Mechanism Analysis Of Hydrogen Blisters And Research On Its Preventive Measures In Wet H₂S Environment

With the application of large and complicated petrochemical equipment and a large number of high sulfur high acid crude oil of refining, safety problems of the equipment that caused by hydrogen damage become more and more serious. The corrosion and protection of equipment has been the important subject in petrochemical enterprise.So the mechanism analysis of hydrogen blisters in the equipment and research on its preventive measures is of great significance.Firstly, this paper take dry gas desulfurization absorption tower inside hydrogen blister and low gas tank outside hydrogen blister as the research object. The causes of blisters were investigated by means of macroscopic examication,chemical composition analysis, metallographic examines, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) and mechanical property test and combined with the equipment operation condition.The results showed that the hydrogen sulfide concentration in the medium and S, P content in the steel are high, while there are a lot of MnS inclusions,mezzanine and banded structure are the main reasons for the formation of hydrogen blister.Electrochemical hydrogen charging device and measurement of the released hydrogen device were set up.Hydrogen diffusion regularity of 20g material and the influence of hydrogen on material mechanics behavior were researched.The results showed that hydrogen in the steel induced decline of strength and plasticity with the increase of hydrogen, but the yield strength does not decrease significantly.When charging current and time reached to a certain extent, the diffused hydrogen content in the steel no longer increased, the hydrogen atoms formed hydrogen molecules at some defects such as inclusions.With the increase of hydrogen concentration,the hydrogen damage degree of steel becomes serious.The fracture mechanism is changed at the edge of tensile fracture surface after hydrogen charging, the fracture mode was changed from ductile fracture to brittle fracture.But the center of tensile fracture surface is still the same as the uncharged sample.the fracture morphology were characteristic of ductile dimple fracture pattern.The diameter and depth of ductile dimple were smaller than uncharged hydrogen sample.but the number of ductile dimple was increased,which means that the loss of plastic properties was increased.On the basis of engineering case analysis, experimental study and the hydrogen blister forming mechanism, the engineering method and the suggestions of hydrogen blisters repaired welding and protective measures were provided.The chemical plating technology was used to modify the performance of the material surface of the equipment.The results showed that the Ni-P alloy plating have good preventive effect for the hydrogen blisters.