ASTM E285-80(1996)e1
(Test Method)Standard Test Method for Oxyacetylene Ablation Testing of Thermal Insulation Materials
Standard Test Method for Oxyacetylene Ablation Testing of Thermal Insulation Materials
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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e1
Designation: E 285 – 80 (Reapproved 1996)
Standard Test Method for
Oxyacetylene Ablation Testing of Thermal Insulation
Materials
This standard is issued under the fixed designation E 285; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Section 12 was added editorially in May 1996.
1. Scope of the material is determined by dividing the original thickness
by the time to burn-through. The insulating effectiveness is
1.1 This test method covers the screening of ablative mate-
determined from back-face temperature measurements. Insula-
rials to determine the relative thermal insulation effectiveness
tion index numbers are computed by dividing the times for
when tested as a flat panel in an environment of a steady flow
temperature changes of 80, 180, and 380°C, from the initial
of hot gas provided by an oxyacetylene burner.
ambient temperature, by the original thickness. The insulation-
1.2 This test method should be used to measure and describe
to-density performance is computed by dividing the insulation
the properties of materials, products, or assemblies in response
index by the density of the panel.
to heat and flame under controlled laboratory conditions and
3.2 The general characteristics of the oxyacetylene heat
should not be used to describe or appraise the fire hazard of
source are:
materials, products, or assemblies under actual fire conditions.
3.2.1 Heat Flux—835 W/cm (cold-wall calorimeter).
However, results of this test method may be used as elements
3.2.2 Velocity—210 m/s (cold, unreacted gases).
of a fire risk assessment which takes into account all of the
3.2.3 Neutral flame conditions.
factors which are pertinent to an assessment of the fire hazard
of a particular end use.
4. Significance and Use
1.3 This standard does not purport to address all of the
4.1 This test method is intended to screen the most obvious
safety concerns, if any, associated with its use. It is the
poor materials from further consideration. Since the combus-
responsibility of the user of this standard to establish appro-
tion gases more closely resemble the environment generated in
priate safety and health practices and determine the applica-
rocket motors, this test method is more applicable to screening
bility of regulatory limitations prior to use.
materials for nozzles and motor liners than for aerodynamic
1.4 The values stated in SI units are to be regarded as the
heating.
standard.
4.2 The environment for any specific high-temperature ther-
2. Referenced Documents mal protection problem is peculiar to that particular applica-
tion. The conditions generated by the oxyacetylene heat source
2.1 ASTM Standards:
in this test method represent only one set of conditions; they do
D 792 Test Methods for Density and Specific Gravity (Rela-
2 not simulate any specific application. Thus, the test results
tive Density) of Plastics by Displacement
cannot be used to predict directly the behavior of materials for
2.2 Federal Standards:
specific environments, nor can they be used for design pur-
BB-A-106a Acetylene, Technical, Dissolved
poses. However, over a number of years, the test has been
BB-O-925a Oxygen, Technical, Gas and Liquid
useful in determining the relative merit of materials, particu-
3. Summary of Test Method
larly in weeding out obviously poor materials from more
advanced data-generation programs. It has also been consid-
3.1 Hot combustion gases are directed along the normal to
ered for use as a production quality-control test for rocket
the specimen until burn-through is achieved. The erosion rate
insulation materials.
4.3 The tester is cautioned to use prudence in extending the
This test method is under the jurisdiction of ASTM Committee E-21 on Space
usefulness of the test method beyond its original intent,
Simulation and Applications of Space Technology and is the direct responsibility of
Subcommittee E21.08 on Thermal Protection. namely, screening. For situations having environments widely
Current edition approved Dec. 8, 1980. Published February 1981. Originally
different from those of the test, the user is urged to modify the
published as E 285 – 65T. Last previous edition E 285 – 70.
oxyacetylene burner conditions to suit his requirements or
Annual Book of ASTM Standards, Vol 08.01.
