1、Designation: C 356 03Standard Test Method forLinear Shrinkage of Preformed High-Temperature ThermalInsulation Subjected to Soaking Heat1This standard is issued under the fixed designation C 356; the number immediately following the designation indicates the year oforiginal adoption or, in the case o
2、f revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This test me
3、thod covers the determination of the amountof linear shrinkage and other changes that occur when apreformed thermal insulating material is exposed to soakingheat. This test method is limited to preformed high-temperatureinsulation that is applicable to hot-side temperatures in excessof 200F (93C), w
4、ith the exception of insulating fire brickwhich is covered by Test Method C 210.1.2 The values stated in inch-pound units are to be regardedas the standard. The values given in parentheses are providedfor information only.1.3 This standard does not purport to address all of thesafety concerns, if an
5、y, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:C 168 Terminology Relating to Thermal Insulation2C
6、210 Test Methods for Reheat Change of Insulating Fire-brick3C411 Test Method for Hot Surface Performance of High-Temperature Thermal Insulation23. Terminology3.1 DefinitionsTerminology C 168 shall apply to theterms used in this test method.4. Significance and Use4.1 Linear shrinkage, as used in this
7、 test method, refers tothe change in linear dimensions that has occurred in testspecimens after they have been subjected to soaking heat for aperiod of 24 h and then cooled to room temperature.4.2 Most insulating materials will begin to shrink at somedefinite temperature. Usually the amount of shrin
8、kage in-creases as the temperature of exposure becomes higher. Even-tually a temperature will be reached at which the shrinkagebecomes excessive. With excessive shrinkage, the insulatingmaterial has definitely exceeded its useful temperature limit.When an insulating material is applied to a hot surf
9、ace, theshrinkage will be greatest on the hot face. The differentialshrinkage which results between the hotter and the coolersurfaces often introduces strains and may cause the insulationto warp. High shrinkage may cause excessive warpage andthereby may induce cracking, both of which are undesirable
10、.High shrinkage may also open gaps at the insulation joints toan excessive extent rendering the application less efficient andmore hazardous. In order to predict the limit of permissibleshrinkage in service, the degree of linear shrinkage to betolerated by specimens of an insulating material when su
11、b-jected to soaking heat must be determined from experience.4.3 It is recognized that a fixed relation between linearshrinkage under soaking heat and actual shrinkage in servicecannot be established for different types of insulating materials.Generally the amount of shrinkage increases with time ofe
12、xposure. The amount and rate of increase varies from onematerial to another. In addition, the various types of materialsmay have different amounts of maximum permissible shrink-age. Therefore, each product must define its own specific limitsof linear shrinkage under soaking heat.5. Apparatus5.1 Furn
13、aceA gas-fired or electrically heated muffle fur-nace, having a size sufficient to accommodate at least four testspecimens and two dummy specimens, 6 by 212 by 112 in.(152.4 by 63.5 by 38.1 mm) (Note 1), spaced so as to allow aclearance of at least12 in. (12.7 mm) on all surfaces of everytest specim
14、en. The temperature of the furnace shall be con-trolled throughout the volume occupied by the specimens towithin 6 1 % of the desired temperature. A furnace-temperature indicator or recorder is required.1This test method is under the jurisdiction ofASTM Committee C16 on ThermalInsulation and is the
15、direct responsibility of Subcommittee C16.31 on Chemical andPhysical Properties.Current edition approved May 10, 2003. Published June 2003. Originallyapproved in 1960. Last previous edition approved in 1997 as C 356 87 (1997).2Annual Book of ASTM Standards, Vol 04.06.3Annual Book of ASTM Standards,
16、Vol 15.01.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.NOTE 1If the structure is not homogeneous throughout its thickness,or if thinner materials are under test, the specimen should be testedwithout altering the original thickness
17、. For smaller ovens, unable toaccommodate the required number of specimens, it will be necessary tomake several test batches in order to secure the minimum number ofspecimens required.5.2 OvenA controlled-temperature conditioning ovenwith range up to at least 250F (121C).5.3 Specimen-Measuring Appar
18、atusAn instrument suit-able for measuring a gage length up to 6 in. (152.4 mm), andhaving an accuracy of measurement of 0.002 in. (0.05 mm) orbetter. Care must be taken, by the use of proper measuringtechniques, to ensure reproduction of any measurement towithin 0.01 in. (0.2 mm). It is particularly
19、 important to avoidcrushing the ends of the specimens during measurement,especially in the case of soft materials.NOTE 2Avernier caliper may be used. Reference points, such as pins,inserted near the ends of the specimen, serve to improve reproducibilitywithout specimen damage; or metal strips may be
20、 inserted between thespecimen ends and the jaws of the caliper. Other instruments suggested aredilatometers or comparators. One suitable type of comparator4is equippedwith a fine adjustment. It has a long-range, continuous dial indicator. Thedial is attached to a wide-face (12-in. (12.7-mm) diameter
21、 flat) buttonpoint which is held against the specimen by internal spring pressure. Whenthe point is lifted12 in. (12.7 mm), the pressure is about 50 g,corresponding to a bearing force of 0.6 psi (4.8 kPa), and suitable for verysoft materials. For harder materials, an additional weight of 0.25 lb (0.
