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The design service life is determined by the design unit based on the expected service life of the container. The expected service life of the container is specified in writing by the client who commissioned the design to the design agency. The design service life of pressure vessels shall be specified in the design drawings. The design service life of pressure vessels is not identical to their actual service life. Users of pressure vessels shall conduct regular inspections and grading of the vessels in accordance with the requirements of the current regulations, namely the \"Technical Regulations for Safety Inspection of Fixed Pressure Vessels\" TSG21-2016. When the operating conditions of the container change, the corrosion rate should be re-evaluated based on actual measurement data to determine the new service life of the container. For vessels with periodic variations in operating temperature or pressure, the number of cycles of such temperature or pressure changes during the design life shall be specified in the design drawings. The design service life of containers should comply with the following requirements: (1) Thick-walled hydrogenation reactors made of chromium-molybdenum steel or high-alloy steel with a nominal thickness of ≥50 mm: not less than 30 years; (2) Other reactors, columns with a diameter of ≥4 m, or a weight of ≥100 t, or a total height of ≥60 m, high-pressure heat exchanger shells, containers with a nominal thickness of ≥50 mm, and spherical storage tanks: not less than 20 years; (3) Other columns, containers, heat exchanger shells, and tube banks: not less than 15 years.