ASTM D6616 Standard Test Method for Measuring Viscosity at High Shear Rate by Tapered Bearing Simulator Viscometer at 100°C
8. Sampling
8.1 Fifty millilitres of a representative sample of fresh or used test oil is placed in a 50 mL syringe equipped with attached filter holder and 10-µ filter disk in preparation for injection into the TBS viscometer.

NOTE 7 - It is important to always use a filter and filter disk to prevent larger particles from entering the rotor-stator gap. However, it is also important to note that the TBS viscometer will work with heavily particle laden used oils as long as they are passed through the 10-µ filter.

9. Preparation of Apparatus
9.1 Set up stator cooling method, air or liquid, according to the manufacturer's directions.

NOTE 8 - When analyzing relatively viscous oils, stator cooling is necessary. This is particularly the case at lower operating temperatures such as 100°C where simple radiation from the stator through the stator housing is not sufficient to carry away the heat generated by viscous resistance to shear.

9.1.1 Air Cooling - Connect cooling air tubing to the ports on the stator housing and the back of the console following directions given by the manufacturer in the Owner's Manual. This will permit use of the flow meter on the left side of the console to adjust the cooling-air flow rate.
9.1.1.1 Set the airflow rate at 100 SCFH.

NOTE 9 - Once airflow rate has been set, it is important that this level be maintained throughout calibration and operation. If desired, the air may be passed through a copper coil in a chilling bath containing water, ice, or dry ice, as necessary, to obtain desired stator temperature. The cooling level must be kept constant.

9.1.2 Liquid Cooling - Connect liquid cooling bath tubing from bath pump to the stator housing and the back of the console using insulated tubing according to the manufacturer's directions.

9.2 If some days or weeks have elapsed since last use of the TBS viscometer, follow the manufacturer's instructions regarding set-up and alignment of the rotor in the stator, checking the accuracy of the RTD and, if necessary, adjusting to 100.0°C. Shut the power off and go to 9.3.

NOTE 10 - Directions for preparation of the tapered bearing simulator viscometer and console are supplied with the equipment. One of the most important directions to be followed is the alignment ofthe rotor and stator before initial use of the viscometer. For those TBS Models (other than Model 2100E) requiring bearing inspection, low bearing hysteresis and bearing cleanliness are also important to obtaining reliable data.

NOTE 11 - Bearing hysteresis should be checked every few months and ifthe values ofincreasing and decreasing torque are significantly different, the bearing should be cleaned and re-checked by hysteresis measurements.

9.3 If the TBS viscometer has been turned off for some period of time (>1 h), make sure the motor is off and slowly (~2 min) inject 50 mL of R-2400 into the stator while turning the rotor using the upper Siamese collet connecting the motor shaft and the drive wire slowly between the thumb and forefinger.

9.4 If the TBS Viscometer has been operating at 100°C, proceed to Section 11 unless recalibration is desired.
9.4.1 If recalibration is desired, proceed to 10.2.

10. Calibration
10.1 If the operating position of the rotor in the stator has already been established in previous work at 100°C, proceed to Section 12.

10.2 If the operating position of the rotor in the stator must be established from a cold start for operation at 100°C, follow the manufacturer's instructions to find the rubbing contact position of the rotor with the stator by rotating the upper Siamese collet between the thumb and forefinger as the rotor is slowly lowered by using the elevator wheel (see Note 12).

NOTE 12 - The indicator dial reading decreases when the rotor and platform are raised and vice-versa. Exercise care in using the TBS elevator wheel to move the rotor in the direction intended by the indicating arrow on top of the wheel (clockwise to simultaneously raise both the platform and rotor, counter clockwise to lower both).

10.2.1 After finding the rubbing contact position, turn the elevator wheel clockwise (see Note 12) to raise the platform and the rotor by decreasing the depth indicator dial reading by 0.5 mm.

10.2.2 After making sure that the MOTOR switch is in the off position, turn on the POWER switch and permit the electronic components of the console to warm up for a suitable length of time according to the manufacturer's instructions.

10.2.3 Set the console's temperature controller to 100.0°C and permit the stator to begin warming up to that temperature. Do not turn on the motor.

NOTE 13 - The viscosity of the oil decreases exponentially with temperature and it is important that the motor not be started at higher viscosities than 20 to 30 mPa·s (cP) to protect the wire drive shaft.

10.2.4 When the stator temperature has reached 70°C, turn on the motor while pushing the red bouncer button on the console or gently holding the platform ball away from the load-cell platen (see Note 2) by lightly pushing clockwise on the brass pulley post set into the motor turntable. (This is not required or possible with Model 2100E.)

