Non-destructive evaluation and characterisation of high-temperature hydrogen attack in carbon steel pressure vessels

A non-destructive testing approach capable of evaluating high-temperature hydrogen attack (HTHA) in pressure vessels made of carbon steel is presented. The approach, involving non-collinear wave mixing of ultrasonic waves, is applied to a test sample extracted from a retired pressure vessel exposed to hydrogen. Results show that the non-linear ultrasonic approach is capable of detecting and assessing HTHA damage through the thickness of the pressure vessels. The method only requires access to the vessels' outside surface, which makes it very attractive for field inspections.