ASTM D3241-24

Standard Test Method for Thermal Oxidation Stability of Aviation Turbine Fuels

SIGNIFICANCE AND USE
5.1 The test results are indicative of fuel performance during gas turbine operation and can be used to assess the level of deposits that form when liquid fuel contacts a heated surface that is at a specified temperature.
SCOPE
1.1 This test method covers the procedure for rating the tendencies of gas turbine fuels to deposit decomposition products within the fuel system.  
1.2 The differential pressure values in mm Hg are defined only in terms of this test method.  
1.3 The deposition values stated in SI units shall be regarded as the referee value.  
1.4 The pressure values stated in SI units are to be regarded as standard. The psi comparison is included for operational safety with certain older instruments that cannot report pressure in SI units.  
1.5 No other units of measurement are included in this standard.  
1.6 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For specific warning statements, see 6.1.1, 7.1, 7.3, 12.1.1, and Annex A6.  
1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 29-Feb-2024
• ICS: 75.160.20 - Liquid fuels
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.J0.03 - Combustion and Thermal Properties

Relations

• Replaces: ASTM D3241-23ae1 - Standard Test Method for Thermal Oxidation Stability of Aviation Turbine Fuels
• Effective Date: 01-Mar-2024
• Refers: ASTM D1655-24 - Standard Specification for Aviation Turbine Fuels
• Effective Date: 15-Mar-2024
• Referred By: ASTM D7566-23b - Standard Specification for Aviation Turbine Fuel Containing Synthesized Hydrocarbons
• Effective Date: 01-Mar-2024
• Referred By: ASTM D6615-22 - Standard Specification for Jet B Wide-Cut Aviation Turbine Fuel
• Effective Date: 01-Mar-2024
• Referred By: ASTM D7671-21 - Standard Test Method for Corrosiveness to Silver by Automotive Spark–Ignition Engine Fuel–Silver Strip Method
• Effective Date: 01-Mar-2024
• Referred By: ASTM D1655-23a - Standard Specification for Aviation Turbine Fuels
• Effective Date: 01-Mar-2024
• Referred By: ASTM D7223-21 - Standard Specification for Aviation Certification Turbine Fuel
• Effective Date: 01-Mar-2024
• Referred By: ASTM D6469-20 - Standard Guide for Microbial Contamination in Fuels and Fuel Systems
• Effective Date: 01-Mar-2024
• Referred By: ASTM D8147-24 - Standard Specification for Special-Purpose Test Fuels for Aviation Compression-Ignition Engines
• Effective Date: 01-Mar-2024
• Referred By: ASTM D5677-17(2023) - Standard Specification for Fiberglass (Glass-Fiber-Reinforced Thermosetting-Resin) Pipe and Pipe Fittings, Adhesive Bonded Joint Type, for Aviation Jet Turbine Fuel Lines
• Effective Date: 01-Mar-2024
• Referred By: ASTM D7667-21 - Standard Test Method for Determination of Corrosiveness to Silver by Automotive Spark-Ignition Engine Fuel-Thin Silver Strip Method
• Effective Date: 01-Mar-2024
• Referred By: ASTM D4054-23 - Standard Practice for Evaluation of New Aviation Turbine Fuels and Fuel Additives
• Effective Date: 01-Mar-2024

Overview

ASTM D3241-24: Standard Test Method for Thermal Oxidation Stability of Aviation Turbine Fuels specifies procedures to evaluate the tendency of aviation turbine fuels to form deposits in fuel systems operating at high temperatures. By simulating fuel exposure to heated surfaces under controlled conditions, the method provides critical insights into oxidative fuel stability. The results are indicative of real-world fuel performance in gas turbine engines and help predict deposit formation that can impact fuel system reliability, efficiency, and maintenance.

ASTM D3241-24 is recognized internationally for assessing aviation turbine fuel quality and is referenced by regulatory bodies and the aviation industry worldwide.

Key Topics

• Fuel Deposit Measurement: This standard focuses on determining the amount and characteristics of oxidative deposits that form when jet fuel contacts a hot surface.
• Heater Tube Rating: After testing, heater tubes are visually or instrumentally inspected and rated according to a discrete scale, reporting the severity and type of deposits.
• Controlled Test Conditions: The method specifies sample preparation, operating temperatures, fuel flow rates, and tube metallurgy to ensure consistency and reliability.
• Differential Pressure Monitoring: Pressure drop across a precision filter is measured to evaluate the accumulation of insoluble decomposition products.
• Safety and Material Requirements: Procedures detail the use of safe sampling containers and cleaning solvents, exclude copper/zinc materials, and emphasize appropriate safety practices.
• International Applicability: Developed in line with WTO principles, ASTM D3241-24 is accepted globally and serves as a referee test for jet fuel oxidation stability.

Applications

The practical value of ASTM D3241-24 lies in its application throughout the aviation and fuel refining industries:

• Jet Fuel Qualification: Used to qualify new fuel batches before their use in commercial and military aviation, ensuring they meet stability and cleanliness requirements.
• Fuel Quality Control: Supports ongoing fuel monitoring in storage, transport, and airport fueling infrastructure to detect degradation before use.
• Engine and Fuel System Protection: By predicting deposit formation, the standard helps prevent filter plugging and fouling of critical engine components.
• Regulatory and Contractual Compliance: Satisfies requirements from international aviation authorities, defense agencies, and fuel suppliers.
• Research and Development: Assists in testing new fuel formulations for improved oxidative stability, including biofuels and sustainable aviation fuels.
• Performance Investigation: Used in troubleshooting to identify fuel-related causes of engine deposits or fuel system failures.

Related Standards

ASTM D3241-24 should be used in conjunction with other key standards and practices for a comprehensive approach to aviation fuel quality:

• ASTM D1655 – Specification for Aviation Turbine Fuels
• ASTM D4057 – Practice for Manual Sampling of Petroleum and Petroleum Products
• ASTM D4306 – Practice for Aviation Fuel Sample Containers for Tests Affected by Trace Contamination
• ASTM D4175 – Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
• ISO 3274 / ISO 4288 – Surface texture measurement for apparatus calibration
• E177 / E691 – Practices for evaluating test method precision and bias

These complementary standards cover sampling, terminology, test equipment requirements, and related analytical methods, supporting robust aviation fuel quality management.

