1、Designation: E285 08 (Reapproved 2015)Standard Test Method forOxyacetylene Ablation Testing of Thermal InsulationMaterials1This standard is issued under the fixed designation E285; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, th
2、e year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the screening of ablative mate-rials to determine the relative thermal insulation ef
3、fectivenesswhen tested as a flat panel in an environment of a steady flowof hot gas provided by an oxyacetylene burner.1.2 This test method should be used to measure and describethe properties of materials, products, or assemblies in responseto heat and flame under controlled laboratory conditions a
4、ndshould not be used to describe or appraise the fire hazard ofmaterials, products, or assemblies under actual fire conditions.However, results of this test method may be used as elementsof a fire risk assessment which takes into account all of thefactors which are pertinent to an assessment of the
5、fire hazardof a particular end use.1.3 The values stated in SI units are to be regarded as thestandard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and h
6、ealth practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D792 Test Methods for Density and Specific Gravity (Rela-tive Density) of Plastics by Displacement2.2 Federal Standards:3BB-A-106C Acetylene, Technical, DissolvedBB-O-92
7、5A Oxygen, Technical, Gas and Liquid3. Summary of Test Method3.1 Hot combustion gases are directed along the normal tothe specimen until burn-through is achieved. The erosion rateof the material is determined by dividing the original thicknessby the time to burn-through. The insulating effectiveness
8、 isdetermined from back-face temperature measurements. Insula-tion index numbers are computed by dividing the times fortemperature changes of 80, 180, and 380C, from the initialambient temperature, by the original thickness. The insulation-to-density performance is computed by dividing the insulatio
9、nindex by the density of the panel.3.2 The general characteristics of the oxyacetylene heatsource are:3.2.1 Heat Flux835 W/cm2(cold-wall calorimeter).3.2.2 Velocity210 m/s (cold, unreacted gases).3.2.3 Neutral flame conditions.4. Significance and Use4.1 This test method is intended to screen the mos
10、t obviouspoor materials from further consideration. Since the combus-tion gases more closely resemble the environment generated inrocket motors, this test method is more applicable to screeningmaterials for nozzles and motor liners than for aerodynamicheating.4.2 The environment for any specific hig
11、h-temperature ther-mal protection problem is peculiar to that particular applica-tion. The conditions generated by the oxyacetylene heat sourcein this test method represent only one set of conditions; they donot simulate any specific application. Thus, the test resultscannot be used to predict direc
12、tly the behavior of materials forspecific environments, nor can they be used for design pur-poses. However, over a number of years, the test has beenuseful in determining the relative merit of materials, particu-larly in weeding out obviously poor materials from moreadvanced data-generation programs
13、. It has also been consid-ered for use as a production quality-control test for rocketinsulation materials.4.3 The tester is cautioned to use prudence in extending theusefulness of the test method beyond its original intent,namely, screening. For situations having environments widelydifferent from t
14、hose of the test, the user is urged to modify the1This test method is under the jurisdiction of ASTM Committee E21 on SpaceSimulation and Applications of Space Technology and is the direct responsibility ofSubcommittee E21.08 on Thermal Protection.Current edition approved May 1, 2015. Published June
15、 2015. Originallyapproved in 1965 as E285 65T. Last previous edition approved in 2008 asE285 08. DOI: 10.1520/E0285-08R15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, ref
16、er to the standards Document Summary page onthe ASTM website.3Available from Standardization Documents Order Desk, Bldg. 4 Section D, 700Robbins Ave., Philadelphia, PA 19111-5098, Attn: NPODS.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United S
17、tates1oxyacetylene burner conditions to suit his requirements orperhaps change to a different heat-generating device thatprovides better simulation.5. Apparatus5.1 GeneralThe apparatus shall consist of an oxyacety-lene burner, a specimen holder, and means for measuring thetime to burn-through and fo
18、r recording the back-face tempera-ture history of the specimen. Auxiliary apparatus all consist ofa calorimetric device to measure heat-transfer rate as specifiedin 5.5.5.2 Heat SourceThe hot-gas source shall consist of awelding torch with suitable storage for acetylene and oxygen,together with suit
