Calculated thickness, design thickness, nominal thickness, effective thickness, steel thickness
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Thickness is the most important structural parameter of pressure vessels; it is one of the fundamental conditions that ensure structural strength, structural stiffness, and service life under specified load conditions. Therefore, the various thicknesses that ensure the reliability of pressure vessels are technical requirements strictly specified in the standards. 1 Calculate the thickness: Take the operating pressure into account, and calculate the thickness using the methods and formulas specified in the standards. The external pressure member refers to the minimum thickness required to meet stability requirements. 2 Design thickness: The design thickness is the sum of the calculated thickness and the corrosion allowance; it is the thickness that ensures the container’s strength, stiffness, or stability under specified loading conditions, while also ensuring the prescribed design life. 3 Nominal thickness: The design thickness plus the negative deviation of the steel thickness, rounded up to the specified thickness. It is generally the thickness indicated on the design drawings. 4 Effective thickness: Nominal thickness minus corrosion allowance and negative deviation of steel thickness. The thickness that determines the actual load-carrying capacity of a container is generally used to verify its strength and stability, and it is also the key parameter for determining the maximum allowable operating pressure. 5 Steel thickness: The steel thickness of a pressure vessel shell refers to the thickness of the material actually used to manufacture that shell element, that is, the thickness specified in the material certificate; it is the thickness that determines the technical requirements for the vessel.
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1. The calculated thickness is the minimum required thickness obtained using standard formulas, in order to meet the stability requirements of the component under external pressure conditions. 2. The design thickness is the calculated thickness plus a corrosion margin, to ensure the strength and stability of the container under load and over its design life. 3. The nominal thickness is obtained by adding the negative deviation of the steel thickness to the design thickness and then rounding it according to the specifications. It is usually the thickness indicated on the design drawings. 4. The effective thickness is the nominal thickness minus the corrosion allowance and the negative deviation of the steel thickness; it is crucial for verifying the load-bearing capacity and stability of the container. 5. The steel thickness refers to the actual thickness of the material used to manufacture the pressure vessel shell, as specified in the steel quality certificate. .
Excerpt from: HG/T 20580-2020