Hydrogen attack in a welded reactor

Reactors for hydrocracking and hydrotreating are exposed to high hydrogen p ressures at elevated temperature. The critical failure mechanism in these v essels is hydrogen attack, i.e. chemically-driven damage accumulation leadi ng to intergranular failure. These rectors are typically manufactured by ci rcumferential welding of forged belts made of 2.25Cr-1Mo steel, and the ass ociated microstructural changes make these weldments especially suspectible to hydrogen attack. This paper summarizes a recently developed model that links the chemistry of hydrogen attack with the mechanical behavior through a damage model. This model is then incorporated into a finite element mode l and used to calculate the deformation and damage evolution, stress distri bution and failure time of a welded reactor under internal hydrogen pressur e.