REG NASA-LLIS-3097-2010 Lessons Learned - Impurities in Propellant-Grade Ammonia Can Lead to Corrosion and Poor Hardware Performance.pdf

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1、Public Lessons Learned Entry: 3097Lesson Info:Lesson Number: 3097Lesson Date: 2010-05-18Submitting Organization: KSC Submitted by: Annette PittSubject: Impurities in Propellant-Grade Ammonia Can Lead to Corrosion and Poor Hardware Performance Abstract: Leaks in the Space Shuttle ammonia boiler syste

2、m, as well as a single instance of a boiler shutdown during postflight operation, led to a review of the materials and processes used in the ammonia boiler. Failure analysis was performed and concluded that the corrosion was caused by high levels of chloride in the procured ammonia and that the shut

3、down was due to high levels of polyethylene oxide (PEO) in the propellant-grade ammonia. Since the switch to higher-purity, technical-grade ammonia, there have been no ammonia boiler leaks or shutdowns.Description of Driving Event: From 1990 to 1998 there have been three incidents of corrosion-induc

4、ed leaks in the boiler, one leak that was expedited by corrosion, and a single case of boiler shutdown.Lesson(s) Learned: High levels of chlorides in propellant-grade ammonia attack the base metal of the boiler (347 stainless steel) and initiate pitting corrosion. Moisture provides the required elec

5、trolyte to support the corrosion process. In addition, the propellant-grade ammonia had higher levels of other contaminants, specifically polyethylene oxide (PEO). The PEO is a plasticizer that can clog heat exchanger passages, significantly reducing performance.Recommendation(s): Ensure compatibili

6、ty of the components and materials as part of the engineering process. Procure technical-grade ammonia for flight hardware use. Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: Ammonia Boiler Flush PresentationClick here to download communication document. Mission Direct

7、orate(s): Space OperationsAdditional Key Phrase(s): 1.Environmental Control and Life Support Systems1.Engineering design and project processes and standards1.Long term sustainability and maintenance planningAdditional Info: Project: Space Shuttle ProgramApproval Info: Approval Date: 2010-08-26 Approval Name: mbell Approval Organization: HQProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-