煤化工废热锅炉管板环缝返修

Rework of Tube-Plate Girth Weld in Coal Chemical Waste Heat Boilers

煤化工净化装置的低压废热锅炉管箱侧管板环焊缝设计结构没有考虑制造工艺要求,环焊缝内侧(内坡口)焊接时没有焊接打磨空间,在制造施焊过程中无法有效去除施焊产生的先天微小缺陷,焊缝缺陷在锅炉运行10年后扩展,经检测严重超过了标准要求。保持原设计结构返修,同样没有焊接打磨空间,包括大量老缺陷无法清除。最后决定采用的修复方案为:将缺陷环缝整圈割除、在管板侧堆焊延长筒体长度(翻边长度)、同时加工缩短管箱侧筒体长度;并将对接焊缝的X型坡口由外浅内深型改成外深内浅型,给内坡口焊接留下充足打磨空间。由于锅炉筒体壁厚和一侧的管板壁厚大,从筒体堆焊到对接焊的电加热预热、伴热、消氢是修复工艺控制的关键。

Coal chemical purification device of low pressure waste heat boiler tube box side of the tube sheet of the design of the annular weld structure without considering the structure of the manufacturing process requirements,circumferential weld inside(groove)welding without adequate welding burnish need space,in the manufacturing process is unable to effectively remove welding process of welding the tiny defects,congenital annular weld defect extension after 10 years of operation in boiler operation,via detecting defects seriously over the standard requirements.Maintain the original design structure repair,again no welding and polishing space,including a large number of old defects cannot be removed.Finally,the repair technology adopted is as follows:the whole circle of boiler defect circular joint is cut off,the tube length(flanging length)is extended by surfacing at the side of tube plate,and the tube length at the side of tube box is shortened by processing.In addition,the X-groove of butt weld was changed from the form of outer shallow and inner deep to the form of outer deep and inner shallow,leaving enough polishing space for the welding of inner groove.Because the wall thickness of the boiler cylinder and the wall thickness of the tube plate on one side are large,the electric preheating,heat tracing and hydrogen elimination from the tube surfacing welding to butt welding are the key points to control the repair process.