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Keywords: ASTM D3241, thermal oxidation stability, aviation turbine fuel testing, jet fuel deposits, heater tube rating, fuel quality control, oxidative stability, jet engine fuel systems, aviation fuel standards, deposit formation, aviation industry, fuel performance assessment, regulatory compliance.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D3241 − 24
Designation 323/22
Standard Test Method for
1,2
Thermal Oxidation Stability of Aviation Turbine Fuels
This standard is issued under the fixed designation D3241; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope* 2. Referenced Documents
2.1 ASTM Standards:
1.1 This test method covers the procedure for rating the
tendencies of gas turbine fuels to deposit decomposition D1655 Specification for Aviation Turbine Fuels
D4057 Practice for Manual Sampling of Petroleum and
products within the fuel system.
Petroleum Products
1.2 The differential pressure values in mm Hg are defined
D4175 Terminology Relating to Petroleum Products, Liquid
only in terms of this test method.
Fuels, and Lubricants
1.3 The deposition values stated in SI units shall be re-
D4306 Practice for Aviation Fuel Sample Containers for
garded as the referee value.
Tests Affected by Trace Contamination
E177 Practice for Use of the Terms Precision and Bias in
1.4 The pressure values stated in SI units are to be regarded
ASTM Test Methods
as standard. The psi comparison is included for operational
E691 Practice for Conducting an Interlaboratory Study to
safety with certain older instruments that cannot report pres-
Determine the Precision of a Test Method
sure in SI units.
2.2 ISO Standards:
1.5 No other units of measurement are included in this
ISO 3274 Geometrical Product Specifications (GPS)—
standard.
Surface texture: Profile method—Nominal characteristics
1.6 This standard does not purport to address all of the
of contact (stylus) instruments
safety concerns, if any, associated with its use. It is the
ISO 4288 Geometrical Product Specifications (GPS)—
responsibility of the user of this standard to establish appro-
Surface texture: Profile method—Rules and procedures
priate safety, health, and environmental practices and deter-
for the assessment of surface texture
mine the applicability of regulatory limitations prior to use.
2.3 ASTM Adjuncts:
For specific warning statements, see 6.1.1, 7.1, 7.3, 12.1.1, and
Color Standard for Heater Tube Deposit Rating
Annex A6.
3. Terminology
1.7 This international standard was developed in accor-
dance with internationally recognized principles on standard-
3.1 Definitions:
ization established in the Decision on Principles for the
3.1.1 For definitions of terms used in this test method, refer
Development of International Standards, Guides and Recom-
to Terminology D4175.
mendations issued by the World Trade Organization Technical
3.2 Definitions of Terms Specific to This Standard:
Barriers to Trade (TBT) Committee.
3.2.1 deposits, n—oxidative products laid down on the test
area of the heater tube or caught in the test filter, or both.
3.2.1.1 Discussion—Fuel deposits will tend to predominate
at the hottest portion of the heater tube, which is between the
This test method is under the jurisdiction of ASTM International Committee
D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct 30 mm and 50 mm position.
responsibility of Subcommittee D02.J0.03 on Combustion and Thermal Properties.
The technically equivalent standard as referenced is under the jurisdiction of the
Energy Institute Subcommittee SC-B-8. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved March 1, 2024. Published March 2024. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
ɛ1
approved in 1973. Last previous edition approved in 2023 as D3241 – 23a . DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/D3241-24. the ASTM website.
2 4
This test method has been developed through the cooperative effort between Available from International Organization for Standardization (ISO), 1, ch. de
ASTM and the Energy Institute, London. ASTM and IP standards were approved by la Voie-Creuse, CP 56, CH-1211 Geneva 20, Switzerland, http://www.iso.org.
ASTM and EI technical committees as being technically equivalent but that does not Available from ASTM International Headquarters. Order Adjunct No.
imply both standards are identical. ADJD3241. Original adjunct produced in 1986.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D3241 − 24
3.2.2 heater tube, n—an aluminum coupon controlled at 6. Apparatus
elevated temperature, over which the test fuel is pumped. 6
6.1 Aviation Fuel Thermal Oxidation Stability Tester —Six
3.2.2.1 Discussion—The heater tube is resistively heated
models of suitable equipment may be used as indicated in
and controlled in temperature by a thermocouple positioned
Table 1.
inside. The critical test area is the thinner portion, 60 mm in
6.1.1 Portions of this test may be automated. Refer to the
length, between the shoulders of the heater tube. Fuel inlet to
appropriate user manual for the instrument model to be used
the heater tube is at the 0 mm position, and fuel exit is at
for a description of detailed procedure. A manual is provided
60 mm.
with each test rig. (Warning—No attempt should be made to
3.3 Abbreviations: operate the instrument without first becoming acquainted with
3.3.1 ΔP—differential pressure. all components and the function of each.)
6.1.2 Certain operational parameters used with the instru-
4. Summary of Test Method
ment are critically important to achieve consistent and correct
results. These are listed in Table 2.
4.1 This test method for measuring the high temperature
stability of gas turbine fuels uses an instrument that subjects
6.2 Heater Tube Deposit Rating Apparatus:
the test fuel to conditions that can be related to those occurring
6.2.1 Visual Heater Tube Rater (VTR), the tuberator de-
in gas turbine engine fuel systems. The fuel is pumped at a
scribed in Annex A1.
fixed volumetric flow rate through a heater, after which it
6.2.2 Standardization of Metrology Requirements:
enters a precision stainless steel filter where fuel degradation
6.2.2.1 Number of Measured Points—1200 in the ratable
products may become trapped.
area of the heater tube (between 5 mm and 55 mm above the
4.1.1 The apparatus uses 450 mL of test fuel ideally during
bottom shoulder of the heater tube).
a 2.5 h test. The essential data derived are the amount of
deposits on a heater tube, and the rate of plugging of a 17 μm
nominal porosity precision filter located just downstream of the The following equipment, as described in Table 1 and RR:D02-1309, was used
to develop this test method. The following equipment, as described in Table 1 and
heater tube.
determined as equivalent in testing as detailed in RR:D02-1631, is provided by PAC,
8824 Fallbrook Drive, Houston, TX 77064. The following equipment, as described
5. Significance and Use
in Table 1 and determined as equivalent in testing as detailed in RR:D02-1728, is
provided by Falex Corporation, 1020 Airpark Dr., Sugar Grove, IL, 60554-9585.
5.1 The test results are indicative of fuel performance
The following equipment as described in Table 1 and determined as equivalent in
during gas turbine operation and can be used to assess the level
testing as detailed in RR:D02-2071, is provided by AD Systems (www.adsystems-
of deposits that form when liquid fuel contacts a heated surface
sa.com), 5, Allée de Cindais, 14320 Saint André sur Orne, France. This is not an
that is at a specified temperature. endorsement or certification by ASTM International.
TABLE 1 Instrument Models
Instrument Model Pressurize With Principle Differential Pressure by
A
230 hydraulic syringe Transducer + Printout
A
240 hydraulic syringe Transducer + Printout
B
230 Mk III hydraulic dual piston (HPLC Type) Transducer + Printout
C
F400 hydraulic dual piston (HPLC Type) Transducer + Printout
D, E
230 Mk IV hydraulic single piston (HPLC Type) Transducer + Printout
F
TO10 hydraulic dual syringe Transducer + Printout
A
See RR:D02-1309.
B
See RR:D02-1631.
C
See RR:D02-1728.
D
See RR:D02-1757.
E
There are two versions of the 230 Mk IV instrument; one with an inline internal non-consumable filter located upstream of the 0.45 μm pre-filter and one without. Only
the 230 Mk IV instruments without the inline internal non-consumable filter were included in RR:D02-1757 and have been determined by ASTM Committee D02 to be
equivalent to the other apparatus listed above in Table 1. There are no external markings on the instruments to indicate which apparatus contains the inline internal
non-consumable filter. Contact the manufacturer for further information on removal of the inline internal non-consumable filter.
F
See RR:D02-2071.
D3241 − 24
TABLE 2 Critical Operating Characteristics of D3241
Item Definition
Test apparatus Tube-in-shell heat exchanger as illustrated in Fig. 1 and dimen-
sions in Fig. A5.1.
Heater Tube:
A, B, C, D, E
Heater tube Specially fabricated heater tube that produces controlled heated
test surface; new one for each test.
E
Heater Tube identification Each heater tube shall be physically identified with a unique serial
number, identifying the manufacturer and providing traceability to
the original material batch.
Heater Tube metallurgy 6061-T6 Aluminum, plus the following criteria
a) The Mg:Si ratio shall not exceed 1.9:1
b) The Mg Si percentage shall not exceed
1.85 %
Heater Tube surface polish over circumference of center section Rotational cut buffing technique with polishing compound to
achieve mechanical surface finish.
Heater Tube dimensions: Dimension Tolerance
F
Heater Tube length, mm 161.925 ±0.254
Center section length, mm 60.325 ±0.051
Outside diameters, mm
Shoulders 4.724 ±0.025
Center section 3.175 ±0.051
Inside diameter, mm 1.651 ±0.051
Total indicator runout, mm, max 0.013
Mechanical surface finish, nm, over circumference in center 50 ± 20
section in accordance with ISO 3274 and ISO 4288 using the
mean of four 1.25–measurements
Test filter nominal 17 μm stainless steel mesh filter element to trap deposits;
new one for each test
Stainless Steel Mesh Twilled Dutch Weave, 304 Stainless Steel, 165 × 1400 Mesh (tol-
erance; 4 % on 1400 and 2 % on 165) with Warp Diameter =
0.0028 in. and Shute Diameter = 0.0016 in.
Instrument parameters:
Sample volume 600 mL of sample is aerated, then 450 mL ± 45 mL of this aerated
fuel shall be pumped during the heating phase for a valid test
Aeration rate 1.5 L ⁄min dry air through sparger
Flow during test 3.0 mL ⁄min ± 10 % (2.7 mL/min minimum to 3.3 mL/min maxi-
mum)
Pump mechanism positive displacement or piston syringe
Cooling bus bars cooled in accordance with instrument manufacturer
instruction, to maintain consistent tube temperature profile
Thermocouple (TC) Type J, Inconel sheathed, or Type K, Inconel sheathed
Operating pressure:
System 3.45 MPa ± 10 % on sample by hydraulically transmitted force
against control valve outlet restriction
At test filter differential pressure (∆P) measured across test filter by electronic
transducer in mm Hg
Operating temperature:
For test as stated in specification for fuel
Uniformity of run maximum deviation of ±2 °C from specified temperature
Calibration Models 230 and 240 – Three point calibration including tin (see
7.5) at 232 °C, lead (see 7.4) at 327 °C for high point and ice +
water for low point reference
All other models – Two point calibration using pure lead at 327 °C
for high point and ice + water for low point reference
A
D3241/IP 323 Thermal Stability is a critical aviation fuel test, the results of which are used to assess the suitability of jet fuel for aviation operational safety and regulatory
compliance. The integrity of D3241/IP 323 testing requires that heater tubes meet the regulations of D3241 Table 2 and give equivalent D3241 results to the heater tubes
supplied by the original equipment manufacturer (OEM).
B
The following equipment, heater tubes, manufactured by PAC, 8824 Fallbrook Drive, Houston, TX 77064, was used in the development of this test method. This is not
an endorsement or certification by ASTM International.
C