perhaps change to a different heat-generating device that
Available from Standardization Documents Order Desk, Bldg. 4 Section D, 700
Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
E 285
provides better simulation. 5.2.3 Fuel Storage and Manifold—A minimum of three
acetylene cylinders shall be tapped simultaneously through a
5. Apparatus
manifold and suitable pressure regulators. Cylinders shall be
5.1 General—The apparatus shall consist of an oxyacety- stored in an upright position and held at room temperature for
at least 1 h, or until at equilibrium with room temperature,
lene burner, a specimen holder, and means for measuring the
time to burn-through and for recording the back-face tempera- before using. The complete bank of cylinders shall be changed
when the gage reads 0.7 MPa (100 psi). Acetylene storage
ture history of the specimen. Auxiliary apparatus all consist of
a calorimetric device to measure heat-transfer rate as specified tanks shall be protected by a check valve against accidental
backflow from the torch. The acetylene shall be maintained at
in 5.5.
5.2 Heat Source—The hot-gas source shall consist of a 294.2 K (70°F) when possible (Note 3). The purity of acetylene
gas shall conform with Federal Specification BB-A-106a. The
welding torch with suitable storage for acetylene and oxygen,
together with suitable manifolds, flow regulators, and flow and minimum acetylene content shall be 98 %.
pressure indicators, as shown schematically in Fig. 1.
NOTE 3—If this is not possible, the flow rate shall be corrected to 294.2
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
oxygen shall be maintained at 294.2 K when possible (Note 4).
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
shall be located in the storage space and a single-stage pressure
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. A variation of 65 % in gas flow rate due to instrumen-
tation inaccuracies shall be permissible. The total flow rate of
unreacted gases shall be 6.37 standard m /h (294.2 K, 0.1 MPa)
(225 standard ft /h (70.0°F, 14.7 psia)), and the volume ratio of
oxygen to acetylene shall be 1.20, which corresponds to
FIG. 1 Schematic Diagram of Gas System
essentially a neutral (oxygen-free) atmosphere.
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
manufacturers’ instructions and calibration charts that are furnished with
shall be mounted so that the flame can be made to contact the
1 the flowmeters.
specimen in less than ⁄2 s from the time of actuation.
5.2.8 Flow-Pressure Gages—Suitable pressure gages shall
NOTE 1—Both a solenoid-powered mechanism and a hand-operated
be located at the exit (downstream) side of the flowmeters to
system of levers and push rods have been found to be adequate for this
monitor metered gas pressure. These gages shall be capable of
purpose.
supplying pressure measurements to maintain an accurate flow
5.2.2 Torch Tip—The tip shall be a Victor welding nozzle,
of gases in accordance with the specifications stated in 5.2.7.
Type 4, No. 7, equipped with a water jacket to minimize
damage to the tip (Note 2). Details of the water jacket are
NOTE 5—Pressure gages graduated 0 to 50 psig for oxygen and 0 to 30
psig for acetylene, both in 1-psig increments, have been found to be
shown in Figs. 2 and 3 and the torch tip is shown in Fig. 4.
suitable.
NOTE 2—Proprietary designation cannot be avoided because of the
5.2.9 Temperature-Measuring Devices—Gas temperatures
broad spectrum of heat flux and flame patterns produced by competitive
shall be measured with thermocouples, thermistors, or other
torch tips of similar size. The Victor torch tip was selected on the basis of
popularity, reproducibility of test results, and the relatively high heat flux
suitable devices located at the exit (downstream) side of the
it produces.
flowmeters. Accuracy shall be within 61.0K(61.8 F).
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.
E 285
FIG. 2 Details of Water Jacket for Oxyacetylene Torch
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.
5.4 Back-Face Temperature Measurement—The back-face
temperature history shall be measured with a No. 28 AWG
gage Chromel-Alumel thermocouple.
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
thermocouple junction.
5.4.1 Thermocouple Mounting—A spring-loaded, two-hole
FIG. 3 Assembly of Water Jacket for Oxyacetylene Torch
ceramic support rod no larger than 3.2 mm ( ⁄8 in.) in diameter
5.2.10 Piping, Hoses, and Needle Valves—Any combina- shall be used to maintain good contact between the thermo-
tion of piping, tubing, hoses, and needle valves may be couple and the back surface of the specimen.
employed that have sufficient flow capacity to allow the fuel 5.4.2 Temperatu
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