REG NASA-LLIS-0217-1992 Lessons Learned - Galileo Retro Propulsion Module Oxidizer Leak During Loading.pdf

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1、Lessons Learned Entry: 0217Lesson Info:a71 Lesson Number: 0217a71 Lesson Date: 1992-11-18a71 Submitting Organization: JPLa71 Submitted by: B. J. WagonerSubject: Galileo Retro Propulsion Module Oxidizer Leak During Loading Abstract: During propellant loading operations for the Galileo retro propulsio

2、n module prior to launch, an oxidizer loading flex line developed a small leak. The leak was caused by an electrostatic charge generated by the flow of the non-conductive oxidizer through the teflon flex line, discharging to the wire mesh covering.Investigate the suitability of using flex lines not

3、susceptible to this type of failure. Verify that electrostatic buildup can be controlled or contained. Consider using new flex lines when hazardous loading operations are performed. Determine maximum flow rates that will prevent electrostatic discharges. Description of Driving Event: During final pr

4、opellant loading operations for the Galileo retro propulsion module in preparations for launch at Kennedy Space Center, an oxidizer loading flex line developed a small leak. No damage to the spacecraft (protected by plastic) or to personnel (protected by scape suits) occurred from the highly toxic,

5、volatile nitrogen tetroxide oxidizer dripping and vaporizing from the line.Microscopic examination of the flex line leak area revealed that the leak was caused by an electrostatic charge generated by the flow of the non-conductive oxidizer through the teflon flex line, discharging to the wire mesh c

6、overing. Initial damage may have been caused by carbonized tracks in the teflon line developed during the line cleaning process.Approved procedures for cleaning, proof and leak testing had been performed on the flex line prior to use in the loading process. This particular line was approximately twe

7、lve years old.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Additional Keyword(s): ESDReference(s): PFR #54310Lesson(s) Learned: Even if a propellant loading flex line has successfully passed proof and leak tests, a leak can develop when oxidizer i

8、s flowing through it, as a result of electrostatic discharge through the wall of the line.Recommendation(s): 1. Investigate the suitability of using flex lines not susceptible to this type of failure (i.e. stainless steel bellows).2. Re-examine the loading procedures to minimize the failure mode, an

9、d verify by testing that electrostatic buildup can be controlled or contained.3. Consider using new flex lines when hazardous loading operations are performed.4. Investigate the physics of this failure type and determine maximum flow rates that will prevent, by a conservative margin, electrostatic d

10、ischarges for each combination of non-conducting fluid through non-conducting tubes used in spaceflight operations.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): a71 Hazardous/Toxic Waste/Materialsa71 Launch Proce

11、ssa71 Parts Materials & ProcessesAdditional Info: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Approval Info: a71 Approval Date: 1990-03-19a71 Approval Name: Carol Dumaina71 Approval Organization: 125-204a71 Approval Phone Number: 818-354-8242Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-