一般来说,管子的直径可分为外径,内径,公称直径.1.无缝钢管外径用字母D来表示,其后附加外直径尺寸和壁厚.例如外径为108mm的无缝钢管,壁厚为5mm,用D108*5表示.2.镀锌钢管采用DN表示.3.在设计图纸中所以要用公称直径,目的是为了根据公称直径可以确定管子,管件,阀门,法兰,垫片等结构尺寸,公称尺寸用DN表示,如果在设计图纸中采用外径表示,也应该作出管道规格对照表,表明某种管道的公称直径,壁厚.世界各国应用的标准体系虽然多,大体可分成两大类,即大外径系列和小外径系列.大外径系列:(DN---公称直径.￠---外径)DN15---￠22mm.DN20---￠27mm.DN25---￠34mm.DN32---￠42mm.DN40---￠48mm.DN50---￠60mm.DN65---￠76(73)mm.DN80---￠89mm.DN100---￠114mm.DN125---￠140mm.DN150---￠168mm.DN200---￠219mm.DN250---￠273mm.DN300---￠324mm.DN350---￠360mm.DN400---￠406mm.DN450---￠457mm.DN500---￠508mm.DN600---￠610mm.小外径系列:DN15---￠18mm.DN20---￠25mm.DN25---￠32mm.DN32---￠38mm.DN40---￠45mm.DN50---￠57mm.DN65---￠73mm.DN80---￠89mm.DN100---￠108mm.DN125---￠133mm.DN150---￠159mm.DN200---￠219mm.DN250---￠273mm.DN300---￠325mm.DN350---￠377mm.DN400---￠426mm.DN450---￠480mm.DN500---￠530mm.DN600---￠630mm.一般标准钢管都可从材料表中查得每米重量.要是非标准钢管可通过量得实际尺寸来计算其重量.重量=(外径-壁厚)*壁厚*π*长度*7.85重量单位---吨.其于单位---米.钢管公称直径（英寸与毫米对照表1）外径壁厚重量英寸毫米.单位毫米.英寸.公斤/米.磅/英尺.1/8”10.310S1.240.0490.280.191/8”10.3STD-401.730.0680.370.251/8”10.3XS-802.410.0950.480.321/4”13.710S1.650.0650.500.341/4”13.7STD-402.240.0880.640.431/4”13.7XS-803.020.1190.810.553/8”17.110S1.650.0650.640.433/8”17.1STD-402.310.0910.850.573/8”17.1XS-803.200.1261.110.751/2”21.35S1.050.0420.530.361/2”21.310S2.110.0831.010.681/2”21.3STD-402.770.1091.280.861/2”21.3XS-803.730.1471.631.101/2”21.31604.780.1881.971.331/2”21.3XXS7.470.2942.571.733/4”26.75S1.650.0651.030.693/4”26.710S2.110.0831.290.873/4”26.7STD-402.870.1131.701.143/4”26.7XS-803.910.1542.221.493/4”26.71605.560.2192.931.973/4”26.7XXS7.820.3083.682.481”33.45S1.650.0651.310.881”33.410S2.770.1092.121.421”33.4STD-403.380.1332.531.701”33.4XS-804.550.1793.272.181”33.41606.350.2504.282.881”33.4XXS9.090.3585.513.7111/4”42.25S1.650.0651.671.1211/4”42.210S2.770.1092.721.8311/4”42.2STD-403.560.1403.432.3111/4”42.2XS-804.850.1914.513.0311/4”42.21606.350.2505.673.8111/4”42.2XXS9.700.3827.855.2811/2”48.35S1.650.0651.921.2911/2”48.310S2.770.1093.142.1111/2”48.3STD-403.680.1454.092.7511/2”48.3XS-805.080.2005.473.6811/2”48.31607.140.2817.324.9211/2”48.3XXS10.150.4009.656.492”60.35S1.650.0652.411.622”60.32.110.0833.062.062”60.310S2.770.1093.972.672”60.33.180.1254.523.042”60.3STD-403.910.1545.493.692”60.3XS-805.540.2187.565.082”60.31608.740.34411.237.552”60.3XXS11.070.43613.589.1321/2”73.05S2.110.0833.732.5121/2”73.010S3.050.1205.323.5721/2”73.0304.780.1888.125.4621/2”73.0STD-405.160.2038.725.8621/2”73.0XS-807.010.27611.527.7421/2”73.01609.530.37515.0810.1421/2”73.0XXS14.020.55220.6013.843”88.95S2.110.0834.563.073”88.92.770.1095.954.003”88.910S3.050.1206.524.383”88.93.180.1256.794.563”88.93.580.1417.615.123”88.93.960.1568.385.633”88.9STD-405.490.21611.417.673”88.9XS-807.620.30015.4310.373”88.916011.130.43821.5614.493”88.9XXS15.240.60027.9618.7931/2”101.65S2.110.0835.233.5231/2”101.610S3.050.1207.495.0331/2”101.6304.780.18811.537.7531/2”101.6STD-405.740.22613.719.2131/2”101.6XS-808.080.31818.8312.654...
