6. Apparatus
6.1 Mini-Rotary Viscometer, consisting of one or more viscometric cells including a calibrated rotor-stator assembly, which are contained in a temperature-controlled aluminum block.
6.1.1 The viscometric cell has the following nominal dimensions:
6.2 Weights:
6.2.1 Yield Stress Measurement - A set of nine disks and a disk holder, each with a mass of 10 g ± 0.1 g.
6.2.2 Viscosity Measurement - Weight with mass of 150 g ± 1.0 g.
6.3 Temperature Measuring Device - Use either a DCT meeting the requirements described in 6.3.1 or liquid-in-glass thermometers as described in 6.3.2. A calibrated DCT or calibrated low temperature liquid-in-glass thermometer shall be used as the thermometer for temperature measurement below 25 °C independent of the instrument's temperature control, and shall be located in the thermowell.
NOTE 2 - The display device and sensor must be correctly paired. Incorrect pairing will result in temperature measurement errors and possibly irreversible damage to the electronics of the display.
6.3.1 Digital contact thermometer requirements:
NOTE 3 - With respect to DCT probe immersion depth, a procedure to determine minimum depth can be found in Guide E2877, Section 5.3, or Test Methods E644, Section 7.
6.3.1.1 The DCT calibration drift shall be checked at least annually by either measuring the ice point or against a reference thermometer in a constant temperature bath at the prescribed immersion depth to ensure compliance with 6.3.1. With respect to an ice bath, Practice E563 provides guidance on the preparation and use of an ice bath. However, for this use, variance from the specific steps, such as water source, is permitted provided preparation is consistent. The basis for the variance is due to the reference being used to track change in calibration not verification.
NOTE 4 - When a DCT's calibration drifts in one direction over several calibration checks, that is, ice point, it may be an indication of deterioration of the DCT.
6.3.2 For liquid-in-glass, LiG, thermometers, two are required. One LiG shall be a calibrated 76 mm partial immersion thermometer with a scale from +5 °C to 1 degree less than the lowest test temperature in 0.2 °C subdivisions. This low temperature LiG thermometer shall have a report of calibration showing the temperature deviation at each calibrated test temperature. The second LiG thermometer shall be a 76 mm partial immersion thermometer graduated from at least +70 °C to 90 °C in 1 °C subdivisions, which is used to verify the preheat temperature.
6.3.2.1 Calibration Check - Verify the low temperature thermometer at least annually against a reference thermometer in a constant temperature bath or an ice bath. The thermometer is to be inserted to its immersion depth. If using an ice bath, the ice point reading is to be taken within 60 min after the thermometer has been at test temperature for at least 3 min. If the corrected temperature reading deviates from the reference thermometer or the ice point then repeat this calibration check. If the thermometer deviates from the reference value on two successive checks then a full thermometer recalibration is needed.
6.3.2.2 Recalibration - A complete recalibration of the liquid-in-glass thermometer, while permitted, is not necessary in order to meet the accuracy ascribed to liquid-in-glass thermometer's design until the thermometers corrected measured temperature deviates from the reference thermometer or ice point by one scale division, or until five years has elapsed since the last full calibration.
6.4 Temperature Control System - Regulates the mini-rotary viscometer block temperature in accordance with the temperature requirements described in Table X1.1.
6.5 Cell Cap - A cover inserted into the top of the viscometer cell to minimize room air circulation into the cells is required for thermoelectrically cooled instruments. The cell cap is a stepped cylinder 38 mm ± 1 mm in length made of a low thermal conductivity material, for example, thermoplastic such as acetyl copolymers that have known solvent resistivity and are suitable for use between the temperature ranges of this test method. The top half is 28 mm ± 1 mm in diameter and the bottom half is 19 mm in diameter with a tolerance consistent with the cell diameter. The tolerance on the bottom half is such that it will easily fit into cell but not allow the cap to contact the rotor shaft. The piece has a center bore of 11 mm ± 1 mm. The cap is made in two halves to facilitate placement in the top of the cell.
6.5.1 Cell caps shall not be used in the direct refrigeration instruments, since such use would block the flow of cold, dry air into the stators to keep them frost-free.
6.6 Supply of Dry Gas - A supply of dry filtered dry gas to minimize moisture condensation on the upper portions of the instrument.
6.6.1 For thermoelectric cooled instruments, which use cell caps, the dry gas supply is connected to the housing cover. The supply of dry gas is discontinued when the cover is removed for the measurement phase of the test.
6.7 Locking Pin - A device to keep the rotor from turning prematurely and able to stop the rotor at the nearest half revolution by interaction with the rotor crossbar.
7. Reagents and Materials
7.1 Low Cloud-Point, Newtonian Oil, a calibration oil of approximately 30 Pa•s viscosity at -20 °C for calibration of the viscometric cells. The calibration oil shall be obtained from suppliers complying with ISO Guide 34 and ISO 17025 with traceability to a national metrology institute (NMI).
7.2 Methanol, commercial or technical grade of dry methanol is suitable for the cooling bath.
7.3 Oil Solvent, commercial heptanes or similar solvent is suitable.
7.4 Acetone, technical grade of acetone is suitable provided it does not leave a residue upon evaporation.
8. Sampling
8.1 A representative sample of test oil free from suspended solid material and water is necessary to obtain valid results. If the sample in its container is received below the dew-point temperature of the room, allow to warm to room temperature before opening.