Stiffness in pressure vessels
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When designing pressure vessels, if stiffness needs to be calculated, what conditions must the stiffness meet? What conditions need to be met to be considered compliant? ? I asked for advice! ! !
The so-called stiffness should be reflected in the acceptance of the wall thickness, I guess. In GB150, there are formulas for film stress, and our formula for calculating wall thickness is also based on such film stress, using the allowable stress of the steel material. In practice, some stiffness values may be determined through practical experience; of course, calculations should also be used to ensure economic and rational use of materials. For example, the bending modulus of commonly used steel sections is one of the necessary calculation parameters.
When the wall thickness requirements are met, the container is too large; reinforcement plates need to be added to it, and then it is necessary to check whether the stiffness meets the requirements. So how should this calculation be carried out?
The stiffness of pressure vessels is generally reflected in the yield strength ratio of the material. Materials used for pressure vessels are required to not only have a high yield limit but also a certain yield strength ratio (σs/σb). The yield strength ratio reflects a material’s ability to withstand external loads; the lower this ratio, the higher the reliability of structural components. In the event of overload, plastic deformation occurs, which increases the strength of the metal material and prevents immediate failure.
The stiffness of pressure vessels under internal pressure is calculated using an external pressure of 0.1 MPa. If you think the stiffness of your design is not sufficient, you can certainly refer to standards or empirical values for the external pressure value; 0.1 seems to be the value specified in ASME
Regarding the stiffness of girders in engineering applications, it is usual to verify that the bending normal stress σ ≤ [σ], the shear stress at the supports γ ≤ [σ], the deflection at the mid-span f ≤ a fixed value, and the relative deflection L/[ ] ≤ 1/250. For pressure vessels subjected to external pressures, it is necessary to ensure that the allowable external pressure stress [P] ≥ P.
In GB150, 3.5.6 specifies the minimum thickness of the shell after processing, excluding any corrosion allowance: a) for carbon steel and low-alloy steel containers, it shall be not less than 3 mm; b) for high-alloy steel containers, it shall be not less than 2 mm. Is this a requirement related to stiffness?
What is mentioned on the 7th floor refers to the stiffness requirements
Additionally, there are large horizontal vessels with very low pressure; they have large diameters and lengths, and their wall thicknesses cannot be too thin – this can also be considered a stiffness issue
For internal pressure, it must meet the requirements of clause GB1503.5.6; for external pressure, hypothetical calculations shall be carried out in accordance with page 29 of GB150, and the results must satisfy the values specified in the tables
The requirements specified in GB1503.5.6 are merely minimum values; such regulations do not take specific circumstances into account. It’s best to have a reasonable calculation method