Service Life Analysis Of The High Temperature Superheater Outlet Header In A 600MW Supercritical Boiler

Comparing with the other thick-wall components in boiler, the high temperature superheater outlet header works under the higher pressure and the maximum temperature during the operation, is more inclined to damage. As one of the most important thick-wall equipments in the boiler, the header has an impact on the performance of the entire boiler or even the unit. The life loss of the header mainly depends on the stresses which it is bearing. During the process of altering load, the variation of the pressure and temperature make the stresses of the header greatly change. In the case of high temperature, big variable stresses in frequent not only make the header fatigue damage but also creep damage. Because of the interaction between fatigue and creep, the header's service life becomes short.In the paper, the ANSYS software was adopted to analyze the service life of the high temperature superheater outlet header in a 600MW supercritical boiler. Primarily, half of the combination which is made up of the header and the steam inlet pipes was taken as the calculation model according to the symmetrical structure. And then, the transient temperature field was calculated according to the real operation data, Based on the temperature field, the thermal stress, the mechanical stress and the total stress were obtained. The life loss were worked out by the method of fatigue-creep damage analysis which is on the basis of elastic analysis.The results show that: under the altering load operation, the change in the difference of the wall temperature was accord to thermal stress's change; the ratio of mechanical stress and pressure in the header's inner side was constant; at the latter part of the operation when the thermal stress is small, the ratio of total stress and pressure was also constant; the mechanical stress was accounted for a larger proportion in total stress; the most dangerous point(node 56) was on the cylinder and pipe's intersection line which was in the inner side; the fatigue loss and creep loss were both within the material's envelope line.At the end, the calculation of the header's life loss provided the theoretical support for the bearing-pressure element's life management in the power plant.