The low-temperature, low-shear-rate viscosity of automatic transmission fluids, gear oils, torque and tractor fluids, and industrial and automotive hydraulic oils (see Annex A4) are of considerable importance to the proper operation of many mechanical devices. Measurement of the viscometric properties of these oils and fluids at low temperatures is often used to specify their acceptance for service. This test method is used in a number of specifications.
This test method describes how to measure apparent viscosity directly without the errors associated with earlier techniques using extrapolation of experimental viscometric data obtained at higher temperatures.
Note 18212;Low temperature viscosity values obtained by either interpolation or extrapolation of oils may be subject to errors caused by gelation and other forms of non-Newtonian response to spindle speed and torque. Only in the case of known Newtonian oils at the temperature desired is interpolation acceptable for the purpose of calibrating the spindle and glass cell (see Annex A1).
1.1 This test method covers the use of Brookfield viscometers of appropriate torque for the determination of the low-shear-rate viscosity of lubricants. The test is applied over the viscosity range of 500 to 900 000 mPa·s within a low temperature range appropriate to the capacity of the viscometer head.
1.2 The range of viscosity used to generate the precision data for this test method was from 1000 to 900 000 mPa·s. Appendix X4 lists another interlaboratory study that specifically targeted hydraulic fluid ranging from 500 to 1700 mPa·s.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3.1 The test method uses the SI unit, milliPascal-second (mPa·s), as the unit of viscosity. (1 cP = 1 mPa·s).
1.4 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 and health practices and determine the applicability of regulatory limitations prior to use.
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