NOTE 14 - For TBS Models 500, 600, and SS, it is good practice to always press on and hold the bouncer button, or otherwise push the contact ball away from the load-cell platen before turning the motor on or off. This use ofthe bouncer button prevents the initial start-up or shutdown surge of the motor from causing the contact ball to hammer on the platen of the sensitive load-cell.

NOTE 15 - Sufficient warm-up time is important for consistency and precision. Operating with R-2400 adds the effect of viscous heating to the electrical heating of the stator and speeds the process.

10.2.5 When the temperature stabilizes at 100.0 +/- 0.2°C, go to Section 11.

10.3 If the TBS viscometer is already operating but at temperatures higher than 100°C, set the temperature control to 100.0°C and slowly (~1 min) inject 50 mLofidling oil into the stator through the fill tube. Ifusing air cooling, turn the dry gas flow-meter knob on the console to maximum flow rate (100 SCFH). If using liquid cooling, start circulation.
10.3.1 When the temperature reaches 100.0 +/- 0.2°C and while the motor is turning, slowly (~1 min) inject 50 mL of Newtonian calibration oil, R-2400.

10.4 Maintain appropriate air or liquid cooling rate.

11. Setting the Rotor Position at 1•10(6)s(-1) Shear Rate - the Reciprocal Torque Intercept
NOTE 16 - In all data collected for the determination ofviscosity, torque and temperature, equilibrium is necessary. Normally, this is reached within 5 min after injection of oil having a viscosity less than about 12-15 mPa·s (cP). However, with oils that are more viscous, the time to establish equilibrium may extend to 7 or 8 min at 100°C. Under all circumstances, equilibrium is assumed within 10 min of injection, at which point values should be taken and the next step in the method begun.

11.1 R-2400 Newtonian Oil - Establish the reciprocal torque information for R-2400 Newtonian oil by turning on the strip-chart recorder and slowly (~1 min) injecting 50 mL of R-2400 calibration oil.
11.1.1 Press and hold the bouncer button, then turn off the motor (see Note 14). Proceed to find rubbing contact of the rotor with the stator as described in 10.2.

11.1.2 After finding the rubbing contact position, use the elevator to raise the platform and the rotor by ~0.15 mm to the nearest exact whole tenth (0.100) millimetre value on the depth indicator dial (see Table 2, Example).

NOTE 17 - When the rotor is raised and lowered, the indicator dial needle should be read as exactly as possible (to the third decimal place by estimating between dial markings) at each position. Parallax in reading the dial indicator should be avoided by placing the eye at the same level as the dial. A magnifying glass can be further helpful.

11.1.3 While pushing the red bouncer button on the console turn motor on (see Note 14).

11.1.4 Hold the red bouncer button in the depressed position and adjust the torque readout to zero (0000 on the dial) according to the manufacturer's instructions.

11.1.5 When torque/temperature equilibrium has been reached (see Note 16) at this initial position, press the bouncer button briefly (see Note 2) and release. As soon as the computer-simulated or actual strip-chart recorder again shows constant torque/temperature traces (see Note 16), record the torque value given by the data recording equipment as well as the rotor (platform) position shown by the depth indicator dial.

11.1.6 Continue with, and complete 11.1.7 through 11.1.9.4 without using bouncer button again.

11.1.7 Use the elevator to move the rotor (platform) up exactly 0.100 mm (see Note 17 and Table 2). Again, record the rotor (platform) position and the indicated torque after torque/temperature equilibrium is achieved (see Note 16).

11.1.8 Again raise the rotor (platform) progressively and exactly 0.100 mm (see Note 17) three more times for a total of five sets of decreasing values of indicated torque with increasing rotor (platform) height as in Table 2 (see Example) and record the torque and rotor height values.

NOTE 18 - The full sequence required is shown in Table 2 and provides five sets of torque/height data for each of R-2400 and NNR-10.

11.1.9 Calculate the reciprocals of the torque values collected in 11.1 through 11.1.8 (see Table 2) for the Newtonian reference oil R-2400.
11.1.9.1 Linearly regress the rotor height (platform) position versus the reciprocal torque values found for these rotor heights. Record the slope, intercept, and correlation coefficient, R, of this best line.

11.1.9.2 The value of R should be equal to or greater than (≥) 0.999.

11.1.9.3 If R is less than (<) 0.999, slowly (~1 min) re-inject 50 mL of R-2400 and repeat 11.1.2 through 11.1.9.2 using special care to set and record the exact values of height to the third decimal place on the depth indicator dial (see Note 17). Recalculate the value of R.

11.1.9.4 Ifthe value ofR is now acceptable, proceed to 11.2. If the value of R is still not high enough, contact the manufacturer of the TBS.

