1、Designation: D4425 09 (Reapproved 2014)Standard Test Method forOil Separation from Lubricating Grease by Centrifuging(Koppers Method)1This standard is issued under the fixed designation D4425; the number immediately following the designation indicates the year oforiginal adoption or, in the case of
2、revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers a procedure for determining thetendency of lubricating grease to separat
3、e oil when subjected tohigh centrifugal forces.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility
4、 of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D217 Test Methods for Cone Penetration of LubricatingGrease3. Terminology3.1 Definitions:3.1.1 lubric
5、ating grease, na semi-fluid to solid product ofa thickener in a liquid lubricant.3.1.1.1 DiscussionThe dispersion of the thickener forms atwo-phase system and immobilizes the liquid lubricant bysurface tension and other physical forces. Other ingredients arecommonly included to impart special proper
6、ties. D2173.1.2 thickener, nin lubricating grease, a substance com-posed of finely-divided particles dispersed in a liquid to formthe productss structure.3.1.2.1 DiscussionThickeners can be fibers (such as vari-ous metallic soaps) or plates or spheres (such as certainnon-soap thickeners), which are
7、insoluble or, at most, only veryslightly soluble in the liquid lubricant. The general require-ments are that the solid particles be extremely small, uniformlydispersed, and capable of forming a relatively stable, gel-likestructure with the liquid lubricant.3.2 Symbols:a = distance from top of grease
8、 surface to tube mouth(mm).b = height of liquid column in an inverted test tube (mm).d = test tube inside diameter (mm).H = accumulated test time at a given reading (h).K36 = resistance to centrifugal separation (V/H).r = measured at the maximum radius of rotation (mm).rpm = rotational speed (r/min)
9、.V = volume of separated oil, as a percentage of theoriginal grease volume (%).Vg= grease volume in a test tube (cm3).Vo= volume of separated oil (cm3).Vt= test tube total volume (cm3).A = angle of rotor, between the test tube axis and axis ofrotation (degrees). = rotational speed (rad/s).G = relati
10、ve centrifugal acceleration.3.3 The relative effect of centrifugal forces, when related tothe gravitational standard acceleration (9.81 m/s2), is notedwith the symbol G. It can be calculated as follows:G 5 1.02 310243 r 32(1)orG 5 1.12 310263 r 3rpm2(2)4. Summary of Test Method4.1 Pairs of centrifug
11、e tubes are charged with greasesamples and are placed in the centrifuge. The grease samplesare subjected to a centrifugal force equivalent to a G value of36 000, at 50C 6 1C, for specific periods of time. Theresistance of the grease to separate the oil is then defined as aratio of the percent of oil
12、 separated to the total number of hoursof testing.5. Significance and Use5.1 This test method is useful in evaluating the degree towhich a grease would separate into fluid and solid componentswhen subjected to high centrifugal forces. Flexible shaft1This test method is under the jurisdiction of Comm
13、ittee D02 on PetroleumProducts, Liquid Fuels, and Lubricants and is the direct responsibility of Subcom-mittee D02.G0.03 on Physical Tests.Current edition approved Oct. 1, 2014. Published November 2014. Originallyapproved in 1984. Last previous edition approved in 2009 as D4425 09. DOI:10.1520/D4425
14、-09R14.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, P
15、O Box C700, West Conshohocken, PA 19428-2959. United States1couplings, universal joints, and rolling element thrust bearingsare examples of machinery which subject lubricating greases tolarge and prolonged centrifugal forces. This test method hasbeen found to give results that correlate well with re
16、sults fromactual service. The test method may be run at other conditionswith agreement between parties but the precision noted in thistest method will no longer apply.36. Apparatus6.1 High-Speed Centrifuge, capable of developing a G valueof 36 000. Mount the unit on a flat level surface to allowunre
17、stricted air flow to the motor. This is essential for longmotor life. The centrifuge should be equipped with:6.1.1 Fixed Angle Rotor, multiple place, which can sustain aG value of 36 000.6.1.2 Thermometer, preferably of a dial type, installed sothat the temperature in the vicinity (5 to 15 mm) of th
