Reasons Analysis on Leakage of Heat Exchanger Stainless Steel Tubes

By means of macro examination, chemical composition analysis, mechanical property test, corrosion test, fracture analysis, energy spectrum analysis and metallographic examination, the leakage reasons of stainless steel heat exchanger tubes of unit 3 high pressure heater No.6 group were investigated. The results show that the leakage of the stainless steel heat exchanger tubes was mainly caused by pitting corrosion and crevice corrosion of chloride ions and oxygen in the media (condensate water during running and stopping stages) between the inner drilling wall of shields and the outer wall of the failure tubes, which destroyed the tube surface passivation film and formed pits. The micro-cracks gradually propagated under the action of heat stress, shock stress and vibration stress, and finally stress corrosion cracking and vibration fatigue cracking happened, which resulted in the leakage of the tubes.