ASTM E285-80(2002)
(Test Method)Standard Test Method for Oxyacetylene Ablation Testing of Thermal Insulation Materials
Standard Test Method for Oxyacetylene Ablation Testing of Thermal Insulation Materials
SIGNIFICANCE AND USE
This test method is intended to screen the most obvious poor materials from further consideration. Since the combustion gases more closely resemble the environment generated in rocket motors, this test method is more applicable to screening materials for nozzles and motor liners than for aerodynamic heating.
The environment for any specific high-temperature thermal protection problem is peculiar to that particular application. The conditions generated by the oxyacetylene heat source in this test method represent only one set of conditions; they do not simulate any specific application. Thus, the test results cannot be used to predict directly the behavior of materials for specific environments, nor can they be used for design purposes. However, over a number of years, the test has been useful in determining the relative merit of materials, particularly in weeding out obviously poor materials from more advanced data-generation programs. It has also been considered for use as a production quality-control test for rocket insulation materials.
The tester is cautioned to use prudence in extending the usefulness of the test method beyond its original intent, namely, screening. For situations having environments widely different from those of the test, the user is urged to modify the oxyacetylene burner conditions to suit his requirements or perhaps change to a different heat-generating device that provides better simulation.
SCOPE
1.1 This test method covers the screening of ablative materials to determine the relative thermal insulation effectiveness when tested as a flat panel in an environment of a steady flow of hot gas provided by an oxyacetylene burner.
1.2 This test method should be used to measure and describe the properties of materials, products, or assemblies in response to heat and flame under controlled laboratory conditions and should not be used to describe or appraise the fire hazard of materials, products, or assemblies under actual fire conditions. However, results of this test method may be used as elements of a fire risk assessment which takes into account all of the factors which are pertinent to an assessment of the fire hazard of a particular end use.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
1.4 The values stated in SI units are to be regarded as the standard.
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Designation:E285–80 (Reapproved 2002)
Standard Test Method for
Oxyacetylene Ablation Testing of Thermal Insulation
Materials
This standard is issued under the fixed designation E285; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Summary of Test Method
1.1 This test method covers the screening of ablative mate- 3.1 Hot combustion gases are directed along the normal to
rials to determine the relative thermal insulation effectiveness the specimen until burn-through is achieved. The erosion rate
when tested as a flat panel in an environment of a steady flow of the material is determined by dividing the original thickness
of hot gas provided by an oxyacetylene burner. by the time to burn-through. The insulating effectiveness is
1.2 Thistestmethodshouldbeusedtomeasureanddescribe determined from back-face temperature measurements. Insula-
the properties of materials, products, or assemblies in response tion index numbers are computed by dividing the times for
to heat and flame under controlled laboratory conditions and temperature changes of 80, 180, and 380°C, from the initial
should not be used to describe or appraise the fire hazard of ambient temperature, by the original thickness.The insulation-
materials, products, or assemblies under actual fire conditions. to-density performance is computed by dividing the insulation
However, results of this test method may be used as elements index by the density of the panel.
of a fire risk assessment which takes into account all of the 3.2 The general characteristics of the oxyacetylene heat
factors which are pertinent to an assessment of the fire hazard source are:
of a particular end use. 3.2.1 Heat Flux—835 W/cm (cold-wall calorimeter).
1.3 This standard does not purport to address all of the 3.2.2 Velocity—210 m/s (cold, unreacted gases).
safety concerns, if any, associated with its use. It is the 3.2.3 Neutral flame conditions.
responsibility of the user of this standard to establish appro-
4. Significance and Use
priate safety and health practices and determine the applica-
4.1 This test method is intended to screen the most obvious
bility of regulatory limitations prior to use.
