长输管道敷设中弯头和弯管的预制与安装

长输管道弯头、弯管的预制和安装存在着错边量大、切割弯头角度偏差过大、因弯头切割不合理而造成焊接时使母材机械性能变化、使用后弯头变形或破裂等问题，为此，提出了如下改进意见：从设计到施工，对管道每一转折点应认真测量，预制厂按实测数据弯制；预制时要在弯头、弯管两端留有一定长度的直管段；在安装中，对弯头、弯管不切割，按编号“对号入座”；直缝钢管弯制时，应将焊缝置于中性轴线上；用有环向焊缝的直缝管弯制时，其

Prefabrication and Installation of Bends and Elbows for Long Distance Pipeline

Prefabrication and installation of elbows and bends for long distance pipeline may encounter such problems as considerable offset.big deviation of bending angle,variation of material properties during welding due to improper bend cutting,and deformation or damage undertaking during service. It is pointed out that care shall be taken from design to construction to every turning point over the line and elbows and bends prefabricated accodingly. Straight sections of proper length shall be reserved during prefabrication at both ends of the elbows and bends. Every elbow or bend shall be installed in its own place with no need for cutting. When bending pipes of longitudinal weld,the weld shall be positioned along the natural axial line,or,if the pipe has a girth weld,with a 30?cross angle with the natural axial.