ASTM D6743-06(2011)
(Test Method)Standard Test Method for Thermal Stability of Organic Heat Transfer Fluids
Standard Test Method for Thermal Stability of Organic Heat Transfer Fluids
SIGNIFICANCE AND USE
Heat transfer fluids degrade when exposed to sufficiently high temperatures. The amount of degradation increases as the temperature increases or the length of exposure increases, or both. Due to reactions and rearrangement, degradation products can be formed. Degradation products include high and low boiling components, gaseous decomposition products, and products that cannot be evaporated. The type and content of degradation products produced will change the performance characteristics of a heat transfer fluid. In order to evaluate thermal stability, it is necessary to quantitatively determine the mass percentages of high and low boiling components, as well as gaseous decomposition products and those that cannot be vaporized, in the thermally stressed heat transfer fluid.
This test method differentiates the relative stability of organic heat transfer fluids at elevated temperatures in the absence of oxygen and water under the conditions of the test.
The user shall determine to his own satisfaction whether the results of this test method correlate to field performance. Heat transfer fluids in industrial plants are exposed to a variety of additional influencing variables. Interaction with the plant’materials, impurities, heat build-up during impaired flow conditions, the temperature distribution in the heat transfer fluid circuit, and other factors can also lead to changes in the heat transfer fluid. The test method provides an indication of the relative thermal stability of a heat transfer fluid, and can be considered as one factor in the decision-making process for selection of a fluid.
The accuracy of the results depends very strongly on how closely the test conditions are followed.
This test method does not possess the capability to quantify or otherwise assess the formation and nature of thermal decomposition products within the unstressed fluid boiling range. Decomposition products within the unstressed fluid boiling range may represent a significant po...
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 &si-value;
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 warning statements, see 7.2, 8.8, 8.9, and 8.10.
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Designation:D6743–06 (Reapproved 2011)
Standard Test Method for
Thermal Stability of Organic Heat Transfer Fluids
This standard is issued under the fixed designation D6743; 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 D2887 Test Method for Boiling Range Distribution of
Petroleum Fractions by Gas Chromatography
1.1 Thistestmethodcoversthedeterminationofthethermal
D4175 Terminology Relating to Petroleum, Petroleum
stability of unused organic heat transfer fluids. The procedure
Products, and Lubricants
is applicable to fluids used for the transfer of heat at tempera-
2.2 DIN Norms:
turesbothaboveandbelowtheirboilingpoint(referstonormal
51528 Determination of the Thermal Stability of Unused
boiling point throughout the text unless otherwise stated). It is
Heat Transfer Fluids
applicable to fluids with maximum bulk operating temperature
between 260°C (500°F) and 454°C (850°F). The procedure
3. Terminology
shall not be used to test a fluid above its critical temperature. In
3.1 Definitions:
this test method, the volatile decomposition products are in
3.1.1 thermal stability, n—the resistance to permanent
continuous contact with the fluid during the test. This test
changes in properties caused solely by heat. D4175
method will not measure the thermal stability threshold (the
3.2 Definitions of Terms Specific to This Standard:
temperature at which volatile oil fragments begin to form), but
3.2.1 decomposition products that cannot be vaporized,
instead will indicate bulk fragmentation occurring for a speci-
n—materials from the thermally stressed heat transfer fluid,
fied temperature and testing period. Because potential decom-
from which those fractions that can be vaporized are removed
position and generation of high pressure gas may occur at
by distillation procedures, that are quantitatively determined as
temperatures above 260°C (500°F), do not use this test method
residues in a bulb tube distillation apparatus.
for aqueous fluids or other fluids which generate high-pressure
3.2.2 fluid within the unstressed fluid boiling range, n—any
gas at these temperatures.
fluid components with boiling point between the initial boiling
1.2 DIN Norm 51528 covers a test method that is similar to
point and final boiling point of the unstressed fluid.
this test method.
3.2.3 gaseous decomposition products, n—materials with
1.3 The applicability of this test method to siloxane-based
boiling points below room temperature, at normal pressure,
heat transfer fluids has not been determined.
such as hydrogen and methane, that escape upon opening the
1.4 The values stated in SI units are to be regarded as
test cell and that can be determined by measuring the mass
standard. The values given in parentheses are for information
immediately thereafter.
only.
3.2.4 high boiling components, n—materials from the ther-
1.5 This standard does not purport to address all of the
mally stressed heat transfer fluid, with boiling points above the
safety concerns, if any, associated with its use. It is the
final boiling point of the unstressed heat transfer fluid, but
responsibility of the user of this standard to establish appro-
which can still be separated by distillation from the heat
priate safety and health practices and determine the applica-
transfer fluid by means of classical separation procedures.
bility of regulatory limitations prior to use. For specific
3.2.5 low boiling components, n—materials from the ther-
warning statements, see 7.2, 8.8, 8.9, and 8.10.
mally stressed heat transfer fluid, with boiling points below the
2. Referenced Documents initial boiling point of the unstressed heat transfer fluid.
3.2.6 mass percentage of high boiling components, n—the
2.1 ASTM Standards:
percentage of thermally stressed heat transfer fluid with a
boiling point above the final boiling point of the unstressed
This test method is under the jurisdiction of ASTM Committee D02 on
fluid.
