笔者工作实践中发现,在直接供暖的采暖系统中,一些WNS燃气热水锅炉运行了一至二个采暖季之后,经常在回燃室前管板第二回程入口处的管口上出现热疲劳裂纹的现象。管口出现径向穿透性的裂纹,有部分裂纹还延伸到管板上,裂纹的纵向长度可达到25mm,裂纹的分布与形状如图1所示。停炉检查,可以在回燃室前管板及靠近管板的一段管壁上看到有一层水垢。越靠近管子根部,水垢的厚度越 The author found in practice, in the direct heating of the heating system, some WNS gas-fired hot water boiler operation after one or two heating season, often in the back chamber front tube plate at the entrance of the second return thermal fatigue cracks phenomenon. Radial permeability of the nozzle appears cracks, some of the cracks also extend to the tube plate, the longitudinal crack length can reach 25mm, crack distribution and shape shown in Figure 1. Stop the furnace inspection, you can see a layer of scale in the back of the combustion chamber before the tube plate and a tube wall near the tube plate. The closer the pipe root, the more the thickness of scale