ASTM D6743-01

Standard Test Method for Thermal Stability of Organic Heat Transfer Fluids

SCOPE
1.1 This test method covers the determination of the thermal stability of unused organic heat transfer fluids. The procedure is applicable to fluids used for the transfer of heat at temperatures both above and below their boiling point (refers to normal boiling point throughout the text unless otherwise stated). It is applicable to fluids with maximum bulk operating temperature between 260°C (500°F) and 454°C (850°F). The procedure shall not be used to test a fluid above its critical temperature. In this test method, the volatile decomposition products are in continuous contact with the fluid during the test. This test method will not measure the thermal stability threshold (the temperature at which volatile oil fragments begin to form), but instead will indicate bulk fragmentation occurring for a specified temperature and testing period. Because potential decomposition and generation of high pressure gas may occur at temperatures above 260°C (500°F), do not use this test method for aqueous fluids or other fluids which generate high-pressure gas at these temperatures.
1.2 DIN Norm 51528 covers a test method that is similar to this test method.
1.3 The applicability of this test method to siloxane-based heat transfer fluids has not been determined.
1.4 The values stated in SI are the standard. The values provided in parentheses are for information only.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific precautionary statements, see 7.2, 8.8, 8.9 and 8.10.

General Information

• Status: Historical
• Publication Date: 09-Dec-2001
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.L0 - Industrial Lubricants and Engineering Sciences of High Performance Fluids and Solids

Relations

• Replaced By: ASTM D6743-01e1 - Standard Test Method for Thermal Stability of Organic Heat Transfer Fluids
• Effective Date: 10-Dec-2001
• Referred By: ASTM D5372-20 - Standard Guide for Evaluation of Hydrocarbon Heat Transfer Fluids
• Effective Date: 10-Dec-2001
• Referred By: ASTM D7863-22 - Standard Guide for Evaluation of Convective Heat Transfer Coefficient of Liquids
• Effective Date: 10-Dec-2001
• Referred By: ASTM D7665-22 - Standard Guide for Evaluation of Biodegradable Heat Transfer Fluids
• Effective Date: 10-Dec-2001

Standards Content (Sample)

NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
An American National Standard
Designation: D 6743 – 01
Standard Test Method for
Thermal Stability of Organic Heat Transfer Fluids
This standard is issued under the fixed designation D 6743; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 51528 Determination of the Thermal Stability of Unused
Heat Transfer Fluids
1.1 This test method covers the determination of the thermal
stability of unused organic heat transfer fluids. The procedure
3. Terminology
is applicable to fluids used for the transfer of heat at tempera-
3.1 Definitions:
tures both above and below their boiling point (refers to normal
3.1.1 thermal stability, n—the resistance to permanent
boiling point throughout the text unless otherwise stated). It is
changes in properties caused solely by heat. D 4175
applicable to fluids with maximum bulk operating temperature
3.2 Definitions of Terms Specific to This Standard:
between 260°C (500°F) and 454°C (850°F). The procedure
3.2.1 decomposition products that cannot be vaporized,
shall not be used to test a fluid above its critical temperature. In
n—materials from the thermally stressed heat transfer fluid,
this test method, the volatile decomposition products are in
from which those fractions that can be vaporized are removed
continuous contact with the fluid during the test. This test
by distillation procedures, that are quantitatively determined as
method will not measure the thermal stability threshold (the
residues in a bulb tube distillation apparatus.
temperature at which volatile oil fragments begin to form), but
3.2.2 gaseous decomposition products, n—materials with
instead will indicate bulk fragmentation occurring for a speci-
boiling points below room temperature, at normal pressure,
fied temperature and testing period. Because potential decom-
such as hydrogen and methane, that escape upon opening the
position and generation of high pressure gas may occur at
test cell and that can be determined by measuring the mass
temperatures above 260°C (500°F), do not use this test method
immediately thereafter.
for aqueous fluids or other fluids which generate high-pressure
3.2.3 high boiling components, n—materials from the ther-
gas at these temperatures.
mally stressed heat transfer fluid, with boiling points above the
1.2 DIN Norm 51528 covers a test method that is similar to
final boiling point of the unstressed heat transfer fluid, but
this test method.
which can still be separated by distillation from the heat
1.3 The applicability of this test method to siloxane-based
transfer fluid by means of classical separation procedures.
heat transfer fluids has not been determined.
3.2.4 low boiling components, n—materials from the ther-
1.4 The values stated in SI are the standard. The values
mally stressed heat transfer fluid, with boiling points below the
provided in parentheses are for information only.
initial boiling point of the unstressed heat transfer fluid.
1.5 This standard does not purport to address all of the
3.2.5 mass percentage of high boiling components, n—the
safety concerns, if any, associated with its use. It is the
percentage of thermally stressed heat transfer fluid with a
responsibility of the user of this standard to establish appro-
boiling point above the final boiling point of the unstressed
priate safety and health practices and determine the applica-
fluid.
bility of regulatory limitations prior to use. For specific
3.2.6 mass percentage of low boiling components, n—the
precautionary statements, see 7.2, 8.8, 8.9 and 8.10.
percentage of thermally stressed heat transfer fluid with a
2. Referenced Documents boiling point below the initial boiling point of the unstressed
fluid.
2.1 ASTM Standards:
3.2.7 original fluid, n—any fluid components with boiling
D 2887 Test Method for Boiling Range Distribution of
point between the initial boiling point and final boiling point of
Petroleum Fractions by Gas Chromatography
the unstressed fluid.
D 4175 Terminology Relating to Petroleum, Petroleum
3.2.8 test cell, n—an ampoule constructed from stainless
Products, and Lubricants
steel tubing and sealed with compression fittings at each end.
2.2 DIN Norms:
3.2.9 thermally stressed, adj—subjected to heating, as de-
scribed in this test method.
This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
D02.L0on Industrial Lubricants.
Current edition approved Dec. 10, 2001. Published February 2002. Available from Beuth Verlag GmbH, Burrgrafen Strasse 6, 1000 Berlin 30
Annual Book of ASTM Standards, Vol 05.02. Germany.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 6743
4. Summary of Test Method 6.5 Balance—The balance shall be capable of measuring
mass to the nearest 0.01 g.
4.1 Charge the test fluid in a thermal stability test cell
purged with nitrogen and tightly seal the test cell to remove and
7. Preparation of Apparatus
preclude introduction of oxygen and water from the atmo-
7.1 Test Cell—The test cell used shall always be a clean,
sphere. Heat the fluid in an oven at a given temperature and for
new ampoule. Reuse of ampoules is not permitted.
a given period of time. Determine the boiling range of the
7.2 Cleaning of Test Cell—A new test cell shall be cleaned
heated fluid by gas chromatography (GC) analysis and com-
by washing with a suitable volatile solvent such as acetone and
pare it to the boiling range of pure, unused fluid.
dried. (Warning—Use adequate safety precautions with all
5. Significance and Use
solvents and cleaners.)
5.1 Heat transfer fluids degrade when exposed to suffi-
8. Procedure
ciently high temperatures. The amount of degradation in-
creases as the temperature increases or the length of exposure 8.1 Determine the initial boiling point (IBP) and final
increases, or both. Due to reactions and rearrangement, degra- boiling point (FBP) of the unstressed heat transfer fluid by GC,
dation products can be formed. Degradation products include in accordance with Test Method D 2887 with the following
high and low boiling components, gaseous decomposition requirements: the column shall be wall-coated open tubular
products, and products that cannot be evaporated. The type and type of 7.5 to 10 m length with a 100 % polydimethylsiloxane
content of degradation products produced will change the film thickness of 0.88 μm, the detector shall be flame ionization
performance characteristics of a heat transfer fluid. In order to type, the initial oven temperature shall be set to 35°C (95°F)
evaluate thermal stability, it is necessary to quantitatively eliminating cryogenic cooling, the calibration mixture shall
determine the mass percentages of high and low boiling cover the boiling range from n-C to n-C. The following GC
components, as well as gaseous decomposition products and parameters are recommended: oven temperature rate 10°C
those that cannot be vaporized, in the thermally stressed heat (18°F) per minute, oven final temperature 375°C (707°F), time
transfer fluid. at oven final temperature 3 min, injector initial temperature
