After putting into operation over 20000h

the tubeburst of T91 and T92 superheater tubes in one power plant had been frequently occurred. The structural and mechanical properties of original tubes

operating tubes

and bursted tubes have been detected

the results show that the tubeburst is resulting from long term overtemperature operation

and there being a lot of oxide layer on the steam side of T22 tube

the oxide layer peeling off and depositing near the tube elbow below at the moment of startup and shutdown

making the T91 and T22 superheater tubes to be opertemperature in a short time

and finally tubeburst occurred.