REG NASA-LLIS-0445--1994 Lessons Learned - O-Rings for Critical Seal Locations - Scout Program.pdf

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1、Lessons Learned Entry: 0445Lesson Info:a71 Lesson Number: 0445a71 Lesson Date: 1994-07-22a71 Submitting Organization: LERCa71 Submitted by: Maria HavenhillSubject: O-Rings for Critical Seal Locations - Scout Program Description of Driving Event: In the time period of 1960-1975, a generic problem was

2、 encountered on several Scout Vehicle components containing elastomer O-Rings. During the Scout Production Procurement, components such as regulators and hydraulic actuators were a source of problems due to leakage after initial acceptance tests. An extensive investigation and long surveillance peri

3、od determined the cause of the leakages to be the O-Ring set.The type of set used was not the well-known permanent set of an elastomer, but rather a much shorter time duration. This was to allow the elastomer to seat in its permanent position in the groove, allow distribution of lubricant, etc. Corr

4、ective action was to allow a time period after component assembly and acceptance testing.Further information can also be obtained by contacting the Reliability and Quality Division of Loral Vought Systems at P.O. Box 650003, Dallas, TX, 75265-0003 or calling (214) 603-1000.Lesson(s) Learned: In crit

5、ical seal locations and/or large number usage, O-Rings should be 100% inspected per MIL-STD-413B to avoid any leakage.Recommendation(s): 1. Apply criteria from MIL-STD-413B regarding inspection and shelf life usage.2. Allow a time period, after assembly, before testing components with dynamic O-Ring

6、s and soft seats to allow for permanent setting to take place.3. Avoid seals made of elastomers which are susceptible to compression set for long term use or Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-storage.Evidence of Recurrence Control Effec

7、tiveness: Fewer problems and failures of components utilizing elastomers.Documents Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): a71 Parts Materials & ProcessesAdditional Info: Approval Info: a71 Approval Date: 1996-09-13a71 Approval Name: Sell Jamesa71 Approval Organization: 501-4a71 Approval Phone Number: 216-433-8618Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-