ANALYSIS OF HIGH TEMPERATURE CREEP ON THE NUT CONNECTION COMPONENTS OF A 600MW SUPERCRITICAL STEAM TURBINE

A model of the nut connection components of a 600MW supercritical steam turbine was established by finite element analysis to investigate the influence of creep on the nut connection components. Due to the complex structure and the multi-axial loadings, Cocks-Ashby coefficients were used to depict the multi-axial creep behavior. Multi-axial creep deformation criteria (MCDC) and multi-axial creep rupture criteria (MCRC) were used to assess the structure reliability. In addition, sealing performance of the nut connection components in the creep time of 2 X 10(5) hours was numerically investigated in terms of the contact pressure and the radial contact length. The results demonstrated that the creep strength of the nut connection components after 2 X 10(5) hours could maintain the safety operation of the nut connection components. The contact pressure distribution and the radial contact length in circumferential could prevent the leakage steam flow from the high pressure zone to the low pressure zone.