A test protocol to establish equivalence of heater tubes is on file at ASTM International Headquarters and may be obtained by requesting Research Report RR:D02-1550.
D
The following equipment, heater tube and filter kits, manufactured by Falex Corporation, 1020 Airpark Dr., Sugar Grove, IL, 60554-9585, was run through the test
protocol in RR:D02-1550 and determined as equivalent to the equipment used to develop the test method. This test is detailed in RR:D02-1714. This is not an endorsement
or certification by ASTM International.
E
An electronic recording device, such as a radio-frequency identification device (RFID), may be embedded into the heater tube rivet located at the bottom of the heater
tube. Tube identification data may be stored on an electronic recording device, such as a RFID, embedded into the heater tube.
F
Tube length measurements are only applicable to the aluminum portion of the heater tube. Additions, such as an RFID, do not contribute to the length measurement of
the heater tube.
D3241 − 24
pink color indicating absorption of water. (Warning—Do not
inhale dust or ingest. May cause stomach disorder.)
7.4 Lead, 99.9 % minimum purity.
7.5 Tin, 99.0 % minimum purity.
8. Sampling
8.1 General Requirements—The choice of construction ma-
terials is an important factor, particularly in the case of aviation
turbine fuel, where thermal stability can be degraded by the
presence of very low concentration of copper. The use of
copper or copper alloys shall be eliminated wherever possible
by the use of alternative materials such as stainless steel or
FIG. 1 Standard Heater Tube Test Section, Essential to All D3241
Test Instruments aluminum. Zinc and cadmium are two other metals that
adversely affect product quality. Copper, copper alloys (such as
brass), zinc-rich (galvanized) coatings, cadmium alloys, and
(1) Circumferential Resolution—(number of points mea-
cadmium plating shall not be used in sampling aviation fuels
sured on the heater tube circumference), 24 points equally
for evaluation under this test method.
spaced.
8.1.1 Sampling Containers—Sampling containers shall be
(2) Longitudinal Resolution—(number of points measured
in accordance with the requirements for thermal stability
on the 50 mm ratable length of the heater tube), 50 points
testing described in Practice D4306.
equally spaced.
8.1.2 Sampling Equipment—Sampling equipment fabricated
6.2.2.2 Standard Spot—Thickest average deposit area de-
from copper or its alloys shall not be used for sampling in
scribed by either a 2×3 or 3×2 (longitudinal × circumferential)
accordance with this test method. Sampling equipment shall be
arrangement of adjoining thickness measurement points,
in accordance with the requirements for aviation fuel described
amongst the 1200 measured by the metrology techniques.
in Practice D4057.
6.2.3 Interferometric (Heater) Tube Rater (ITR)—the tu-
9. Standard Operating Conditions
berator described in Annex A2.
6.2.4 Ellipsometric (Heater) Tube Rater (ETR)—the tubera-
9.1 Standard conditions of the test method are as follows:
tor described in Annex A3.
9.1.1 Fuel Quantity, 450 mL minimum for test plus about
6.2.5 Multi-Wavelength Ellipsometric (Heater) Tube Rater
50 mL for system.
(MWETR)—the tuberator described in Annex A4.
9.1.2 Fuel Pre-Treatment—Filter the fuel through a single
layer of “qualitative” quality, medium-flow, cellulose filter
6.3 Because jet fuel thermal oxidation stability is defined
paper. Filter should be a pleated (folded) circular shape and
only in terms of this test method, which depends upon, and is
fitted into a conical funnel to filter fuel. Filter paper grades 2V,
inseparable from, the specific equipment used, the test method
MN514, or better, are recommended. After filtration, aerate the
shall be conducted with the equipment used to develop the test
fuel for 6 min at 1.5 L ⁄min air flow rate for a maximum of
method or equivalent equipment.
1000 mL sample using a coarse 12 mm borosilicate glass gas
7. Reagents and Materials dispersion tube.
9.1.3 Fuel System Pressure, 3.45 MPa (500 psi) 610 %
7.1 Use methyl pentane, 2,2,4-trimethylpentane, or
gauge.
n-heptane as a general cleaning solvent. General cleaning
9.1.4 Thermocouple Position, at 39 mm.
solvent shall be 95 mol % purity, minimum. This solvent will
9.1.5 Fuel System Prefilter Element, filter paper of 0.45 μm
effectively clean internal metal surfaces of apparatus before a
pore size.
test, especially those surfaces (before the heater tube test
9.1.6 Heater Tube Control Temperature, preset as specified
section) that contact fresh sample. (Warning—Extremely
in applicable specification.
flammable. Harmful if inhaled (see Annex A6).)
9.1.7 Fuel Flow Rate, 3.0 mL ⁄min 6 10 %.
7.2 Use a nylon bristle brush and trisolvent to clean internal
9.1.8 Minimum Fuel Pumped During Test, 405 mL.
(working) surface of heater tube test section only. Trisolvent is
9.1.9 Test Duration, 150 min 6 2 min.
an equal mix of acetone (1), toluene (2), and isopropanol (3).
9.1.10 Bus Bar Cooling—Cooling system designs can be
All three components of trisolvent shall be 95 mol % purity,
different between instrument models, and must be operated and
minimum. (Warning—(1) Extremely flammable, vapors may
maintained in accordance with the manufacturer’s require-
cause flash fire; (2) and (3) Flammable. Vapors of all three
ments. For systems equipped with cooling fluid circulation
harmful. Irritating to skin, eyes, and mucous membranes.) Use
system, adjust the fluid flow to approximately 39 L ⁄h, or center
a nylon bristle brush that makes stiff contact with the inner
of green range on cooling fluid meter.
walls of the heater tube test section.
9.1.11 Power Setting, internally set for computer models.
7.3 Use dry calcium sulfate + cobalt chloride granules (97 +
10. Preparation of Apparatus
3 mix) or other self-indicating drying agent in the aeration
dryer. This granular material changes gradually from blue to 10.1 Cleaning and Assembly of Heater Tube Test Section:
D3241 − 24
10.1.1 Clean the inside surface of the heater tube test section 12.1.1 Filter and aerate sample using standard operating
using a nylon brush saturated with trisolvent to remove all conditions (see A5.2.9). (Warning—All jet fuels must be
deposits. Replace the nylon brush when it shows signs of wear considered flammable except JP5 and JP7. Vapors are harmful
(such as missing bristles) and no longer makes stiff contact (see A6.3, A6.6, and A6.7).)
with inner walls of heater tube test section.
NOTE 3—Before operating, see Warning in 6.1.1.
10.1.2 Check the heater tube to be used in the test for
NOTE 4—Test method results are known to be sensitive to trace
surface defects and straightness by referring to the procedure in
contamination from sampling containers. For recommended containers,
refer to Practice D4306.
A1.10. Be careful, also, to avoid scratching the heater tube
shoulder during the examination, since the heater tube shoulder
12.1.2 Maintain temperature of sample between 15 °C and
must be smooth to ensure a seal under the flow conditions of
32 °C during aeration.
the test.
12.1.3 Allow no more than 1 h to elapse between the end of
10.1.3 Assemble the heater tube test section using new
aeration and the start of the heating of the sample.
items: (1) visually checked heater tube, (2) test filter, and (3)
12.2 Final Assembly:
three O-rings. Inspect insulators to be sure they are undam-
12.2.1 Check all lines to ensure tightness.
aged.
12.2.2 Recheck thermocouple position at 39 mm.
NOTE 1—Heater tubes must not be reused. Tests indicate that magne-
12.2.3 Make sure drip receiver is empty.
sium migrates to the heater tube surface under normal test conditions.
Surface magnesium may reduce adhesion of deposits to reused heater
12.3 Power Up and Pressurization:
tube.
12.3.1 Turn POWER to ON.
10.1.4 During assembly of the heater tube test section, 12.3.2 Inspect the system for leaks. Depressurize the system
handle the heater tube carefully so as not to touch center part as necessary to tighten any leaking fittings.
of heater tube. IF THE CENTER OF HEATER TUBE IS 12.3.3 Set controls to the standard operating conditions.
TOUCHED, REJECT THE HEATER TUBE SINCE THE 12.3.4 Use a heater tube control temperature as specified for
CONTAMINATED SURFACE MAY AFFECT THE
the fuel being tested. Apply any thermocouple correction from
DEPOSIT-FORMING CHARACTERISTICS OF THE the most recent calibration (see A5.2.8).
HEATER TUBE.
NOTE 5—The test can be run to a maximum tube temperature of about
350 °C. The temperature at which the test should be run and the criteria for
10.2 Cleaning and Assembly of Remainder of Test Compo-
judging results are normally embodied in fuel specifications.
nents:
10.2.1 Perform the following steps in the order shown prior
12.4 Start Up:
to running a subsequent test.
12.4.1 Use procedure for each model as described in the
appropriate User Manual.
NOTE 2—It is assumed that the apparatus has been disassembled from
12.4.2 Some instrument models may do the following steps
previous test (see Annex A5 or appropriate user manual for assembly/
disassembly details). automatically, but verify that:
12.4.2.1 No more than 1 h maximum elapses from aeration
10.2.2 Inspect and clean components that contact test
to start of heating.
sample and replace any seals that are faulty or suspect.
12.4.2.2 The test filter bypass valve is closed as soon as the
10.2.3 Install the prepared heater tube test section (as
heater tube temperature reaches the test level, so fuel flows
described in 10.1.1 – 10.1.4).
through the test filter (see A5.2.6).
10.2.4 Assemble pre-filter with new element and install.
12.4.2.3 DP transducer is set to zero once DP stabilizes (see
10.2.5 Check thermocouple for correct reference position,
A5.2.6).
then lower into standard operating position.
12.4.3 Check fuel flow rate against Standard Operating
10.2.6 On Models 230 and 240, make sure the water beaker
Conditions by timing flow or counting the drip rate during first
is empty.
15 min of test. (See X1.5.)
11. Calibration and Standardization Procedure
NOTE 6—When counting drop rate, the first drop is counted as drop 0,
11.1 Perform checks of key components at the frequency
and time is started. As drop 20 falls, total time is noted.
indicated in the following (see Annexes or user manual for
12.5 Test:
details).
12.5.1 Record filter pressure drop every 30 min minimum
11.1.1 Thermocouple—Calibrate a thermocouple when first
during the test period.
installed and then at least every 6 months (see A5.2.8).
12.5.2 If the filter pressure drop begins to rise sharply and it
11.1.2 Differential Pressure Cell—Standardize once a year
is desired to run a full 150 min test, a bypass valve common to
or when installing a new cell (see A5.2.6).
all models must be opened in order to finish the test. See
11.1.3 Aeration Dryer—Check at least monthly and change
appropriate User Manual for details on operation of the bypass
if color indicates significant absorption of water (see 7.3).
system (see A5.2.2).
11.1.4 Metering Pump—Perform two checks of flow rate for
12.5.3 Make another flow check within final 15 min before
each test as described in Section 12.
shutdown (see 12.4.3 and accompanying note). (See X1.5.)
12. Procedure
12.6 Heater Tube Profile—If a heater tube temperature
12.1 Preparation of Fuel Test Sample: profile is desired, obtain as described in X1.4.
D3241 − 24
12.7 Shutdown: 13.2 Return the heater tube to original container and retain
12.7.1 Shut down the instrument; some models may do this as appropriate.
automatically.
14. Report
12.7.1.1 For applicable models after shutdown, turn FLOW
SELECTOR VALVE to VENT to relieve pressure.
14.1 Report the following information:
12.7.1.2 For Models 230 and 240, the piston actuator will
14.1.1 The heater tube control temperature. This is the test
retreat automatically.
temperature of the fuel.
12.7.1.3 Measure the amount of spent fluid pumped during
14.1.2 Heater tube deposit rating(s).
the test.
14.1.3 Maximum pressure drop across the filter during the
(1) For the Models 230 and 240, measure effluent water in
test or the time required to reach a pressure differential of
drip receiver, then empty.
25 mm Hg.
(2) For other models, measure the fuel in the receipt