poor materials from further consideration. Since the combus-
1.4 The values stated in SI units are to be regarded as the
standard. tiongasesmorecloselyresembletheenvironmentgeneratedin
rocket motors, this test method is more applicable to screening
2. Referenced Documents
materials for nozzles and motor liners than for aerodynamic
2.1 ASTM Standards: heating.
D792 TestMethodsforDensityandSpecificGravity(Rela- 4.2 Theenvironmentforanyspecifichigh-temperaturether-
tive Density) of Plastics by Displacement mal protection problem is peculiar to that particular applica-
2.2 Federal Standards: tion.Theconditionsgeneratedbytheoxyacetyleneheatsource
BB-A-106a Acetylene, Technical, Dissolved inthistestmethodrepresentonlyonesetofconditions;theydo
BB-O-925a Oxygen, Technical, Gas and Liquid not simulate any specific application. Thus, the test results
cannot be used to predict directly the behavior of materials for
specific environments, nor can they be used for design pur-
This test method is under the jurisdiction of ASTM Committee E21 on Space
poses. However, over a number of years, the test has been
Simulation andApplications of SpaceTechnology and is the direct responsibility of
useful in determining the relative merit of materials, particu-
Subcommittee E21.08 on Thermal Protection.
Current edition approved Dec. 8, 1980. Published February 1981. Originally
larly in weeding out obviously poor materials from more
published as E 285 – 65T. Last previous edition E 285 – 70.
advanced data-generation programs. It has also been consid-
Annual Book of ASTM Standards, Vol 08.01.
3 ered for use as a production quality-control test for rocket
AvailablefromStandardizationDocumentsOrderDesk,Bldg.4SectionD,700
Robbins Ave., Philadelphia, PA 19111-5098, Attn: NPODS. insulation materials.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E285
4.3 The tester is cautioned to use prudence in extending the damage to the tip (Note 2). Details of the water jacket are
usefulness of the test method beyond its original intent, shown in Figs. 2 and 3 and the torch tip is shown in Fig. 4.
namely, screening. For situations having environments widely
NOTE 2—Proprietary designation cannot be avoided because of the
different from those of the test, the user is urged to modify the
broad spectrum of heat flux and flame patterns produced by competitive
oxyacetylene burner conditions to suit his requirements or
torch tips of similar size.TheVictor torch tip was selected on the basis of
perhaps change to a different heat-generating device that popularity, reproducibility of test results, and the relatively high heat flux
it produces.
provides better simulation.
5.2.3 Fuel Storage and Manifold—A minimum of three
5. Apparatus
acetylene cylinders shall be tapped simultaneously through a
5.1 General—The apparatus shall consist of an oxyacety-
manifold and suitable pressure regulators. Cylinders shall be
lene burner, a specimen holder, and means for measuring the stored in an upright position and held at room temperature for
time to burn-through and for recording the back-face tempera-
at least 1 h, or until at equilibrium with room temperature,
ture history of the specimen.Auxiliary apparatus all consist of before using.The complete bank of cylinders shall be changed
a calorimetric device to measure heat-transfer rate as specified
when the gage reads 0.7 MPa (100 psi). Acetylene storage
in 5.5.
tanks shall be protected by a check valve against accidental
5.2 Heat Source—The hot-gas source shall consist of a
backflow from the torch. The acetylene shall be maintained at
welding torch with suitable storage for acetylene and oxygen,
294.2K(70°F)whenpossible(Note3).Thepurityofacetylene
together with suitable manifolds, flow regulators, and flow and
gas shall conform with Federal Specification BB-A-106a. The
pressure indicators, as shown schematically in Fig. 1.
minimum acetylene content shall be 98%.
NOTE 3—Ifthisisnotpossible,theflowrateshallbecorrectedto294.2
K in accordance with the flow rate specified in 5.2.7.The gas temperature
shall not be allowed to exceed 299 K (79°F) or go below 289 K (61°F).
Flow rates are corrected to 294.2 K because most manufacturers use this
temperature as standard for calibration charts.
5.2.4 Oxygen Storage—A minimum of one oxygen tank
shall be tapped through suitable pressure regulators. The
oxygenshallbemaintainedat294.2Kwhenpossible(Note4).
