Let’s talk about oil products specifications and its main properties. Since within the main product groups, we can encounter literally hundreds of individual products, each tailored for a specific use and adjusted to environmental concerns, price level or a combination of those. Hence the quality of a physical oil products is described in product specification or product “spec” as we say in vernacular. A product specification is a list of properties deemed as acceptable for the customer or for the regulatory bodies of the given jurisdiction.
Such properties are defined either as opposite ends of the range (namely maximum and minimum results of the given tests) or as a range itself. More general, descriptive requirements for the tests are also in use, we often talk in such instances about “clear and bright” substance with an “acceptable odour” as a part of its specification. Some of the tests are also quiet complex, require advanced equipment and try to simulate an environment under which the product will be used. Please refer below to the key properties specified for in case of different products.
Penetration (“pen test”) measures the hardness of bitumen, low penetration indicator equals harder bitumen.
Ductility being the property of bitumen that makes it possible to undergo considerable deformation or elongation, specified as the distance in cm., to which a standard sample is elongated without breaking.
Flash point, the lowest temperature at which diesel may vaporize and form an ignitable mixture. Requires an ignition source to be measured.
Cold filter plugging point (CFPP), important especially in the colder, northern hemisphere, gives an estimate for the lowest temperature at which fuel will still flow through standardized filtration system in the engine.
Cetane number, diesel uses cetane numbers as a measurement of how well it combusts, literally cetane number tests the period of delay of ignition after the fuel enters the combustion chamber.
Sulphur content, a range of oil products tend to contain small amounts of sulphur. Sulphur can be harmful as a corrosive and when it burns produce sulphur oxides. Health and environmental concerns made regulatory bodies to specify its maximum allowed amounts in fuels.
Octane number, specifies how much the fuel can be compressed before it spontaneously ignites.
Vapour Pressure, as discussed before (RVP).
Benzene content, regulations set limits for the amount of benzene in gasoline and for the benzene emissions number, a calculated parameter that relates gasoline composition to predicted emissions of benzene from vehicles. Benzene is also a natural constituent of oil and an elementary petrochemical and as a component of gasoline it increases its octane number. On the other hand it is carcinogenic, hence the limitations on its amount.
Lead content, most jurisdictions banned leaded fuel, lead component has been implementing to increased octane number.
Oxygenates, typically used as additives to reduce CO and soot, created during burning of fuel.
-Jet kerosine (Jet Fuel)
Flash point, as previously described
Freezing point, the lowest temperature at which the fuel is still free of solid hydrocarbon crystals that can restrict its flow.
Aromatics, inclusion of aromatics compund in jet fuels have its pluses and minuses. Aromatics when burning increase a polution level. However, at the same time aromatics compund in jet fuel cause some types of elastomers used in aircraft fuel systems to swell. Lack of aromatics in alternative jet fuels, cause industry concerns, that elastomers may shrink and lead to fuels leakage (more research is underway).
Thermal Stability, one of the most important properties since fuel also serves as a heat exchange medium in the engine and airframe of the aircraft. Jet fuel is used to get rid of heat from engine oil, hydraulic ﬂuid, and air conditioning equipment.
Heating of the fuel speeds up gum and particulate formation, gums and particles may deposit on fuel ﬁlters and heat exchangers of the aircraft and lead to reduction of fuel ﬂow. It all leads to operational issues of the aircraft and increase maintenance costs. Here is a link to an excellent article on this important property of jet fuel, published by Australian Department of Defence: http://www.dtic.mil/dtic/tr/fulltext/u2/a431064.pdf
PONA number determines quality of Naphta. Various grades of naphtha are produced depending on PONA specification (65/12, 70/10) and so on. First digits signifies the minimum allowable total parafins percentage and the second a maximum allowable aromatics percentage. Pona number is directly correlated with pricing.
(No)lead, content as discussed
Pour point, the temperature at which gasoil loses its flow characteristics. High pour point generally equals a high paraffin content.
Flash point, as discussed
Sulphur content, as discussed
Independent, third party organizations as the Institute of Petroleum (IP) and the American Society for Testing Methods (ASTM) set industry wide recognized standarts for testing methods and acceptable (or not) outcomes.
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