ASTM D6616 Standard Test Method for Measuring Viscosity at High Shear Rate by Tapered Bearing Simulator Viscometer at 100°C
6. Apparatus
6.1 Tapered Bearing Simulator Viscometers (TBS) - a viscometer consisting of a motor connected to a slightly tapered rotor that fits into a matched stator. Several models of the TBS are in use. All of these are capable of analyzing test oils at 100°C but earlier models are more limited in their upper viscosity range.

6.2 Different models of the tapered bearing simulator (TBS) have the following upper levels of operating viscosities at 1·10(6)s(-1) shear rate:
6.2.1 Model Series 400 (similar to Fig. 1) - ~14 mPa·s (cP), dual speed.

6.2.2 Model Series 500 (Fig. 1) - ~16 mPa·s (cP) single speed.

6.2.3 Model Series 600 (Fig. 2) - ~100 mPa·s (cP) (usually liquid cooled), dual speed.

6.2.4 Model Series SS (SuperShear) (similar to Fig. 1) - ~20 mPa·s (cP), multi-speed.

6.2.5 Model Series 2100 E (Fig. 3) - ~20 mPa·s (cP) (see Note 2), multi-speed.

NOTE 2 - TBS Models 500, 600, and SS use a so-called bouncer to automate unloading and reloading the load cell just before taking a torque reading. (All automated units apply the bouncer at the appropriate point of operation as part of their program.) If a bouncer is not on the TBS model used (Model 400), the effect is generated by placing the thumb on the brass weight pin and turning the turntable slightly in a clockwise direction and quickly releasing the turntable. The bearingless Models 2100 E do not require unloading the cell since there is no turntable bearing.

6.3 Automated System for Calibration, Injection, and Data Analysis Programs - An automated program for the Tapered Bearing Simulator, simulating the manual method has been used.

6.4 Console - The console shown in Fig. 4 is similar in Models 400, 500, and 600. Consoles for Series SS and 2100 E have provisions for changing motor speed. All consoles contain the power source for the load cell, thermoregulator circuit, stator-heating element, and motor. They also contain the circuitry for regulating and monitoring the temperature of the oil in the stator as well as the amplifier and digital readout of the load cell.

NOTE 3 - The thermoregulator circuit of the TBS viscometers has evolved as improvements have been made in the solid-state temperature controller and heater. To achieve the 5 min analysis time specified in this test method requires a late model solid-state controller with automatic reset coupled to a thermo-foil stator heater with small heat inertia or a fast-responding thermoregulated liquid bath.

6.5 Cooling Systems - Two cooling systems are available for TBS viscometer work at 100°C: forced air cooling and liquid bath cooling. The stator housing is prepared for the former but must be modified for the latter according to directions from the manufacturer.

6.6 Glass Syringe - A 50-mL glass syringe equipped with a Luer needle lock fits the tip of the filling tube for injection of test oil into the test cell. Smaller glass and plastic syringes can be used ifany air bubble in the fill tube caused by the exchange of syringes is first pulled up into the next syringe to be used.

6.7 Filter Assembly - A unit made of a filter holder and nominal 10-µ filter is interposed between the syringe and the filling tube to remove particles capable of damaging the rotor/stator cell.

6.8 Data Recording Equipment - Some form of recording the torque and temperature data produced by the tapered bearing simulator is desired in order to (1) determine torque/temperature equilibrium and (2) determine the torque with sufficient precision to calculate viscosity to the second decimal place. Early in the use of the TBS viscometer, a strip-chart recorder was used, later an automated, computer-based recording system was developed with both a computer-simulated strip chart and with data digitally recorded.

NOTE 4 - Although the console has a torque indicator that can be used for determining viscosity, it has been found that the small oscillatory variation of torque with time makes desirable the recording and analysis of the torque output more precise, particularly when determining torque equilibrium.

6.8.1 Strip-chart Recorder:
6.8.1.1 If a strip-chart recorder is used to record the torque and temperature output signals, use the manufacturer's directions for calibrating and setting up the strip chart for recording torque/temperature data (see Note 5). The torque reading must be in milliVolts and the temperature in °C with a full-scale chart range of 20° to 120°C.

6.8.1.2 Use a chart speed of 1 cm/min for recording.

6.8.1.3 Set and, when necessary, reset, the strip chart torque voltage to that which will permit recording the torque as much as possible on the upper two-thirds of the chart paper for maximum sensitivity.

6.8.1.4 Factor the resulting voltage values to calculate the correct values of torque.

NOTE 5 - Although the digital information from the torque output meter on the viscometer console can be, and is, used for recording additional test information, it is desirable to use a two-pen, strip-chart recorder or its computer equivalent since this provides a continuous torque/temperature record of torque/temperature equilibrium necessary for precision in calibration and in calculating viscosity.

6.8.2 Computer Accumulation of Torque and Temperature Data - Computer recording of digital data can also be used for the test method. Such programs should show data for both torque and stator temperature. Torque information should be capable of permitting the calculation of viscosity to the second decimal place.

7. Materials
7.1 Reference Newtonian Calibration Oils, Newtonian oils of known dynamic viscosity at 100°C. Table 1 shows the dynamic viscosity values of five Newtonian oils used in developing the information for this test method.

7.2 Idling Oil - See 3.2.1 for information and use.

7.3 Non-Newtonian Reference Oil, essential in setting the rotor/stator gap to 1·10(6)s(-1) shear rate. The nominal level of apparent viscosity of non-Newtonian reference oil, NNR-10 used in applying this test method is given in Table 1.

7.4 Polar Solvent, such as dimethyl sulfoxide is used to dissolve any deposits on the rotor/stator surfaces after extended use.

7.5 Source of moderate pressure (<100 PSI) dry air or nitrogen.

NOTE 6 - Depending on room temperatures, higher torque levels at 100°C and 1·10(6)s(-1) may require air or other gas cooling. Use of dry gas is required (to keep moisture from entering the stator housing).