STP1479

    Proactive Mitigation of PCTFE-Related Ignition Hazards in Oxygen Systems: II. Testing of Inventoried “At-Risk” PCTFE Parts and Hazard Analyses of Corresponding Ground Service Equipment at the Kennedy Space Center

    Published: Jan 2006


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    Abstract

    Revelations of excessive property variation in polychlorotrifluoroethylene (PCTFE) semifin- ished and finished parts led to concerns that leaks or part failure could occur in service, possibly leading to catastrophic component or system failure by flow friction and/or kindling chain mechanisms. Such concerns led to the issuances of an internal Kennedy Space Center (KSC) Problem Advisory and a Government-Industry Data Exchange Program Materials Advisory on PCTFE. The advisories led to an engineering analysis review of PCTFE-containing ground support equipment used in “at-risk” high-pressure oxygen and air systems at KSC. Representative PCTFE replacement parts used in “at-risk” systems were removed from inventory and tested. Tests included determination of (1) dimensional stability by thermomechanical analysis and metrology, (2) percent crystallinity by specific gravity, and (3) the effect of annealing on engineering tolerances. While dimensional instability was determined not to be a major issue in existing inventories, establishing traceability back to the semifinished article (starting rod or sheet stock) was often not possible. Percent crystallinity varied widely depending on part origin and thickness. Annealing was found to lead occasionally to out-of-tolerance parts. The pneumatic impact ignition threshold of PCTFE in enriched air was also determined at pressures up to 41.4 MPa. Results show that ignition does not occur at ambient oxygen concentrations. Last, hazard analyses were performed on “at-risk” systems. Two problematic designs were discovered, but based on operational histories, a recommendation was made to redesign or repair and replace on a noninterference basis.

    Keywords:

    PCTFE, polychlorotrifluoroethylene, problem advisory, high-pressure gaseous oxygen systems, hazard analysis, flow friction, kindling chain


    Author Information:

    Waller, JM
    Materials Scientist, Honeywell Technology Solutions Inc., NASA Johnson Space Center White Sands Test Facility, Las Cruces, NM

    Murray, KA
    Engineers, United Space Alliance, NASA Kennedy Space Center, Cape Canaveral, FL

    Staveland, AR
    Engineering Specialist, United Space Alliance, NASA Kennedy Space Center, Cape Canaveral, FL

    Faughnan, PD
    Materials Engineer, NASA-Kennedy Space Center, FL

    Tyre, D
    Engineers, United Space Alliance, NASA Kennedy Space Center, Cape Canaveral, FL

    Smith, SR
    Mechanical Engineers, Honeywell Technology Solutions Inc., NASA Johnson Space Center White Sands Test Facility, Las Cruces, NM

    Gallus, T
    Mechanical Engineers, Honeywell Technology Solutions Inc., NASA Johnson Space Center White Sands Test Facility, Las Cruces, NM

    Newton, BE
    Engineer, Wendell Hull & Associates, Inc., Las Cruces, NM

    Hshieh, F-Y
    Special Projects Scientist, Honeywell Technology Solutions Inc., NASA Johnson Space Center White Sands Test Facility, Las Cruces, NM

    Beeson, HD
    Office Chief, NASA Johnson Space Center White Sands Test Facility, Las Cruces, NM


    Paper ID: STP37660S

    Committee/Subcommittee: G04.01

    DOI: 10.1520/STP37660S


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