3公称通径和钢管外径本标准适用的钢管外径包括A、B两个系列,A系列为国际通用系列(俗称英制管)、B系列为国内沿用系列(俗称公制管)。.其公称通径DN和钢管外径按表3一1规定。表3-1公称通径和钢管外径(mm)公称通径DN101520,253240506580钢管A17.221.326.933.742.448.360.376.188.9外径B1418名323845577689公称通径DN100125150200250300350400450500钢管114.3139.7168.3219.1273323.9355.6406.4457508外径B108133159219273325377426480530公称通径DN600700800900100012001400160018002000钢管A610711813914101612191422162618292032外径B630720820920102012201420162018202020PN25.0MPa(250bar)管法兰适用的钢管外径系列按表3一2规定,表3-2PN25.0MPa(250bar)管法兰适用的钢管外径系列(mm)公称通径DN106580100125150200250A101.6127钢管外径152.4177.8244.5298.5同表3一B102127159180一3