同心异径管 偏心异径管 高压异径管 Concentric Reducer Eccentric Reducer High-pressure Reducer 碳钢异径管 /CS Reducer 公称通径 Nominal Diameter 坡口处外径 Outside Diameter 端面至端面的距离 End to End D1*D2 DN NPS A 系列 B 系列 H 20×15 3/4 ×1/2 26.9 ×21.3 25×18 38 20×10 3/4 ×3/8 26.9 ×17.3 25×14 38 25×20 1×3/4 33.7 ×26.9 32×25 51 25×15 1×1/2 33.7 ×21.3 32×18 51 32×25 1.1/4 ×1 42.4 ×33.7 38×32 51 32×20 1.1/4 ×3/4 42.4 ×26.9 38×25 51 32×15 1.1