Reasons for Leakage Failure of Stainless Steel Heat Exchange Tubes

A number of shell and tube heat exchangers in a chemical enterprise leaked one after another after 3-4 years of service. After disassembly, a large number of 304 stainless steel heat exchange tubes were found to be cracked or perforated. The failure reasons of stainless steel tubes were analyzed by means of macroscopic morphology analysis, scanning electron microscopy and energy spectrum analysis, metallographic examination, chemical composition analysis, intergranular corrosion test and residual stress measurement. The results showed that intergranular corrosion and stress corrosion were the main reasons for the cracking and perforation of the heat exchange tubes. The heat exchange tube material 304 stainless steel was sensitive to intergranular corrosion. There was obvious residual tensile stress on both the inner and outer walls of the heat exchange tubes. And there were corrosive elements such as S and Cl in the medium. Stress corrosion cracking happened in the heat exchange tube material due to the coexistance of the above three necessary conditions for stress corrosion cracking at the same time.