In a chemical enterprise, at the bottom of the economizer and the low temperature water inlet end of pipes side, cracks appeared at the root of the outer wall fins of the tube bundle of stainless steel heat exchange pipe, some of which penetrated the pipe wall and led to leakage. The causes of leakage were investigated by means of crack fracture macroscopic and SEM analysis, metallographic analysis, and media analysis. Experimental results showed that cracks were originated from the root of the outer wall fins of the tube bundle, which was stress corrosion cracking(SCC). The corrosion medium was the dew point condensate containing chlorine and sulfur of the flue gas in the shell side of the economizer. Most cracks were located at the dead corner of circulation of flue gas, where the flue gas was almost stationary. Moreover, the inlet temperature of the economizer device was not constant. During startup and shutdown stage, there would be low temperature water flowing into the pipe of the device. All the above aggravated the formation of dew point condensate in the flue gas. Furthermore, the acid dew point was analyzed and calculated under the condition that the maximum volume fraction of sulfur in the flue gas was 0.01%. Also, it was pointed out that a thermostatic device should be added at the upstream of the tube side to avoid the inflow of low temperature water; and the structure of the economizer was suggested to be changed to avoid the occurrence of dead corner of circulation of flue gas as far as possible.
