1、Designation: C356 17Standard Test Method forLinear Shrinkage of Preformed High-Temperature ThermalInsulation Subjected to Soaking Heat1This standard is issued under the fixed designation C356; the number immediately following the designation indicates the year oforiginal adoption or, in the case of
2、revision, the 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.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope1.1 This test
3、method 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 150F (66C),
4、 with the exception of insulating fire brickwhich is covered by Test Method C210.1.2 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.3
5、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 health practices and determine the applica-bility of regulatory limitations prior to use.1.4 This internatio
6、nal standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Commit
7、tee.2. Referenced Documents2.1 ASTM Standards:2C168 Terminology Relating to Thermal InsulationC210 Test Method for Reheat Change of Insulating FirebrickC411 Test Method for Hot-Surface Performance of High-Temperature Thermal Insulation3. Terminology3.1 DefinitionsTerminology C168 shall apply to the
8、termsused in this test method.4. Significance and Use4.1 Linear shrinkage, as used in this 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 insulati
9、ng materials will begin to shrink at somedefinite temperature. Usually the amount of shrinkage 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
10、exceeded its useful temperature limit.When an insulating material is applied to a hot surface, 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
11、 may cause excessive warpage andthereby may induce cracking, both of which are undesirable.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, th
12、e degree of linear shrinkage to betolerated by specimens of an insulating material when sub-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 differe
13、nt types of insulating materials.Generally the amount of shrinkage increases with time ofexposure. 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
14、 define its own specific limitsof linear shrinkage under soaking heat.5. Apparatus5.1 FurnaceA gas-fired or electrically heated mufflefurnace, having a size sufficient to accommodate at least four1This test method is under the jurisdiction ofASTM Committee C16 on ThermalInsulation and is the direct
15、responsibility of Subcommittee C16.31 on Chemical andPhysical Properties.Current edition approved May 1, 2017. Published June 2017. Originallyapproved in 1960. Last previous edition approved in 2010 as C356 10. DOI:10.1520/C0356-17.2For referenced ASTM standards, visit the ASTM website, www.astm.org
16、, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis internation
17、al standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee
18、.1test specimens 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 specimen. The temperature of the furnace shall be con-trolled throughout the volume occupied by the specimens to
19、within 6 1 % of the desired temperature. A furnace-temperature indicator or recorder is required.NOTE 1If the structure is not homogeneous throughout its thickness,or if thinner materials are under test, then test the specimen at the originalthickness. For smaller ovens, unable to accommodate the re
20、quired numberof specimens, it will be necessary to make several test batches in order tosecure the minimum number of specimens required.5.2 OvenAcontrolled-temperature conditioning oven withrange up to at least 250F (121C).5.3 Specimen-Measuring ApparatusAn instrument suit-able for measuring a gauge
21、 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 important to avoidcrushing the ends of the spec
22、imens during measurement,especially in the case of soft materials.NOTE 2Reference points, such as pins, inserted near the ends of thespecimen, serve to improve reproducibility without specimen damage; orit is acceptable to insert metal strips may be inserted between the specimenends and the jaws of
23、the caliper. Suggested instruments are dilatometers,vernier caliper, or comparators. One suitable type of comparator isequipped with a fine adjustment. It has a long-range, continuous dialindicator. The dial is attached to a wide-face (12-in. (12.7-mm) diameterflat) button point which is held agains
24、t the specimen by internal springpressure. When the point is lifted12 in. (12.7 mm), the pressure is about50 g, corresponding to a bearing force of 0.6 psi (4.8 kPa), and suitable forvery soft materials. For harder materials, an additional weight of 0.25 lb(0.114 kg) may be applied, making the load
25、of the specimen, at12 in. (12.7mm) compression of the spring, about 1.9 psi (13.1 kPa). Directly beneaththe button point is another wide-face button point tapped to the base of thecomparator. The comparator is adjustable and requires a set of steelshaftings,12 in. (12.7 mm) in diameter, having lengt
26、hs at 1-in. (25.4-mm)intervals from 1 to 6 in. (25.4 to 152.4 mm), to zero the comparatoraccurately.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 All samples that will be required to complete the
