Toward Risk-based Inspection of Hydrogen Technologies: a Methodology for the Calculation of the Damage Factor of Hydrogen Embrittlement

Abstract

Hydrogen is considered a promising energy carrier to achieve the ambitious target of a zero-emission society in the forthcoming years. Despite its environmental advantages, hydrogen-induced material damages represent a serious safety concern. Hence, inspection and maintenance activities must be performed to guarantee the equipment's integrity. The risk-based inspection (RBI) is the most beneficial methodology for inspection planning but has never been adopted for components operating in hydrogen environments. The probability of failure of each piece of equipment is quantified through the definition of the damage factor, a parameter that accounts for the damage mechanism likely to occur. Hydrogen embrittlement (HE) is the main active degrading mechanism in equipment exposed to hydrogenated environments; if not appropriately accounted for, it can cause failures at unexpectedly low stress levels. This study aims to bridge a gap in knowledge by proposing a qualitative methodology to assess the degradation of equipment operating in hydrogenated environments and potentially subjected to HE. The environmental severity is estimated based on the operating conditions, while the material’s susceptibility depends on microstructure, strength, and adoption of post-weld heat treatments. This study could set the basis for the application of the RBI methodology to industrial equipment for producing, handling, and storing hydrogen. Hence, it will facilitate the inspection and maintenance of emerging hydrogen technologies.