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
3.2.7 mass percentage of low boiling components, n—the
D02.L0.06 on Non-Lubricating Process Fluids.
percentage of thermally stressed heat transfer fluid with a
Current edition approved May 1, 2011. Published August 2011. Originally
approved in 2001. Last previous edition approved in 2006 as D6743–06. DOI: boiling point below the initial boiling point of the unstressed
10.1520/D6743-06R11.
fluid.
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
Standards volume information, refer to the standard’s Document Summary page on AvailablefromDeutschesInstitutfurNormunge.V.(DIN),Burggrafenstrasse6,
the ASTM website. 10787 Berlin, Germany, http://www.din.de.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6743–06 (2011)
NOTE 1—Where tubing with SI dimensions is not readily available, the
3.2.8 test cell, n—an ampoule constructed from stainless
use of tubing with inch-pound dimensions is acceptable.
steel tubing and sealed with compression fittings at each end.
3.2.9 thermally stressed, adj—subjected to heating, as de-
6.2 Heating Oven—The oven shall be capable of being
scribed in this test method.
controlled within 6 1°C (6 1.8°F) at test temperature.The test
temperature selected will typically be between 260°C (500°F)
4. Summary of Test Method
and 427°C (800°F), depending on the fluid being tested.
6.3 Bulb Tube Distillation Apparatus—This apparatus shall
4.1 Charge the test fluid in a thermal stability test cell
be capable of heating to at least 250°C (482°F) and pressure
purgedwithnitrogenandtightlysealthetestcelltoremoveand
down to at least 0.1 mm Hg.
preclude introduction of oxygen and water from the atmo-
6.4 Dewar Flask—The flask is used to hold the test cells
sphere. Heat the fluid in an oven at a given temperature and for
during cooling after removal from the heating oven.
a given period of time. Determine the boiling range of the
6.5 Balance—The balance shall be capable of measuring
heated fluid by gas chromatography (GC) analysis and com-
mass to the nearest 0.01 g.
pare it to the boiling range of pure, unused fluid.
7. Preparation of Apparatus
5. Significance and Use
7.1 Test Cell—The test cell used shall always be a clean,
5.1 Heat transfer fluids degrade when exposed to suffi-
new ampoule. Reuse of ampoules is not permitted.
ciently high temperatures. The amount of degradation in-
7.2 Cleaning of Test Cell—A new test cell shall be cleaned
creases as the temperature increases or the length of exposure
by washing with a suitable volatile solvent such as acetone and
increases, or both. Due to reactions and rearrangement, degra-
dried. (Warning—Use adequate safety precautions with all
dation products can be formed. Degradation products include
solvents and cleaners.)
high and low boiling components, gaseous decomposition
products, and products that cannot be evaporated.The type and
8. Procedure
content of degradation products produced will change the
8.1 Determine the initial boiling point (IBP) and final
performance characteristics of a heat transfer fluid. In order to
boiling point (FBP) of the unstressed heat transfer fluid by GC,
evaluate thermal stability, it is necessary to quantitatively
in accordance with Test Method D2887 with the following
determine the mass percentages of high and low boiling
requirements: the column shall be wall-coated open tubular
components, as well as gaseous decomposition products and
type of 7.5 to 10 m length with a 100 % polydimethylsiloxane
those that cannot be vaporized, in the thermally stressed heat
filmthicknessof0.88µm,thedetectorshallbeflameionization
transfer fluid.
type, the initial oven temperature shall be set to 35°C (95°F)
5.2 This test method differentiates the relative stability of
eliminating cryogenic cooling, the calibration mixture shall
organic heat transfer fluids at elevated temperatures in the
cover the boiling range from n-C to n-C . The following GC
5 60
absence of oxygen and water under the conditions of the test.
parameters are recommended: oven temperature rate 10°C
5.3 The user shall determine to his own satisfaction whether
(18°F) per minute, oven final temperature 375°C (707°F), time
the results of this test method correlate to field performance.
at oven final temperature 3 min, injector initial temperature
Heat transfer fluids in industrial plants are exposed to a variety
100°C (212°F), injector temperature rate 10°C (18°F) per
of additional influencing variables. Interaction with the plant’s
minute, injector final temperature 375°C (707°F), detector
materials, impurities, heat build-up during impaired flow
temperature 375°C (707°F).
conditions, the temperature distribution in the heat transfer
8.2 Measure the mass of a clean, dry test cell including
fluid circuit, and other factors can also lead to changes in the
compression fittings to the nearest 0.01 g. Pour the unstressed
heat transfer fluid. The test method provides an indication of
heat transfer fluid into the clean, dry test cell in a vertical
the relative thermal stability of a heat transfer fluid, and can be
position. The quantity of heat transfer fluid transferred to the
considered as one factor in the decision-making process for
test cell shall be 27 g 6 0.2 g. Invert the test cell in a vertical
selection of a fluid.
