Finite element analysis on creep damage for main steam pipelines in a power plant based on damage mechanics

Damage will occur in main steam pipelines subjected to high temperature and high pressure in the period of long-term service. Therefore, it is important to predict the damage and service life of the pipelines. Based on the modified Karchanov-Rabotnov constitutive equation, the user subroutines computing the damage of the pipe element and 3D solid element were compiled and coupled with ABAQUS finite element code. Creep tests were performed at serviced at 540°C for 10CrMo910 pipe material, and the creep material constants in the modified creep damage constitutive equations were obtained by fitting the creep test data. Based on this, the creep damage prediction was carried out for the steam pipelines serviced at high temperature in a power plant. The damage distribution and maximum damage location of the pipelines were obtained. Furthermore, the local creep damage analysis of a taper pipe serviced at high temperature was also carried out because tapered pipe used in the main steam pipeline is one of weakness in the piping system. Damage distribution and evolution in the analyzed taper pipe were obtained, and stress redistribution in the period of creep damage was discussed. According to the results obtained above, the life evaluation of the pipeline and the taper pipe were performed.