Hi all,
I'm having a big problem with a TFA from a huge turbine purchaser which states that he wants zero dead weight loads during erection on the turbine nozzles, based on NEMA SM-23 item 8.4.5, ("the dead weight load should be entirely supported by pipe hangers or supports").I reply, stating that this intrepetation is impossible because if we have even a short straight pipe segment between the last support and the nozzle, the dead weight load will be divided between these two restraints.Actually the piping layout that I have is a spring hanger support a curve then a vertical pipe with a flange that connect to the turbine nozzle. He wants that with the nozzle disconnected, the spring supports all the dead weight load. I reply, saying that the spring was calculated for operational case with the nozzle connected and if it carries all the dead weight load with the nozzle disconnected, it would be designed not for operation but for installation wihich is not the purpose. Have one of you faced a similar problem ? How can I defeat this misunderstanding interpretation of NEMA ? Any help ?

Thank you in advance.

There have been many posts on this, you could try the search facility. Turbine vendors often want to see the equipment disconnected to prove zero load on their flange and no movements of the pipe when cold. That means the spring supports must be designed for the nozzle free load.

I concur with Moverz and add... also I suggest you size the spring assuming it is close proximity to the connection with the connection free in Y look at the online help describing spring cans for the free code.

After this you simply state that all things which can be done for this matter have been done and the load is thus....

Thank you John and Moverz for your promptly response...
I agree with the vendors with respect there must be no residual (from erection) efforts on turbine nozzle, but if I sized my spring considering that the nozzle is free in Y axis, the spring will take all dead weight in cold position and when I run with the nozzle connected,dividing dead weight between the spring and the nozzle, actually I will have a reaction against the nozzle higher than it really is, because I would have selected a bigger spring considering nozzle disconnected. What should I do, design for operation or installation?

PS : My nozzle is at the bottom of the turbine and movement is 3,5mm down.

Ahhh good explanation... a "constant" support can be used to eliminate variability. Therefore one could use said constant even though one might not be required.

Thank you John!!!

Best regards,
Luiz Castro

Is this additional reaction passing or failing ur nozzle in NEMA calcs (in ope condn)? If so you can use a const spring as suggested by Mr.Luf.

For rotating equipments it is always a good engg practice to calibrate springs with nozzle free and let the springs carry all the load!

One thing to keep in mind - your travel stops need to be in place while the flange is disconnected. It is true that the operating load of your spring needs to be sized for the operating state, but you don't want to try to design a spring to carry a piping load with no movement when one of the end points of the system is missing.

You should be able to run a case, replacing your spring with a hard support (or actually just defining it as rigid stiffness), with the flange disconnected and see what your displacments are. If your system is properly supported, you should have very little displacement at the flange.

While it's true that it is impossible to get "zero" load at a flange in any condition, the piping system should be well supported so that the flange isn't sagging or listing wildly while the millwright's are trying to get the system lined up.