ASTM D4741 Measuring Viscosity at High Temperature and High Shear Rate by Tapered-Plug Viscometer
10. Procedure
10.1 Switch on the heating bath, circulating pump and viscometer electronic unit at least 3 h before carrying out any determinations.
10.2 Lower the rotor into the stator until the frame contacts the ball-stop. Continue winding the handwheel until the lifting mechanism is definitely disengaged.
10.3 Check that the dial gage reading is that obtained at 9.8.3.
10.4 Carry out the severity check as in 9.8.
10.5 Introduce the test oil as detailed in 9.7.1.
10.6 Remove the sample by the side arm and charge with test oil.
10.7 Carry out operations 9.7.1 and 9.7.2 to obtain a torque result, which is the average of two determinations that agree within 1 %.
NOTE 8 - When the viscometer is to be left non-operational for more than a few minutes, it is recommended that the rotor be raised slightly by means of the handwheel. To avoid damage to the equipment, the rotor must always be raised when the heating is switched off.
11. Calculation
11.1 Using the torque result calculated in 10.7, read the viscosity value from the calibration graph. Alternatively, calculate the viscosity from the regression of viscosity on torque obtained with the calibration oils. A test report sheet is attached as Appendix X1.
