The leakage at drain water-level in lower half part of barrel shell of the high-pressure heater for 600 MW unit in one power plant had occurred many times.In order to analyse the causes resulting in said leakages

on-line temperature and stress measurement have been carried out for the high-pressure heater no.3

and the temperature field and stress field simulation being calculated and analysed by using ANSYS finite software.Results of analysis show that the leakage of enveloped shell makes the barrel shell at drain water-level to produce obvious temperature gradient and comparatively high alternating stress

causing the barrel shell to be damaged from fatigue

and finally resulting in leakage.