11.2 Non-Newtonian Reference Oil, NNR-10 - Establish the reciprocal torque information for the non-Newtonian reference oil, NNR-10 by slowly (~1 min) injecting 50 mL of non-Newtonian reference oil NNR-10 and setting the rotor (platform) height to the exact initial position previously used for the Newtonian Reference oil, R-2400 in 11.1.2 (see Note 17).
11.2.1 Establish temperature/torque equilibrium, then record the rotor (platform) position indicated by the depth indicator dial and use the bouncer button once only to initiate the series of reciprocal torque determinations. Do not use the bouncer button again while establishing the reciprocal torque values.

11.2.2 Repeat the rotor (platform) adjusting, torque-collecting sequence in 11.1.2 through 11.1.9 using identical rotor (platform) positions. Record all values ofrotor (platform) position, resultant torques, and reciprocal torque values (see Notes 17 and 18).
11.2.2.1 As in 11.1.9.1, linearly regress the rotor (platform) position versus reciprocal torque values collected in 11.2 for the non-Newtonian reference oil, NNR-10. Record the slope, intercept, and correlation coefficient.

11.2.2.2 The value of R should be equal to or greater than (≥) 0.999. If the value of R is acceptable, record and proceed to 11.3.

11.2.2.3 If the value of R is less than 0.999, repeat 11.2.1 through 11.2.2.2 with particular attention to setting, reading, and recording the values of platform position and torque. If the value of R is still less than 0.999, contact the manufacturer.

11.3 Determination of Reciprocal Torque Intersection Position for 1·10(6)s(-1) Shear Rate:
11.3.1 Calculate and record the reciprocal torque value, 1/Ti, for the intersection point of the linear equations of 11.1 and 11.2 (see Note 19 and Fig. 5). This provides the experimentally determined rotor operating position for 1·10(6)s(-1) shear rate.

NOTE 19 - The linear equation obtained from 11.1 using Newtonian reference oil R-2400 is H = m/T + b in which m is the slope and b the intercept and H and 1/T are rotor height and reciprocal torque. The linear equation obtained from 11.2 using reference oil NNR-10 is H8 = n/T8 + c in which n is the slope and c the intercept, and H8 and 1/T8 are rotor height and reciprocal torque at the intersection point Hi = Hi' as well as 1/Ti = 1/Ti'. Setting equation H = m/T+ b = H' = n/T' + c: m/Ti + b = n/Ti + c and 1/Ti = (c-b)/(m-n) substituting 1/T = (c-b)/m-n) into H = m/T+ b = Hi = [m(c-b)/(m-n)] + b; the intersection height for 1·10(6)s(-1).

12. Calibration of TBS Rotor and Stator
12.1 Set rotor position exactly to that indicated by 11.3.1 (see Note 17).

12.2 Check Rotor Position at 1·10(6)s(-1) Shear Rate:
NOTE 20 - Slow expansion of the rotor and stator after start up of the TBS viscometer may slightly change the originally determined position of the rotor at 1·10(6)s(-1) shear rate and it is prudent to recheck the rotor position and to make slight adjustments, if necessary.

12.2.1 Slowly (~1 min) inject 50 mL of Newtonian reference oil, R-2400, and allow for torque/temperature equilibration (see Note 16). Apply the bouncer button briefly, allow the torque value to stabilize, and record torque.

NOTE 21 - In determinations of viscosity using all TBS viscometer models except Model 2100 E, it is necessary to use the bouncer button once after temperature/torque equilibrium has been established. See Note 2.

12.2.2 Slowly (~1 min) inject 50 mL of non-Newtonian reference oil, NNR-10, again allow for torque/temperature equilibration (see Note 16). Apply the bouncer button briefly, allow the torque value to stabilize, and record torque.

12.2.3 Calculate the NNR-10/R-2400 viscosity ratio from the values on the container.

12.2.4 If the torque ratio NNR-10/R-2400 is within +/- 0.015 of the viscosity ratio of 12.2.3, proceed to 12.3.

12.2.5 If the torque ratio NNR-10/R-2400 is greater than 1.015, lower the rotor (platform) 0.010 mm for each 0.010 unit of ratio greater than 1.000 (see Notes 12 and 17); repeat 12.2.1 and 12.2.2, and recalculate the NNR-10/R-2400 torque ratio.
12.2.5.1 If the NNR-10/R-2400 torque ratio is still greater than 1.015, repeat 12.2.1 and 12.2.2 until the proper value is obtained.

