ASTM D91-02(2007)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
An American National Standard
Designation:D91–02 (Reapproved 2007)
Standard Test Method for
,
1 2
Precipitation Number of Lubricating Oils
ThisstandardisissuedunderthefixeddesignationD 91;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscript
epsilon (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.
1. Scope 5. Apparatus
5.1 Centrifuge Tube, cone-shaped, conforming to the di-
1.1 This test method covers the determination of the pre-
cipitation number of steam cylinder stocks and black oils, and mensions given in Fig. 1, and made of thoroughly annealed
can be used for other lubricating oils. glass. The graduations, numbered as shown in Fig. 1, shall be
1.2 The values stated in acceptable SI units are to be clearanddistinct,andthemouthshallbeconstructedinashape
regarded as the standard. suitable for closure with a cork. Scale-error tolerances and
1.3 This standard does not purport to address all of the smallest graduations between various calibration marks are
safety concerns, if any, associated with its use. It is the given in Table 1 and apply to calibrations made with air-free
responsibility of the user of this standard to establish appro- water at 20°C.
priate safety and health practices and determine the applica- 5.2 Centrifuge, meeting all the safety requirements for
bility of regulatory limitations prior to use. normal use and capable of whirling two or more filled
centrifuge tubes at a speed which can be controlled to give a
2. Referenced Documents
relative centrifugal force (rcf) between 600 and 700 at the tip
2.1 ASTM Standards: of the tubes. The revolving head, trunnion rings, and trunnion
D 4057 Practice for Manual Sampling of Petroleum and
cups, including the rubber cushion, shall be soundly con-
Petroleum Products structed to withstand the maximum centrifugal force capable of
D 4177 Practice for Automatic Sampling of Petroleum and
being delivered by the power source. The trunnion cups and
Petroleum Products cushions shall firmly support the tubes when the centrifuge is
in motion.The centrifuge shall be enclosed by a metal shield or
3. Terminology
case strong enough to eliminate danger if any breakage occurs.
3.1 Definitions of Terms Specific to This Standard:
Calculate the speed of the rotating head by means of the
3.1.1 ASTM precipitation number, of lubricating oils,
following equation:
n—the number of millilitres of precipitate formed when 10 mL
rpm 5 1337 rcf/d (1)
=
of lubricating oil are mixed with 90 mLofASTM precipitation
naphtha, and centrifuged under the conditions of the test.
where:
rcf = relative centrifugal force, and
4. Significance and Use
d = diameter of swing, in mm, measured between tips of
4.1 Fully refined petroleum oils normally contain no naph-
opposite tubes when in rotating position.
tha insoluble material. Semirefined or black oils frequently Table 2 shows the relationship between diameter swing, rcf,
contain some naphtha insoluble material (sometimes referred
and revolutions per minute.
to as asphaltenes). This test measures the amount of naphtha
6. Reagent
insoluble material in the oil. This quantity is reported as the
precipitation number. 6.1 Hexanes, Reagent Grade.(Warning—Extremely flam-
mable, harmful if inhaled.)
NOTE 1—Precipitation naphtha is sometimes referred to or sold by
This test method is under the jurisdiction of ASTM Committee D02 on
other names, such as petroleum naphtha, petroleum ether, ligroine,
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
D02.06 on Analysis of Lubricants. petroleumbenzin,andindustrialnaphtha.Oneshouldconfirmthatitmeets
Current edition approved May 1, 2007. Published June 2007. Originally
the requirements shown in 6.1.
approved in 1921. Last previous edition approved in 2002 as D 91 – 02.
This test method has been adopted for use by government agencies to replace
7. Sampling
Method 3101 of Federal Test Method Standard No. 791b.
7.1 For sampling techniques, see Practices D 4057 or Prac-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
tice D 4177.
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D91–02 (2007)
at 32 to 35°C for
...