Hi Siv,
You should model the piping right up to the turbine connections (nozzles) and use the turbine OEM's provided displacements at that point (use the method of C nodes that you describe. Typically the turbine manufacturer will tell you that their springs, supporting the valves and their piping were chosen (by them) such that they support exactly the weight of their valves and their pipe (up to and including the valves). Of course to get the flexibility of their piping right in the model you will still have to know the diameter and wall thickness of their pipe. So you will want to model the turbine OEM's pipe and the rigid links that you use in the model to represent their valves as having zero density (as that weight is supported by the springs). You will have to support your piping fairly close to the valves and then appropriately place your supports on the piping that you design.
Also, you may have a very significant wall thickness difference between "your pipe" and the valve nozzles that you are going to be welding the pipe to. There are Code limits on how much wall thickness mismatch you can have at butt welds. To get the butt welds right you may have to use a "transition piece" with a tapered wall thickness between "your pipe" and the valves. Pay attention to the choice of material for the "transition piece".
Please send me a private message.
Regards, John.
Edited by John Breen (02/02/07 11:15 AM)
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John Breen