12.2.6 Ifthe NNR-10/R-2400 torque ratio is less than 0.985, raise the rotor (platform) 0.010 mm for each 0.010 unit of ratio less than 1.000 (see Notes 12 and 17), repeat 12.2.1 and 12.2.2, and recalculate the NNR-10/R-2400 torque ratio.
12.2.6.1 If the NNR-10/R-2400 torque ratio is still less than 0.985, repeat 12.2.1 and 12.2.2 until the proper value is obtained.

NOTE 22 - The test method given in 12.2 is a quick and precise method of readjusting rotor (platform) position to the appropriate shear rate and can be used at any time.

12.3 Simultaneously initiate the calibration and recheck the operationally correct rotor (platform) position by slowly injecting Newtonian reference oil R-2200 and waiting until torque/temperature equilibrium is obtained (see Section 15). Use the bouncer button after torque/temperature equilibrium, allow the torque value to stabilize, and record torque.
12.3.1 Repeat 12.3 for Newtonian reference oil R-2450 and record resulting torque.

12.3.2 Use the known viscosities of Newtonian reference oils R-2200 and R-2450 and the torque values from 12.3 and 12.3.1 to calculate the slope, mv, and intercept, bv, of the line connecting these two pairs of values with indicated torque as variable Ti, and viscosity as variable V, in Eq 1.
V = mV·Ti + bV

12.3.3 Use the value of torque for non-Newtonian reference oil NNR-10 from 12.2.3 and substitute it into Eq 1. Calculate the value of the viscosity of NNR-10 and compare to the viscosity value of NNR-10 on the container. If the viscosity value is within +/- 2 % of the value on the container, proceed to 12.4.
12.3.3.1 If the value of NNR-10 is not within +/- 2 % of the container value, first check the NNR-10/R-2400 torque ratio by slowly (~1 min) injecting 50 mL of R-2400 (see 12.2.1), obtaining the torque value. Then use the last determined value of NNR-10 from 12.2.2 to re-calculate the NNR-10/R-2400 torque ratio.
(1) If the NNR-10/R-2400 torque ratio is within 1.000 +/- 0.015, return to 12.3 and re-run 12.3 to 12.3.3.
(2) Ifthe NNR-10/R-2400 torque ratio is outside of 1.000 +/- 0.015, return to the appropriate 12.2.5 or 12.2.5.1, re-establish the correct rotor position, and proceed through the subsequent 12.3 to 12.3.3.
(3) If repeat efforts do not produce a viscosity value for NNR-10 within 2 % of the container value, contact the instrument manufacturer.

12.3.3.2 When the NNR-10/R-2400 torque ratio is within 1.000 +/- 0.015, and the value of NNR-10 is within 2 % of the container value, record the new setting of the rotor (platform) and proceed to 12.4.

12.4 Continue the calibration of 12.3 by sequentially and slowly (~1 min) injecting 50 mL of Newtonian reference oils R-2300, R-2400, R-2350, and non-Newtonian NNR-10 in that order. For each reference oil, immediately after the torque/temperature equilibrium is attained (see Note 16), use the bouncer technique (see Notes 2 and 21), and record torques for each reference oil.

12.5 Using the known viscosity and torque values at 100.0°C for the five Newtonian reference oils R-2200 and R-2450 from 12.3, and R-2300, R-2400, and R-2350 from 12.4, linearly regress the viscosity and torque values of all five calibration oils and determine the slope, intercept, and correlation coefficient, R.
12.5.1 The correlation coefficient should result in a value ≥0.999. If so, go to 12.6.
12.5.1.1 If the value of R is less than 0.999, repeat 12.3 through 12.4.

12.5.1.2 If there is still a problem in obtaining the desired correlation coefficient, contact the instrument manufacturer.

12.6 Use the torque value of NNR-10 from 12.4 in Eq 1 and calculate the viscosity of NNR-10.
12.6.1 The viscosity value determined for NNR-10 should be within 2 % of the value on the container. If so, proceed to Section 7.

12.6.2 If the viscosity value determined for NNR-10 is not within 2 % of the value on the container, from the torques of R-2400 and NNR-10 obtained in 12.4, test ifthe torque ratio of NNR-10/R-2400 is 1.000 +/- 0.015.
12.6.2.1 If the NNR-10/R-2400 torque ratio is within 1.000 +/- 0.015, repeat the calibration steps of 12.3 through 12.5.

12.6.2.2 If the NNR-10/R-2400 torque ratio is outside of 1.000 +/- 0.015, adjust the rotor height (platform) according to 12.2 until the correct torque ratio value is obtained and then repeat the calibration steps of 12.3 through 12.5.

12.6.2.3 If the viscosity of NNR-10 is still not within 2 % agreement with the value on the container, contact the instrument manufacturer.