14.1.4 If the normal 150 min test time was not completed,
container.
for example, if the test is terminated because of pressure drop
12.7.1.4 If the amount of water or fuel measured is less than
failure, also report the test time that corresponds to this heater
405 mL, the test shall be rejected.
tube deposit rating.
12.8 Disassembly:
NOTE 7—Either the heater tube rating or the ∆P criteria, or both, are
12.8.1 Disconnect fuel inlet line to the heater tube test used to determine whether a fuel sample passes or fails the test at a
specified test temperature.
section.
12.8.2 Disconnect the heater tube test section.
14.1.5 Spent fuel at the end of a normal test (see 12.7.1.3).
12.8.2.1 Remove the heater tube from the heater tube test
14.1.6 Heater tube serial number may be reported.
section carefully so as to avoid touching the center part of
15. Precision and Bias
heater tube, and discard the test filter.
12.8.2.2 Flush the heater tube with recommended general
15.1 An interlaboratory study of oxidative stability testing
cleaning solvent (see 7.1) from top down. If the heater tube is
was conducted in accordance with Practice E691 by eleven
grasped from the top, do not wash solvent over gloves or bare
laboratories, using thirteen instruments including two models
fingers. Allow to dry, return the heater tube to original
with five fuels at two temperatures for a total of ten materials.
container, mark with identification and hold for evaluation.
Each laboratory obtained two results from each material.
12.8.3 Disconnect and remove any containers.
15.1.1 The terms repeatability and reproducibility in this
12.8.3.1 Discard water and fuel to waste disposal.
section are used as specified in Practice E177.
12.8.4 Disconnect gas dispersion tube (i.e., sparger).
15.2 Precision—It is not possible to specify the precision of
12.8.4.1 Flush gas dispersion tube (i.e., sparger) with rec-
this test method because it has been determined that test
ommended general cleaning solvent (see 7.1). Allow solvent to
method results cannot be analyzed by standard statistical
fully dry before using the gas dispersion tube (i.e., sparger) for
methodology.
another test.
15.3 Bias—This test method has no bias because jet fuel
13. Heater Tube Evaluation
thermal oxidative stability is defined only in terms of this test
method.
13.1 Rate the deposits on heater tube in accordance with
Annex A1, Annex A2, Annex A3, or Annex A4 as directed by
16. Keywords
the specification referencing this method and record data.
13.1.1 When a specification allows multiple rating 16.1 differential pressure; fuel decomposition; oxidative
deposits; heater tube deposits; thermal stability; turbine fuel
techniques, the method providing deposit measurements in SI
units is preferred.
13.1.2 When the rating techniques do not agree, the method
Supporting data have been filed at ASTM International Headquarters and may
providing measurements in SI units shall be regarded as the
be obtained by requesting Research Report RR:D02-1309. Contact ASTM Customer
referee. Service at [e-mail].
D3241 − 24
ANNEXES
(Mandatory Information)
A1. TEST METHOD FOR VISUAL RATING OF HEATER TUBES
A1.1 Scope
A1.1.1 This method covers a procedure for visually rating A1.7 Test Samples (Heater Tube)
the heater tube produced by Test Method D3241.
A1.7.1 Handle the heater tube carefully so as not to touch
A1.1.2 The final result from this test method is a heater tube the center portion at any time.
color rating based on an arbitrary scale established for this test
NOTE A1.1—Touching the center of the heater tube will likely contami-
method plus two additional yes/no criteria that indicate the
nate or disturb the surface of the heater tube, deposit, or both, which must
presence of an apparent large excess of deposit or an unusual
be evaluated in pristine condition.
deposit, or both.
A1.8 Standard Operating Conditions
A1.2 Referenced Documents
A1.8.1 Inside of Light Box, opaque black.
A1.2.1 Adjunct:
A1.8.2 Light Source, three 30 W incandescent bulbs, clear,
Color Standard for Heater Tube Deposit Rating
reflective type; all shall be working for optimum viewing.
A1.3 Terminology
A1.8.3 Bulb Positions, one above, two below, each directed
toward heater tube holder and color standard.
A1.3.1 abnormal—a heater tube deposit color that is neither
peacock nor like those of the Color Standard.
A1.8.4 Magnification, 2×, covering viewing window.
A1.3.1.1 Discussion—This refers to deposit colors such as
A1.8.5 Evaluators—Use persons who can judge colors, that
blues and grays that do not match the Color Standard.
is, they should not be color blind.
A1.3.2 peacock—A multicolor, rainbow-like heater tube
A1.9 Calibration and Standardization
deposit.
A1.3.2.1 Discussion—This type of deposit is caused by
A1.9.1 No standardization is required for this test apparatus,
interference phenomena where deposit thickness exceeds the
but since the Color Standard is known to fade, store it in a dark
quarter wave length of visible light.
place.
A1.3.3 Heater Tube Rating—A ten-step discrete scale from
NOTE A1.2—The lifetime of the Color Standard is not established when
0 to >4 with intermediate levels for each number starting with
continuously or intermittently exposed to light. It is good practice to keep
1 described as less than the subsequent number. a separate Standard in dark (no light) storage for periodic comparison with
the Standard in regular use. When comparing, the optimum under the light
A1.3.3.1 Discussion—The scale is taken from the five
conditions are those of the heater tube rating box.
colors—0, 1, 2, 3, 4—on the ASTM Color Standard. The
A1.9.2 Standardization of Rating Technique:
complete scale is: 0, <1, 1, <2, 2, <3, 3,< 4, 4, >4. Each step is
A1.9.2.1 In rating a heater tube, the darkest deposits are
not necessarily of the same absolute magnitude. The higher the
most important. Estimate grades for the darkest uniform
number, the darker the deposit rating.
deposit, not for the overall average color of the deposit area.
A1.4 Summary of Test Method
A1.9.2.2 When grading, consider only the darkest continu-
ous color that covers an area equal or larger than a circle of size
A1.4.1 This test method uses a specially constructed light
one-half the diameter of the heater tube.
box to view the heater tube. The heater tube is positioned in the
A1.9.2.3 Ignore an axial (that is, longitudinal) deposit streak
box using a special heater tube holder. Uniformity of the new
that is less in width than one-quarter the diameter of the heater
heater tube surface is judged under the optimum light condi-
tube regardless of the length of the streak.
tions of the box. Color of the heater tube is judged under light
A1.9.2.4 Ignore spots, axial (that is, longitudinal) streaks, or
and magnification by comparing to the Color Standard plate
scratches on a heater tube that are considered heater tube
slid into optimum position immediately behind the heater tube.
defects. These will normally not be present, since the heater
A1.5 Significance and Use
tube is examined before use to eliminate defective heater tubes.
A1.5.1 The final heater tube rating is assumed to be an
A1.10 Pretest Rating of Heater Tubes
estimate of condition of the degraded fuel deposit on the heater
tube. This rating is one basis for judging the thermal oxidative A1.10.1 Examine the heater tube without magnification in
stability of the fuel sample. laboratory light. If a defect is visible, discard the heater tube.
Then examine the center (thinner area) of the heater tube
A1.6 Apparatus
between 5 mm and 55 mm above the bottom shoulder using the
A1.6.1 Heater Tube Deposit Rating Apparatus—The colors Tuberator. If a defect is seen, establish its size. If it is larger
of deposits on the heater tube are rated by using a tuberator and than 2.5 mm , discard the heater tube. Fig. A1.1 provides an
the ASTM Color Standard. illustration of defect areas equivalent to 2.5 mm .
D3241 − 24
A1.11.2.3 If the darkest heater tube deposit color being
rated is in the obvious transition state between any two
adjacent color standards, the rating should be recorded as less
than the darker (that is, higher number) standard.
A1.11.2.4 In the event the heater tube has deposits which do
not match the normal Color Standard colors, use the following
rules for rating. With reference to standard terms:
(1) If the heater tube deposit is peacock color, rate this as
Code P, but also rate any heater tube deposit that shows normal
deposit color; or
(2) If the heater tube deposit contains an abnormal color,
rate this as Code A, but also rate any heater tube deposit that
shows normal deposit color.
A1.11.3 Remove the rated heater tube and return to its
original container.
A1.12 Report
A1.12.1 Report the numerical rating for the heater tube
deposit plus A or P, or both, with additional description, if
applicable.
A1.12.1.1 When reporting the overall rating, report the
maximum rating, and, if there are colors present that do not
match the Color Standard, report these also.
FIG. A1.1 Defect Areas
A1.12.1.2 If there are only P or A, or both, deposits, report
only these and do not attempt to estimate a numerical grade.
A1.10.2 Examine the heater tube for straightness by rolling
A1.12.2 Examples:
the heater tube on a flat surface and noting the gap between the
A1.12.2.1 Example 1—A heater tube has a maximum de-
flat surface and the center section. Reject any bent heater tube.
posit falling between Color Standard Codes 2 and 3 with no
other colors present. The overall heater tube rating would be
A1.11 Procedure
less than 3.
A1.11.1 Set Up:
A1.12.2.2 Example 2—The darkest deposit on a heater tube
A1.11.1.1 Snap the upper end of the heater tube into the
matches a Code 3, but there is also a peacock deposit present.
clamp of the holder for the heater tube.
The overall rating of the heater tube would be reported as 3P.
A1.11.1.2 Push the heater tube against the stop of the holder
A1.12.2.3 Example 3—A heater tube has a deposit that
for the heater tube.
matches Color Standard Code 1 and also has an abnormal
A1.11.1.3 Slide the holder with the heater tube over the
deposit. The overall heater tube rating would be reported as
guide rod into the tuberator.
1A.
A1.11.1.4 Rotate the holder and position the heater tube
such that the side with the darkest deposit is visible. A1.13 Precision and Bias
A1.11.1.5 Insert the ASTM Color Standard into the tubera-
A1.13.1 Precision—The precision of the procedure in Test
tor.
Method D3241 for measuring heater tube deposit rating by this
A1.11.2 Evaluation: method was evaluated by the subcommittee and is reported in
A1.11.2.1 On completion of the test, compare the darkest RR:D02-1786.
heater tube deposit color, between 5 mm and 55 mm above the
A1.13.2 Bias—The procedure in Test Method D3241 for
bottom shoulder, with the ASTM Color Standard. Only rate a
determining heater tube deposit rating has no bias because the
deposit if the area is greater than 2.5 mm and the width of any
value of heater tube deposit rating is defined only in terms of
axial (that is, longitudinal) streak or spot is greater than
the test method.
0.8 mm. Fig. A1.1 provides an illustration of spots or axial
streaks with an area equivalent to 2.5 mm .
Supporting data have been filed at ASTM International Headquarters and may
A1.11.2.2 When the darkest heater tube deposit color cor-
be obtained by requesting Research Report RR:D02-1786. Contact ASTM Customer
responds to a color standard, that number should be recorded. Service at [e-mail].
D3241 − 24
A2. TEST METHOD FOR THICKNESS DEPOSIT RATING OF HEATER TUBES—INTERFEROMETRIC METHOD
A2.1 Scope A2.2.1.4 deposit volume—the volume of deposit present on
the test section of the heater tube expressed in mm .
A2.1.1 This annex describes a procedure for the interfero-
A2.2.1.4.1 Discussion—The deposit volume is derived by
metric thickness deposit rating in the range of 0 nm to 1200 nm
integration of the area under the deposit profile.
of heater tubes produced by Test Method D3241—Thermal
A2.2.1.5 interferometry—a technique used for measuring
Oxidation Stability of Aviation Turbine Fuels.
the optical properties of surfaces (refractive index and absorp-
A2.1.2 The final result from this rating procedure is an
