(Received 20 November 2008; accepted 19 August 2009)
Published Online: 11 September 2009
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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.
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
Stock #: JAI102240