SYMPOSIA PAPER
Published:
01 January 2009
STP48825S
Verification of the ASTM G-124 Purge Equation
SourceASTM 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.
Author Information
Robbins, Katherine, E.
Vanderbilt Univ., Nashville, TN
Davis, Samuel, Eddie
NASA George C. Marshall Space Flight Center, Huntsville, AL
Herald, Stephen, D.
NASA George C. Marshall Space Flight Center, Huntsville, AL
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Details
Developed by Committee: G04
Pages: 68–79
DOI: 10.1520/STP48825S
ISBN-EB: 978-0-8031-8407-7
ISBN-13: 978-0-8031-7508-2