Evaluation of a Failed High-Pressure Gauge Bourdon Tube

A 20,000 psi gauge measuring nitrogen gas pressure failed during testing in late 2025. This gauge was fabricated with a NI-SPAN-C^® Alloy 902 bourdon tube. The glass lens from the front of the gauge was ejected and flew across the room during the failure, causing operator distress, but no physical injuries.

The gauge failed due to a crack that formed on the bourdon tube inner diameter and progressed over time toward the outer diameter. This crack was caused by cyclical loading conditions and progressed in a fatigue manner. When the wall thickness of the bourdon tube was unable to support the internal nitrogen gas pressure, (measured at greater than 20,000 psi for more than 44 seconds during the test failure event), a catastrophic rupture of the bourdon tube wall occurred which then caused the gauge body to become overpressurized rapidly. The instantaneous pressure increase exceeded the capacity of the vent hole in the body to relieve quickly enough, which then allowed the glass to be ejected from its retaining ring on the front of the gauge body.

This gage was at least 15 years old since a label on the gauge indicated it had been cleaned for oxygen service in February 2010. Although the specific cleaning process in 2010 was not determined, a typical cleaning process chemistry was provided.

The goal of this presentation is to document the failure of the bourdon tube and if possible, determine the root cause.

Recommendations for safe gauge usage, as described in ANSI/ASME Specification B40.100 Pressure Gauges and Gauge Attachments, will also be reviewed.