18、e rotorcan be measured.6.1.3 Air Choke, installed at the air inlet of the centrifugechamber, and used to control the temperature if the unit lacksan automatic temperature control. Some designs require outletchoking as well.6.1.4 Centrifuge Tubes, made of transparent material, ca-pable of withstandin
19、g a G value of 36 000 for 100 h minimum(Note 1).NOTE 1Polypropylene tubes were found to be the most durable.6.2 Balance, having a capacity of about 100 g with aminimum sensitivity of 0.1 g.7. Sampling7.1 The sample presented for analysis should be largeenough to make possible the selection of a repr
20、esentativeportion for testing. Each run will require approximately 0.5 gfor each cubic centimetre of tube capacity . Examine for anyindication of non-homogeneity such as oil separation, phasechanges, or gross contamination. If any abnormal conditionsare found, obtain a new sample.7.2 The sample temp
21、erature at time of loading is to bebetween 15C and 35C.8. Preparation of Apparatus8.1 Inspect the centrifuge unit paying particular attention tothe cleanliness of the rotor which will be unbalanced by anysurface deposits.8.2 Examine the required number of tubes to be used for thetest, rejecting any
22、with surface scratches or imperfections.9. Procedure9.1 For each grease, two centrifuge tubes are required. Newtubes must be used for each test and they must be handled withcare to avoid scratches.9.1.1 Determine the total volume, V, in cubic centimetres, ofeach tube by filling with water and then p
23、ouring into agraduated cylinder and measuring.9.1.2 Measure the inside diameter, d, in millimetres with avernier caliper.9.2 Take grease samples from the container without includ-ing any free oil found on the grease surface.9.3 Charge each tube with approximately 0.5 g of grease foreach cubic centim
24、eter of tube capacity (example:7gofgreasein a tube of 14 cm3) taking care that the difference in mass ofeach does not exceed 0.3 g to minimize centrifuge imbalance.9.4 Place the tubes in diametrically opposite compartmentsif all rotor compartments are not used. Always use evennumbers of tubes.9.5 Th
25、e centrifuge lid must always be closed when the rotoris turning. The rotor should never be touched while rotating.9.6 Operate the centrifuge at a G value of 1000 for 3 min toeliminate any trapped air bubbles in the grease charge.9.7 Measure the distance, a, in millimetres from the top ofthe test tub
26、e to the closest point on the grease surface as shownin Fig. 1, and calculate the grease volume as in 10.1.9.8 Replace the tubes in the rotor head, close the lid, andbring the speed up to a relative acceleration, G, of 36 000.Consult manufacturers instructions for proper speed.9.9 At the end of the
27、test interval, the rotor must come to acomplete stop before opening the lid.9.10 Measure the amount of oil separated as follows:9.10.1 Cover the mouth of the tube with a piece of hardrubber or plastic material and invert for 1 to 2 min or until allthe oil flows to the top of the tube.9.10.2 Measure
28、the height, b, of the separated oil inmillimetres, as shown in Fig. 2.9.11 Calculate the oil volume as indicated in 10.2.9.12 Calculate the percent of oil separated from the greaseas indicated in 10.3.3Detailed discussion is found in Calistrat, M. M., Grease Separation underCentrifugal Forces, ASME
29、Paper 75-PTG-3. Presented at the Joint ASLE-ASMELubrication Conference, Oct. 2123, 1975. FIG. 1 Measuring Grease VolumeD4425 09 (2014)29.13 If the test is to be continued, return the tubes to theirrespective compartments in the centrifuge rotor. When thecovering over the tube mouth is removed all ad
30、hering oil mustbe returned to the tubes.9.14 Measure the amount of oil separation after one or moreof the following time periods: 6, 12, 24, 48, or 96 cumulativehours of testing at a G value of 36 000. No more than 72 h ofinterruption is acceptable between two test periods.9.15 The normal duration o
31、f a test is 24 cumulative hours.9.15.1 The test can be extended to 48 or 96 h if desired, butspecial reporting conditions prevail (see 11.4.2).10. Calculation10.1 Calculate the grease volume to the nearest cm3asfollows:Vg5 Vt2FSa1d2 tan AD 0.785 d2! 31023G(3)where:Vg= grease volume, cm3,Vt= tube vol
