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
10. Calibration
10.1 Proceed to Section 11 if the operating position has already been established.
10.2 Activating the Console - Be sure the MOTOR switch on the console is in the OFF position. Then, turn on the POWER switch. Leave the console in this standby condition for at least 1 h before using the tapered bearing simulator-viscometer.
10.3 Oil in Test Cell:
10.3.1 If there is no oil in the test cell, slowly inject 50 mL of the idling oil or other suitable oxidation-resistant fluid.
10.3.2 When there is oil in the test cell, proceed with the determination of the stored position as described in 10.4. If this position has been determined, proceed to 10.5.
10.4 Determining the Stored Position:
10.4.1 Bring the operating temperature to 150°C by setting the thermostat on the console.
10.4.2 Be careful not to touch the hot upper stator surface when the following operation is performed. Slowly lower the rotor into the stator by means of the height adjustment wheel on the elevator assembly while turning the flexible shaft connecting the motor and the rotor with the fingers until slight rubbing contact is felt between the rotor and the stator. Then slowly continue to lower the rotor in small increments (approximately 1/10 of the smallest division or 0.001 mm until further turning is prevented (without forcing rotation)). This is the point of rubbing contact. Record the micrometer reading to the third decimal place (that is, estimate the last place from the needle position between the minor division marks). All subsequent readings of the micrometer dial will be to the nearest 0.001 mm.
10.4.3 Raise the rotor to a position 0.50 mm (500 micrometres) above the contact position. Record this reading as the stored position.
10.4.3.1 It is important to observe whether the micrometer reading is 0.50 mm smaller or 0.50 mm larger than the reading at the contact position. For units that have mechanical micrometers, the reading for the stored position will be 0.50 mm smaller than that recorded for the contact position. If an electronic micrometer is used, the reading for the stored position will be 0.50 mm larger than that recorded for the contact position. See 3.2.6.1.
10.5 Determination of the Reciprocal Torque Intercept (Rti) to Determine Rotor Position for 1 x 10(6) s(-1) Shear Rate:
10.5.1 With the rotor in the stored position, gently move the motor turntable clockwise a few degrees to disengage the ball from contact with the platen, hold the motor housing firmly in this position, set the speed switch to HI and flip the motor switch to the ON position. Release the grip on the motor and let the reaction torque of the spinning motor bring the ball into contact with the load cell platen (See Fig. 4).
10.5.2 Let the motor run at least 1 h before proceeding to 10.5.3.
10.5.3 Fill the test cell with NNR-03 non-Newtonian reference oil by either of the methods described in 10.5.3.1 or 10.5.3.2. See Section 8 for sampling precautions. After the test cell has been filled, all subsequent injections should be made with the motor running. (If this is a first time operation or after the viscometer has been idled for more than an hour, make a second injection after waiting the requisite 5 min 30 s.)
10.5.3.1 Fill the syringe with 50 +/- 3 mL of oil. Slowly inject the oil into the inlet tube of the test cell at a rate of approximately 2 mL/s. Fluids with viscosities greater than 4 cP at 150°C can be preheated to about 40°C to make the injection rate easier to meet.
10.5.3.2 A different injection procedure may be used when the amount of test fluid is limited. Fill the syringe with 30 mL of fluid and make three 10-mL injections, waiting 10 s between each injection.
10.5.3.3 Note the time when the injection is completed.
10.5.4 Stabilize the temperature at 150 +/- 0.2°C by regulation of the temperature controller on the console. Air circulation to the stator housing may be required for supplementary cooling of fluids with viscosities greater than 9 cP. Five minutes after injection proceed to 10.5.5.
NOTE 4 - A temperature controller with automatic reset and a thermo-foil heater are required to achieve 150 +/- 0.2°C within the specified 5 min.
10.5.5 Separate the load-cell/motor-turntable contact as in starting (see 10.5.1), then shut off the motor. Reconfirm the rotor/stator contact position determined in 10.4.2. Now, raise the rotor to a position 0.10 mm above the contact position just established.
10.5.6 Restart the motor using the technique described in 10.5.1.
10.5.7 Disengage the turntable contact ball from the platen of the load cell and at the same time set the torque indicator reading to zero if it has drifted more than +/- 2 display units from zero. See Fig. 3 for the location of the zero adjustment port or knob.
10.5.8 Record the torque indicator reading and the rotor position when the temperature is stabilized at 150 +/- 0.2°C.
10.5.9 Raise the rotor to a position that is 0.20 mm above the contact position and repeat 10.5.8.
10.5.10 Repeat 10.5.8 at rotor heights 0.30 and 0.40 mm above the contact position which now gives four values of rotor height and torque readout for analysis in 10.5.12.
10.5.11 Return the rotor to the stored position obtained in 10.4.3, fill the test cell with R-400 calibration oil, and repeat 10.5.6 through 10.5.10.
10.5.12 Calculate the reciprocals of the four values of indicated torque. Use these and the associated rotor height values to generate linear regression analyses for the NNR-03 and R-400. A correlation coefficient of 0.999 or higher (close to unity) is required for both NNR-03 and R-400 data.
10.5.13 Determine the intersection of these two straight lines to obtain the rotor height position at which 1 x 10(6) s(-1) shear rate will be generated by the viscometer.
NOTE 5 - A number of pocket calculators have linear regression analysis programs built into them and can be programmed to determine the intersection point of NNR-03 and R-400 as well. A preprogrammed calculator can be obtained commercially. Alternatively, but not as accurately, the Rti can be determined by graphical analysis on linear coordinate paper using the Y-axis for rotor height and the X-axis for reciprocal indicated torque.
NOTE 6 - If the lines do not intersect or the calculated intersection position would require the rotor to be inserted into the stator near (within 0.01 mm) or beyond the contact position, repeat 10.5.3 through 10.5.13, starting at a point 0.5 mm above the contact position. This algebraic/graphical analysis is based on the torque response of R-400 and NNR-03 fluids and assumes that these fluids have equivalent viscosities at 1 x 10(6) s(-1) shear rate and 150°C. In cases where the rotor/stator cell is contaminated with heavy oxidation deposits or the surfaces of the cell have been damaged, it may not be possible to reach the gap necessary for a shear rate of 1 x 10(6) s(-1) operation. If the intersection still is not obtained after the second attempt, it will be necessary to sonically clean the rotor/stator cell or in cases of surface damage, to re-lap those rotor and stator surfaces exposed to high shear.
10.5.14 Move the rotor to the reciprocal torque intercept position, Rti, and proceed to 11.2.
