ASTM_C_335_-_C_335M_-_17.pdf

Designation:C335/C335M17Standard Test Method forSteady-State Heat Transfer Properties of Pipe Insulation1This standard is issued under the fixed designation C335/C335M;the number immediately following the designation indicates the yearof 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()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 method covers the measurement of the steady-state heat transfer properties of pipe insulations.Specimentypes include rigid,flexible,and loose fill;homogeneous andnonhomogeneous;isotropic and nonisotropic;circular or non-circular cross section.Measurement of metallic reflectiveinsulation and mass insulations with metal jackets or otherelements of high axial conductance is included;however,additional precautions must be taken and specified specialprocedures must be followed.1.2 The test apparatus for this purpose is a guarded-end orcalibrated-end pipe apparatus.The guarded-end apparatus is aprimary(or absolute)method.The guarded-end method iscomparable,but not identical to ISO 8497.1.3 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard.The values stated ineach system may not be exact equivalents;therefore,eachsystem shall be used independently of the other.Combiningvalues from the two systems may result in non-conformancewith the standard.1.4 When appropriate,or as required by specifications orother test methods,the following thermal transfer propertiesfor the specimen can be calculated from the measured data(see3.2):1.4.1 The pipe insulation lineal thermal resistance andconductance,1.4.2 The pipe insulation lineal thermal transference,1.4.3 The surface areal resistance and heat transfercoefficient,1.4.4 The thermal resistivity and conductivity,1.4.5 The areal thermal resistance and conductance,and1.4.6 The areal thermal transference.NOTE1In this test method the preferred resistance,conductance,andtransference are the lineal values computed for a unit length of pipe.Thesemust not be confused with the corresponding areal properties computed ona unit area basis which are more applicable to flat slab geometry.If theseareal properties are computed,the area used in their computation must bereported.NOTE2Discussions of the appropriateness of these properties toparticular specimens or materials may be found in Test Method C177,TestMethod C518,and in the literature(1).21.5 This test method allows for operation over a wide rangeof temperatures.The upper and lower limit of the pipe surfacetemperature is determined by the maximum and minimumservice temperature of the specimen or of the materials used inconstructing the apparatus.In any case,the apparatus must beoperated such that the temperature difference between theexposed surface and the ambient is sufficiently large enough toprovide the precision of measurement desired.Normally theapparatus is operated in closely controlled still air ambientfrom 15 to 30C,but other temperatures,other gases,and othervelocities are acceptable.It is also acceptable to control theouter specimen surface temperature by the use of a heated orcooled outer sheath or blanket or by the use of an additionaluniform layer of insulation.1.6 The use any size or shape of test pipe is allowableprovided that it matches the specimens to be tested.Normallythe test method is used with circular pipes;however,its use ispermitted with pipes or ducts of noncircular cross section(square,rectangular,hexagonal,etc.).One common size usedfor interlaboratory comparison is a pipe with a circular crosssection of 88.9-mm diameter(standard nominal 80-mm 3-in.pipe size),although several other sizes are reported in theliterature(2-4).1.7 The test method applies only to test pipes with ahorizontal or vertical axis.For the horizontal axis,the literatureincludes using the guarded-end,the calibrated,and thecalibrated-end cap methods.For the vertical axis,no experi-ence has been found to support the use of the calibrated orcalibrated-end methods.Therefore the method is restricted tousing the guarded-end pipe apparatus for vertical axis mea-surements.1.8 This test method covers two distinctly different types ofpipe apparatus,the guarded-end and the calibrated or1This test method is under the jurisdiction ofASTM Committee C16 on ThermalInsulation and is the direct responsibility of Subcommittee C16.30 on ThermalMeasurement.Current edition approved May 1,2017.Published October 2017.Originallyapproved in 1954.Last previous edition approved in 2010 as C335/C335M 101.DOI:10.1520/C0335_C0335M-17.2The boldface numbers in parentheses refer to the references at the end of thistest method.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesThis international standard was develo