ASTM D892 standard test method for foaming characteristics of lubricating oils
10. Procedure
10.1 Sequence I - Without mechanical shaking or stirring, decant approximately 200 mL of sample into a beaker. Heat to 49 more or less 3°C (120 more or less 5°F) and allow to cool to 24 more or less 3°C (75 more or less 5°F). See Option A for stored sample (see 10.5). Each step of the procedure described in 10.3 and 10.4, respectively, shall be carried out within 3 h after completion of the previous step. In 10.5.1, the test shall be carried out as soon as compatible with the temperature specification and not more than 3 h after immersion of the cylinder in the 93.5°C (200°F) bath.
10.2 Pour the sample into the 1000-mL cylinder until the liquid level is at the 190-mL mark. Immerse the cylinder at least to the 900-mL mark in the bath maintained at 24 more or less 0.5°C (75 more or less 1°F). When the oil has reached the bath temperature, insert the gas diffuser and the air-inlet tube with the air source disconnected, and permit the gas diffuser to soak for about 5 min. Connect the air-outlet tube to the air volume measuring device. At the end of 5 min, connect to the air source, adjust the air flow rate to 94 more or less 5 mL/min, and force clean dry air through the gas diffuser for 5 min more or less 3 s, timed from the first appearance of air bubbles rising from the gas diffuser. At the end of this period, shut off the air flow by disconnecting the hose from the flow meter and immediately record the volume of foam; that is, the volume between the oil level and the top of the foam. The total air volume which has passed through the system shall be 470 more or less 25 mL. Allow the cylinder to stand for 10 min more or less 10 s and again record the volume of foam.
10.3 Sequence II - Pour a second portion of sample into a cleaned 1000-mL cylinder until the liquid level is at the 180-mL mark. Immerse the cylinder at least to the 900-mL mark in the bath maintained at 93.5 more or less 0.5°C (200 more or less 1°F). When the oil has reached a temperature of 93 more or less 1°C (199 more or less 2°F), insert a clean gas diffuser and air-inlet tube and proceed as described in 10.2, recording the volume of foam at the end of the blowing and settling periods.
10.4 Sequence III - Collapse any foam remaining after the test at 93.5°C (200°F) (10.3), by stirring. Cool the sample to a temperature below 43.5°C (110°F) by allowing the test cylinder to stand in air at room temperature, then place the cylinder in the bath maintained at 24 more or less 0.5°C (75 more or less 1°F). After the oil has reached bath temperature, insert a cleaned air-inlet tube and gas diffuser and proceed as described in 10.2, recording the foam value at the end of the blowing and settling periods.
10.5 Some lubricants with modern additives can pass their foam requirements when blended (with the antifoam properly dispersed in small particle sizes) but fail to meet the same requirements after two or more weeks’ storage. (It appears that the polar dispersant additives have the potency to attract and hold antifoam particles, such that the apparent increased antifoam size results in decreased effectiveness to control foam in Test Method D892.) However, if the same stored oil is merely decanted and poured into engines, transmissions, or gear boxes and those units operated for a few minutes, the oil again meets its foam targets. Similarly, decanting the stored oil into a blender, followed by agitation as described for Option A (see 10.5.1), redisperses the antifoam held in suspension and the oil again will give good foam control in Test Method D892. For such oils, Option A can be used. On the other hand, if the antifoam is not dispersed into sufficiently small particles when the oil is blended, the oil cannot meet its foam requirements. If this freshly blended oil were vigorously stirred according to Option A, it is very possible that the oil would then meet its foam targets whereas the plant blend would never do so. Therefore, it is inappropriate and misleading to apply Option A for quality control of freshly made blends.
10.5.1 Option A - Clean the container of a 1-L (1-qt), high-speed blender using the procedure given in 9.1.1. Place 500 mL of sample measured from 18 to 32°C (65 to 90°F) into the container, cover, and stir at maximum speed for 1 min. Because it is normal for considerable air to be entrained during this agitation, allow to stand until entrained bubbles have dispersed and the temperature of the oil has reached 24 more or less 3°C (75 more or less 5°F). Within 3 h following the agitation (solvents with equivalent cleaning and solvency characteristics may be substituted for toluene), start with testing as specified in 10.2.
NOTE 12 - In case of viscous oils, 3 h can be insufficient time to disperse the entrained air. If a longer time is required, record the time as a note on the results.
11. Alternative Procedure
11.1 For routine testing a simplified testing procedure can be used. This procedure differs from the standard method in only one respect. The total air volume used during the 5-min blowing period is not measured after the air has passed through the gas diffuser. This eliminates the volume measuring equipment and the airtight connections necessary to carry the exit air from the graduated cylinder to the volume measuring device, but requires that the flowmeter be correctly calibrated and that the flow rate be carefully controlled. Results obtained by this procedure shall be reported as D892 - IP 146 (Alternative).
