Verification of the ASTM G-124 Purge Equation

    Volume 6, Issue 10 (November 2009)

    ISSN: 1546-962X

    CODEN: JAIOAD

    Published Online: 11 September 2009

    Page Count: 9


    Robbins, Katherine E.
    Student Researcher, Dept. of Mathematics, Vanderbilt Univ., Nashville, TN

    Davis, Samuel Eddie
    Materials Engineer, Materials Combustion Research Facility, Materials Test Branch, NASA George C. Marshall Space Flight Center, Huntsville, AL

    Herald, Stephen D.
    Test Group Lead Engineer, InfoPro Corporation, Materials Test Branch, Materials Combustion Research Facility, NASA George C. Marshall Space Flight Center, Huntsville, AL

    (Received 20 November 2008; accepted 19 August 2009)

    Abstract

    ASTM G-124 seeks to evaluate combustion characteristics of metals in high-purity (>99 %) oxygen atmospheres. ASTM G-124 provides the following equation to determine the minimum number of purges required to reach this level of purity in a test chamber: n = −4/log10(Pa/Ph), where n is the total number of purge cycles required, Ph is the absolute pressure used for the purge on each cycle, and Pa is the atmospheric pressure or the vent pressure. The origin of this equation is not known and has been the source of frequent questions as to its accuracy and reliability. This paper provides the derivation of the G-124 purge equation, and experimentally explores the equation to determine if it accurately predicts the number of cycles required.


    Paper ID: JAI102240

    DOI: 10.1520/JAI102240

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    Author
    Title Verification of the ASTM G-124 Purge Equation
    Symposium Twelfth International Symposium on Flammability and Sensitivity of Materials in Oxygen-Enriched Atmospheres, 2009-10-09
    Committee G04