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The furnace tubes of the cycle hydrogen heater in a petrochemical company’s high-pressure hydrogenation unit have accumulated 140,000 hours of operation, far exceeding the designed service life of 100,000 hours. To assess its remaining service life, the enterprise conducts on-site inspections and sample analyses, and combines chemical composition, microstructural analysis, and mechanical property tests to make a comprehensive assessment of the condition of the furnace tubes. The results show that the minimum wall thickness of the straight section of the furnace tube is 10 mm, with no significant thinning ； Both penetrant testing and ultrasonic testing of the welds revealed no defects, and it was rated as grade 1 acceptable ； The fracture surface from the room temperature impact test showed characteristics of ductile fracture, indicating that the material retained good toughness ； Through high-temperature endurance strength tests at 620°C, the remaining service life was further estimated, providing a basis for formulating a scientific replacement plan. In another case, a chemical plant conducted an analytical examination of the tubes in a methane-to-hydrogen conversion reactor that had been in use for over 6 years and operated at a temperature of 910°C. It was found that although there were no bulges or cracks on the surface, an oxide chromium layer and chromium-depleted regions at the grain boundaries had formed on the inner wall ； A large number of fine carbides and early \"creep voids\" are present in the microstructure” ； Although there are no visible abnormalities, the material has begun to degrade, with an estimated remaining lifespan of about 2 years. In addition, several hydrogen and methanol production facilities have adopted digital high-frequency eddy current testing systems such as LEOSCAN, which enable the scanning of hundreds of furnace tubes during operation within 2 days, allowing each tube to be inspected in 2 minutes ； The sensitivity allows for the detection of internal wall cracks as small as 0.3 mm.