ASTM D4683 for measuring viscosity at high shear rate and high temperature
ASTM D4683 standard test method for measuring viscosity at high shear rate and high temperature by tapered bearing simulator
11. Procedure
11.1 Equipment Activation:
11.1.1 If the tapered bearing simulator-viscometer has been turned off, activate console in accordance with 10.2.

11.1.2 If there is no oil in the test cell, inject fluid in accordance with 10.3.1.

11.1.3 Bring the operating temperature to 150°C.

11.1.4 Turn on the motor in accordance with instructions in 10.5.1. Let the motor run for at least 1 h before proceeding to 10.5.3 where the reciprocal torque intersection ( Rti) will be determined.

11.2 Viscosity/Torque Response of Calibration and Test Oils:
11.2.1 With the rotor being driven by the motor at Rti, inject the R-200 calibration oil in accordance with 10.5.3 and wait until the temperature stabilizes at 150 +/- 0.2°C. Five and one-half min after completing the injection, check the no-load torque reading according to the technique in 10.5.7. Record the torque indicator reading for R-200. Follow this procedure to obtain torque indicator readings for R-500 and NNR-03.

11.2.2 Using the torque indicator readings for R-200 and R-500, and the certified viscosities for these oils, make a preliminary appraisal of the calibration constants c and d using the following equation:
V = c + d(Tr)
where:
V = certified viscosity of the oil, cP (mPa•s),
Tr = torque indicator reading,
c = Y-axis intercept, cP (mPa•s), and
d = slope of the best line, cP/Tr.

11.2.3 Solve Eq 1 as recommended in 11.1 using the torque indicator reading determined for the NNR-03. The resulting viscosity should be within 1 % of the certified viscosity value. If it is not, and the determined viscosity value is too high, lower the rotor by 0.01 mm for each 0.01 cP higher than the certified viscosity value. The opposite adjustment is used if the value for NNR-03 is too low (that is, raise the rotor 0.01 mm for each 0.01 cP lower than certified). After such adjustment, repeat 11.2.1 through 11.2.3. If still outside the 2 % range, determine the Rti again following the instructions in 10.5.

11.2.4 Choose a first test oil and fill the TBS Viscometer according to 10.5.3.1 or, if a limited quantity of the test oil is available, use procedure 10.5.3.2.

11.2.5 Wait 5 1/2 min, then check the no-load torque response in accordance with 10.5.7 and record the torque indicator reading as soon as the temperature is stabilized at 150 +/- 0.2°C.

11.2.6 If desired, continue testing with up to three (additional) unknown oils.

11.2.7 Proceed to collect torque readings for the calibration oils R-400 and R-300 respectively.

11.2.8 Gathering the torque readings and certified viscosities on all four reference oils, R-200 and R-500 from 11.2.2, and R-300 and R-400 from 11.2.7, obtain a linear regression analysis of this data. This will give final values for c and d in Eq 1 as well as the correlation coefficient (R).

11.2.9 A correlation coefficient of at least 0.999 is expected for the linear regression analysis of 11.2.8. If a correlation coefficient less than this minimum is obtained, plot the data generated from the calibration to determine if one of the data points falls significantly off the best line through the four points. If so, test the oil corresponding to that point again. If there are no data out of obvious agreement, check the setup of the TBS Viscometer in accordance with the owner's manual and the foregoing steps of calibration.

11.2.10 Calculate the viscosity for each of the test oils and the NNR-03.

11.2.11 When the calibration is complete, inject the cell with NNR-03, wait the requisite 5 1/2 min, and collect the torque reading for the fluid. Use this to calculate the viscosity of NNR-03 according to Eq 1 using the constants found in 11.2.8.

11.2.12 When the calculated viscosity for NNR-03 is still within 1 % of the certified viscosity, proceed to 11.2.14.

11.2.13 If the calculated viscosity for NNR-03 is not within the 1 % range, re-inject NNR-03 into the test cell and repeat the viscosity determination. If the viscosity is again outside the 1 % range, return to 11.2.3.

11.2.14 Evaluate (additional) test oils. Follow each six evaluations with a check evaluation of NNR-03 to ensure staying within the 1 % range of the established value at 10(6) s(-1) shear rate.

11.2.15 If the TBS-Viscometer is unattended (or anticipated to be unattended) for more than 1/2 h, inject 25 mL of idling oil into the cell. Before resuming operation, flush with an additional 25 mL of idling oil and then evaluate the viscosity of NNR-03 to check that it is within 1 % of its certified value.

11.3 Shutdown Procedure - When testing is complete, inject the idling oil and return the rotor to the stored position. Follow directions in 10.5.1 to separate the load-cell/motor-turntable contact when shutting off the motor. Turn the temperature control to ambient. It is prudent to also uncouple the heater cord at the housing or at the back of the console.

NOTE 7 - If another series of tests is to be run the next day, and the rotor/stator cell is protected by overheating and power-failure safety switches, inject 50 mL of idling oil and leave the viscometer at temperature and operating gap. Start the next day with 10.5.3 to determine Rti.

11.4 Test Cell Cleanup:

NOTE 8 - The continuous operation of the viscometer without an occasional flush with a polar organic solvent will eventually lead to a test cell whose operating surfaces will be coated with oxidation debris from the decomposition of the oils. While adjustment of the vertical rotor position can offset the change in operating gap caused by the deposit, and occasional (weekly) flush of the test cell is recommended. As a further precaution, anytime the viscometer is idle at operating gap and temperature, the test cell should be filled with idling oil.

11.4.1 After a routine shutdown in accordance with 11.3 and reaching ambient temperature, fill the test cell with a polar organic solvent.

11.4.2 Following 10.5.1, start the viscometer motor and lower the rotor 0.2 mm below the redetermined stored position.

11.4.3 After 10 min, purge the solvent from the cell with idling fluid using a 60-mL stepwise total injection of one 30-mL injection followed by two 15-mL injections all spaced about 5 min apart.

11.4.4 Shut down the TBS Viscometer as in 11.3 unless further testing is desired. Otherwise testing should be resumed with 10.3.2.

NOTE 9 - If a dirty test cell is suspected and there is a desire to renew operation as soon as possible, shut the motor off, raise the motor platform and remove the rotor (Warning - The rotor will initially be at operating temperature). The rotor can then be sonically cleaned in a water/soap solution. After 15 min of cleaning, dry the rotor, reinstall for operation, and restart operations at 10.3.2.

12. Calculation
12.1 Using the final calibration constants c and d determined in 11.2.8, calculate the dynamic viscosity of each test oil in accordance with Eq 1.