22、114kg) may be applied, making the load of the specimen, at12 in. (12.7 mm)compression of the spring, about 1.9 psi (13.1 kPa). Directly beneath thebutton point is another wide-face button point tapped to the base of thecomparator. The comparator is adjustable and requires a set of steelshaftings,12
23、in. (12.7 mm) in diameter, having lengths at 1-in. (25.4-mm)intervals from 1 to 6 in. (25.4 to 152.4 mm), in order to zero thecomparator accurately.5.4 BalanceA balance, having an accuracy of 0.01 g, forweighing the specimen before and after heating.6. Sampling and Preparation of Test Specimens6.1 A
24、ll samples that will be required to complete the testsshall be selected at one time and in such a manner as to berepresentative of the average of the material.6.2 Specimens for any one test condition shall be selectedfrom the original sample lot so as to be as representative aspossible. The specimen
25、s shall be cut or sawed from full-sizepieces in such a manner that they will be fully representative ofthe entire, full-size piece as well as of the material generally.These specimens shall be cut to size 6 by 212 by 112 in. (152.4by 63.5 by 38.1 mm), in such a mannner that the length andwidth are c
26、ut parallel to the length and width, respectively, ofthe original, full-size piece. If it is impossible to faithfullyrepresent the material by cutting to a 112-in. (38.1-mm) thickspecimen, or for thinner pieces, then the original thickness ofthe material should be tested. Rectangular specimens cut f
27、rompipe covering may be used if the material is homogeneous andif the sections are large enough. If the material is nothomogeneous or the sections are not sufficiently large, thencurved or partly curved segments of a cylinder may be used. Inthis case, the specimens shall preferably be cut to an over
28、-allwidth of 212 in. (63.5 mm), with the sides cut parallel ratherthan on a radius.7. Procedure7.1 Select and prepare a minimum of four test specimens asprescribed in Section 6. Weigh the specimens in the as-receivedcondition and dry them to constant weight following applicablespecifications for the
29、 material unless it has been shown that thedimensional stability is not significantly affected by moisturecontent. In the absence of such specifications the specimenshould be dried in an oven or desiccator at a temperature of 215to 250F (102 to 121C) or at a suitable lower temperature ifthese temper
30、atures would be destructive. If specimens aredried, they should be allowed to cool to room temperature andif necessary held in a desiccator before testing. Other condi-tioning procedures may be used only where agreed uponbetween manufacturer and purchaser. After conditioning andbefore any changes in
31、 dimensions occur, determine the lineardimensions. Make at least one measurement of length and twoeach of width and thickness at points marked so that remea-surements can be made at the same points after soaking heat.7.2 Place the measured and weighed specimens in thefurnace, the temperature of whic
32、h shall not exceed 250F(121C). The specimens shall rest on their 6 by 112-in. (152.4by 38.1-mm) edges, supported by at least three supports (suchas small ceramic triangular bars, or cylindrical rods), which inturn shall be supported on a protective plate. The supportingbars or rods shall be large en
33、ough so that the specimens havea clearance of at least12 in. (12.7 mm) above the protectingplate. Arrange the specimens face to face in a group, butseparated at least12 in. (12.7 mm) from each other. Placedummy blocks or other protective means along the sides of thetwo specimens at each end of the g
34、roup, so as to protect thefaces of these two specimens from radiation losses or gainsfrom the inner surfaces of the furnace. This arrangement of thespecimens will allow free access of the heat to all of theirsurfaces.7.3 Apply the source of heat after the specimens have beenarranged in the furnace.