The purity of oxygen gas shall conform with Federal Specifi-
cation BB-O-925a. The minimum oxygen content shall be
99.5%.
5.2.5 Safety Wall—The acetylene and oxygen storage area
shall be isolated from the torch and the operating area by a
suitable safety wall. For convenience, a two-stage regulator
shallbelocatedinthestoragespaceandasingle-stagepressure
regulator located in the operating area.
5.2.6 Pressure Regulators—The regulators for the oxygen
and the acetylene shall be capable of supplying the flow of
gases specified in 5.2.7.
5.2.7 Flowmeters—The flowmeters for the acetylene and
the oxygen shall be capable of supplying an accurate flow of
gases. Avariation of 65% in gas flow rate due to instrumen-
tation inaccuracies shall be permissible. The total flow rate of
unreactedgasesshallbe6.37standardm /h(294.2K,0.1MPa)
(225standardft /h(70.0°F,14.7psia)),andthevolumeratioof
oxygen to acetylene shall be 1.20, which corresponds to
FIG. 1 Schematic Diagram of Gas System
essentially a neutral (oxygen-free) atmosphere.
4 NOTE 4—Flowmeter and pressure-gage settings are not specified be-
5.2.1 Torch—The torch shall be a Victor Model 315 and
cause they will vary with the size and brand of flowmeter used. Consult
shall be mounted so that the flame can be made to contact the
manufacturers’ instructions and calibration charts that are furnished with
specimen in less than ⁄2 s from the time of actuation.
the flowmeters.
NOTE 1—Both a solenoid-powered mechanism and a hand-operated
5.2.8 Flow-Pressure Gages—Suitable pressure gages shall
system of levers and push rods have been found to be adequate for this
be located at the exit (downstream) side of the flowmeters to
purpose.
monitor metered gas pressure. These gages shall be capable of
5.2.2 Torch Tip—The tip shall be a Victor welding nozzle,
supplying pressure measurements to maintain an accurate flow
Type 4, No. 7, equipped with a water jacket to minimize
of gases in accordance with the specifications stated in 5.2.7.
Fischer-Porter Meter size 4, Fig. 1735, float shape BSVT, equivalent capacity
4 3
Victor Equipment Co., 2800 Airport Rd., Denton, TX 76207. 3.35 standard ft /min air, has been found satisfactory for this purpose.
E285
FIG. 2 Details of Water Jacket for Oxyacetylene Torch
fashion that it can be moved to align and set the distance and
angle (see 8.4 for specifications) between the specimen, or
calorimeter, and the torch tip (Note 7).The back surface of the
specimen shall be unobstructed by the holder for a distance of
25.4 mm (1.00 in.) out from the center of the specimen. Only
materials with a thermal conductivity of 0.2 W/m·K (1.4
Btu·in./h·ft ·°F) or less shall contact the back of the specimen.
The front surface of the specimen shall be unobstructed for a
distance of 48.0 mm (1.89 in.) out from the center of the
specimen. The total area of contact with front and back
2 2
surfaces shall not exceed 52.0 cm (8.06 in. ).
NOTE 6—A lathe bed with the specimen holder mounted on the tool
carriage has been found to be adequate for the purpose. Water cooling of
the holder is recommended to prolong service life.
FIG. 3 Assembly of Water Jacket for Oxyacetylene Torch
5.4 Back-Face Temperature Measurement—The back-face
temperature history shall be measured with a No. 28 AWG
NOTE 5—Pressure gages graduated 0 to 50 psig for oxygen and 0 to 30
gage Chromel-Alumel thermocouple.
psig for acetylene, both in 1-psig increments, have been found to be
suitable.
NOTE 7—For soft specimens, it shall be permissible to attach a thin
copper disk, no larger than 10 mm (0.39 in.) in diameter, to the
5.2.9 Temperature-Measuring Devices—Gas temperatures
thermocouple junction.
shall be measured with thermocouples, thermistors, or other
suitable devices located at
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