ASTM D2532 Test Method for Viscosity and Viscosity Change After Standing at Low Temperature of Aircraft Turbine Lubricants
6. Procedure for Cleaning Viscometers and Filter Screen
6.1 Apply air pressure or suction to the viscometer to remove any previous test specimen. Allow the viscometer to drain for 5 min.
6.1.1 Wash the viscometer four times, inside and out, with fresh toluene (Warning - see Note 3) using suction as required. Allow the viscometer to drain.
NOTE 3 - Warning: Flammable.
6.1.2 Wash the viscometer four times, inside and out, with acetone, and allow to drain for 5 min. Then dry with suction.
6.1.3 Clean the viscometer thoroughly by filling it completely with glass cleaning solution. Allow to drain for 5 min.
6.1.4 Rinse viscometer inside and out with distilled water until all traces of the cleaning solution are completely removed. Allow to drain for 5 min.
6.1.5 Dry in oven at approximately 100°C (212°F).
6.2 Clean the filter screen by first disassembling the screen (if practicable).
6.2.1 Rinse thoroughly with fresh toluene (Warning - see Note 3).
6.2.2 Rinse thoroughly with fresh acetone (Warning - see Note 3).
6.2.3 Dry in oven at approximately 100°C (212°F).
7. Procedure
7.1 For the duration of the test, maintain the bath temperature at the required temperature +/-0.03°C (+/-0.05°F).
7.2 Charge the clean, dry viscometer as prescribed in Test Method D445.
7.2.1 Affix the drying tubes and carefully flush the moist room air from the viscometer by placing vacuum to the drying tubes. Draw the sample into the working capillary and timing bulb so as to preclude the possibility of any traces of residue moisture condensing on the walls of the capillary and timing bulb while the sample cools to test temperature. Moisture must not be allowed to condense on the walls of the working capillary and efflux bulb.
7.2.2 Place the viscometer in the constant-temperature bath, and vertically align the viscometer if a self-aligning holder has not been used.
7.2.3 Make the first determination of kinematic viscosity 35 min +/- 1 min after the viscometer is placed in the bath. Measure the efflux time as specified in Test Method D445. Be careful that the stopcock or pinch clamp joining each arm of the viscometer has been opened to ensure that there is no effect of the drying tubes on the efflux time.
7.3 Measure the kinematic viscosity after standing 3 h at the required temperature. Without removal of the viscometer from the constant-temperature bath, repeat the viscosity determination (7.2.3) at 3 h +/- 5 min after the completion of the initial viscosity determination.
7.4 Measure the kinematic viscosity after standing 72 h at the required temperature. Without removal of the viscometer from the constant-temperature bath (Note 4), repeat the viscosity determination (7.2.3) at 72 h +/- 5 min after the completion of the initial viscosity measurement (Note 1).
NOTE 4 - If, for some reason, such as unavailability of operator attention, it becomes difficult or impractical to maintain the temperature of the bath within the specified +/-0.03°C (+/-0.05°F) variations for the entire time required for completion of the 72-h test, the bath may be put on automatic control capable of holding the required temperature at +/-0.3°C (+/-0.5°F). Optionally, the viscometer may be removed from the bath and placed in the low-temperature storage cabinet or bath described in 5.5. In either case, the viscometer shall be returned to conditions of 0.03°C (+/-0.05°F) and held there for at least 35 min before the viscosity is to be measured again.
8. Calculation
8.1 Calculate the kinematic viscosity as follows:
Kinematic viscosity, mm2/s(cSt) = Ct
where:
C = calibration constant of the viscometer at the required temperature, cSt/s, and
t = efflux time, s.
8.2 Report the viscosity in centistokes at 35 min, 3 h, and 72 h.
8.3 Calculate the percent viscosity change as follows:
Viscosity change, percent = [100(B - A)/A], or [100(C - A)/A]
where
A = viscosity at 35 min,
B = viscosity at 3 h, and
C = viscosity at 72 h.
