大口径长输管道用弯管的设计制造

On the Design and Fabrication of the Bends Used in Large Diameter Pipeline.

在国内外缺少适用于大口径长输管道用的大曲率半径的弯管设计、制造规范的情况下,建议在符合现有规范的条件下设计时,应考虑曲率半径的选取尽可能小,以减小所需弯制设备、芯模的规格尺寸和空间场地;当弯管和与之相连的直管材质不同时,应在壁厚计算公式中乘以两种不同材质的屈服强度比值;为节省投资和合理利用钢材,应慎重确定弯管制造的壁厚减薄量;为保证弯头质量,在选材上不宜选用螺旋焊缝钢管,而应选用高强度低合金钢管或管道钢板制造的直缝管。与热弯工艺相比热推工艺制造的弯管,壁厚均匀,壁厚减薄率大大降低;只要芯模尺寸准确,可使弯管圆度很小;采用热推工艺制造的弯管不会产生褶皱,能保证管道对口质量。建议热推为首选工艺。呼吁国家技术监督部门尽快组织制订适用于石油天然气行业的大口径钢制弯管技术规范。

With the absence of national and international specifications for the design and fabrication of bend pipes with large curvature radius for large diameter pipeline, it is suggested that, as long as the current code can be satisfied , smallest curvature radius shall be selected so as to minimize the sizes of the equipment and moulds for bend fabrication. When the bend and its adjacent straight line are of different materials , the wall thickness of the bend shall be multiplied by the ratio of their yield strengths. Bend wall thickness shall be reduced with care so as to cut down steel consumption. Longitudinally-welded (rather than spiral seamed) bend pipes of high strength and low alloy steel shall be used to guarrantee bend quality. Many more advantages exist in hot pushing pipes than in hot bent pipes : uniform wall thickness, small roundness,and no fold.