Standard Test Method for Low-Temperature Viscosity of Automatic Transmission Fluids, Hydraulic Fluids, and Lubricants using a Rotational Viscometer

Importancia y uso:

5.1 The low-temperature, low-shear-rate viscosity of automatic transmission fluids, gear oils, torque and tractor fluids, and industrial and automotive hydraulic oils (see Appendix X4) 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.

5.2 Initially this test method was developed to determine whether an automatic transmission fluid (ATF) would meet OEM low temperature performance criterion originally defined using a particular model viscometer.6, 7 The viscosity range covered in the original ATF performance correlation studies was from less than 1000 mPa·s to more than 60 000 mPa·s. The success of the ATF correlation and the development of this test method has over time been applied to other fluids and lubricants such as gear oils, hydraulic fluids, and so forth.

5.3 Procedures A, B, C, and D of this test method describe how to measure apparent viscosity directly without the errors associated with earlier techniques that extrapolated experimental viscometric data obtained at higher temperatures.

Note 1: 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.

5.4 Procedures A, B, C, and D; If viscosity measurements are difficult to stabilize or a noticeable decrease in viscosity is seen at a constant speed between an initial measurement made during the 5 s to 10 s after the spindle rotation commences and the stabilized measurement between 60 s and 180 s, then this most likely indicates time-dependent, structural breakdown in the fluid. Some formulated fluid types may form wax structures when soaked at or below a certain low temperature which varies among fluids. The rotating spindle of the viscometer can degrade this structure over time, resulting in a decrease in the apparent viscosity at longer measurement times. This can obscure a higher initial viscosity. It is possible that this high initial viscosity may be detrimental to certain machinery, as historically seen in some automatic transmissions. It was the reason for developing this test.6, 7 It is recommended, that if this phenomenon is observed, the suitability of this fluid for the application is carefully considered. If desired, Test Method D5133 or Test Method D6821 may be used to study the behavior of these fluids.

Subcomité:

D02.07

Referida por:

D4682-18, F0631-15R20, D8085-24, D8210-22, F2084_F2084M-01R24, D8185-23, D8029-23, D6080-18A, D8278-20, D8046-21, F2709-19, D6821-20A, D6158-23, F3350-18R24, D6448-24, D8164-21, D6823-24

Volúmen:

05.01

Número ICS:

75.100 (Lubricants, industrial oils and related products)

Palabras clave:

lubricants; Newtonian oils or liquids; Non-Newtonian oils or fluid;