REG NASA-LLIS-4218-2011 Lessons Learned - Component Leak Check Methods.pdf

1、Public Lessons Learned Entry: 4218 Lesson Info: Lesson Number: 4218 Lesson Date: 2010-06-17 Submitting Organization: KSC Submitted by: Annette Pitt Subject: Component Leak Check Methods Abstract: Component and system leakage measurement techniques should be optimized to provide consistent leak check

2、 data accurate enough to verify acceptability of the component and system in the most cost efficient manor possible. Description of Driving Event: The flow meter leak check methods used to perform Quick Disconnect (QD) interface integrity verifications were found to be less that adequate to verify t

3、he acceptability of the hardware under test. Lesson(s) Learned: When dealing with a component in a semi-closed cavity a very accurate leak check can be performed by purging the cavity with air or nitrogen at a known flow rate, establishing a stable background, pressurizing the component with helium

4、and using a mass spectrometer to measure the change in the helium concentration within the purged cavity. The change in helium concentration can be used in conjunction with the purge effluent flow rate to derive a very accurate leak rate down to the 1 standard cubic inches per minute (SCIM) range. T

5、he accuracy of this type of leak check can be verified by introducing helium into the purged cavity at known flow rates close to the component spec requirement level and verifying the concentrations delta measured by the mass spectrometer corresponds correctly with the value expected for the injecte

6、d helium. Recommendation(s): When performing leak checks of components in semi closed or closed cavities consider using this type of leak check. If the component interface is purged during operations and is sampled by a Hazardous Gas Detection System mass spec to provide real time data on the health

7、 of the component/interface during operations then try and use the already existing purge and sampling capabilities to perform the leak checks. Evidence of Recurrence Control Effectiveness: N/A Documents Related to Lesson: Lesson learned 3177 Development and Evolution of the Main Propulsion Helium S

8、ignature Test Lessons Learned Entry 4256 Development of the Current Mass Spectrometer Requirements and Techniques Mission Directorate(s): Space Operations Additional Key Phrase(s): Systems Engineering and Analysis - Level II/III requirements definition Test & Verification Ground Operations Parts, Ma

9、terials, & Processes Additional Info: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Project: Space Shuttle Program Approval Info: Approval Date: 2011-12-09 Approval Name: mbell Approval Organization: HQ Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-