ASTM D6186-08(2013)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D6186 − 08 (Reapproved 2013)
Standard Test Method for
Oxidation Induction Time of Lubricating Oils by Pressure
Differential Scanning Calorimetry (PDSC)
This standard is issued under the fixed designation D6186; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope reported as the oxidation induction time for the lubricating oil
at the specified test temperature.
1.1 This test method covers the determination of oxidation
induction time of lubricating oils subjected to oxygen at 3.5
4. Significance and Use
MPa (500 psig) and temperatures between 130 and 210°C.
4.1 Oxidation induction time, as determined under the
1.2 The values stated in SI units are to be regarded as
conditions of this test method, may be used as an indication of
standard. No other units of measurement are included in this
oxidation stability. This test method is faster than other oil
standard.
oxidation tests and requires a very small amount of sample. It
1.2.1 Exception—Pressure measurement appears in MPa
maybeusedforresearchanddevelopment,qualitycontrol,and
with psig provided in parentheses for information only.
specification purposes. However, no correlation has been
1.3 This standard does not purport to address all of the
established between the results of this test method and service
safety concerns, if any, associated with its use. It is the
performance.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
5. Apparatus
bility of regulatory limitations prior to use.
5.1 Pressure Differential Scanning Calorimeter (PDSC),
equipped with the following items:
2. Terminology
5.1.1 Sample Enclosure, with capability to 3.5 6 0.2 MPa
2.1 Definitions of Terms Specific to This Standard:
(500 6 25 psig) at 210°C and pressure gauge graduated at
2.1.1 extrapolated onset time, n—a time determined on a
intervals of 200 KPa (28.6 psig) or less.
thermal curve, as the intersection of the extrapolated baseline
5.1.2 Thermal Analyzer.
and a line tangent to the oxidation exotherm constructed at its
5.1.3 Aluminum Solid Fat Index (SFI) Sample Pan—See
maximum rate.
Note 1.
2.1.2 oxidation induction time, (OIT), n— a period of time
5.1.4 Oxidation Stability Software.
during which the oxidation rate accelerates from zero to a
5.1.5 Calibration Software.
maximum and which corresponds to the extrapolated onset
5.1.6 Calibrated Flowmeter, with a capacity of at least 200
time.
mL/min and graduated in intervals of 5 mL or less.
5.1.7 Sample Encapsulation Press.
2.1.3 thermal curve, n—a graph of sample heat flow versus
time.
NOTE 1—It has been found that when oil samples are prepared with SFI
pans which have more consistent surface areas than standard flat bottom
3. Summary of Test Method
pans, reproducibility is improved.
NOTE 2—Stainless steel or copper tubing is compatible with oxygen.
3.1 Asmall quantity of oil is weighed into a sample pan and
NOTE 3—See Fig. 1 for a diagram of a typical test unit.
placed in a test cell. The cell is heated to a specified
temperature and then pressurized with oxygen. The cell is held
6. Reagents and Materials
at a regulated temperature and pressure until an exothermic
6.1 Oxygen, a minimum purity of 99.5 % oxygen by vol-
reaction occurs. The extrapolated onset time is measured and
ume. (Warning—Oxidizer. Gas under pressure. )
6.2 Indium, of not less than 99.9 % indium by mass.
This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
Subcommittee D02.09.0D on Oxidation of Lubricants.
Current edition approved Dec. 1, 2013. Published December 2013. Originally Rhee, In-Sik, “Development of New Oxidation Stability Test Method for
approved in 1997. Last previous edition approved in 2008 as D6186 – 08. DOI: Lubricating Oils Using a Pressure Differential Scanning Calorimeter (PDSC),”
10.1520/D6186-08R13. NLGI Spokesman, Vol 65, No. 3, June 2001, pp. 16–23.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6186 − 08 (2013)
FIG. 1 PDSC Test Unit
7. Calibration
FIG. 2 Calibration Curve for PDSC
7.1 Sample Temperature Calibration:
7.1.1 Weigh approximately 10 mg of indium into an alumi-
num sample pan, insert a lid and crimp the lid to the pan using
ment does not have this function, the control calibration shall
the encapsulation press. Place the crimped pan onto the sample
be followed according to the equipment manufacturer’s rec-
platform in the pressure cell. Seal an empty pan in the same
ommendations.
manner and place it on the reference platform. Set the cell
cover in place and close the cell. 7.3 Cell Base Pressure Gauge Calibration—Conduct the
7.1.2 Open the oxygen cylinder valve slightly and set a calibration using a calibrated pressure transducer or a previ-
pressureof3.5 60.2MPa(500 625psig)onthecellinletline ously calibrated gauge according to the pressure cell manufac-
withthepressureregulator.Partiallyopentheinletvalveonthe turer’s instructions.
cell and allow the pressure to slowly build up in the cell. This
8. Procedure
requires approximately 2 min. Using the outlet valve, adjust
and maintain the oxygen purge rate through the flowmeter at
8.1 Before starting a test, the control thermocouple calibra-
100 6 10 mL/min.
tion shall be conducted at the test temperature (either 210, 180,
7.1.3 Set the thermal analyzer to heat from ambient tem-
155, or 130°C) according to 7.2.1 and 7.2.2. When the test
perature (approximately 22°C) to 180°C at a programmed rate
temperature is not known, conduct the calibration at 210°C.
of 10°C/min. After completion of the run measure the melting
8.2 Weigh 3.0 6 0.2 mg of oil into a new sample pan.
temperature of the indium. If the melting temperature differs
Spread the sample evenly upon the flat portion. Do not spill
from 157.4 6 0.2°C (see Note 4) correct the difference by
any of the sample into the trough portion of the pan. A flat
using either the hardware or software calibration procedure
bottom pan can be used if the sample is placed upon a 0.5 cm
described in the manufacturer’s instruction manual. If the
diameter circle in the center of the pan.
hardware calibration procedure is used, perform the tempera-
ture correction under 3.5 MPa (500 psig) oxygen pressure with 8.3 Place the uncovered pan containing the sample onto the
platform of the cell according to the PDSC manufacturer’s
a 100 mL/min purge rate.Atypical melting calibration curve is
shown in Fig. 2. instructions for placing the sample pan. Place a new empty pan
of the same configuration onto the cell platform according to
NOTE 4—The melting temperature of indium is 156.6°C at atmospheric
the PDSC manufacturer’s instructions for placing the reference
pressure, but has been found to be elevated to 157.4°C under the
pan. Close the cell and the pressure release valve.
conditions of this test method, 3.5 MPa (500 psig) of oxygen.
7.2 Temperature Controller Calibration: 8.4 Beginning at ambient temperature (approximately
22°C), program the sample temperature to increase at a rate of
7.2.1 Remove both the sample pan and the reference pan
from the cell, then close the cell. Slowly pressurize the cell 100°C/min to the test temperature.
with 3.5 6 0.2 MPa (500 6 25 psig) oxygen and adjust the
8.5 Allow the sample to equilibrate at the test temperature
purge rate to 100 6 10 mL/min using the cell outlet valve.
for 2 min.
Select the desired test temperature (either 2
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