Biodiesels at this early stage of their international adoption are precisely specified in kinematic viscosity terms. They differ in degree of instrumentational advancement, and the fact that both viscometers continue to find application is evidence of the continuing methodology which characterises so much of petroleum technology. The two examples chosen above are each compliant with this standard, which has been in use for many decades. There are many viscometers available for use and often their advertisement features ‘ASTM D445’ in bold. This enables it to be used for substances as different as gasoline (lower measurement limit) and hydrocarbon greases (upper measurement limit). The Cannon miniAV®, which can be operated at temperatures up to 100oC, has a kinematic viscosity measurement range of 0.3 to 6000 centistokes. The glasswork shown in the plate is suspended in a water bath to make sure the temperature of measurement is controlled.Īlso conforming to ASTM D445 but able to be used for opaque as well as transparent liquids is the Cannon Instruments miniAV® (below). This viscometer is suitable for transparent liquids only and this prevents application with heavy residues. The illustration below is of a viscometer of fairly simple construction designed for measurement according to ASTM D 445 and ISO 3104. Instruments for measuring viscosity by these means are widely available. Having the same scope and purpose as ASTM D445–12 and ISO 3104: 1994 but not identical in all respects with them are DIN 51366 (Germany) and IP 71 (UK). This is true of ASTM D445–12 which is also ISO 3104: 1994. ISO, as a body drawing together and co-ordinating ‘standards’ worldwide, often adds its own authority to that of a national body having issued a particular standard. In order that a reader should have a feel for these quantities they are given in tabulated form below for a number of liquids.īefore considering instrumentation which conforms to ASTM D445–12 we shall consider further the standard itself and other similar ones. ASTM D445–12 covers the range of kinematic viscosities 0.2 to 300000 mm2 s-1 (2 × 10-7 to 0.3 m2 s-1) and we note that 10-4 m2 s-1 = 1 stoke. This standard involves measuring the time taken for the liquid to descend a calibrated capillary. What Johnson & Auth (1951) called ASTM D445-2T has now become ASTM D445–12 (ASTM International, 2013), which may well have successive revisions. They are analogue quantities, depending on whether momentum, heat or mass is being transferred. Kinematic viscosity has dimensions length2 time-1 as do thermal diffusivity and diffusion coefficient. Johnson & Auth (1951) cites ASTM D445-2T ‘Method of Test for Kinematic Viscosity’, and an examination of this follows. By this time standards bodies had been established in many countries and ISO, an international network of standards bodies, had been formed with its headquarters in Geneva. This created, by the middle of the 20th Century, ASTM standards for the viscosity of petroleum products (Johnson & Auth, 1951). Taking into account the range of applications for petroleum products, from gasoline to heavy residue, viscosity / resistance to flow became important quantities in usage. The earliest ASTM standards for the oil industry were concerned with flash points (Jones, 2005). At that time the oil industry was expanding quickly, and procedures for characterising oil products soon started to come within the scope of ASTM. When the American Society for Testing and Materials (ASTM) came into existence in 1898, its first assignment focused on materials and dimensions for rail tracks.
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