Failure analysis of stress corrosion cracking in heat exchanger tubes during start-up operation

• Failure analysis revealed that heat exchanger tube cracking was caused by SCC.
• Residual tensile stresses due to seal expansion are the stress reason for SCC.
• Steam polluted by chloride during start-up operation is the media reason for SCC.

The cracking failure of a new heat exchanger during first start-up operation has been analyzed. Through the investigation of the operating history of the equipment, analysis of the chemical compositions of tube material and corrosion products, metallographic test of specimens with cracks, the cracking mode can be described as the Stress Corrosion Cracking (SCC) of austenitic stainless steel. This kind of cracking was induced by the chloride in high temperature steam and tensile stress. The residual tensile stress due to seal expansion has been proved by numerical calculation. The pre-heating steam which was polluted by the catalyst with chloride is the main reason for the tube cracking in this case.