Reliability Enhancement in Nondestructive Evaluation: Development of Practical Rules for Vacuum Type Helium Leak Tests
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- 作者：T. Gurunathan ; A. Noorul Haq
- 关键词：Global leakage rate ; Response time ; Spurious signals ; Dummy envelope ; Nitrogen blanket ; Diffusivity
- 刊名：Journal of Nondestructive Evaluation
- 出版年：2017
- 出版时间：March 2017
- 年：2017
- 卷：36
- 期：1
- 全文大小：
- 刊物类别：Engineering
- 刊物主题：Structural Mechanics; Characterization and Evaluation of Materials; Vibration, Dynamical Systems, Control; Classical Mechanics;
- 出版者：Springer US
- ISSN：1573-4862
- 卷排序：36
文摘
In helium leak testing, reliability is an important factor and while attempting to improve this, lot of challenges are being faced. There are contributors for bringing in variations in leak meter readings obtained during system sensitivity check and actual leak test which ultimately affect the final measured leakage rate of test object and they need to be controlled for obtaining reliable results. Response times of leaks are affected by vacuum side volumes, contaminations in vacuum side, leaked gas travel path restrictions on vacuum side and nature of actual leak paths and their gas flow impedances. Hence, actual consideration of real responses of leaks is to be practiced for a reliable test. The traditional concept of using estimate for percentage helium concentration in test hoods is modified by a novel method for its exact determination which improves reliability in tests. Also, practical rules are derived for the reliable identification of leak locations from response time concept. Spurious indications caused by leaks in temporary test rig joints or due to leaks from joints or passages not in the scope of test are other impediments for a reliable test. The response of system changes instantly by spurious indications and hence they require elimination by adopting innovative methods.