tion coefficient) based on studying the pattern of interference
absolute measurement of the thickness and volume of deposit
created by their superposition. In the presence of a thin
on the heater tube that provides a basis for judging the thermal
transparent layer called film, interferometry can also be used to
oxidative stability of the fuel sample. For aircraft fuel systems
provide film thickness information.
performance, deposit thickness and volume are useful param-
A2.2.1.6 standard spot—the mean thickness of the six
eters.
thickest points in a 2.5 mm area, as shown in Fig. A2.6,
A2.1.3 An interlaboratory study was conducted in October
defined in section A1.11.2.1 of this test method.
2011 (see ASTM Research Report RR:D02-1786 for support-
ing data) involving 8 interferometric instruments and 117
A2.3 Summary of Test Method
heater tubes tested in duplicate. The interferometric procedure
A2.3.1 An interferometric apparatus, as shown in Fig. A2.1,
demonstrated objective rating.
is used to rate the deposit on the heater tube. The computer-
NOTE A2.1—The particular technique used for this test method is called
driven software analyzes the interferometric data. The deposit
spectral reflectance.
thickness and deposit volume are derived and displayed.
NOTE A2.2—If this procedure is to be used to rate the heater tube after
the thermal oxidation test, the new heater tube may also be examined by
A2.4 Significance and Use
the same technique to establish a base line or condition of satisfactory
starting quality.
A2.4.1 The final heater tube rating is a direct thickness and
volume measurement of the degraded fuel deposited on the
A2.2 Terminology
heater tube. This rating is one basis for judging the thermal
A2.2.1 Definitions of Terms Specific to This Standard:
oxidative stability of the fuel sample.
A2.2.1.1 deposit—film of oxidized product deposited on the
A2.5 Reagents and Materials
test area of the heater tube after D3241 test procedure.
A2.5.1 Reference Heater Tube —with two reference de-
A2.2.1.2 deposit profile—three-dimensional representation
posits of known and traceable thickness made with silicon
of deposit thickness profile along and around the length of the
dioxide on silicon (Si + SiO ). See Fig. A2.2.
heater tube test section.
A2.2.1.3 deposit thickness—the thickness of deposit present
on the heater tube substrate surface expressed in nanometers,
nm. The sole source of supply of the reference heater tube known to the committee
at this time is AD Systems (www.adsystems-sa.com), available from AD Systems,
5, Allée de Cindais, 14320 Saint André sur Orne, France. If you are aware of
Supporting data have been filed at ASTM International Headquarters and may alternative suppliers, please provide this information to ASTM International
be obtained by requesting Research Report RR:D02-1786. Contact ASTM Customer Headquarters. Your comments will receive careful consideration at a meeting of the
Service at [e-mail]. responsible technical committee, which you may attend
FIG. A2.1 Interferometric Apparatus—General Principle
D3241 − 24
FIG. A2.2 Reference Heater Tube
FIG. A2.3 n and k Values of the Heater Tube
FIG. A2.4 n and K Values of the Deposit Film
D3241 − 24
FIG. A2.5 Circumferential Resolution
FIG. A2.6 Standard Spot
A2.6 Apparatus A2.6.1.5 The instrument can measure the thickness over the
whole length of the heater tube. However, this test method
A2.6.1 Deposit Rater:
describes a procedure to measure the deposit thickness between
A2.6.1.1 Comprising of a suitable UVVIS light source
the 5 mm and the 55 mm points located between the two
(200 nm to 1100 nm), reflected light probe capable to generate
shoulders of the heater tube, as defined in Test Method D3241
a spot light of 200 μm diameter, detector of reflected light for
(Fig. A2.7).
measuring light interferences, heater tube handling assembly,
A2.6.1.6 For the calculation of the film deposit thickness,
heater tube rotating system, optical probe displacement system
and computer-driven software for analyzing the interferometric the computer driven software must be able to automatically
select against wavelength the appropriate refractive index
data.
A2.6.1.2 The instrument must be capable to precisely and value (n) and absorption coefficient value (k) for the substrate
automatically displace the optical probe with the resolution and the deposit film. These values are indicated in the graphs
defined in section A2.8.2.3.
in sections A2.8.2.1 and A2.8.2.2.
A2.6.1.3 The instrument must be able to automatically
A2.7 Test Samples (Heater Tube)
rotate the heater tube with the resolution defined in section
A2.8.2.4.
A2.7.1 Handle the heater tube carefully so as not to touch
A2.6.1.4 The instrument, with its optical probe, must be
the center portion at any time.
able to automatically detect the edge of one of the two
NOTE A2.3—Touching the center (thinner area) of the heater tube will
shoulders of the heater tube; the distance between these two
likely contaminate or disturb the surface of the heater tube, deposit, or
shoulders is 60 mm.
both, which must be evaluated in pristine condition.
The sole source of supply of the deposit rater apparatus known to the
A2.8 Apparatus Preparation
committee at this time is AD systems (www.adsystems-sa.com), model DR 10 –
Deposit Rater, available from AD Systems, 5, Allée de Cindais, 14320 Saint André A2.8.1 Install the apparatus in accordance with the manu-
sur Orne, France. If you are aware of alternative suppliers, please provide this
facturer’s instructions. If any malfunction is indicated refer to
information to ASTM International Headquarters. Your comments will receive
1 the manufacturer’s instructions.
careful consideration at a meeting of the responsible technical committee, which
you may attend. NOTE A2.4—Malfunctions are checked automatically when switching
D3241 − 24
FIG. A2.7 Description of Heater Tube Scanned Surface
on the instrument and during the operation. Any malfunction will be
A2.10 Heater Tube Inspection
automatically indicated.
A2.10.1 Handle the heater tube carefully and do not touch
A2.8.2 Standard Operating Conditions:
the center section at any time.
A2.8.2.1 Heater Tube (Substrate)—refractive index (n) and
A2.10.2 Visually examine the heater tube for straightness by
absorption coefficient (k) values are automatically selected by
rolling the heater tube on a flat dust-free surface and noting the
the computer software using the relationship shown in the
gap between the flat surface and the center section. Heater
graph below (Fig. A2.3).
tubes with a bent center section are not suitable for rating by
NOTE A2.5—The value of n and k index are dependent on the
the DR 10.
metallurgy and surface roughness of the heater tube under examination.
The values on the graphs here above are appropriate for heater tubes used
A2.10.3 Examine the heater tube, without magnification, in
in D3241.
laboratory light for visible mechanical scratches on the centre
A2.8.2.2 Deposit Film—refractive index (n) and absorption section of the heater tube. If such defects are visible, discard
coefficient (k) values are automatically c
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
´1
Designation: D3241 − 23a D3241 − 24
Designation 323/21323/22
Standard Test Method for
1,2
Thermal Oxidation Stability of Aviation Turbine Fuels
This standard is issued under the fixed designation D3241; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
ε NOTE—Editorially updated A4.11 in January 2024.
1. Scope*
1.1 This test method covers the procedure for rating the tendencies of gas turbine fuels to deposit decomposition products within
the fuel system.
1.2 The differential pressure values in mm Hg are defined only in terms of this test method.
1.3 The deposition values stated in SI units shall be regarded as the referee value.
1.4 The pressure values stated in SI units are to be regarded as standard. The psi comparison is included for operational safety
with certain older instruments that cannot report pressure in SI units.
1.5 No other units of measurement are included in this standard.
1.6 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, health, and environmental practices and determine the applicability of
regulatory limitations prior to use. For specific warning statements, see 6.1.1, 7.1, 7.3, 12.1.1, and Annex A6.
1.7 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D1655 Specification for Aviation Turbine Fuels
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
This test method is under the jurisdiction of ASTM International Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility
of Subcommittee D02.J0.03 on Combustion and Thermal Properties. The technically equivalent standard as referenced is under the jurisdiction of the Energy Institute
Subcommittee SC-B-8.
Current edition approved Oct. 1, 2023March 1, 2024. Published October 2023March 2024. Originally approved in 1973. Last previous edition approved in 2023 as
ɛ1
D3241 – 23.D3241 – 23a . DOI: 10.1520/D3241-23AE01.10.1520/D3241-24.
This test method has been developed through the cooperative effort between ASTM and the Energy Institute, London. ASTM and IP standards were approved by ASTM
and EI technical committees as being technically equivalent but that does not imply both standards are identical.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D3241 − 24
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
D4306 Practice for Aviation Fuel Sample Containers for Tests Affected by Trace Contamination
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
2.2 ISO Standards:
ISO 3274 Geometrical Product Specifications (GPS)—Surface texture: Profile method—Nominal characteristics of contact
(stylus) instruments
ISO 4288 Geometrical Product Specifications (GPS)—Surface texture: Profile method—Rules and procedures for the
assessment of surface texture
2.3 ASTM Adjuncts:
Color Standard for Heater Tube Deposit Rating
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms used in this test method, refer to Terminology D4175.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 deposits, n—oxidative products laid down on the test area of the heater tube or caught in the test filter, or both.
3.2.1.1 Discussion—
Fuel deposits will tend to predominate at the hottest portion of the heater tube, which is between the 30 mm and 50 mm position.
3.2.2 heater tube, n—an aluminum coupon controlled at elevated temperature, over which the test fuel is pumped.
3.2.2.1 Discussion—
The heater tube is resistively heated and controlled in temperature by a thermocouple positioned inside. The critical test area is
the thinner portion, 60 mm in length, between the shoulders of the heater tube. Fuel inlet to the heater tube is at the 0 mm position,
and fuel exit is at 60 mm.
3.3 Abbreviations:
3.3.1 ΔP—differential pressure.
4. Summary of Test Method
4.1 This test method for measuring the high temperature stability of gas turbine fuels uses an instrument that subjects the test fuel
to conditions that can be related to those occurring in gas turbine engine fuel systems. The fuel is pumped at a fixed volumetric
flow rate through a heater, after which it enters a precision stainless steel filter where fuel degradation products may become
trapped.
TABLE 1 Instrument Models
Instrument Model Pressurize With Principle Differential Pressure by
A
230 hydraulic syringe Transducer + Printout
A
240 hydraulic syringe Transducer + Printout
B
230 Mk III hydraulic dual piston (HPLC Type) Transducer + Printout
C
F400 hydraulic dual piston (HPLC Type) Transducer + Printout
D, E
230 Mk IV hydraulic single piston (HPLC Type) Transducer + Printout
F
TO10 hydraulic dual syringe Transducer + Printout
A
See RR:D02-1309.
B
See RR:D02-1631.
C
See RR:D02-1728.
D
See RR:D02-1757.
E
There are two versions of the 230 Mk IV instrument; one with an inline internal non-consumable filter located upstream of the 0.45 μm pre-filter and one without. Only
the 230 Mk IV instruments without the inline internal non-consumable filter were included in RR:D02-1757 and have been determined by ASTM Committee D02 to be
equivalent to the other apparatus listed above in Table 1. There are no external markings on the instruments to indicate which apparatus contains the inline internal
