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    An Interlaboratory Comparison of the ASTM C 335 Pipe Insulation Test

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    An interlaboratory round-robin test program has been conducted for comparison of results from the ASTM Test for Thermal Conductivity of Pipe Insulation (C 335-69). Two specimens of glass fiber pipe insulation have been tested over a range of mean temperatures of approximately 50 to 150°C (120 to 300°F). Data from the nine laboratories reporting tests on one specimen show good agreement with an overall expected error of ± 4.2 percent. During the 71/2-year test period, the specimen shows some degradation due to handling as is evident from a loss in weight and from a trend toward a slightly higher conductivity in repeat tests conducted by two laboratories. If this specimen change is considered, it is evident that the test error is approximately ± 3 percent.

    Tests on the second specimen have been limited to fewer laboratories, but similar results are evident. The general conclusion is that good agreement is obtained for the temperature range investigated. It would be desirable, however, to have a standard specimen which could be used up to the temperature limit of the apparatus and which could stand the repeated handling and temperature exposures without change.


    insulation, pipe, thermal coductivity, interlaboratory comparison, round-robin, glass fiber, thermal measurements

    Author Information:

    Hollingsworth, M
    Scientist, Owens-Corning Fiberglas Corp., Granville, Ohio

    Committee/Subcommittee: C16.30

    DOI: 10.1520/STP35735S