Important Information – Disclaimer to the Pressure Vessel Calculator:
The information, calculations, specifications and opinions provided here are for general purposes only and are not intended to constitute professional advice or recommendation of any kind. Outokumpu do not through this calculation tool, document, or discussion related to it, obtain, imply or undertake any liability, warranty or undertaking of any kind.
The aim of this calculation tool is to demonstrate the advantage of using higher strength stainless steels when building pressure vessels. Hence the calculation is conceptual and does not include all parameters and requirements needed to calculate, construct and design a pressure vessel.
The thickness calculation is only based on internal pressure of a cylindrical shell. The equations differ slighly between the different design standards which has been considered here. However, the difference is minor, and the required thickness is essentially calculated as the product of internal pressure and shell radius divided by the product of allowable design stress and joint factor. In addition, for carbon steel vessels you often add a corrosion allowance.
Depending on entered design temperature, applicable material specification or design standard dictates which alloys can be selected for the calculation.
The joint factor is set by the extent of non-destructive testing applied to the welds. For a complete inspection a joint factor of 1 is selected, and with less inspection, a lower value according to the prevailing design standard.
For EN 13445, mechanical properties of hot rolled strip listed in EN 10028-7:2016 for stainless steels are used to estimate the required thickness. The implication of using hot rolled strip values for the calculations is that the allowable design stresses are overestimated by up to 15% for thicker vessels requiring quarto plate, typically above 8-10 mm. Correspondingly, they are underestimated by up to 10% for thinner vessels, e.g., for water heater cylinders, where cold rolled strip is used, typically applicable up to 6 mm.
For ASME Section VIII Division 1 and Division 2, allowable stresses are taken directly from ASME Section II Part D: 2023 (interpolation allowed). Forta LDX 2404 is approved according to Division 1 (Code Case 2780-1). Division 2 (Class 2) allows significantly higher stresses than Division 1. Not all alloys are approved according to Division 2. Sanicro®35 is approved to both Division 1 and 2 according to Code Case 2982-1. Note, maximum applicability temperature is rounded down to nearest fifties, for e.g., duplex stainless steel normally 316°C, here limited to 300°C. For some of the alloys, the mechanical properties vary with the thickness, and has been considered. For carbon steel, up to 60-65 mm thick plates.
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