The stainless steel heat exchange tube in a heating network was cracked and leakage happened only after one and a half year's operation.Based on a series of tests on the cracked pipe

such as macroscopic examination

chemical composition analysis

metallographic analysis

electron microscopic and energy spectrum analysis

stress corrosion cracking was considered as the main reason for tube leakage.Thus

to prevent the heat exchange tube from cracking

it is suggested that indexes like Cl-concentration

dissolved oxygen content and the water hardness of the heating network should be strictly controlled;the heat exchange tube should be washed by using demineralized water as soon as the heater stopped working

so as to decrease the Cl-concentration inside the pipe wall;the tube should be protected by filling with nitrogen instead of water.