2弯管壁厚校核
2.1计算公式
根据《压力管道规范-工业管道 第3部分:设计和计算 》(GB/T20801.3-2006)6.2规定:
内压弯管的计算厚度(位于?2处,最危险处)应按式(4)计算: tw?PDo?????Ej????2????PY?I??????t (4)
当计算弯管的内侧厚度时: I?4?RDo??1 (5)
4?RDo??2当计算弯管的外侧厚度时:
I?4?RDo??1 (6)
4?RDo??2式中 tw—弯管(内、外侧)的计算厚度(mm);
; ?—弯管的转角(度)
I—计算系数;
R—弯管在管子中心线处的弯曲半径(mm);
2.2弯曲半径
根据《工业金属管道工程施工及验收规范》(GB50235-97)中规定:高压钢管的弯曲半径大于管子外径的5倍,其他管子的弯曲半径宜大于管子外径的3.5倍。对于一些在工厂内加工的弯管,最小可以
使R=1.5Do,而在一般情况下R≥3Do,故在计算中选用R=1.5Do和R=3Do两种情况,因为只要这两种情况下的设计壁厚可以符合要求,其他情况下的设计壁厚就都是符合要求的。
2.3常用弯管的设计厚度
设计压钢管外公称钢管规格力径壁厚P(MPa)1.61.61.61.61.61.61.627.527.527.527.527.527.5Do(mm)57578910810815915910122222253257×457×589×5108×4.5108×5159×5159×610×212×222×3.522×425×432×5δ(mm)4554.5556223.544520#20#20#20#20#20#20#0Cr18Ni90Cr18Ni90Cr18Ni90Cr18Ni90Cr18Ni90Cr18Ni9计算系数计算系数计算厚度计算厚度计算厚度许用应力计算系数计算系数计算焊接接(R=1.5Do内(R=1.5Do外(R=1.5Do内(R=1.5Do外(R=3Do内管道材质(50℃情况(R=3Do内侧)(R=3Do外侧)系数头系数下)侧)侧)侧)侧)侧)[σ]t(MPa)130130130130130130130128.375128.375128.375128.375128.375128.375Ej1111111111111I1.251.251.251.251.251.251.251.251.251.251.251.251.25I0.8750.8750.8750.8750.8750.8750.8750.8750.8750.8750.8750.8750.875I1.11.11.11.11.11.11.11.11.11.11.11.11.1I0.928571430.928571430.928571430.928571430.928571430.928571430.928571430.928571430.928571430.928571430.928571430.928571430.92857143Y0.40.40.40.40.40.40.40.40.40.40.40.40.4ts(mm)0.440.440.680.830.831.221.221.211.452.662.663.023.87ts(mm)0.310.310.480.580.580.850.850.871.051.921.922.182.79ts(mm)0.380.380.600.730.731.071.071.081.292.372.372.693.45计算厚度(R=3Do外侧)ts(mm)0.320.320.510.610.610.900.900.921.112.032.032.302.95设计厚度设计厚度厚度负腐蚀裕(R=1.5Do内(R=1.5Do外偏差量侧)侧)C1(mm)C2(mm)0.400.500.500.450.500.500.600.280.280.350.400.400.501.501.501.501.501.501.501.500.000.000.000.000.000.00tsd(mm)2.342.442.682.782.833.223.321.491.733.013.063.424.37tsd(mm)2.212.312.482.532.582.852.951.151.332.272.322.583.29设计厚度(R=3Do内侧)tsd(mm)2.282.382.602.682.733.073.171.361.572.722.773.093.95设计厚度(R=3Do外侧)tsd(mm)2.222.322.512.562.612.903.001.201.392.382.432.703.45弯管的公称壁厚大于设计壁厚,故所选壁厚符合要求。
压力管道强度校核计算表
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