1、Designation: D 91 02 (Reapproved 2007)e1An American National StandardStandard Test Method forPrecipitation Number of Lubricating Oils1, 2This standard is issued under the fixed designation D 91; the number immediately following the designation indicates the year of originaladoption or, in the case o
2、f revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscriptepsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.e1NOTEDeleted Note 1 wit
3、h reference to naphtha editorially in July 2007.1. Scope1.1 This test method covers the determination of the pre-cipitation number of steam cylinder stocks and black oils, andcan be used for other lubricating oils.1.2 The values stated in acceptable SI units are to beregarded as the standard.1.3 Thi
4、s standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility 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 Document
5、s2.1 ASTM Standards:3D 4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD 4177 Practice for Automatic Sampling of Petroleum andPetroleum Products3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 ASTM precipitation number, of lubricating oils,nthe number of mil
6、lilitres of precipitate formed when 10 mLof lubricating oil are mixed with 90 mL of ASTM precipitationnaphtha, and centrifuged under the conditions of the test.4. Significance and Use4.1 Fully refined petroleum oils normally contain no naph-tha insoluble material. Semirefined or black oils frequentl
7、ycontain some naphtha insoluble material (sometimes referredto as asphaltenes). This test measures the amount of naphthainsoluble material in the oil. This quantity is reported as theprecipitation number.5. Apparatus5.1 Centrifuge Tube, cone-shaped, conforming to the di-mensions given in Fig. 1, and
8、 made of thoroughly annealedglass. The graduations, numbered as shown in Fig. 1, shall beclear and distinct, and the mouth shall be constructed in a shapesuitable for closure with a cork. Scale-error tolerances andsmallest graduations between various calibration marks aregiven in Table 1 and apply t
9、o calibrations made with air-freewater at 20C.5.2 Centrifuge, meeting all the safety requirements fornormal use and capable of whirling two or more filledcentrifuge tubes at a speed which can be controlled to give arelative centrifugal force (rcf) between 600 and 700 at the tipof the tubes. The revo
10、lving head, trunnion rings, and trunnioncups, including the rubber cushion, shall be soundly con-structed to withstand the maximum centrifugal force capable ofbeing delivered by the power source. The trunnion cups andcushions shall firmly support the tubes when the centrifuge isin motion. The centri
11、fuge shall be enclosed by a metal shield orcase strong enough to eliminate danger if any breakage occurs.Calculate the speed of the rotating head by means of thefollowing equation:rpm 5 1337 =rcf/d (1)where:rcf = relative centrifugal force, andd = diameter of swing, in mm, measured between tips ofop
12、posite tubes when in rotating position.Table 2 shows the relationship between diameter swing, rcf,and revolutions per minute.6. Reagent6.1 Hexanes, Reagent Grade.(WarningExtremely flam-mable, harmful if inhaled.)1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products a
13、nd Lubricants and is the direct responsibility of SubcommitteeD02.06 on Analysis of Lubricants.Current edition approved May 1, 2007. Published June 2007. Originallyapproved in 1921. Last previous edition approved in 2002 as D 91 02.2This test method has been adopted for use by government agencies to
14、 replaceMethod 3101 of Federal Test Method Standard No. 791b.3For 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.
15、1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.7. Sampling7.1 For sampling techniques, see Practices D 4057 or Prac-tice D 4177.8. Procedure8.1 Add 10 6 1 mL of the oil to be tested in each of twoclean, dry centrifuge tubes at room
16、temperature. Fill each tubeto the 100-mL mark with hexanes and close tightly with asoftened cork (not a rubber stopper). Then invert each tube atleast 20 times, allowing the liquid to drain thoroughly from thetapered tip of the tube each time. Place the tubes in a water bathat 32 to 35C for 5 6 1 mi
17、n. Momentarily remove the corks torelieve any pressure, and invert each tube again at least 20times exactly as before. The success of this method depends toa large degree upon having a thoroughly homogeneous mixturewhich will drain quickly and completely from the tapered tipwhen the tube is inverted
18、.8.2 Balance the two centrifuge tubes or pairs of tubes withtheir respective trunnion cups and place them on opposite sidesof the centrifuge head. Then whirl them for 10 min at a ratesufficient to produce a relative centrifugal force (rcf) between600 and 700 at the tips of the whirling tubes (see 5.
19、2). Repeatthis operation until the volume of sediment in each tuberemains constant for three consecutive readings. In general, notmore than four whirlings will be required for oils having a lowprecipitation number.9. Calculation and Report9.1 Read the volume of the solid sediment at the bottom ofeac
20、h centrifuge tube, estimating to 0.1 mL or closer if possible.If the two readings differ by not more than 0.1 mL, report themean of the two as the ASTM Precipitation Number. If the tworeadings differ by more than 0.1 mL, make two more determi-nations and report the average of the four determinations
21、.10. Precision and Bias10.1 The precision of this test method as determined bystatistical examination of interlaboratory results is as follows:10.2 RepeatabilityThe difference between two test re-sults, obtained by the same operator with the same apparatusunder constant operating conditions on ident
22、ical test material,would in the long run, in the normal and correct operation ofthe test method, exceed the following values only in one casein twenty:Precipitation Number Repeatability0.00 to 1.20 10 % of Mean10.3 ReproducibilityThe difference between two singleand independent results obtained by d
23、ifferent operators work-ing in different laboratories on identical test material would, inthe long run, in the normal and correct operation of the testmethod, exceed the following values only in one case intwenty:Precipitation Number Reproducibility0.00 to 1.20 30 % of Mean10.4 BiasThis procedure is
24、 empirical, precipitation num-ber is defined solely by this procedure, therefore, no statementof bias can be made.11. Keywords11.1 asphaltenes; lubricating oils; precipitation numberNOTEFor volumetric tolerances see Table 1.FIG. 1 ASTM Cone-Shaped Centrifuge TubeTABLE 1 Calibration Tolerances for 20
25、0 mm Centrifuge TubeRange, mL Subdivision, mL Volume Tolerance, mL0to0.1 0.05 60.02Above 0.1 to 0.3 0.05 60.03Above 0.3 to 0.5 0.05 60.05Above 0.5 to 1.0 0.10 60.05Above 1.0 to 2.0 0.10 60.10Above 2.0 to 3.0 0.20 60.10Above 3.0 to 5.0 0.5 60.20Above 5.0 to 10 1.0 60.50Above 10 to 25 5.0 61.00Above 2
26、5 to 100 25 61.00TABLE 2 Rotation Speeds for Centrifuges of Various DiametersDiameter of Swing, mmARpm at 600 rcf Rpm at 700 rcf483 1490 1610508 1450 1570533 1420 1530559 1390 1500AMeasured in millimetres between tips of opposite tubes when in rotatingposition.D 91 02 (2007)e12ASTM International tak
27、es no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own re
28、sponsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addres
29、sed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at th
30、e address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D 91 02 (2007)e13
