We all know that during operating condition, a pipe may undergo plastic deformation. Code takes it in account and therefore the allowable stress range may be greater than yield strength of pipe in hot condition. In reality the pipe can never be stressed beyond yield point and is plasticaly deformed beyond this limit.

Now, while calculating the nozzle loads, the software will actually assume the pipe to expand as per thermal expansion coefficient, calculate moments and stresses till considered temperature and accordingly give the loads.

The nozzle loads thus provided by software will not take any self springing in account.Although there will be stress relieving in the system, due to which the nozzle loads may be much less than value given by software.

In my view, if stresses exceed a certain value, software should calculate the nozzle loads directly based on the yield strength of material, as this is limit to which a material will be stressed.

Can you please correct me where I am wrong or suggest a way which gives us a more reasonable and less conservative estimation of the nozzle loads?