27、 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 specimens shall be cut or sawed from full-sizepieces in
28、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 manner that the length andwidth are cut parallel to the length and width, respectively
29、, 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 shall be tested. Rectangular specimens cut frompipe covering shall be used if the material is
30、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 shall be used. Inthis case, the specimens shall preferably be cut to an over-allwidth of 212 in. (63.5 mm), with the sides
31、 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 material unless it has been shown that thedim
32、ensional stability is not significantly affected by moisturecontent. In the absence of such specifications, dry the specimenin an oven or desiccator at a temperature of 215 to 250F (102to 121C) or at a suitable lower temperature if these tempera-tures would be destructive. If specimens are dried, al
33、lowspecimens to cool to room temperature and if necessary held ina desiccator before testing. Other conditioning procedures areacceptable only where agreed upon between manufacturer andpurchaser. After conditioning and before any changes indimensions occur, determine the linear dimensions. Make atle
34、ast one measurement of length and two each of width andthickness at points marked so that remeasurements can bemade at the same points after soaking heat.7.2 Place the measured and weighed specimens in thefurnace, the temperature of which shall not exceed 250F(121C). The specimens shall rest on thei
35、r 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 enough so that the specimens havea clearance of at least12 in. (1
36、2.7 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 group, so as to protect thefaces of these two specimens from rad
37、iation 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. The rate of heat supply shall becontrolled so that the average
38、rise to the temperature of testshall not exceed 300F (167C)/h (Notes 3 and 4). During theheating-up period, especially in the initial stages, make fre-quent observations to note any signs of combustibility, byopening the furnace door momentarily or, if possible, throughobservation ports.After the fu
39、rnace has reached the desired testtemperature, maintain soaking-heat conditions for a period of24 h, and then cut off the supply of heat. When the furnace hascooled to 200 to 250F (93 to 121C), remove the specimensand place them directly into a desiccator.NOTE 3It is realized that the actual rate of
40、 increase in temperature willnot be uniform. The temperature will rise rapidly at first, and then willcontinue to rise progressively slower as the final temperature is ap-proached. By the statement, “the average rise in temperature shall notexceed 300F (167C)/h,” it is meant, for example, that a fin
41、al temperatureC356 172of 600F (316C) needs to be reached in not less than 2 h, or in not lessthan6hifthetest temperature is to be 1800F (982C).NOTE 4 If it is desired to determine the ability of an insulation towithstand sudden, drastic changes in temperature, or thermal shock, aseparate test for th
42、is condition shall be specified.7.4 When the specimens have cooled to within 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 lengt
43、hs (see 7.1). If anywarpage occurred during the soaking heat, determine 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
44、 lengthof the specimen by measuring the chord connecting the twoedges of the concave surface of the warped specimen, or bymeasuring the chord connecting the two points of originalmeasurement.7.5 Examine the specimens, and note any visible changesthat have occurred during the heating.8. Calculations8
45、.1 Linear ShrinkageCalculate the percentage linear di-mensional change after soaking heat as follows:S 5 L12 L2!/L1# 3100 (1)where:S = percentage linear dimensional change upon soakingheat,L1= average length, width, or thickness of specimen beforesoaking heat, in. (or mm), andL2= average length, wid
46、th, or thickness of specimen aftersoaking heat, 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 L2shallrepresen
47、t the apparent length of the specimen after soakingheat.8.3 Change in WeightCalculate the percent change inweight after soaking heat as follows:C 5 W12 W2!/W1# 3100 (2)where:C = percentage change in weight after soaking heat,W1= weight of specimen before soaking heat, g, andW2= weight of specimen af
48、ter soaking heat, g.9. Report9.1 Report the following 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 in length
49、, width, and thickness,9.1.4 Warpage, if any,9.1.5 Apparent linear shrinkage, 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 that occurred duringthe heating period or during soaking heat, such as flaming,glowing, smoking, smoldering, etc.10. Precision and Bias310.1 BasisFive laboratories tested two products five timeseach for linear shrinkage and wei
