Thermal Stress Model Constraints

[Boghi1990]

Insulated main steam lines running from boiler stop valves to turbine main stop valves. The lines are 18 inches and 12 inches with 8 inch and 7.5 inch insulation thickness. The ambient temperature where this steam lines are installed is about 70F. Steam lines are warmed up during thecold start up, from 100F to 750F with a rate of 200F/hr.

The target of this FEA is to determine the thermal stresses caused ONLY by the temperature distribution in the pipe wall, which is determined from a transient heat transfer analysis. The temperature load is the only load applied in this thermal stress analys.

Attached snap shot shows the sections of the piping I am considering to analyse. I am thinking to use symmetry and slice the piping along its longitudinal axis. I will apply symmetry constraints to the cut out faces of the piping.

I am not sure what kind of constraints could I apply at locations labeled A, B as marked up on the attached snap shot.

I would appreciate any suggestions or advices regarding the type of constraints I need to apply at thoe marked up locations.

Regards,

Bogdan

 

[shaun8567]

Hmm, maybe I'm not understanding your problem correctly, but I don't see how you can apply a symmetry simplification for this geometry.

As for the constraints applied to A and B, this will be tricky because the stiffness and thermal expansion that the modeled geometry would see due to the non-modeled geometry needs to be quantified before you can determine if you can exclude it. One thought that comes to mind is to model the non-yellow geometry with beam elements to capture the thermal expansion and stiffness of the reset of the piping.