non-consumable filter. Contact the manufacturer for further information on removal of the inline internal non-consumable filter.
F
See RR:D02-2071.
Available from International Organization for Standardization (ISO), 1, ch. de la Voie-Creuse, CP 56, CH-1211 Geneva 20, Switzerland, http://www.iso.org.
Available from ASTM International Headquarters. Order Adjunct No. ADJD3241. Original adjunct produced in 1986.
D3241 − 24
4.1.1 The apparatus uses 450 mL of test fuel ideally during a 2.5 h test. The essential data derived are the amount of deposits on
a heater tube, and the rate of plugging of a 17 μm nominal porosity precision filter located just downstream of the heater tube.
5. Significance and Use
5.1 The test results are indicative of fuel performance during gas turbine operation and can be used to assess the level of deposits
that form when liquid fuel contacts a heated surface that is at a specified temperature.
6. Apparatus
6.1 Aviation Fuel Thermal Oxidation Stability Tester —FiveSix models of suitable equipment may be used as indicated in Table
1.
6.1.1 Portions of this test may be automated. Refer to the appropriate user manual for the instrument model to be used for a
description of detailed procedure. A manual is provided with each test rig. (Warning—No attempt should be made to operate the
instrument without first becoming acquainted with all components and the function of each.)
6.1.2 Certain operational parameters used with the instrument are critically important to achieve consistent and correct results.
These are listed in Table 2.
6.2 Heater Tube Deposit Rating Apparatus:
6.2.1 Visual Heater Tube Rater (VTR), the tuberator described in Annex A1.
6.2.2 Standardization of Metrology Requirements:
6.2.2.1 Number of Measured Points—1200 in the ratable area of the heater tube (between 5 mm and 55 mm above the bottom
shoulder of the heater tube).
(1) Circumferential Resolution—(number of points measured on the heater tube circumference), 24 points equally spaced.
(2) Longitudinal Resolution—(number of points measured on the 50 mm ratable length of the heater tube), 50 points equally
spaced.
6.2.2.2 Standard Spot—Thickest average deposit area described by either a 2×3 or 3×2 (longitudinal × circumferential)
arrangement of adjoining thickness measurement points, amongst the 1200 measured by the metrology techniques.
6.2.3 Interferometric (Heater) Tube Rater (ITR)—the tuberator described in Annex A2.
6.2.4 Ellipsometric (Heater) Tube Rater (ETR)—the tuberator described in Annex A3.
6.2.5 Multi-Wavelength Ellipsometric (Heater) Tube Rater (MWETR)—the tuberator described in Annex A4.
6.3 Because jet fuel thermal oxidation stability is defined only in terms of this test method, which depends upon, and is inseparable
from, the specific equipment used, the test method shall be conducted with the equipment used to develop the test method or
equivalent equipment.
7. Reagents and Materials
7.1 Use methyl pentane, 2,2,4-trimethylpentane, or n-heptane as a general cleaning solvent. General cleaning solvent shall be
95 mol % purity, minimum. This solvent will effectively clean internal metal surfaces of apparatus before a test, especially those
surfaces (before the heater tube test section) that contact fresh sample. (Warning—Extremely flammable. Harmful if inhaled (see
Annex A6).)
The following equipment, as described in Table 1 and RR:D02-1309, was used to develop this test method. The following equipment, as described in Table 1 and
determined as equivalent in testing as detailed in RR:D02-1631, is provided by PAC, 8824 Fallbrook Drive, Houston, TX 77064. The following equipment, as described in
Table 1 and determined as equivalent in testing as detailed in RR:D02-1728, is provided by Falex Corporation, 1020 Airpark Dr., Sugar Grove, IL, 60554-9585. The following
equipment as described in Table 1 and determined as equivalent in testing as detailed in RR:D02-2071, is provided by AD Systems (www.adsystems-sa.com), 5, Allée de
Cindais, 14320 Saint André sur Orne, France. This is not an endorsement or certification by ASTM International.
D3241 − 24
TABLE 2 Critical Operating Characteristics of D3241
Item Definition
Test apparatus Tube-in-shell heat exchanger as illustrated in Fig. 1 and dimen-
sions in Fig. A5.1.
Heater Tube:
A, B, C, D, E
Heater tube Specially fabricated heater tube that produces controlled heated
test surface; new one for each test.
E
Heater Tube identification Each heater tube shall be physically identified with a unique serial
number, identifying the manufacturer and providing traceability to
the original material batch.
Heater Tube metallurgy 6061-T6 Aluminum, plus the following criteria
a) The Mg:Si ratio shall not exceed 1.9:1
b) The Mg Si percentage shall not exceed
1.85 %
Heater Tube surface polish over circumference of center section Rotational cut buffing technique with polishing compound to
achieve mechanical surface finish.
Heater Tube dimensions: Dimension Tolerance
F
Heater Tube length, mm 161.925 ±0.254
Center section length, mm 60.325 ±0.051
Outside diameters, mm
Shoulders 4.724 ±0.025
Center section 3.175 ±0.051
Inside diameter, mm 1.651 ±0.051
Total indicator runout, mm, max 0.013
Mechanical surface finish, nm, over circumference in center 50 ± 20
section in accordance with ISO 3274 and ISO 4288 using the
mean of four 1.25–measurements
Test filter nominal 17 μm stainless steel mesh filter element to trap deposits;
new one for each test
Stainless Steel Mesh Twilled Dutch Weave, 304 Stainless Steel, 165 × 1400 Mesh (tol-
erance; 4 % on 1400 and 2 % on 165) with Warp Diameter =
0.0028 in. and Shute Diameter = 0.0016 in.
Instrument parameters:
Sample volume 600 mL of sample is aerated, then 450 mL ± 45 mL of this aerated
fuel shall be pumped during the heating phase for a valid test
Aeration rate 1.5 L ⁄min dry air through sparger
Flow during test 3.0 mL ⁄min ± 10 % (2.7 mL/min minimum to 3.3 mL/min maxi-
mum)
Pump mechanism positive displacement or piston syringe
Cooling bus bars fluid cooled to maintain consistent tube temperature pro-
file
Cooling bus bars cooled in accordance with instrument manufacturer
instruction, to maintain consistent tube temperature profile
Thermocouple (TC) Type J, Inconel sheathed, or Type K, Inconel sheathed
Operating pressure:
System 3.45 MPa ± 10 % on sample by hydraulically transmitted force
against control valve outlet restriction
At test filter differential pressure (∆P) measured across test filter by electronic
transducer in mm Hg
Operating temperature:
For test as stated in specification for fuel
Uniformity of run maximum deviation of ±2 °C from specified temperature
Calibration Models 230 and 240 – Three point calibration including tin (see
7.5) at 232 °C, lead (see 7.4) at 327 °C for high point and ice +
water for low point reference
All other models – Two point calibration using pure lead at 327 °C
for high point and ice + water for low point reference
A
D3241/IP 323 Thermal Stability is a critical aviation fuel test, the results of which are used to assess the suitability of jet fuel for aviation operational safety and regulatory
compliance. The integrity of D3241/IP 323 testing requires that heater tubes meet the regulations of D3241 Table 2 and give equivalent D3241 results to the heater tubes
supplied by the original equipment manufacturer (OEM).
B
The following equipment, heater tubes, manufactured by PAC, 8824 Fallbrook Drive, Houston, TX 77064, was used in the development of this test method. This is not
an endorsement or certification by ASTM International.
C
A test protocol to establish equivalence of heater tubes is on file at ASTM International Headquarters and may be obtained by requesting Research Report RR:D02-1550.
D
The following equipment, heater tube and filter kits, manufactured by Falex Corporation, 1020 Airpark Dr., Sugar Grove, IL, 60554-9585, was run through the test
protocol in RR:D02-1550 and determined as equivalent to the equipment used to develop the test method. This test is detailed in RR:D02-1714. This is not an endorsement
or certification by ASTM International.
E
An electronic recording device, such as a radio-frequency identification device (RFID), may be embedded into the heater tube rivet located at the bottom of the heater
tube. Tube identification data may be stored on an electronic recording device, such as a RFID, embedded into the heater tube.
F
Tube length measurements are only applicable to the aluminum portion of the heater tube. Additions, such as an RFID, do not contribute to the length measurement of
the heater tube.
D3241 − 24
FIG. 1 Standard Heater Tube Test Section, Essential to All D3241 Test Instruments
7.2 Use a nylon bristle brush and trisolvent to clean internal (working) surface of heater tube test section only. Trisolvent is an
equal mix of acetone (1), toluene (2), and isopropanol (3). All three components of trisolvent shall be 95 mol % purity, minimum.
(Warning—(1) Extremely flammable, vapors may cause flash fire; (2) and (3) Flammable. Vapors of all three harmful. Irritating
to skin, eyes, and mucous membranes.) Use a nylon bristle brush that makes stiff contact with the inner walls of the heater tube
test section.
7.3 Use dry calcium sulfate + cobalt chloride granules (97 + 3 mix) or other self-indicating drying agent in the aeration dryer. This
granular material changes gradually from blue to pink color indicating absorption of water. (Warning—Do not inhale dust or
ingest. May cause stomach disorder.)
7.4 Lead, 99.9 % minimum purity.
7.5 Tin, 99.0 % minimum purity.
8. Sampling
8.1 General Requirements—The choice of construction materials is an important factor, particularly in the case of aviation turbine
fuel, where thermal stability can be degraded by the presence of very low concentration of copper. The use of copper or copper
alloys shall be eliminated wherever possible by the use of alternative materials such as stainless steel or aluminum. Zinc and
cadmium are two other metals that adversely affect product quality. Copper, copper alloys (such as brass), zinc-rich (galvanized)
coatings, cadmium alloys, and cadmium plating shall not be used in sampling aviation fuels for evaluation under this test method.
8.1.1 Sampling Containers—Sampling containers shall be in accordance with the requirements for thermal stability testing
described in Practice D4306.
8.1.2 Sampling Equipment—Sampling equipment fabricated from copper or its alloys shall not be used for sampling in accordance
with this test method. Sampling equipment shall be in accordance with the requirements for aviation fuel described in Practice
D4057.
9. Standard Operating Conditions
9.1 Standard conditions of the test method are as follows:
9.1.1 Fuel Quantity, 450 mL minimum for test plus about 50 mL for system.
9.1.2 Fuel Pre-Treatment—Filter the fuel through a single layer of “qualitative” quality, medium-flow, cellulose filter paper. Filter
should be a pleated (folded) circular shape and fitted into a conical funnel to filter fuel. Filter paper grades 2V, MN514, or better,
are recommended. After filtration, aerate the fuel for 6 min at 1.5 L ⁄min air flow rate for a maximum of 1000 mL sample using
a coarse 12 mm borosilicate glass gas dispersion tube.
9.1.3 Fuel System Pressure, 3.45 MPa (500 psi) 610 % gauge.
D3241 − 24
9.1.4 Thermocouple Position, at 39 mm.
9.1.5 Fuel System Prefilter Element, filter paper of 0.45 μm pore size.
9.1.6 Heater Tube Control Temperature, preset as specified in applicable specification.
9.1.7 Fuel Flow Rate, 3.0 mL ⁄min 6 10 %.
9.1.8 Minimum Fuel Pumped During Test, 405 mL.
9.1.9 Test Duration, 150 min 6 2 min.
9.1.10 Cooling Fluid Flow, Bus Bar Cooling—Cooling system designs can be different between instrument models, and must be
operated and maintained in accordance with the manufacturer’s requirements. For systems equipped with cooling fluid circulation
system, adjust the fluid flow to approximately 39 L ⁄h, or center of green range on cooling fluid meter.
9.1.11 Power Setting, internally set for computer models.
10. Preparation of Apparatus
10.1 Cleaning and Assembly of Heater Tube Test Section:
