The radiation-section furnace tubes of ethylene crackers are critical pressure-bearing components, and their failure results from multiple coupled factors, which single evidence cannot fully explain. This paper proposes a multi-evidence diagnostic framework integrating operating conditions, macroscopic damage, geometry, composition/carburization, microstructural degradation, performance, and fracture. Using bulged HB-101 and fractured HB-106 tubes from SL-series crackers, combined with physicochemical testing and condition analysis, the degradation-to-failure mechanisms are systematically revealed. Localized overheating is identified as the most probable root operational cause, supported by operational records, infrared thermography, and microstructural evidence. Flame deflection likely raised the local metal temperature to approximately 1100 °C or above in the bulged zone, accelerating carburization. Alternative contributing causes are discussed. Carburization and carbide coarsening constitute the main degradation pathway, with grain-boundary carbides transforming from network-chain to coarse blocky forms, reducing the high-temperature creep strength and impact toughness. Base-metal creep bulging results from combined overheating, carburization, and creep, while weld brittle cracking arises from welding defects, carburization embrittlement, and thermal stress. This framework enables full-chain attribution from operational causes to failure, supporting failure analysis and the life-cycle safety management of cracking furnace tubes.

To identify the causes of bulge defects in the shell of the post-cooler (E115) at the top of the deisopentane column in the pre-hydrogenation unit of a continuous catalytic reforming unit of a refining and chemical company, systematic test methods including macroscopic observation, chemical composition analysis, room-temperature mechanical property testing, metallographic analysis, and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) analysis were adopted in this study. The results showed that there were two obvious bulges on the E115 shell, slight corrosion pits on the inner wall, delamination defects inside the steel plate, and uneven thickness of the entire plate. The chemical composition and room-temperature mechanical properties of the shell material met the standard requirements, but the hot-rolled banded ferrite + pearlite structure did not conform to the requirements for steel used in wet hydrogen sulfide environments. The corrosion products on the inner wall were mainly sulfides composed of Fe, O, S, and C. The bulge defects were the result of the coupling effect of two factors: wet hydrogen sulfide corrosion environment and inappropriate material selection. The high content of light sulfides in the pre-hydrogenation feedstock formed a severe wet hydrogen sulfide environment, inducing hydrogen-induced cracking (HIC) and hydrogen blistering. The hot-rolled Q345R steel was prone to hydrogen atom capture by hydrogen traps in this environment, and the high pressure generated by hydrogen accumulation led to bulging and delamination. The research results provide a solid theoretical basis for the safe operation and maintenance, as well as failure prevention and control of similar petrochemical equipment. Meanwhile, this study also clarifies the limitations of conventional characterization methods in quantifying hydrogen diffusion behavior and multi-field coupling failure mechanism, and puts forward prospective research directions such as intelligent risk prediction, multi-dimensional microscopic quantitative characterization, and full life cycle evaluation of equipment, which provides a research framework for in-depth analysis of hydrogen-induced failure of pressure vessel steel in a wet hydrogen sulfide environment.

In the urban underground pipeline network system, when the water supply pipe leaks, the water jet mixed with sediment and so on will impact the nearby gas pipe, which will perforate the gas pipe and trigger gas leakage. In this paper, the causes and preventive measures of PE gas pipe perforation and leakage caused by the impact of water flow are investigated, various factors affecting the damage of PE gas pipe in the process of water impact are analyzed, and the physical model of PE gas pipe subject to erosion and wear is established by combining Finnie’s model and Archard’s wear formula. The process of PE gas pipe being pierced by water flow under specific working conditions is simulated and calculated, and corresponding control measures and suggestions are put forward. This study is of reference significance for the prevention and disposal of similar events and provides strong technical support for subsequent pipeline laying, monitoring, and emergency response.