Flange Tables

February 16, 2023

Online slide rule & Data sheets. Click here for our online flange slide rule.
‘DN’ originates from the term ‘Diameter Nominale’. It’s a rough translation of mm for imperial sizes. It assumes that an inch is 25mm (which it’s not, it’s 25.4mm). For example a 10” flange is referred to as a 250mm in lieu of 254mm.
Even the ANSI imperial system is itself not exact in terms of bore size, hence it is termed ‘nominal bore’ as each class has a different bore. Note: metric ANSI equivalents are not different. However, metric AS equivalents of BS can differ slightly in bolt hole size to accommodate metric bolts.
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