19、able manifolds, flow regulators, and flow andpressure indicators, as shown schematically in Fig. 1.5.2.1 TorchThe torch shall be a Victor Model 3154andshall be mounted so that the flame can be made to contact thespecimen in less than12 s from the time of actuation.NOTE 1Both a solenoid-powered mecha
20、nism and a hand-operatedsystem of levers and push rods have been found to be adequate for thispurpose.5.2.2 Torch TipThe tip shall be a Victor welding nozzle,Type 4, No. 7, equipped with a water jacket to minimizedamage to the tip (Note 2).4Details of the water jacket areshown in Figs. 2 and 3 and t
21、he torch tip is shown in Fig. 4.NOTE 2Proprietary designation cannot be avoided because of thebroad spectrum of heat flux and flame patterns produced by competitivetorch tips of similar size. The Victor torch tip was selected on the basis ofpopularity, reproducibility of test results, and the relati
22、vely high heat fluxit produces.5.2.3 Fuel Storage and ManifoldA minimum of threeacetylene cylinders shall be tapped simultaneously through amanifold and suitable pressure regulators. Cylinders shall bestored in an upright position and held at room temperature forat least 1 h, or until at equilibrium
23、 with room temperature,before using. The complete bank of cylinders shall be changedwhen the gage reads 0.7 MPa (100 psi). Acetylene storagetanks shall be protected by a check valve against accidentalbackflow from the torch. The acetylene shall be maintained at294.2 K (70F) when possible (Note 3). T
24、he purity of acetylenegas shall conform with Federal Specification BB-A-106C. Theminimum acetylene content shall be 98 %.NOTE 3If this is not possible, the flow rate shall be corrected to 294.2K in accordance with the flow rate specified in 5.2.7. The gas temperatureshall not be allowed to exceed 29
25、9 K (79F) or go below 289 K (61F).Flow rates are corrected to 294.2 K because most manufacturers use thistemperature as standard for calibration charts.5.2.4 Oxygen StorageA minimum of one oxygen tankshall be tapped through suitable pressure regulators. Theoxygen shall be maintained at 294.2 K when
26、possible (Note 4).The purity of oxygen gas shall conform with Federal Specifi-cation BB-O-925A. The minimum oxygen content shall be99.5 %.5.2.5 Safety WallThe acetylene and oxygen storage areashall be isolated from the torch and the operating area by asuitable safety wall. For convenience, a two-sta
27、ge regulatorshall be located in the storage space and a single-stage pressureregulator located in the operating area.5.2.6 Pressure RegulatorsThe regulators for the oxygenand the acetylene shall be capable of supplying the flow ofgases specified in 5.2.7.5.2.7 FlowmetersThe flowmeters for the acetyl
28、ene andthe oxygen shall be capable of supplying an accurate flow ofgases.5A variation of 65 % in gas flow rate due to instrumen-tation inaccuracies shall be permissible. The total flow rate ofunreacted gases shall be 6.37 standard m3/h (294.2 K, 0.1 MPa)(225 standard ft3/h (70.0F, 14.7 psia), and th
29、e volume ratio ofoxygen to acetylene shall be 1.20, which corresponds toessentially a neutral (oxygen-free) atmosphere.NOTE 4Flowmeter and pressure-gage settings are not specifiedbecause they will vary with the size and brand of flowmeter used. Consultmanufacturers instructions and calibration chart
30、s that are furnished withthe flowmeters.5.2.8 Flow-Pressure GagesSuitable pressure gages shallbe located at the exit (downstream) side of the flowmeters tomonitor metered gas pressure. These gages shall be capable ofsupplying pressure measurements to maintain an accurate flowof gases in accordance w
31、ith the specifications stated in 5.2.7.NOTE 5Pressure gages graduated 0 to 50 psig for oxygen and 0 to 30psig for acetylene, both in 1-psig increments, have been found to besuitable.5.2.9 Temperature-Measuring DevicesGas temperaturesshall be measured with thermocouples, thermistors, or other4Victor
32、Equipment Co., 2800 Airport Rd., Denton, TX 76207.5Fischer-Porter Meter size 4, Fig. 1735, float shape BSVT, equivalent capacity3.35 standard ft3/min air, has been found satisfactory for this purpose.FIG. 1 Schematic Diagram of Gas SystemE285 08 (2015)2suitable devices located at the exit (downstrea
33、m) side of theflowmeters. Accuracy shall be within 61.0K(61.8 F).5.2.10 Piping, Hoses, and Needle ValvesAny combinationof piping, tubing, hoses, and needle valves may be employedthat have sufficient flow capacity to allow the fuel and oxidantto flow and be controlled at the specified flow rates.5.3
34、Specimen HolderThe specimen and the calorimetershall be supported in a suitable fixture arranged in such afashion that it can be moved to align and set the distance andangle (see 8.4 for specifications) between the specimen, orcalorimeter, and the torch tip (Note 6). The back surface of thespecimen
