VISCOSITY AT HIGH SHEAR RATE BY TAPERED BEARING SIMULATOR VISCOMETER AT 100° C: ASTM D6616
EXPLANATION
Viscosity at the shear rate and temperature of this test method is thought to be particularly representative of bearing conditions in large medium speed reciprocating engines as well as automotive and heavy duty engines operating in this temperature regime. The importance of viscosity under these conditions has been stressed in railroad specifications. This test method covers the laboratory determination of the viscosity of engine oils at 100° C and 1.10(6)s(−1) using the Tapered Bearing Simulator (TBS) viscometer.
This test method is similar to Test Method ASTM D4683 which uses the same TBS viscometer to measure high shear viscosity at 150° C. The Newtonian calibration oils used to establish this test method range from approximately 5 to 12 mPa•s (cP 0 at 100° C), and either the manual or automated protocol was used by each participant in developing the test precision. The viscosity range of the test method at this temperature is from 1 mPa•s to above 25 mPa•s, depending on the model of TBS used. The non-Newtonian reference oil used to establish the shear rate of 1.10(6)s(−1) for this test method has a viscosity of approximately 10 mPa•s at 100° C. Application of this method to petroleum products other than engine oils has not been determined in preparing viscometric information for this test method.
TEST SUMMARY
A motor drives a tapered rotor closely fitted inside a matched tapered stator. Appropriate technique establishes operation of the viscometer to yield 1.10(6)s(−1) at a temperature of 100° C at which point test oils are introduced into the gap between the spinning rotor and stationary stator. The rotor exhibits a reactive torque to the viscous resistance of each test oil and the value of this torque response is used to determine the apparent viscosity of the test oil.
TEST PRECISION
Repeatability: 1.2 % of the mean
Reproducibility: 3.5 % of the mean
There is no accepted reference materials suitable for determining the bias of this test method.