35、The rate of heat supply should be heldconstant, or reasonably so, during the heating-up period. Thisrate should be gaged so that the average rise to the temperatureof test shall not exceed 300F (167C)/h (Notes 3 and 4).During the heating-up period, especially in the initial stages,make frequent obse
36、rvations to note any signs of combustibility,by opening the furnace door momentarily or, if possible,through observation ports. After the furnace has reached thedesired test temperature, maintain soaking-heat conditions fora period of 24 h, and then cut off the supply of heat. When thefurnace has co
37、oled to 200 to 250F (93 to 121C), remove thespecimens and place them directly into a desiccator.NOTE 3It is realized that the actual rate of increase in temperaturewill not be uniform. The temperature will rise rapidly at first, and then willcontinue to rise progressively slower as the final tempera
38、ture is ap-proached. By the statement, “the average rise in temperature shall notexceed 300F (167C)/h,” it is meant, for example, that a final temperatureof 600F (316C) should be reached in not less than 2 h, or in not less than6 h if the test temperature is to be 1800F (982C).NOTE 4 If it is desire
39、d to determine the ability of an insulation to4Model NB-60, manufactured by the Federal Products Corp., 7140 Eddy St.,Providence, RI.C356032withstand sudden, drastic changes in temperature, or thermal shock, aseparate test for this condition shall be specified.7.4 When the specimens have cooled to w
40、ithin 10F (5.5C)of room temperature, remove them from the desiccator andremeasure before any changes can occur. Weigh the specimensand measure their dimensions at the exact points which wereused for determining the original lengths (see 7.1). If anywarpage occurred during the soaking heat, determine
41、 theamount of warpage to the nearest 0.01 in. (0.2 mm) inaccordance with Test Method C411. If the warpage exceeds0.04 in. (1.0 mm), the actual length of the specimen as suchshall not be determined. Instead, determine the apparent lengthof the specimen by measuring the chord connecting the twoedges o
42、f the concave surface of the warped specimen, or bymeasuring the chord connecting the two points of originalmeasurement, as the case may be.7.5 Examine the specimens, and note any visible changesthat may have occurred during the heating.8. Calculations8.1 Linear ShrinkageCalculate the percentage lin
43、ear di-mensional change after soaking heat as follows:S 5 L12 L2!/L1# 3 100 (1)where:S = percentage linear dimensional change upon soakingheat,L1= average length, width, or thickness of specimenbefore soaking heat, in. (or mm), andL2= average length, width, or thickness of specimen aftersoaking heat
44、, in. (or mm).8.2 Apparent Linear ShrinkageCalculate the percentageapparent dimensional change after soaking heat when a speci-men has warped excessively (more than 0.04 in. (1.0 mm) bythe same formula as for linear shrinkage, except that L2shallrepresent the apparent length of the specimen after so
45、akingheat.8.3 Change in WeightCalculate the percent change inweight after soaking heat as follows:C 5 W12 W2!/W1# 3 100 (2)where:C = percentage change in weight after soaking heat,W1= weight of specimen before soaking heat, g, andW2= weight of specimen after soaking heat, g.9. Report9.1 Report the f
46、ollowing information:9.1.1 Conditioning procedure followed,9.1.2 Temperature of test, the time to reach temperature, thetime at temperature, and the time for the temperature to drop100F (55.5C) after the heat is turned off,9.1.3 Linear shrinkage,9.1.4 Warpage, if any,9.1.5 Apparent linear shrinkage,
47、 if the warpage is in excessof 0.04 in. (1 mm),9.1.6 Change in weight,9.1.7 Any visible changes in the material after soaking heat,particularly when the changes are not uniform on all faces, and9.1.8 Any evidence of combustibility which may haveoccurred during the heating period or during soaking he
48、at, suchas flaming, glowing, smoking, smoldering, etc.10. Precision and Bias510.1 BasisFive laboratories tested two products five timeseach for linear shrinkage and weight loss under 24 h heat soakat 1200F (649C).10.2 Intralaboratory Precision:10.2.1 ShrinkageAverage within laboratory standard de-vi
49、ation, s, as a percentage of the mean, x, was 21.6 % forSample I and 6.8 % for Sample II.10.2.2 Weight LossAverage within laboratory standarddeviation, s, as a percentage of the mean, x, was 8.8 % forSample I and 5.3 % for Sample II.10.3 Interlaboratory Precision:10.3.1 ShrinkageAverage interlaboratory standard devia-tion, s, as a percentage of the mean, x, was 27.0 % for SampleI and 10.0 % for Sample II.10.3.2 Weight LossAverage interlaboratory standard de-viation, s, as a percentage of the mean, x, was 12.7 % forSample I