32、ume, cm3(see 9.1.1),a = distance to grease surface, mm (see 9.7),d = tube inside diameter, mm (see 9.1.2), andA = angle of the rotor, in degrees. This angle is specified bythe rotor manufacturer.10.2 Calculate the oil volume to the nearest cm3as follows:Vo5 0.785 d2b 31023(4)where:Vo= separated oil
33、volume, cm3, andb = height of the separated oil, mm (see 9.10).10.3 Calculate the amount of oil separated from the greaseto the nearest percent as follows:V 5VoVg3100 (5)where:V = oil separation, in volume percent.11. Report11.1 The amount of oil separated from a lubricating greasesubjected to centr
34、ifugal forces is a function of the G level, theamount of time under test, and the test temperature. Thus, toevaluate the resistance of a grease to separate the oil, thefollowing data are required:11.1.1 The oil separation, in volume percent (see 10.3).11.1.2 The level of centrifugal acceleration, in
35、 G (see 3.1).11.1.3 The duration of the test, in hours.11.1.4 The test temperature, in degrees Celsius.11.2 In order to simplify the testing and reporting of the oilseparation from lubricating greases by centrifuging, the levelof centrifugal acceleration and the test temperature are main-tained cons
36、tant, at a G value of 36 000 and 50C. Hence, theresistance of a grease to separate the oil under centrifugalforces is reported as the fraction K36.K36 5 V/H (6)where:V = oil separation, in volume percent (see 10.3), andH = accumulated time of testing in hours (see 9.13).The fraction K36 should not b
37、e reduced, and the values ofboth V and H should be reported.11.3 The results of two tubes filled with the same grease(see 9.3) are averaged for reporting purposes.11.4 The values for V and H in Eq 6 are those at the time theoil separation stabilizes. This is defined as the time at which theoil separ
38、ation increases by less than 10 % between twoconsecutive readings.11.4.1 If the oil separation does not stabilize before the 24 htest, the 24 h test results are used for reporting.11.4.2 If the testing is extended beyond the 24 cumulativehours, the same conditions in 11.4 apply, except more than 24h
39、 can be used. Examples of calculations can be found inAppendix X1.12. Precision and Bias412.1 PrecisionWhen run under the conditions stated in thetest method, the precision, as determined by statistical exami-nation of interlaboratory results is as follows:12.1.1 RepeatabilityThe difference between
40、successivetest results, obtained by the same operator with the sameapparatus under constant operating conditions on identical testmaterial, would in the long run, in the normal and correctoperation of the test method, exceed 4.8 percentage points (ofthe value of V, 10.3) only in one case in twenty.1
41、2.1.2 ReproducibilityThe difference between two singleand independent results, obtained by different laboratories onidentical test material, would in the long run, in the normal andcorrect operation of test method, exceed 18.7 percentage points(of the value V, 10.3) only in one case in twenty.12.2 B
42、iasThe procedure in this test method has no biasbecause the value of K36 can be defined only in terms of thetest method.4Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D02-1185.FIG. 2 Measuring Separated OilD4425 09 (2014)313. K
43、eywords13.1 centrifuge; grease; lubricating grease; oil separationAPPENDIX(Nonmandatory Information)X1. EXAMPLES OF CALCULATIONSX1.1 Examples for 24 h TestsX1.1.1Cumulative hours, H 61224Oil separation, V 30 32 32K36 = 30/6, because V increased by less than 10 % between the 6 and 12 htests.Cumulativ
44、e hours, H 61224Oil separation, V 30 35 38K36 = 35/12, because V increased by 17 % between the 6 h and 12 h test, butonly 8.5 % between the 12 and 24 h tests.Cumulative hours, H 61224Oil separation, V 30 35 42K36 = 42/24, because the oil separation did not stabilize before the 24 h test.X1.2 Example
45、s for Tests Exceeding 24 hX1.2.1Cumulative hours, H 6122448 96Oil separation, V 30 35 42 44 44K36 = 42/24, because V increased by less than 10% between the 24 h and 48h tests.Cumulative hours, H 6122448 96Oil separation, V 30 35 42 47 48K36 = 47/48, because V increased by less than 10% between the 4
46、8 h and 96h tests.Cumulative hours, H 6122448 96Oil separation, V 30 35 42 47 53K36 = 53/96, because the oil separation did not stabilize before the 96 h test.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this stand
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