Thermal Stress Analysis Constraints
Thermal Stress Analysis Constraints
(OP)
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 needv to apply at thoe marked up locations.
Regards,
Bogdan
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 needv to apply at thoe marked up locations.
Regards,
Bogdan





RE: Thermal Stress Analysis Constraints
RE: Thermal Stress Analysis Constraints
The aim of this FEA is to investigate thermal stresses caused only by the temperature gradients through pipe wall thickness. The overal thermal expansion of the system has been analysed by a piping stress analysis(Caesar II).
I have run the transient heat transfer FEA model for the temperature distribution during the warm up process of the steam lines. I need now to set up and run the linear structural analysis. I am not sure how I could constraint the structural model at the locations(A & B) marked up in the snap shot.
Regards,
Bogdan
RE: Thermal Stress Analysis Constraints
though it does seem a little "odd" ... to want 1/2 the answer ? but then i've been called worse before ...
Quando Omni Flunkus Moritati
RE: Thermal Stress Analysis Constraints
I'm not sure your what code your piping is designed to, but most don't specifically address the stresses due to temperature gradients. An exception is ASME BPVC Section III, NB-3600 for nuclear power piping. It gives simplified rules for evaluating these stresses based on the temperature gradients. It may be worth taking a look at.
RE: Thermal Stress Analysis Constraints
RE: Thermal Stress Analysis Constraints
RE: Thermal Stress Analysis Constraints
RE: Thermal Stress Analysis Constraints
Thank you for your suggestions. If I use the symmetry plane (XY for example), the only constraint applied on the cut plane is Tz=0. One free end of the pipe (left end), is constrained only axially (Tx=0). I did not understand how to constrain the other free end (right end)? What does it mean "by coupling the nodes so they move parallel to the cut face"? Which cut face do you refer at ? If I use this should I constraint the whole face or only a node on that face?
RE: Thermal Stress Analysis Constraints