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Diesel
Fuel Analysis Fuel analysis has become a very important part of all maintenance and purchasing functions. The cost of diesel fuel, although expensive, is small when compared to the problems that may develop without the proper purchase specifications, verification of those specifications, handling, storage and distribution. Generally speaking, most fuel is within the grade; however, on occasion a fuel delivery may be substandard. Fuel will also degrade and become contaminated in storage and transfer. It is almost impossible to retrace the sequence of events leading up to fuel problems unless an accurate record of the quality of the fuel is maintained. This can only be done by periodic laboratory analysis of the fuel.The properties of commercial fuel oils depend on the refining practices employed and the nature of the crude oils from which they are produced. Distillate fuel oils, for example, may be produced within the boiling range of 150 and 400 degrees centigrade (300 and 755 degrees Fahrenheit), having many possible combinations of various properties such as volatility, ignition quality, viscosity, and other characteristics.  Receipt Inspections / Quality Control As a rule, all fuel deliveries should be sampled and tested. The economics of sampling are not only to guarantee the money paid to the supplier was well spent, but also to ensure the integrity of your entire system against unplanned downtime. This fuel delivery could, if contaminated or "off grade," cause enormous problems when mixed with the fuel you already have in the tank. It is wise to arrange in critical applications a system whereby you have the opportunity to sample and test the fuel prior to introducing the fuel into your primary tank(s). This can be done by having the tanker truck leave the trailer on-site until you have completed your testing, or by building a holding tank to accept deliveries for analysis prior to dispensing into your storage tanks. Sampling Storage Tanks Periodic sampling and inspection of stored fuel will reveal several important quality parameters that if gone undetected may cause unnecessary problems in the operation of the diesel generator. During long-term storage of diesel fuel, water, sludge, and microorganisms will accumulate. The early detection of these contaminates will eliminate fuel related problems later on. Sampling Techniques As with any sampling program, a representative and accurate sample is necessary to receive the full benefit of the analysis. The reasons to sample may differ; therefore, the sampling methods will be different. In order to evaluate the concentration of sludge, water, and debris on the bottom of the tank, you will want to take a sample at the lowest point in the system. This sounds easier than it is, since in many situations, the fill tube is the only access to the tank. This causes a situation where, when the tank is filled, the velocity of the filling action washes this area clean of debris, and you are unable to get to the areas beyond the fill pipe. A long sample tube strapped to PVC pipe and angled to the side may be of help. If this is not the situation, a simple bottom sampler will normally suffice. When a sample of fuel for general quality testing is required, a middle and bottom composite will usually suffice. When fuel has been received in good condition and contamination and degradation are the only reason for sampling, you may not require all of the tests that were performed on the original load. An example of testing that is not required would be sulfur, viscosity, cetane, and distillation. If the fuel in storage proves to have no contamination and the stability is acceptable, these values would not change. ASTM D-975 Specifications ASTM Specification D-975 for diesel fuel oils is intended as a statement of permissible limits of significant fuel properties used for specifying the wide variety of commercially available diesel fuel oils. Limiting values of significant properties are prescribed for three grades of diesel fuel oils. These grades and their general applicability of use in diesel engines are broadly indicated as follows: Grade No. 1-D comprises the class of volatile fuel oils from kerosene to the intermediate distillates. Fuels within this grade are applicable for use in high-speed engines in services involving frequent and relatively wide variations in loads and speeds, and also for use in cases where abnormally low fuel temperatures are encountered. Grade No. 2-D includes the class of distillate gas oils of lower volatility. These fuels are applicable for use in high-speed engines in services involving relatively high loads and uniform speeds, or in engines not requiring fuels having the higher volatility or other properties specified for Grade No. 1-D. Grade No. 4-D covers the class of more viscous distillates and blends of these distillates with residual fuel oils. These fuels are applicable for use in low and medium-speed engines employed in services involving sustained loads at substantially constant speed. For more information contact Herguth or call 1-888-HERGUTH (437-4884) |
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