LOSHAN WATER WALL TUBE FAILURE

[ Hazavei ] - Tavanir Company Tehran – Iran

خلاصه مقاله:

In May 1992, one of the Loshan side water wall boiler tube unit #2 was failed. The failure was in form of window opening and the signs of over heating in form of small buldge were seen on the fire side of tube. The tube material was carbon steel with ST35.8III standard and the boiler, drum type with 135 MW. Macroscopy and microscopy studies were carried out on damaged and new samples. The results of investigation have shown that the corrosion from the water side was the main cause of the damage togather with the higher temperature and fatigue cycle of the tube. This resulted in producing longitiudinal cracks like pentration in the inside of water wall surface which was longer and deeper on the fire
side where the tube broke in form of window opening. Although the cause of the failure looked like to be by hydrogen crack or Hydrogen embrittlement were seen.