1、Lessons Learned Entry: 0066Lesson Info:a71 Lesson Number: 0066a71 Lesson Date: 1992-03-26a71 Submitting Organization: KSCa71 Submitted by: David PenningtonSubject: Dewar Vent Plumbing Description of Driving Event: A liquid helium dewar used to service payload experiments ruptured and damaged ceiling
2、 tiles and a copy machine. In order to service the payload experiments, the dewar converts normal liquid helium to superfluid helium. During this process, air was ingested into the vent line through a valve stem. The ingested air froze, forming a solid blockage. The failure analysis of the liquid he
3、lium dewar revealed that 4 of the 8 valves used in the system were not designed for use in vacuum systems.Lesson(s) Learned: Oxygen frozen in the vent line of the liquid helium dewar caused the dewar to become overpressurized and rupture.Recommendation(s): Ensure all dewars are designed and fitted w
4、ith valves designed to be used in systems utilizing vacuum pressures during operation.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Mission Directorate(s): N/AAddition
5、al Key Phrase(s): a71 Cryogenic Systemsa71 Packaging Handling StorageAdditional Info: Approval Info: a71 Approval Date: 1994-06-02a71 Approval Name: James G. Klinea71 Approval Organization: KSC/HEIa71 Approval Phone Number: 407-867-7614Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
