Predicting petrochemical reactor wall degradation using hydrogen-saturated samples

Predicting the failure-free operation of petrochemical reactors is an important task that ensures the safe functioning of the petrochemical industry, but in the case of deformation-free brittle failure, it is impossible to make an adequate forecast based on the results of regulated technical control. One of the sources of such failure is hydrogen embrittlement. To solve the problem of forecasting without producing large-sized cuttings from the walls of the equipment, a comparison was made of the mechanical properties of samples cut from the walls of a destroyed petrochemical reactor after long-term operation and samples made from a sheet of the same steel grade and saturated by the cathodic polarization method to the same concentration that was measured in the walls of the studied reactor. The thickness of the sheet metal from which the walls were made was equal to the thickness of the sheet from which the model samples were made. The samples were cut along and across the rolling direction. A comparative study of the behavior of identical model and «operational» samples was conducted, taking into account the development of operational damage, the direction of cutting out standardized samples for mechanical isothermal tests, and the time of sample curing after hydrogenation. A regulated calculation of the residual life of the reactor was carried out based on the mechanical characteristics of the samples cut out from it. A fundamental difference in the mechanical characteristics of the model and «operational» samples was found. The strength and yield strengths of the model samples do not change, while those cut out of the reactor are 30% less than the original ones. This difference does not allow using the saturation of model samples by the cathodic polarization method to predict hydrogen degradation of steel elements of petrochemical equipment. The insufficiency of the regulated non-destructive testing methods in technical diagnostics is shown, since they do not take into account the possibility of forming deformation-free hydrogen cracking of the equipment walls. It is shown that the methodology for the regulated calculation of the residual service life carried out during the examination, both on the basis of the actual strength properties of samples cut from the equipment in operation and using the mechanical characteristics of model hydrogenated samples cut in different directions relative to the rolling direction, requires revision.

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