10.1.1 Clean the inside surface of the heater tube test section using a nylon brush saturated with trisolvent to remove all deposits.
Replace the nylon brush when it shows signs of wear (such as missing bristles) and no longer makes stiff contact with inner walls
of heater tube test section.
10.1.2 Check the heater tube to be used in the test for surface defects and straightness by referring to the procedure in A1.10. Be
careful, also, to avoid scratching the heater tube shoulder during the examination, since the heater tube shoulder must be smooth
to ensure a seal under the flow conditions of the test.
10.1.3 Assemble the heater tube test section using new items: (1) visually checked heater tube, (2) test filter, and (3) three O-rings.
Inspect insulators to be sure they are undamaged.
NOTE 1—Heater tubes must not be reused. Tests indicate that magnesium migrates to the heater tube surface under normal test conditions. Surface
magnesium may reduce adhesion of deposits to reused heater tube.
10.1.4 During assembly of the heater tube test section, handle the heater tube carefully so as not to touch center part of heater tube.
IF THE CENTER OF HEATER TUBE IS TOUCHED, REJECT THE HEATER TUBE SINCE THE CONTAMINATED
SURFACE MAY AFFECT THE DEPOSIT-FORMING CHARACTERISTICS OF THE HEATER TUBE.
10.2 Cleaning and Assembly of Remainder of Test Components:
10.2.1 Perform the following steps in the order shown prior to running a subsequent test.
NOTE 2—It is assumed that the apparatus has been disassembled from previous test (see Annex A5 or appropriate user manual for assembly/disassembly
details).
10.2.2 Inspect and clean components that contact test sample and replace any seals that are faulty or suspect.
10.2.3 Install the prepared heater tube test section (as described in 10.1.1 – 10.1.4).
10.2.4 Assemble pre-filter with new element and install.
10.2.5 Check thermocouple for correct reference position, then lower into standard operating position.
10.2.6 On Models 230 and 240, make sure the water beaker is empty.
D3241 − 24
11. Calibration and Standardization Procedure
11.1 Perform checks of key components at the frequency indicated in the following (see Annexes or user manual for details).
11.1.1 Thermocouple—Calibrate a thermocouple when first installed and then at least every 6 months (see A5.2.8).
11.1.2 Differential Pressure Cell—Standardize once a year or when installing a new cell (see A5.2.6).
11.1.3 Aeration Dryer—Check at least monthly and change if color indicates significant absorption of water (see 7.3).
11.1.4 Metering Pump—Perform two checks of flow rate for each test as described in Section 12.
12. Procedure
12.1 Preparation of Fuel Test Sample:
12.1.1 Filter and aerate sample using standard operating conditions (see A5.2.9). (Warning—All jet fuels must be considered
flammable except JP5 and JP7. Vapors are harmful (see A6.3, A6.6, and A6.7).)
NOTE 3—Before operating, see Warning in 6.1.1.
NOTE 4—Test method results are known to be sensitive to trace contamination from sampling containers. For recommended containers, refer to Practice
D4306.
12.1.2 Maintain temperature of sample between 15 °C and 32 °C during aeration.
12.1.3 Allow no more than 1 h to elapse between the end of aeration and the start of the heating of the sample.
12.2 Final Assembly:
12.2.1 Check all lines to ensure tightness.
12.2.2 Recheck thermocouple position at 39 mm.
12.2.3 Make sure drip receiver is empty.
12.3 Power Up and Pressurization:
12.3.1 Turn POWER to ON.
12.3.2 Inspect the system for leaks. Depressurize the system as necessary to tighten any leaking fittings.
12.3.3 Set controls to the standard operating conditions.
12.3.4 Use a heater tube control temperature as specified for the fuel being tested. Apply any thermocouple correction from the
most recent calibration (see A5.2.8).
NOTE 5—The test can be run to a maximum tube temperature of about 350 °C. The temperature at which the test should be run and the criteria for judging
results are normally embodied in fuel specifications.
12.4 Start Up:
12.4.1 Use procedure for each model as described in the appropriate User Manual.
12.4.2 Some instrument models may do the following steps automatically, but verify that:
12.4.2.1 No more than 1 h maximum elapses from aeration to start of heating.
D3241 − 24
12.4.2.2 The test filter bypass valve is closed as soon as the heater tube temperature reaches the test level, so fuel flows through
the test filter (see A5.2.6).
12.4.2.3 DP transducer is set to zero once DP stabilizes (see A5.2.6).
12.4.3 Check fuel flow rate against Standard Operating Conditions by timing flow or counting the drip rate during first 15 min of
test. (See X1.5.)
NOTE 6—When counting drop rate, the first drop is counted as drop 0, and time is started. As drop 20 falls, total time is noted.
12.5 Test:
12.5.1 Record filter pressure drop every 30 min minimum during the test period.
12.5.2 If the filter pressure drop begins to rise sharply and it is desired to run a full 150 min test, a bypass valve common to all
models must be opened in order to finish the test. See appropriate User Manual for details on operation of the bypass system (see
A5.2.2).
12.5.3 Make another flow check within final 15 min before shutdown (see 12.4.3 and accompanying note). (See X1.5.)
12.6 Heater Tube Profile—If a heater tube temperature profile is desired, obtain as described in X1.4.
12.7 Shutdown:
12.7.1 Shut down the instrument; some models may do this automatically.
12.7.1.1 For applicable models after shutdown, turn FLOW SELECTOR VALVE to VENT to relieve pressure.
12.7.1.2 For Models 230 and 240, the piston actuator will retreat automatically.
12.7.1.3 Measure the amount of spent fluid pumped during the test.
(1) For the Models 230 and 240, measure effluent water in drip receiver, then empty.
(2) For other models, measure the fuel in the receipt container.
12.7.1.4 If the amount of water or fuel measured is less than 405 mL, the test shall be rejected.
12.8 Disassembly:
12.8.1 Disconnect fuel inlet line to the heater tube test section.
12.8.2 Disconnect the heater tube test section.
12.8.2.1 Remove the heater tube from the heater tube test section carefully so as to avoid touching the center part of heater tube,
and discard the test filter.
12.8.2.2 Flush the heater tube with recommended general cleaning solvent (see 7.1) from top down. If the heater tube is grasped
from the top, do not wash solvent over gloves or bare fingers. Allow to dry, return the heater tube to original container, mark with
identification and hold for evaluation.
12.8.3 Disconnect and remove any containers.
12.8.3.1 Discard water and fuel to waste disposal.
12.8.4 Disconnect gas dispersion tube (i.e., sparger).
D3241 − 24
12.8.4.1 Flush gas dispersion tube (i.e., sparger) with recommended general cleaning solvent (see 7.1). Allow solvent to fully dry
before using the gas dispersion tube (i.e., sparger) for another test.
13. Heater Tube Evaluation
13.1 Rate the deposits on heater tube in accordance with Annex A1, Annex A2, Annex A3, or Annex A4 as directed by the
specification referencing this method and record data.
13.1.1 When a specification allows multiple rating techniques, the method providing deposit measurements in SI units is preferred.
13.1.2 When the rating techniques do not agree, the method providing measurements in SI units shall be regarded as the referee.
13.2 Return the heater tube to original container and retain as appropriate.
14. Report
14.1 Report the following information:
14.1.1 The heater tube control temperature. This is the test temperature of the fuel.
14.1.2 Heater tube deposit rating(s).
14.1.3 Maximum pressure drop across the filter during the test or the time required to reach a pressure differential of 25 mm Hg.
14.1.4 If the normal 150 min test time was not completed, for example, if the test is terminated because of pressure drop failure,
also report the test time that corresponds to this heater tube deposit rating.
NOTE 7—Either the heater tube rating or the ∆P criteria, or both, are used to determine whether a fuel sample passes or fails the test at a specified test
temperature.
14.1.5 Spent fuel at the end of a normal test (see 12.7.1.3).
14.1.6 Heater tube serial number may be reported.
15. Precision and Bias
15.1 An interlaboratory study of oxidative stability testing was conducted in accordance with Practice E691 by eleven laboratories,
using thirteen instruments including two models with five fuels at two temperatures for a total of ten materials. Each laboratory
obtained two results from each material.
15.1.1 The terms repeatability and reproducibility in this section are used as specified in Practice E177.
15.2 Precision—It is not possible to specify the precision of this test method because it has been determined that test method
results cannot be analyzed by standard statistical methodology.
15.3 Bias—This test method has no bias because jet fuel thermal oxidative stability is defined only in terms of this test method.
16. Keywords
16.1 differential pressure; fuel decomposition; oxidative deposits; heater tube deposits; thermal stability; turbine fuel
Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:D02-1309. Contact ASTM Customer
Service at [e-mail].
D3241 − 24
ANNEXES
(Mandatory Information)
A1. TEST METHOD FOR VISUAL RATING OF HEATER TUBES
A1.1. Scope
A1.1.1 This method covers a procedure for visually rating the heater tube produced by Test Method D3241.
A1.1.2 The final result from this test method is a heater tube color rating based on an arbitrary scale established for this test method
plus two additional yes/no criteria that indicate the presence of an apparent large excess of deposit or an unusual deposit, or both.
A1.1.3 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
A1.1 Scope
A1.1.1 This method covers a procedure for visually rating the heater tube produced by Test Method D3241.
A1.1.2 The final result from this test method is a heater tube color rating based on an arbitrary scale established for this test method
plus two additional yes/no criteria that indicate the presence of an apparent large excess of deposit or an unusual deposit, or both.
A1.2. Referenced Documents
A1.2.1 Adjunct:
Color Standard for Heater Tube Deposit Rating
A1.3. Terminology
A1.3.1 abnormal—a heater tube deposit color that is neither peacock nor like those of the Color Standard.
A1.3.1.1 Discussion—This refers to deposit colors such as blues and grays that do not match the Color Standard.
A1.3.2 peacock—A multicolor, rainbow-like heater tube deposit.
A1.3.2.1 Discussion—This type of deposit is caused by interference phenomena where deposit thickness exceeds the quarter wave
length of visible light.
A1.3.3 Heater Tube Rating—A ten-step discrete scale from 0 to >4 with intermediate levels for each number starting with 1
described as less than the subsequent number.
D3241 − 24
A1.3.3.1 Discussion—The scale is taken from the five colors—0, 1, 2, 3, 4—on the ASTM Color Standard. The complete scale
is: 0, <1, 1, <2, 2, <3, 3,< 4, 4, >4. Each step is not necessarily of the same absolute magnitude. The higher the number, the darker
the deposit rating.
A1.4. Summary of Test Method
A1.4.1 This test method uses a specially constructed light box to view the heater tube. The heater tube is positioned in the box
using a special heater tube holder. Uniformity of the new heater tube surface is judged under the optimum light conditions of the
box. Color of the heater tube is judged under light and magnification by comparing to the Color Standard plate slid into optimum
position immediately behind the heater tube.
A1.5. Significance and Use
A1.5.1 The final heater tube rating is assumed to be an estimate of condition of the degraded fuel deposit on the heater tube. This
rating is one basis for judging the thermal oxidative stability of the fuel sample.
A1.6. Apparatus
A1.6.1 Heater Tube Deposit Rating Apparatus—The colors of deposits on the heater tube are rated by using a tuberator and the
ASTM Color Standard.
A1.7. Test Samples (Heater Tube)
A1.7.1 Handle the heater tube carefully so as not to touch the center portion at any time.
