8. Sampling
8.1 Sample Size - Sufficient sample (at least 0.4 kg (1 lb)) to overfill the cup of the standard grease worker is required. If the sample size is insufficient and penetration ranges from NLGI 0 to 4, use Test Method D 1403. If the full-scale penetration value calculated in Test Method D 1403 is above 200, at least three times the amount needed to fill the one-quarter or one-half scale worker cup is required.
8.1.1 For block penetration, obtain a sufficient size sample of the grease, which must be hard enough to hold its shape, to permit cutting from it a 50-mm (2-in.) cube as a test specimen.
8.2 Sample Preparation - Samples are prepared for the various cone penetration test methods as follows:
8.2.1 Unworked Penetration - Place the empty grease worker cup, or dimensionally equivalent rigid container, and an appropriate amount of the sample in a metal container in the temperature bath maintained at 25°C for sufficient time to bring the temperature of the sample and the worker cup to 25 more or less 0.5°C (77 more or less 1°F). If the initial sample temperature differs from 25°C by more than about 8°C (15°F), or if an alternative method of bringing the sample to 25°C is used, allow sufficient additional time to ensure that the specimen is at 25 more or less 0.5°C before proceeding. Also, if the sample is larger than 0.4 kg (1 lb), allow sufficient additional time to ensure that the specimen is at 25 more or less 0.5°C. Testing may proceed if the specimen is at a uniform temperature of 25 more or less 0.5°C. Transfer the specimen, preferably in one lump, to overfill the cup of the grease worker or other container. Make this transfer in such a manner that the grease will be worked as little as possible. Jar the cup to drive out trapped air and pack the grease with the spatula, with as little manipulation as possible, to obtain a cupful without air pockets. Scrape off the excess grease extending above the rim by moving the blade of the spatula, held inclined toward the direction of motion at an angle of 45°, across the rim of the cup (Fig. 2). Do not perform any further leveling or smoothing of the surface throughout the determination of unworked penetration and determine the measurement immediately.
8.2.1.1 The penetrations of soft greases are dependent upon the diameter of the container. Therefore, greases having unworked penetrations greater than 265 should be tested in containers having the same diameter limitations as those of the worker cup. The results on greases having penetrations less than 265 are not significantly affected if the diameter of the container exceeds that of the worker cup.
8.2.2 Worked Penetration - The following sections describe the procedure for preparation of samples for worked penetration:
8.2.2.1 Working - Transfer sufficient specimen to the cup of the clean grease worker to fill it heaping full (mound up about 13 mm (0.5 in.) at the center), avoiding the inclusion of air by packing with the spatula. Jar the cup from time to time as it is being packed to remove any air inadvertently entrapped. Assemble the worker and, with the vent cock open, depress the plunger to the bottom. Insert a thermometer through the vent cock so that its tip is in the center of the grease. Place the assembled worker in the temperature bath maintained at 25°C (77°F) (Note 2) until the temperature of the worker and its contents is 25 more or less 0.5°C as indicated by the thermometer. If the initial sample temperature differs from 25°C by more than about 8°C (15°F), or if an alternative method of bringing the sample to 25°C is used, allow sufficient additional time to ensure that the specimen is at 25 more or less 0.5°C before proceeding. Also, if the sample is larger than 0.4 kg (1 lb), allow sufficient additional time to ensure that the specimen is at 25 more or less 0.5°C . Testing may proceed when the specimen is at a uniform temperature of 25 more or less 0.5°C. Remove the worker from the bath. If a water bath was used, wipe any excess water from the outer surfaces of the worker. Remove the thermometer and close the vent cock. Subject the grease to 60 full (67 to 71.5 mm (2 5/8 to 2 13/16 in.)) double strokes of the plunger, completed in about 1 min, and return the plunger to its top position. Open the vent cock, remove the cover and plunger, and return to the cup as much of the grease clinging to the plunger as can readily be removed.
NOTE 2 - If it is desired to immerse the worker above the joint between the cup and cover, take care that the joint is watertight in order to prevent the entrance of water to the worker.
8.2.2.2 Preparing Sample for Measurement—Jar the cup sharply on the bench or floor and pack the grease down with a spatula to fill the holes left by the plunger and to remove any air pockets (Note 3). Scrape off the excess grease extending over the rim by moving the blade of the spatula, held inclined toward the direction of motion at an angle of 45°, across the rim of the cup (Fig. 2), retaining the portion removed (Note 4).
NOTE 3 - The jarring should be only as vigorous as required to remove the entrapped air without splashing the specimen from the cup. In performing these operations, a minimum of manipulation should be used, as any agitation of the grease may have the effect of increasing the working beyond the specified 60 strokes.
NOTE 4 - Particularly when testing soft greases, retain the grease removed from the cup in scraping to provide a full cup for subsequent tests. Keep the outside of the rim of the cup clean so that the grease forced by the penetrometer cone to overflow the cup may be returned to the cup prior to preparing the specimen for the next test.
8.2.3 Prolonged Worked Penetration - Fill a clean grease worker cup and assemble the worker as described in 8.4.2. Subject the grease specimen to the prescribed number of double strokes (Note 5). Immediately after the working is concluded, place the worker in the temperature bath to bring the test specimen temperature to 25 more or less 0.5°C (77 more or less 1°F) within 1.5 h. Remove the worker from the temperature bath and subject the grease to a further 60 full (67 to 71.5 mm (2 5/8 to 2 13/16 in.)) double strokes of the plunger, completed in about 1 min, and return the plunger to its top position. Open the vent cock, remove the cover and plunger, and return to the cup as much of the grease clinging to the plunger as can readily be removed. Jar the cup sharply on the bench or floor and pack the grease down with a spatula to fill the holes left by the plunger and to remove any air pockets (Note 3). Scrape off the excess grease extending over the rim by moving the blade of the spatula, held inclined toward the direction of motion at an angle of 45°, across the rim of the cup (Fig. 2), retaining the portion removed (Note 4).
NOTE 5 - In order to minimize leakage during working, special attention should be paid to the seal in the worker cover.
8.2.3.1 Temperature - Maintain the temperature of the room used for the test within the range from 15 to 30°C (59 to 86°F). No further control of the worker temperature is necessary; but, before starting the test, the grease should have been in the room for sufficient time to bring its temperature within the range from 15 to 30°C.
8.2.4 Block Grease - By means of the specified grease cutter, cut as a test specimen from the sample at room temperature a cube about 50 mm (2 in.) on the edge (Fig. 3(a)). While holding this specimen so that the unbeveled edge of the cutter is toward it (Fig. 3(b)), slice off a layer about 1.5 mm (1/16 in.) in thickness from each of the three faces adjacent to a single corner, which can be truncated for identification (Fig. 3(c) and Note 6). Take care not to touch those portions of the newly exposed faces which are to be used for testing or to set a prepared face against the base plate or guide of the cutter. Bring the temperature of the prepared specimen to 25 more or less 0.5°C (77 more or less 1°F) by placing it in a temperature bath maintained at 25°C (77°F) for at least 1 h. If the initial sample temperature differs from 25°C by more than about 8°C (15°F), or if an alternative method of bringing the sample to 25°C is used, allow sufficient additional time to ensure that the specimen is at 25 more or less 0.5°C (77 more or less 1°F) before proceeding.
NOTE 6 - The testing of three faces is intended to equalize in the final value the effect of fiber orientation in testing fibrous greases. Smooth textured, nonfibrous greases can be tested on one face only, when agreed upon between the interested parties.
