汽包现场焊接修复时的变形及其控制

Deformation Monitoring and Control for the Boiler Drum Under Welding Repair

汽包修复时筒体产生过大的塑性变形将严重影响其安全运行与使用寿命。结合某火电机组汽包管接头更换修复工程,设置10组变形监测点,对修复时汽包变形的大小、方向进行了全过程监测。监测结果显示,修复过程中汽包轴向膨胀伸长量较理论计算值小;汽包垂向发生上挠变形而不是下垂。产生这种现象的原因在于:修复过程中汽包筒体存在周向温差与内外壁温差,汽包膨胀伸长量超过吊杆偏移极限后汽包膨胀受阻。理论分析与工程实践表明,避免汽包修复产生永久塑性变形的技术关键是:控制汽包筒体温差,减轻汽包膨胀阻碍,减小焊接残余应力,控制吊杆温度在合理范围。

Serious plastic deformation of drum tank under welding repair would affect its operation and life significantly. When connection-tube sockets of the boiler drum was repaired in a power plant, 10 deformation measure devices were put up to monitor and record deform- ation direction and scale in details. Measure showed that expansion volume alone tank＇s length direction was less that calculation volume and tank bent upward but no downward alone vertical direction. Two reasons resulted in such deformation. One was tank tempera- ture gradient around drum tank＇s circumference and wall thickness direction respectively. Another was hangers as expansion obstruction. Both research and engineering results indicate that technical keys to avoid drum plastic deformation include controlling drum tank temperature gradient, relieving drum expansion obstruction, decreasing welding residual stress, controlling suitable hanger temperature, and etc.