35、shall be unobstructed by the holder for a distance of25.4 mm (1.00 in.) out from the center of the specimen. Onlymaterials with a thermal conductivity of 0.2 W/mK (1.4Btuin./hft2F) or less shall contact the back of the specimen.The front surface of the specimen shall be unobstructed for adistance of
36、 48.0 mm (1.89 in.) out from the center of thespecimen. The total area of contact with front and backsurfaces shall not exceed 52.0 cm2(8.06 in.2).NOTE 6A lathe bed with the specimen holder mounted on the toolcarriage has been found to be adequate for the purpose. Water cooling ofthe holder is recom
37、mended to prolong service life.5.4 Back-Face Temperature MeasurementThe back-facetemperature history shall be measured with a No. 28 AWGgage Chromel-Alumel thermocouple.NOTE 7For soft specimens, it shall be permissible to attach a thincopper disk, no larger than 10 mm (0.39 in.) in diameter, to thet
38、hermocouple junction.5.4.1 Thermocouple MountingA spring-loaded, two-holeceramic support rod no larger than 3.2 mm (18 in.) in diametershall be used to maintain good contact between the thermo-couple and the back surface of the specimen.5.4.2 Temperature Data RecordingThe thermocouple emfshall be re
39、corded as back-face temperature, in degrees Celsius,as a function of time during the test. The data acquisitionsystem (DAS) shall have a sampling rate of1sorless.Provision shall also be provided to record the starting time ofthe test.5.4.3 Starting SwitchAn electric switch shall be installedon the t
40、orch mechanism to provide a “test start” event signalfor the DAS for the erosion rate measurement.5.5 CalorimeterThe cold wall heat flux of the hot-gassource shall be measured by using a calorimetric device.FIG. 2 Details of Water Jacket for Oxyacetylene TorchFIG. 3 Assembly of Water Jacket for Oxya
41、cetylene TorchE285 08 (2015)35.6 Burn-Through DetectorA device such as a mirror,photocell, or direct visual means shall be used to detectburn-through of the specimen for termination of the test. Ifpossible, this should also be included as an event record on theDAS.5.6.1 TimerThe DAS shall provide ti
42、ming increments of0.1-s, or less, to measure the time to burn-through of thespecimen.6. Test Specimen6.1 The test specimen shall be a square, flat panel 6.35 60.41 mm (0.250 6 0.016 in.) thick.6.2 The dimensions of length and width shall both be 101.6+ 0.0, 0.71 mm (4.000 +0.000, 0.028 in.).6.3 Five
43、 replicates of each type of specimen shall be tested.6.4 The thickness and density of the specimen shall bemeasured before the test.6.4.1 The density shall be measured in accordance with TestMethods D792. If the immersing fluid is known to haveadverse effects on the specimen, the density shall be de
44、ter-mined by a simple weight-to-volume calculation wherein thevolume is determined by scaling the specimen.6.4.2 The thickness at the point of flame impingement shallbe determined with suitable micrometer calipers or equivalent.Reasonable care shall be taken to avoid depressing softspecimens.7. Cali
45、bration7.1 The DAS should be calibrated at frequent intervalsusing known reference voltages. The frequency of calibrationand exact procedure are not given here because of the largevariety of data systems and standard voltage devices on themarket.7.2 The heat flux should be measured at the start of e
46、achtesting day and at any time during testing when there is asuspicion of faulty torch operation, such as an irregularlyshaped flame or an unusual color or noise in the flame. Thetorch tip should be replaced if the heat flux is outside thespecifications listed below.7.2.1 Mount the calorimeter in th
47、e specimen holder andconnect to the DAS. Align the center of the calorimeter withthe center line of the torch (Note 8) and set the correct distancebetween the calorimeter face and the end of the torch tip. Makeheat-flux measurements at on-axis positions of 19.00 and 25.406 0.30 mm (0.748 and 1.000 6
48、 0.012 in.).NOTE 8A metal rod, thin enough to slide into the torch port has beenfound to be suitable for aligning the central axes of the copper cylinder (ofthe calorimeter) and the torch tip. Absolute alignment is difficult becauseof the uncertainty of the exact location of the axis of the hot gas
49、withrespect to the axis of the torch tip. Moreover, since the torch port has avariable inside diameter, the aligning tool cannot be rigidly held in placeto locate the axis. Best results have been obtained by inserting the tool intothe torch port and slowly rotating the tool so that its free end describes acircle. Alignment adjustments are then made until the circle described isconcentric with the copper cylinder of the calorimeter. Special care shouldbe taken to avoid damaging the internal contour of the torch tip with thealigning
