How is the inch value converted to nominal diameter in millimeters?
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I work for an oil refining company, where the diameter of pipes is indicated using the nominal diameter DN. Occasionally, inches are also used as a unit of measurement; 4 inches corresponds to DN100, 2 inches to DN50, and 3 inches to DN80. Could any expert out there tell me how to make these conversions?
It needs to be rounded off, in accordance with the standard.
Go and check the American standards ASME B36.10M or ASME B36.19M; they contain relevant information. 1/4\"~12\", the outer diameter requires lookup in a table ； For 14\" and above, you can simply multiply by 25.4 mm; thus, the outer diameter for 14\" is 14*25.4=355.6 mm, and for 20\" it is 20*25.4=508 mm.
There is no direct conversion formula; the nominal diameter sizes in metric and imperial systems are different, and only a rough correspondence exists.
Generally, the nominal diameter DN/25 corresponds to its inch value
One inch is 25.4 mm