The dimensions of the Class900 long neck flange DN80 are even larger than those of the DN65 version
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These past few days, while checking the dimensions of the Class900 long-neck flange DN80, I found that they are smaller than those of the DN65 version. Checking the errata for May 2012 shows no changes. Moreover, all the dimensions of Class 900 DN80 pipe flanges are smaller than those of DN65. I think this is clearly a mistake; surely the experts responsible for formulating the standards at the Chemical Equipment Center were confused and failed to notice this error. I hope those responsible for publishing books at the Chemical Equipment Center have some sense of responsibility and avoid producing such shoddy books. This is the standard, and it has a tremendous impact.
That’s correct; for CLASS900 flanges, as well as flanges with a diameter of DN80 or less, the design pressure rating is higher than that for flanges with a diameter larger than DN80.
Look at the explanation on the top right side of page 269