NOTE A1.1—Touching the center of the heater tube will likely contaminate or disturb the surface of the heater tube, deposit, or both, which must be
evaluated in pristine condition.
A1.8 Standard Operating Conditions
A1.8.1 Inside of Light Box, opaque black.
A1.8.2 Light Source, three 30 W incandescent bulbs, clear, reflective type; all shall be working for optimum viewing.
A1.8.3 Bulb Positions, one above, two below, each directed toward heater tube holder and color standard.
A1.8.4 Magnification, 2×, covering viewing window.
A1.8.5 Evaluators—Use persons who can judge colors, that is, they should not be color blind.
A1.9. Calibration and Standardization
A1.9.1 No standardization is required for this test apparatus, but since the Color Standard is known to fade, store it in a dark place.
NOTE A1.2—The lifetime of the Color Standard is not established when continuously or intermittently exposed to light. It is good practice to keep a
D3241 − 24
separate Standard in dark (no light) storage for periodic comparison with the Standard in regular use. When comparing, the optimum under the light
conditions are those of the heater tube rating box.
A1.9.2 Standardization of Rating Technique:
A1.9.2.1 In rating a heater tube, the darkest deposits are most important. Estimate grades for the darkest uniform deposit, not for
the overall average color of the deposit area.
A1.9.2.2 When grading, consider only the darkest continuous color that covers an area equal or larger than a circle of size one-half
the diameter of the heater tube.
A1.9.2.3 Ignore an axial (that is, longitudinal) deposit streak that is less in width than one-quarter the diameter of the heater tube
regardless of the length of the streak.
A1.9.2.4 Ignore spots, axial (that is, longitudinal) streaks, or scratches on a heater tube that are considered heater tube defects.
These will normally not be present, since the heater tube is examined before use to eliminate defective heater tubes.
A1.10 Pretest Rating of Heater Tubes
A1.10.1 Examine the heater tube without magnification in laboratory light. If a defect is visible, discard the heater tube. Then
examine the center (thinner area) of the heater tube between 5 mm and 55 mm above the bottom shoulder using the Tuberator. If
a defect is seen, establish its size. If it is larger than 2.5 mm , discard the heater tube. Fig. A1.1 provides an illustration of defect
areas equivalent to 2.5 mm .
A1.10.2 Examine the heater tube for straightness by rolling the heater tube on a flat surface and noting the gap between the flat
surface and the center section. Reject any bent heater tube.
FIG. A1.1 Defect Areas
D3241 − 24
A1.11. Procedure
A1.11.1 Set Up:
A1.11.1.1 Snap the upper end of the heater tube into the clamp of the holder for the heater tube.
A1.11.1.2 Push the heater tube against the stop of the holder for the heater tube.
A1.11.1.3 Slide the holder with the heater tube over the guide rod into the tuberator.
A1.11.1.4 Rotate the holder and position the heater tube such that the side with the darkest deposit is visible.
A1.11.1.5 Insert the ASTM Color Standard into the tuberator.
A1.11.2 Evaluation:
A1.11.2.1 On completion of the test, compare the darkest heater tube deposit color, between 5 mm and 55 mm above the bottom
shoulder, with the ASTM Color Standard. Only rate a deposit if the area is greater than 2.5 mm and the width of any axial (that
is, longitudinal) streak or spot is greater than 0.8 mm. Fig. A1.1 provides an illustration of spots or axial streaks with an area
equivalent to 2.5 mm .
A1.11.2.2 When the darkest heater tube deposit color corresponds to a color standard, that number should be recorded.
A1.11.2.3 If the darkest heater tube deposit color being rated is in the obvious transition state between any two adjacent color
standards, the rating should be recorded as less than the darker (that is, higher number) standard.
A1.11.2.4 In the event the heater tube has deposits which do not match the normal Color Standard colors, use the following rules
for rating. With reference to standard terms:
(1) If the heater tube deposit is peacock color, rate this as Code P, but also rate any heater tube deposit that shows normal
deposit color; or
(2) If the heater tube deposit contains an abnormal color, rate this as Code A, but also rate any heater tube deposit that shows
normal deposit color.
A1.11.3 Remove the rated heater tube and return to its original container.
A1.12. Report
A1.12.1 Report the numerical rating for the heater tube deposit plus A or P, or both, with additional description, if applicable.
A1.12.1.1 When reporting the overall rating, report the maximum rating, and, if there are colors present that do not match the
Color Standard, report these also.
D3241 − 24
A1.12.1.2 If there are only P or A, or both, deposits, report only these and do not attempt to estimate a numerical grade.
A1.12.2 Examples:
A1.12.2.1 Example 1—A heater tube has a maximum deposit falling between Color Standard Codes 2 and 3 with no other colors
present. The overall heater tube rating would be less than 3.
A1.12.2.2 Example 2—The darkest deposit on a heater tube matches a Code 3, but there is also a peacock deposit present. The
overall rating of the heater tube would be reported as 3P.
A1.12.2.3 Example 3—A heater tube has a deposit that matches Color Standard Code 1 and also has an abnormal deposit. The
overall heater tube rating would be reported as 1A.
A1.13. Precision and Bias
A1.13.1 Precision—The precision of the procedure in Test Method D3241 for measuring heater tube deposit rating by this method
was evaluated by the subcommittee and is reported in RR:D02-1786.
A1.13.2 Bias—The procedure in Test Method D3241 for determining heater tube deposit rating has no bias because the value of
heater tube deposit rating is defined only in terms of the test method.
A2. TEST METHOD FOR THICKNESS DEPOSIT RATING OF HEATER TUBES—INTERFEROMETRIC METHOD
A2.1 Scope
A2.1.1 This annex describes a procedure for the interferometric thickness deposit rating in the range of 0 nm to 1200 nm of heater
tubes produced by Test Method D3241—Thermal Oxidation Stability of Aviation Turbine Fuels.
A2.1.2 The final result from this rating procedure is an absolute measurement of the thickness and volume of deposit on the heater
tube that provides a basis for judging the thermal oxidative stability of the fuel sample. For aircraft fuel systems performance,
deposit thickness and volume are useful parameters.
A2.1.3 An interlaboratory study was conducted in October 2011 (see ASTM Research Report RR:D02-1786 for supporting data)
involving 8 interferometric instruments and 117 heater tubes tested in duplicate. The interferometric procedure demonstrated
objective rating.
Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:D02-1786. Contact ASTM Customer
Service at [e-mail].
Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:D02-1786. Contact ASTM Customer
Service at [e-mail].
D3241 − 24
NOTE A2.1—The particular technique used for this test method is called spectral reflectance.
NOTE A2.2—If this procedure is to be used to rate the heater tube after the thermal oxidation test, the new heater tube may also be examined by the same
technique to establish a base line or condition of satisfactory starting quality.
A2.2 Terminology
A2.2.1 Definitions of Terms Specific to This Standard:
A2.2.1.1 deposit—film of oxidized product deposited on the test area of the heater tube after D3241 test procedure.
A2.2.1.2 deposit profile—three-dimensional representation of deposit thickness profile along and around the length of the heater
tube test section.
A2.2.1.3 deposit thickness—the thickness of deposit present on the heater tube substrate surface expressed in nanometers, nm.
A2.2.1.4 deposit volume—the volume of deposit present on the test section of the heater tube expressed in mm .
A2.2.1.4.1 Discussion—
The deposit volume is derived by integration of the area under the deposit profile.
A2.2.1.5 interferometry—a technique used for measuring the optical properties of surfaces (refractive index and absorption
coefficient) based on studying the pattern of interference created by their superposition. In the presence of a thin transparent layer
called film, interferometry can also be used to provide film thickness information.
A2.2.1.6 standard spot—the mean thickness of the six thickest points in a 2.5 mm area, as shown in Fig. A2.6, defined in section
A1.11.2.1 of this test method.
A2.3 Summary of Test Method
FIG. A2.1 Interferometric Apparatus—General Principle
D3241 − 24
FIG. A2.2 Reference Heater Tube
FIG. A2.3 n and k Values of the Heater Tube
FIG. A2.4 n and K Values of the Deposit Film
A2.3.1 An interferometric apparatus, as shown in Fig. A2.1, is used to rate the deposit on the heater tube. The computer-driven
software analyzes the interferometric data. The deposit thickness and deposit volume are derived and displayed.
D3241 − 24
FIG. A2.5 Circumferential Resolution
FIG. A2.6 Standard Spot
A2.4 Significance and Use
A2.4.1 The final heater tube rating is a direct thickness and volume measurement of the degraded fuel deposited on the heater tube.
This rating is one basis for judging the thermal oxidative stability of the fuel sample.
A2.5 Reagents and Materials
A2.5.1 Reference Heater Tube —with two reference deposits of known and traceable thickness made with silicon dioxide on
silicon (Si + SiO ). See Fig. A2.2.
The sole source of supply of the reference heater tube known to the committee at this time is AD systemsSystems (www.adsystems-sa.com), available from AD systems,
P.A. Portes de la Suisse Normande, Systems, 5, Allée de Cindais, 14320 Saint André sur Orne, France. If you are aware of alternative suppliers, please provide this information
to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of the responsible technical committee, which you may attend
D3241 − 24
A2.6 Apparatus
A2.6.1 Deposit Rater:
A2.6.1.1 Comprising of a suitable UVVIS light source (200 nm to 1100 nm), reflected light probe capable to generate a spot light
of 200 μm diameter, detector of reflected light for measuring light interferences, heater tube handling assembly, heater tube rotating
system, optical probe displacement system and computer-driven software for analyzing the interferometric data.
A2.6.1.2 The instrument must be capable to precisely and automatically displace the optical probe with the resolution defined in
section A2.8.2.3.
A2.6.1.3 The instrument must be able to automatically rotate the heater tube with the resolution defined in section A2.8.2.4.
A2.6.1.4 The instrument, with its optical probe, must be able to automatically detect the edge of one of the two shoulders of the
heater tube; the distance between these two shoulders is 60 mm.
A2.6.1.5 The instrument can measure the thickness over the whole length of the heater tube. However, this test method describes
a procedure to measure the deposit thickness between the 5 mm and the 55 mm points located between the two shoulders of the
heater tube, as defined in Test Method D3241 (Fig. A2.7).
A2.6.1.6 For the calculation of the film deposit thickness, the computer driven software must be able to automatically select
against wavelength the appropriate refractive index value (n) and absorption coefficient value (k) for the substrate and the deposit
film. These values are indicated in the graphs in sections A2.8.2.1 and A2.8.2.2.
A2.7 Test Samples (Heater Tube)
A2.7.1 Handle the heater tube carefully so as not to touch the center portion at any time.
NOTE A2.3—Touching the center (thinner area) of the heater tube will likely contaminate or disturb the surface of the heater tube, deposit, or both, which
must be evaluated in pristine condition.
FIG. A2.7 Description of Heater Tube Scanned Surface
The sole source of supply of the deposit rater apparatus known to the committee at this time is AD systems (www.adsystems-sa.com), model DR 10 – Deposit Rater,
available from AD systems, P.A. Portes de la Suisse Normande, Systems, 5, Allée de Cindais, 14320 Saint André sur Orne, France. If you are aware of alternative suppliers,
please provide this information to ASTM International Headquarters. Your comments will receive careful consid
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