Diesel fuel grades

Today s diesel fuel grades are blends which may contain straight-run distillate, cycle oil, various gas oils, and heavy cracked distillates. Kerosene or jet fuel may be blended into the diesel to improve the low-temperature viscosity and handling characteristics of the fuel. 

Lighter fuel oil grades contain many of the same blend components as diesel fuel grades. Heavier fuel oils such as 5 and 6 contain vacuum gas oils and residual fractions. 

Fuel grade is based primarily upon the viscosity of the fuel and the intended application. Both diesel fuel and fuel oil grades exist. Diesel fuel grades and their intended applications are outlined in TABLE 3-12. 

TABLE 3-12. ASTM D-975 Diesel Fuel Grades and Applications... 

Various common liquids have different flashpoints, so different containers can be used for storage at jobsites. For example, common diesel fuel grades have flash points below 140°F. This would make them flammable liquids and they must be stored in safety cans or Department of Transportation (DOT) approved containers. Some grades of kerosene have flash points greater than 140°F and do not need to be stored in safety cans or DOT approved containers. 

Specifications and test methods for diesel fuel (normal and severe cold grades) (from the standard NF EN 590 see AFNOR information document M15-007 and M15-022). 

Diesel fuel kinematic viscosity is measured by ASTM D445, and is reported in units of mm /s at 40°C. Desired viscosity is a function of fuel grade and ranges from a minimum of 1.3 mm /s for 1-D to a maximum of 24 mm /s for 4-D. 

ASTM specifications for different grades of diesel fuel are summarized in Table 11. 

Liquid fuels for ground-based gas turbines are best defined today by ASTM Specification D2880. Table 4 Hsts the detailed requirements for five grades which cover the volatility range from naphtha to residual fuel. The grades differ primarily in basic properties related to volatility eg, distillation, flash point, and density of No. 1 GT and No. 2 GT fuels correspond to similar properties of kerosene and diesel fuel respectively. These properties are not limited for No. 0 GT fuel, which allows naphthas and wide-cut distillates. For heavier fuels. No. 3 GT and No. 4 GT, the properties that must be limited are viscosity and trace metals. 

This condition is of concern only when equipment operates in subzero ambient temperatures. Since diesel fuel extracted from crude oil contains a quantity of paraffin wax, at some low ambient temperatures this paraffin will precipitate and create wax crystals in the fuel. This can result in plugging of the fuel filters, resulting in a hard or no-start condition. Any moisture in the fuel can also form ice ciystals. Cloud point temperatures for various grades of diesel and other fuels should be at least 12°C (21.6°F) below the ambient temperature. In cases where cloud point becomes a problem, a fuel water separator and a heater are employed. 

Conversion of heterocyclic aromatic compounds or other aromatic fuel components to paraffins by hydroprocessing can help increase the cetane number of diesel fuel. Fuel paraffins have significantly higher cetane number values than fuel aromatics. For this reason, the cetane number of ultra-low sulfur diesel fuel will typically be one to five numbers greater than higher-sulfur grade fuels. 

Grades 1-D and 2-D are most commonly used in truck, railroad, and some stationary engines. Grade No. 4-D fuels are used in marine and certain industrial diesel applications. Fuel oil grades and their intended applications are outlined in TABLE 3-13. Federal diesel fuel oil classifications are provided in TABLE 3-14. 

Arctic grade diesel fuel oil is recommended for use in environments with ambient temperatures lower than -25.6°F (-32°C). It is intended for use in high-speed automotive-type diesel engines, pot-type burner space heaters, and nonaircraft turbine engines. It is not intended for use in slow-speed stationary engine applications. 

Marine gas oil (MGO) Grade DMA Grade DMA is blended from straight-run and cracked gas oils. This fuel is sometimes identical to 2 diesel fuel and is used in high-speed engines. 

Fuel oil No. I is also a high grade Diesel fuel and has to compete with its use for that purpose. Furthermore, it is also an excellent cracking stock and therefore competes with gasoline. The question of how popular it will remain is consequently entirely one of economics, and certainly the burner that can handle all qualities of No. 2 has a distinct economic advantage over that requiring No. 1. In 1950, fuel oil No. 1 represented 16% of the total domestic fuel oil business. 

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