ASTM C421-08 (2020) pdf free.Standard Test Method for Tumbling Friability of Preformed Block-Type and PreformedPipe-Covering-Type Thermal lnsulation.
This test method covers determination of the mass lossof preformed block-type and preformed pipe-covering-typethermal insulation as a result of a combination of abrasion andimpact produced by a laboratory tumbling mechanism.
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.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 appropriate safety,health,and environmental practices and determine the applicability of regulatory limitations prior to use.This international 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 TechnicalBarriers to Trade (TBT) Committee.
Several test methods for measuring mass loss by abrasion and impact of preformed block-type and preformedpipe-covering-type thermal insulation have been used previ-ously. It is believed that no single test method completelycovers all factors involving such forces for different kinds ofmaterials，but this test method is intended to provide aprocedure that gives reproducible results.It is used for comparing the mass loss by tumbling before and after a specifictreatment of the insulation,as agreed upon by the purchaserand the manufacturer.
The precision of this test method is given inTable 1.The difference between successiveresults obtained by the same operator with the same apparatusunder constant operating conditions on identical test materialswould exceed the values given for repeatability in Table 1 onlyin one case in twenty.The difference between two singleand independent results obtained by different operators working in different laboratories on identical material would exceedthe values given for reproducibility in Table 1 only in one casein twenty.No information can be presented on the bias ofthe procedure in this test method because no material having anaccepted reference value is available.ASTM C421 pdf download.