Failure Analysis on 20G Water Wall Tube of Boiler in Thermal Power Plant
The causes of 20G water wall tube explosion of boiler in a thermal power plant were analyzed through macro analysis,microstructure observation,room temperature tensile property test,phase and composition analysis.The results show that the cracking originates from the inner wall of water wall tube.There is obvious corrosion thinning in the wall thickness at and near the burst.The microstructure of the inner wall near the burst is ferrite and pearlite,pearlite generates spheroidization,and the cracks and oxides appear along the grain boundary.Combined with the operating conditions of the boiler,it is speculated that the water wall tube produces local oxygen corrosion and hydrogen corrosion in the crud accumulation area on both sides of the welding seam.It is suggested to control the water quality,take protective measures during boiler shutdown,reduce the scale of furnace pipe,carry out wall thickness inspection of welded joint and replace the pipeline that does not meet the thickness requirements in time.
water wallfailure analysis20Goxygen corrosionmicrostructure
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