5.2 This test method differentiates the relative stability of 100°C (212°F), injector temperature rate 10°C (18°F) per
organic heat transfer fluids at elevated temperatures in the minute, injector final temperature 375°C (707°F), detector
absence of oxygen and water under the conditions of the test. temperature 375°C (707°F).
8.2 Measure the mass of a clean, dry test cell to the nearest
5.3 The user shall determine to his own satisfaction whether
the results of this test method correlate to field performance. 0.01 g. Pour the unstressed heat transfer fluid into the clean,
dry test cell. The quantity of heat transfer fluid transferred to
Heat transfer fluids in industrial plants are exposed to a variety
of additional influencing variables. Interaction with the plant’s the test cell shall be 27 g 6 0.2 g. Invert the test cell and allow
materials, impurities, heat build-up during impaired flow it to drain until all free-flowing material has been removed.
conditions, the temperature distribution in the heat transfer More viscous fluids may require as long as 15 min to drain
fluid circuit, and other factors can also lead to changes in the completely. Measure the mass of the test cell and its remaining
heat transfer fluid. The test method provides an indication of contents to the nearest 0.01 g.
the relative thermal stability of a heat transfer fluid, and can be 8.3 Adjust the heating oven to the proper test temperature.
considered as one factor in the decision-making process for Measure the mass of a clean, dry test cell to the nearest 0.01 g.
selection of a fluid. Blow nitrogen into the clean, dry test cell for 2 min at 60 to 70
5.4 The accuracy of the results depends very strongly on mL/min.
how closely the test conditions are followed.
NOTE 2—To ensure accurate results, at least three test cells containing
samples of the same heat transfer fluid should be heated simultaneously.
6. Apparatus
8.4 Pour the thermally unstressed heat transfer fluid into the
6.1 Test Cell—The test cell shall be a new, clean ampoule
clean, dry test cell. The quantity of heat transfer fluid trans-
made from ASTM A-269 grade 316L stainless steel tubing, 25
ferred to the test cell shall be 27 g 6 0.2 g.
mm (1 in.) outside diameter, 2 mm (0.083 in.) wall thickness.
8.5 Completely displace the air remaining in the gas space
The test cell shall be 0.152 6 0.003 m (6 6 0.125 in.) in length
in the test cell by introducing high purity nitrogen beneath the
and sealed with compression fittings at each end.
liquid surface near the bottom of the test cell at 30 to 35
NOTE 1—Where tubing with SI dimensions is not readily available, the
mL/min for 12 min at ambient temperature.
use of tubing with inch-pound dimensions is acceptable.
8.6 Carefully seal the test cell and measure its mass to the
6.2 Heating Oven—The oven shall be capable of being nearest 0.01 g.
controlled within 6 1°C (6 1.8°F) at test temperature. The test 8.7 Insert the test cell vertically in the oven. The test
temperature selected will typically be between 260°C (500°F) temperature shall be maintained throughout the entire test
and 427°C (800°F), depending on the fluid being tested. duration and controlled in such a way that the temperature of
6.3 Bulb Tube Distillation Apparatus—This apparatus shall the test liquid does not deviate by more than 6 1°C (6 1.8°F)
be capable of heating to at least 250°C (482°F) and vacuum to at any location, including the heated wall. Temperature shall be
at least 0.7 mm Hg. measured and recorded throughout the test. If test cells
6.4 Dewar Flask—The flask is used to hold the test cells containing different fluids are tested at the same time, the test
during cooling after removal from the heating oven. cells shall be distributed symmetrically inside the oven to
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 6743
minimize the effect of oven temperature variation on the mass of the residue in the distillation flask to the nearest 0.01
results. The test duration shall be the time from attaining the g. The fraction of still volatile components in the residue shall
test temperature to the time the heat supply is cut off. The test be below 0.1 % by mass, relative to the total mass of heat
duration at the specified test temperature shall be a minimum of transfer fluid.
500 h. Five hundred hours is the preferred test duration;
NOTE 3—The heat transfer fluid is not further thermally damaged by the
however, a longer test duration may be used. Thermal degra-
distillation process.
dation cannot be assumed to be linear with time. Therefore, the
8.16 Compare the GC test results from the thermally
stability of two fluids can only be compared at the same test
stressed sample to those of the unstressed heat transfer fluid.
temperature and test duration.
8.8 Protect the oven from heat transfer fluid that may spill in
9. Calculation
case of damage by placing a collecting pan under the test cell.
9.1 The distillation curves of the heated samples and of the
(Warning—If fluid leaks out due to improper sealing of the
original heat transfer fluid are determined by way of simulated
test cell, there may be the potential of flammable vapors inside
distillation by gas chromatography, in accordance with Test
the oven. The oven design and installation should consider this
Method D 2887 (with the exceptions noted in 8.1). Determine
possibility.)
the initial boiling point and the final boiling point of the
8.9 At the conclusion of the heating period, shut off the
thermally stressed and unstressed heat transfer fluid.
oven. Do not immediately remove the test cell. Allow the oven
9.2 The components of the heated samples are subdivided as
and the test cell to cool to ambient temperature to reduce the
follows:
internal pressure. (Warning—Pressure inside the test cell may
9.2.1 Gaseous decomposition products (G).
reach several thousand kPa during the test.)
9.2.2 Low boiling components (LB).
8.10 Remove the test cell from the oven. (Warning—Use
9.2.3 Original fluid (F).
adequate safety precautions when removing the test cells from
9.2.4 High boiling components (HB).
the oven in case some portion of the equipment is still hot.)
9.2.5 Decomposition products that cannot be vaporized (R).
8.11 Carefully measure the mass of the test cell to the
9.2.6 Unstressed fluid remaining in the test cell (FR).
nearest 0.01 g. If the evaporation loss of gaseous decomposi-
9.2.7 Material remaining in the test cell after heating (MR).
tion products is calculated at greater than 0.5 mass %, the test
9.2.8 Decomposition products remaining in the test cell
should be repeated since this would indicate tube leakage.
(DR).
8.12 Place the test cells in a Dewar flask containing a
9.3 The mass percentage m (G) is determined by subtracting
cooling mixture of acetone or isopropanol and dry ice. Allow
the mass of the opened test cell measured in 8.12 from the mass
the test cells to cool to at least –55°C (–67°F). The duration of
of the sealed test cell in 8.6, dividing by the mass of fluid
cooling is approximately 5 to 10 min. Open the test cell
...