SYMPOSIA PAPER Published: 01 January 2006
STP37660S

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

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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.

Author Information

Waller, JM
Honeywell Technology Solutions Inc., NASA Johnson Space Center White Sands Test Facility, Las Cruces, NM
Murray, KA
United Space Alliance, NASA Kennedy Space Center, Cape Canaveral, FL
Staveland, AR
United Space Alliance, NASA Kennedy Space Center, Cape Canaveral, FL
Faughnan, PD
NASA-Kennedy Space Center, FL
Tyre, D
United Space Alliance, NASA Kennedy Space Center, Cape Canaveral, FL
Smith, SR
Honeywell Technology Solutions Inc., NASA Johnson Space Center White Sands Test Facility, Las Cruces, NM
Gallus, T
Honeywell Technology Solutions Inc., NASA Johnson Space Center White Sands Test Facility, Las Cruces, NM
Newton, BE
Wendell Hull & Associates, Inc., Las Cruces, NM
Hshieh, F-Y
Honeywell Technology Solutions Inc., NASA Johnson Space Center White Sands Test Facility, Las Cruces, NM
Beeson, HD
NASA Johnson Space Center White Sands Test Facility, Las Cruces, NM
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Details
Developed by Committee: G04
Pages: 286–297
DOI: 10.1520/STP37660S
ISBN-EB: 978-0-8031-5513-8
ISBN-13: 978-0-8031-3405-8