A 2×350MW supercritical combined heat and power generation boiler No. 1 detection and treatment of delayed cracking in the fillet weld of the large plate girder

The main girder of the utility boiler is the most important load-bearing component of the boiler, and its importance is self-evident. If a quality accident occurs during the later use process, it will cause disastrous consequences to the power plant for rectification. This article mainly discusses the fillet weld connecting the web plate and the wing plate of the main girder of No. 1 boiler of a newly built 2×350MW supercritical cogeneration unit. During the inspection before leaving the factory, it was found that there were crack defects in the fillet weld. After being placed for a period of time, the cracks increased in number and length, which proved that the cracks in the fillet weld of the main girder had delayed characteristics and belonged to delayed cracks. This article discusses the detection process of the delayed cracks of the main girder and analyzes the causes of the delayed cracks from the aspects of material characteristics and manufacturing process. Because the delayed cracks have the characteristics of unpredictable occurrence time and extremely great harmfulness once they occur, the main girder is definitely scrapped and new materials are re-fed to process a new main girder. Eventually, the problem is completely solved and major equipment hidden dangers are eliminated for the power plant.