Are the minimum required thickness and effective thickness the same concept?
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Is the minimum required thickness in the boiler strength calculation sheet the same as the effective thickness in the pressure pipeline strength calculation sheet?
Minimum required thickness and effective thickness are not the same concept. The minimum required thickness refers to the smallest amount of material needed for a component to meet requirements such as strength, stiffness, and stability, whereas the effective thickness typically denotes the usable thickness of the material after taking into account factors such as corrosion and wear. In the calculation documents for boilers and pressure pipelines, although both of these parameters are related to the material thickness, they focus on different aspects and their calculation methods may vary. .
The calculation formulas are all thickness + C1 + C2
Yes, in the calculations for boiler strength and pressure pipeline strength, the commonly used formula involves the thickness required for calculation plus additional thicknesses C1 and C2. Among them, C1 usually represents the corrosion margin, while C2 may represent the allowable thinning during welding or manufacturing processes or other factors. This method of calculation is intended to ensure the safety and reliability of components in actual use. In this way, the final value obtained is the total thickness of the material required. .
In fact, it’s the same everywhere: Minimum required thickness: the smallest thickness necessary for the equipment to function properly; calculation method: δ = calculated thickness + corrosion allowance + machining loss + material negative deviation. Effective thickness: the nominal thickness minus the corrosion allowance and negative deviation. Generally, the effective thickness is ≥ the minimum required thickness.
This post was last edited by zfeir on 2025-2-12 08:28. The minimum required thickness is the safety critical wall thickness calculated based on the allowable stress； The effective thickness is the actual wall thickness in use, which is determined based on the actual thickness of the selected material, after deducting the corrosion allowance, machining allowance, and the allowable dimensional tolerances of the material. When the effective thickness is less than the minimum required thickness, the calculation determines it to be unsafe.
The minimum required thickness refers to the smallest material thickness needed for boiler components (such as the drum, furnace shell, tube sheet, etc.) under specific conditions of pressure, temperature, corrosion margin, etc. It is different from the concept of effective thickness in pressure pipelines and pressure vessels, as the effective thickness is greater than or equal to the minimum required thickness.