May 2009

Diesel Fuel Analysis FAQs
by Ambrose Hughey, OMA I
Portland Laboratory Manager

How much biodiesel is in my fuel?
Determine your biodiesel blend content for OEM or supply/purchasing requirements. OEM warranties specify requirements for the fuel used with their products. Most OEMs allow use of biodiesel blends with up to 5% biodiesel, with some allowing up to 20% without voiding the warranty. The biodiesel content of your blend can be determined by using FTIR analysis.

Does my fuel have the appropriate viscosity?
If the viscosity is too low, fuel injection pump and injector leakage can occur. Proper viscosity affects the fuel’s ability to lubricate fuel system components and properly atomize during injection.

Does my diesel fuel have good ignition quality properties, thereby providing good cold start performance?
Cetane index is used to estimate the natural cetane number of diesel fuel. Note: The cetane index is not affected by cetane number improvers. Cetane number is a measure of the ignition quality of diesel fuel. Cetane number is essentially a measure of a fuel's ignition delay: the time period between the start of injection and the actual start of fuel combustion. Generally, fuels with higher cetane numbers provide a shorter ignition delay period than fuels with lower cetane numbers.

Will my fuel perform well in low temperature applications?
Measure low temperature operability of your fuel by cloud point, cold filter plugging point, and/or pour point. The cloud point is the temperature at which the fuel begins to display a wax haze or cloud. Use of fuel at or below its cloud point may cause operability issues due to the wax crystals triggering fuel system plugging.

Is my aged fuel suitable for use?
Have an expanded analysis performed on your aged fuel to monitor the effects of long-term storage. In general, diesel fuel oils have adequate storage stability for normal use. For long-term storage of fuel (more than 12 months), a fuel monitoring program is an important part of a long-term storage program. Periodic sampling and analysis will provide the means by which to make important decisions regarding your aged fuel, its storage, and its suitability for continued use.

How stable is my fuel?
High temperature stability analysis determines the relative oxidative and thermal stability of the fuel. In general, modern fuel systems are designed to return the non-injected portion of the fuel back to the tank. This returned fuel has been highly pressurized and heated, which promotes polymerization and breakdown of the fuel, thereby creating carbon particulate. As more fuel is pressurized, heated, and recirculated, the amount of this carbon particulate generated in the system increases, leading to possible injector failure and filter plugging. This same method can also be used to determine the relative storage stability of diesel fuel.

How clean is my fuel?
Particulate contamination analysis measures the cleanliness of fuel by determining the total particulate amount. Another major source of contamination is water. Water contamination can lead to corrosion within the fuel system. Microorganisms require water to grow and, since most microbial growth occurs at the fuel water interface, keeping fuel systems dry will greatly reduce the likelihood of microbial contamination outbreaks and its related problems. Measure your fuel’s water content to make certain your fuel is dry. One of the potential problems with microbial contamination is the increased potential for filter plugging. The waste created by microbial growth, rather than the microbes themselves, create a potential cause of premature filter plugging. If there is a known water contamination issue currently or in the past in a fuel system, a check for microbial contamination is recommended. When possible, water should be drained from tanks regularly.

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TEST PACKAGE DESCRIPTION

TESTS INCLUDED

F1

Appearance, Water by Karl Fischer, Microbial Growth, Particulate Contamination, Water and Sediment

BASIC Analysis Package for Fuel Cleanliness

F2

API Gravity, Appearance, Cetane Index, Distillation, Flashpoint, Viscosity @ 40C, Water and Sediment

BASIC Analysis Package for Fuel Quality

F3

Appearance, Color, Water by Karl Fischer, Accelerated Stability, Microbial Growth, Acid Number, Particulate Contamination, Water and Sediment

ROUTINE Analysis Package for Fuel Long-Term Storage and Storage Conditions

F4

API Gravity, Appearance, Cetane Index, Color, Copper Strip Corrosion @ 50C, Water by Karl Fischer, Distillation, Accelerated Stability, Microbial Growth, Acid Number, Particulate Contamination, Viscosity @ 40C, Water and Sediment

COMPREHENSIVE Analysis Package for Fuel Long-Term Storage and Storage Conditions

F5

API Gravity, Appearance, Cetane Index, Water by Karl Fischer, Distillation, Flashpoint, Microbial Growth, Particulate Contamination, Viscosity @ 40C, Water and Sediment, Sulfur

COMPREHENSIVE Analysis Package for Fuel Quality and Cleanliness

WINTER

Cloud Point, Pour Point, Cold Filter Plugging Point

BASIC Analysis Package for Cold Temperatures

TANK B

Microbial Growth, Water and Sediment

BASIC Analysis Package for Tank Bottoms