position and allow it to drain until all free-flowing material has
5.4 The accuracy of the results depends very strongly on
been removed. More viscous fluids may require as long as 15
how closely the test conditions are followed.
min to drain completely.At the end of the draining period, tap
5.5 This test method does not possess the capability to
the test cell to remove a drop clinging to the open end of the
quantify or otherwise assess the formation and nature of
test cell – do not wipe away any fluid. Measure the mass of the
thermal decomposition products within the unstressed fluid
test cell and its remaining contents including compression
boiling range. Decomposition products within the unstressed
fittings to the nearest 0.01 g.
fluid boiling range may represent a significant portion of the
NOTE 2—The intent is to perform this step only once for each heat
total thermal degradation.
transfer fluid being tested at this time.
8.3 Measure the mass of a clean, dry test cell including
6. Apparatus
compressionfittingstothenearest0.01g.Introducehighpurity
6.1 Test Cell—The test cell shall be a new, clean ampoule
nitrogen using tubing at the bottom of the clean, dry test cell
made fromASTMA-269 grade 316L stainless steel tubing, 25
for 2 min at 60 to 70 mL/min.
mm (1 in.) outside diameter, 2 mm (0.083 in.) wall thickness.
The test cell shall be 0.152 6 0.003 m (6 6 0.125 in.) in length
NOTE 3—To ensure accurate results, at least three test cells containing
and sealed with compression fittings at each end. samples of the same heat transfer fluid should be heated simultaneously.
D6743–06 (2011)
8.4 Pour the thermally unstressed heat transfer fluid into the measurementinaglassbottlethatishermeticallysealed.Invert
clean, dry test cell. The quantity of heat transfer fluid trans- the test cell and allow it to drain until all free-flowing material
ferred to the test cell shall be 27 g 6 0.2 g. has been removed. More viscous fluids may require as long as
15 min to drain completely. At the end of the draining period,
8.5 Completely displace the air remaining in the gas space
tapthetestcelltoremoveadropclingingtotheopenendofthe
in the test cell by introducing high purity nitrogen using tubing
test cell – do not wipe away any fluid. Measure the mass of the
just above the liquid surface of fluid inside the test cell at 30 to
test cell and its remaining contents including compression
35 mL/min for 12 min at ambient temperature.
fittings to the nearest 0.01 g.
8.6 Carefully seal the test cell and measure its mass to the
8.13 Visually observe the appearance of the fluid sample for
nearest 0.01 g.
any insolubles, or other changes in the fluid. Examples include
8.7 Insert the test cell vertically in the oven. Adjust the
high pressure upon opening the test cell, appearance of fouling
heating oven to the proper test temperature. The time to
in the head space of the test cell and evidence of a leak from
achieve proper test temperature should be approximately 3 h.
the test cell. Observations shall be noted in the report.
The test temperature shall be maintained throughout the entire
8.14 Determinethemasspercentageoflowandhighboiling
test duration and controlled in such a way that the temperature
components in the thermally stressed sample, in accordance
ofthetestliquiddoesnotdeviatebymorethan 61°C(61.8°F)
with Test Method D2887 using the same equipment and
at any location, including the heated wall.Temperature shall be
requirements as specified in 8.1.
measured and recorded throughout the test at least once per
8.15 The decomposition products that cannot be vaporized
day. If test cells containing different fluids are tested at the
are determined separately in a bulb tube distillation apparatus.
same time, the test cells shall be distributed symmetrically
Measure approximately4gofthe thermally stressed heat
inside the oven to minimize the effect of oven temperature
transfer fluid into the distillation flask. Record the mass to the
variationontheresults.Thetestdurationshallbethetimefrom
nearest 0.01 g. Apply vacuum slowly by means of a vacuum
attaining the test temperature to the time the heat supply is cut
pump. Pressure shall be 0.1 mm Hg 6 0.01 mm Hg at the end
off. The test duration at the specified test temperature shall be
of distillation. Heat the bulb tube distillation apparatus slowly
a minimum of 500 h. The preferred test duration is 500 61h,
to 250°C (482°F). Avoid any delays in boiling. Continue
however, a longer test duration may be used. Thermal degra-
distillation for at least 30 min after constant mass of distillation
dation cannot be assumed to be linear with time.Therefore, the
residue is achieved. Measure the mass of the residue in the
stability of two fluids can only be compared at the same test
distillation flask to the nearest 0.01 g.
temperature and test duration.
8.8 Protecttheovenfromheattransferfluidthatmayspillin
NOTE 4—Theheattransferfluidisnotfurtherthermallydamagedbythe
case of damage by placing a collecting pan under the test cell.
distillation process.
(Warning—If fluid leaks out due to improper sealing of the
8.16 Com
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