Eddy Current Testing of COPVs

Project OverviewAn Eddy Current scanner has been developed that rapidly inspects composite overwrapped metallic pressure vessels liners and thin wall metallic pressure vessels for small external and internal surface cracks. Flaws detection sensitivity is greater than any other inspection method currently available.

RelevanceFlaw detection in metallic liners used in Composite Overwrapped Pressure Vessels (COPVs) has been a major problem, especially considering the trend toward thinner liners. Flaws can grow with vessel pressure cycling causing leakage or possible vessel rupture. To preclude this, the liner must be inspected prior to wrapping. The industry has used florescent dye penetrants to inspect for flaws, however this is time consuming, subject to human error, and lacks the necessary sensitivity and consistency for critical flaws in thin vessels. Furthermore, dye penetrant cannot be used to inspect the liner after wrapping when autofrettage can grow flaws.

OutcomeFollowing fabrication of an internal eddy current probe, numerous scans were recorded to determine the sensitivity of the system. The system was able to detect flaws as shallow as 0.006” with widths as narrow as 0.003”. The team is currently working to acquire test articles containing even narrower flaws in order to push the limits of the system. Key members of the test team include NASA Project Manager Regor Saulsberry, operators and experimenters Ralph Lucero, Kyle Carver, Charles Nichols, Paul Spencer, and NASA graduate student Dan Wentzel who is the internal probe designer.

External and Internal Eddy Current System Internal Eddy Current Attachment Low Resolution Internal Survey Scan

Zoom View of Indications from the Survey Scan Shown Above

Internal Attachment Scanning a Specialized Flanged Test Article

External Application of an Eddy Current Probe