What is the difference between Class 1 and Class 2 vessels under ASME Section VIII-2, \"Other Rules for the Construction of Pressure Vessels\"?

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This post was last edited by WallaceLee on 2022-8-9 at 14:18. Version 2017 of ASME Section VIII – 2, \"Additional Rules for the Construction of Pressure Vessels,\" introduced the concepts of Class 1 and Class 2 vessels: In summary, the differences between these two classes lie in four aspects: design stress strength, design rules, load combination scenarios when using elastoplastic methods, and the documentation required for design and manufacturing. I. Design stress intensity: For various yield ratio conditions, for the same material at the same temperature, the design stress intensity of Category 2 containers shown in Tables 5A/5B is greater than that of Category 1 containers shown in Tables 2A/2B. For containers designed using the same design rules, Class 2 containers have thinner calculated wall thicknesses than Class 1 containers, resulting in higher material utilization. II. According to Section 4.1.1.5 of the design codes ASME VIII – 2 (2017 edition), for Class 1 vessels, analytical design as described in Chapter 5 cannot replace the design based on the rules in Chapter 4; for Class 2 vessels, as in the 2015 edition, analytical design may be used, and the wall thickness can be less than that specified in the rule-based design, but it must still be greater than the minimum value required by Section 4.1.2 plus an allowance for corrosion. III. Load condition combinations when using the elastoplastic method: The difference between the two types of containers lies in the value of the load coefficient β. When using the elastoplastic method for verification, since the load coefficient is related to the design coefficient of the minimum tensile strength, the load coefficients for the design and test conditions of the two types of containers are different. IV. Documentation required for design and manufacture: For Category 1 containers designed in accordance with the rules in Chapter 4, when fatigue analysis is waived, there is no need for a registered professional engineer to certify the user’s design documentation or the manufacturer’s design report. For Category 1 containers designed using the analysis methods outlined in Chapter 5, when fatigue analysis is waived, there is no need for a registered professional engineer to certify the user’s design documentation, but the manufacturer’s design report must be certified. The above four points are a brief summary of the differences between the two types of vessels as specified in ASME Section VIII-2, \"Additional Rules for the Construction of Pressure Vessels.\" Please feel free to add or discuss any other differences. :D