ASTM D7945-20

5.1 Many petroleum products are used as lubricants and the correct operation of the equipment depends upon the appropriate viscosity of the liquid being used. In addition, the viscosity of many petroleum fuels is important for the estimation of optimum storage, handling, and operational conditions. Thus, the accurate determination of viscosity is essential to many product specifications.

5.2 Density is a fundamental physical property that can be used in conjunction with other properties to characterize both the light and heavy fractions of petroleum and petroleum products and in this test method is used for the calculation from dynamic to kinematic viscosity.

1.1 This test method covers the measurement of dynamic viscosity and density for the purpose of derivation of kinematic viscosity of petroleum liquids, both transparent and opaque. The kinematic viscosity, ν, in this test method is derived by dividing the dynamic viscosity, η, by the density, ρ, obtained at the same test temperature. This test method also calculates the temperature at which petroleum liquids attain a specified kinematic viscosity using Practice D341.

1.2 The result obtained from this test method is dependent upon the behavior of the sample and is intended for application to liquids for which primarily the shear stress and shear rate are proportional (Newtonian flow behavior).

1.3 The range of kinematic viscosity covered by this test method is from 0.5 mm²/s to 1000 mm²/s in the temperature range between –40 °C to 120 °C; however the precision has been determined only for fuels and oils in the range of 2.06 mm²/s to 476 mm²/s at 40 °C and 1.09 mm²/s  to 107 mm²/s at 100 °C (as stated in Section 12 on Precision and Bias). For jet fuels, the precision of kinematic viscosity has been determined in the range of 2.957 mm²/s to 5.805 mm²/s at –20 °C and 5.505 mm²/s to 13.03 mm²/s at –40 °C (as stated in Section 12 on Precision and Bias), and the precision of the temperature at 12 mm²/s (cSt) has been determined in the range of –38.3 °C to –58.1 °C (as stated in Section 13 on Precision and Bias). The precision has only been determined for those materials, viscosity ranges, and temperatures as indicated in Section 12 on Precision and Bias. The test method can be applied to a wider range of materials, viscosity, and temperature. For materials not listed in Section 12 on Precision and Bias, the precision and bias may not be applicable.

1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.