ASTM D2983 for low-temperature viscosity of lubricants by Brookfield viscometer
ASTM D2983 standard test method for low-temperature viscosity of lubricants measured by Brookfield Viscometer
6. Apparatus
6.1 Brookfield Viscometer - Analog Model LVT or more recent digital models (for example, LVDV-II+) are required. Make certain that the viscometer is calibrated and in good working order prior to operation.
6.2 Viscometer Spindle - Uninsulated viscometer No. 4 spindle or insulated No. 4B2 spindle may be used. Periodically (depending on use, but at least every 3 months) inspect for wobble of the spindles. The run-out (wobble) of the spindle must not exceed 1 mm. Contact the manufacturer for measuring details. For No. 4B2 spindles, ensure firm adhesion of the lower part of the spindle. A number of spindles are needed for multiple determinations. See Fig. 1 for diagram.
6.3 Spindle Clip - A thin clip or spacer that supports the spindle at proper immersion depth during cool-down.
6.4 Test Cell - A glass test tube 22 to 22.5 mm in inside diameter and 115 6 5 mm in overall length.
6.5 Cell Stopper (Fig. 2) - A cap that fits onto the test cell with a hole large enough for the spindle to turn with sufficient clearance.
6.6 Insulated Cell Carrier (Fig. 2) - A balsa wood block with windows that keeps the test cell cold during testing.
NOTE 2 - A liquid bath,6,8 with a viewing window, held at the specified temperature, within 0.1°C, can be used in place of the test cell carrier (see also Note 10).
6.7 Cold Cabinet - A top-opening cold cabinet with an air-circulation device may be used (see Note 3). To minimize disturbance, it is recommended that the cabinet has an inner cover with hand-holes for sample insertion and removal. The cold cabinet must cool the sample to a chosen constant test temperature over a range from +5° to -40°C and hold that temperature within more or less 0.3°C. The air circulation device and the turntable must be able to be switched off prior to fully opening the bath top. Mechanically refrigerated liquid baths may be used for apparent viscosity determinations. A European procedure, CEC L18-A-80, describes the use of such baths. A liquid bath can be used for sample conditioning if it can duplicate the sample cooling rates outlined in Annex A2. The main advantage of a liquid bath over an air bath is more precise temperature control and thus more precise apparent viscosity measurement.
NOTE 3 - Liquid baths are available that can cool at the proper rate and maintain the selected test temperature within 0.1°C of the set point for the 16-h soak-period portion of the test. Details on liquid baths can be found in the manufacturer's manual.
6.8 Turntable - This device contains the cell rack. The turntable should rotate at a speed of 3 to 5 rpm. This item is often supplied with the cold cabinet. The turntable is not required for a liquid bath.
6.9 Temperature Sensing Devices - Use certified or other calibrated thermometric devices of equal or greater accuracy that cover the range from +5° to -40°C with 0.1°C (or finer) increments. For air-bath-style cold cabinets, it is recommended to use IP Brookfield Viscometer Total Immersion Thermometers:
IP 94C -45° to -35°C ASTM 122C
IP 95C -35° to -25°C ASTM 123C
IP 96C -25° to -15°C ASTM 124C
IP 97C -15° to -5°C ASTM 125C
and ASTM 63C (-8° to +32°C)) in conjunction with a calibrated resistance temperature detector (RTD) device. The RTD must be effectively calibrated at 0°C and -40°C. The thermometers can be compared to the RTD in order to get an accurate reading. Store thermometers in an upright position to help maintain calibration. Make certain that there are no separations in the column.
6.9.1 For liquid baths, use certified or other calibrated thermometric devices of equal or greater accuracy that cover the range from +5 to -40°C with 0.1°C (or finer) increments (consult the bath manufacturer for calibration details). As with the air bath, compare these results with an RTD in order to verify an accurate reading. For further verification of the temperature control in air or liquid baths, see Annex A4.
6.10 Blank Sample - A fluid that is close in chemistry to those being tested for the purpose of determining the temperature experienced within a sample.
7. Use of Reference Fluids
7.1 The use of standard reference fluids, detailed in Annex A3 and Annex A4, was developed to ensure more precise control of the apparent viscosity measurements. Each new spindle should be run with a reference oil prior to testing samples to ensure accurate results. With analog viscometers, the procedure to calculate expected reference fluid dial readings and interpret observed reference fluid dial readings is given in Annex A3. Although the dial reading limits listed in Annex A3 are typical of the data received from several extensive round robins, more precise control is both desirable and possible with digital equipment.
