One difficulty which frequently occurs when calculating „Klöpperböden“ according to DIN 28011 which are subject to corrosion is the UG-32(j) requirement regarding the maximum crown radius. UG-32 states that the “inside crown radius to which an unstayed head is dished shall be not greater than the outside diameter of the skirt of the head”. DIN 28011 determines the crown radius of a newly fabricated “Klöpperboden” to be identical with D0. According to ASME Code Interpretation VIII-1-86-175 this requirement does not only apply to new, but also to corroded heads. Thus this requirement cannot be met by any “Klöpperboden” subject to inside corrosion.
Some calculation programs (e.g. Compress, PV Elite) provide the user with the option to consider or to ignore this interpretation. In the latter case the program will not report any deficiency. Since the calculation form above always uses L = D0 (even if you calculate the corroded condition), please consider that a new Klöpperboden subject to corrosion does not meet DIN 28011. It has to be ordered with a crown radius of D0 - corrosion.
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