⁰ F without the addition of these chemicals and the crystals will plug the filters and starve the engine, if the fuel gets that cold.
¨ ASTM D-2274 and EMD Diesel Fuel Stability Test — The two tests are for the same parameters and are very similar as to how they are conducted. Sometimes the EMD is also referred to as the DuPont test because E.I. DUPONT manufactures many of the chemicals used to stabilize fuels and helped develop the test.
The test is to measure the amount of oxidation, or predict the aging stability of a fuel. As a fuel gets older or is exposed to higher temperatures, it degrades and the quality gets worse. At first the fuel gets darker and the color goes bad. This does not affect the fuel’s ability to burn.
The fuel then starts to form black particulate and this is a problem. In bad fuel it looks like small particles of soot and they are visible to the naked eye. It is these particles that try to go through the filters and plug the filters and/or plug the injectors. They are so small that many can go through the filters and start to form a deposit on the injector surfaces and are not hydrocarbon soluble. These deposits keep building and can eventually plug the injectors.
These two tests are conducted the same way. The only difference is that in one test the fuel is capped with air, and in the other test pure oxygen is used. The societies also rate the test differently in readings of the strainer pads.
Fuel is put into test tubes. Fuel with no chemicals added and also fuel with chemicals added in various concentrations are used. These are put into special ovens and sealed. Air is put under pressure and pumped into the apparatus in one test; oxygen in the other. With the artificial atmosphere under pressure, the entire apparatus is then heated to a specific temperature and held there for 16 hours. The fuel is then cooled down and removed. After that, the fuel is strained through white test pads to collect all of the particulate that has formed in the fuel. These pads are then compared to a published standard to determine the rating.
AM Fleet can stabilize most fuels against detrimental particulate for a period approaching and exceeding two years, with no degradation. Desert conditions tend to shorten the time span and colder temperature conditions will definitely lengthen the time. However, in colder climates freezing water and wax crystallization can cause other problems and must be treated with other chemicals.
¨ ASTM D-665-60-A and NACE TM 01-72 — These tests both test the effectiveness of a corrosion inhibitor in diesel fuel. TM stands for test method and the number is the reference number to the spindle test. ASTM is also a spindle test which uses a synthetic sea water for sixteen (16) hours, whereas the NACE test uses distilled water for a four (4) hour test period.
The tests are conducted using special equipment designed just for the testing formation of rust and particulate. A series of beakers are filled with a mixture of fuel, some with various concentrations of a corrosion inhibitor added to them. A specific amount of the appropriate water is then added to all beakers. The beakers are then put on a special stand and into each beaker a clean, polished, steel spindle is suspended. The fuel is then stirred with the water for the specified time periods. After they are removed and the amount of rust and particulate is determined, the spindles are rated. The rating system varies somewhat, but a B+ or better rating is generally considered passing.
¨ ASTM D-1094 — This is probably the most critical test in fuel. It is because water is a factor in so many problems with diesel fuel. Contrary to popular belief, the water present in fuel is not usually due to condensation. It is true that a small amount of it is, but the vast majority is introduced when the fuel is put into the tank. You buy the water when you buy the fuel and it comes with it.
Water gets into the fuel in numerous ways. It is present in the refining process when the fuel is distilled and not properly removed. The refiners pump the fuel into tankage and under old standards would hold for 72 hours for the water to drop out. The efficiency of this operation depends on the time they hold it in tankage and how much demulsifier they circulate in system. It also depends upon how much material they draw off the tank bottoms after the water has settled out.
That is the start of how water gets into fuel. The next step is the transportation of the fuel, which usually included pipelines. Through these same pipelines they usually ship a lot of (aqueous) water chemicals. These can be agricultural products, mining chemicals, and any variety of other chemicals. They commonly run a buffer zone of liquid through the pipelines between product and sometimes a plug, called a pig. During this phase, large amounts of contaminate between product can occur and are sometimes introduced into the fuels.
The final method that in which water is introduced into the fuel is through poor handling at the refinery, pipelines, racks, tank trucks, underground and failed tanks, and built-up water bottoms.
The test itself is very simple. The test is often used in the determination of how well chemicals work with the fuel in shedding water in jet fuel. For jet fuel you must also use the W.I.S.M. test to comply.
To conduct this test, a number of fuels, (some with chemicals at different treating rates in them) are put into beakers. A specific amount of water is put into the container. The containers are shaken vigorously and then put of a viewing rack. The fuels are then timed to see how long it takes for the water to completely settle to the bottom of the container and create a completely clear interface between the fuel and the water. If you re-shake the containers, the water should continue to rapidly separate time and again under the same parameters. The clarity of the fuel and the water phase is rated.
Water DOES NOT burn, CANNOT be made to burn (even by adding chemicals to it), and is corrosive and freezes easily. Water changes the density of the mixture that is introduced into the engine for combustion, thereby altering ratios. Water causes an uneven burning pattern in the cylinders because it will not burn, and by also cooling some of the fuel below the ignition point. This unburned fuel goes out the exhaust and is wasted and it also makes starting more difficult. Water contaminates cause unburned or partially burned fuel, and the resultant uneven ignition is substantial and extremely harmful to the engine. The wasted fuel is emitted from the engine going up the stack. You can see it.
Water also has one other disadvantage that is important – it acts as a host to bacteria. Bacteria grow where water and fuel meet in the layer or interface. The live bacteria and dead bacteria, if not treated to drop into the water phase, will cause problems. They foul filters and block or plug injectors. They also do not burn and will cause carbon and other deposits to form in the combustion chambers.