Hi All;

This may be a very basic question but I could not find a satisfying solution around.

I am observing an analysis of a power plant which is done before. There are two main connection point sets including the turbine and the boiler. The stress values (displacements and the allowable forces-moments) of the turbine are given at right on the turbine which can be assumed as rigid after implying the displacement values.
But the problem I can not solve is about the boiler side. The terminal points are somewhere inside the piping( ofcourse the rest of piping seems very complicated at boiler part). At the terminal points the displacements and the resulting force-moment values are given for operating and earthquake conditions. But is this appropriate to use these values indepently. Is not the geometry of the rest of the piping will affect the results?
A more basic question is how we can do this kind of analysis including more than one party?

What is the practical and theoritical solution for this problem?
Best Regards;

Dear,

Beyond the terminal points indicated in equipment (boiler & steam turbine in your case) vendor documents, piping stress analyst's engineering jurisdiction ceases to exist. Imposed displacements & allowable force/moment at these terminal point isolate equipment design from piping design.

Where such isolation is not possible, structural simulation of the equipment is included in piping model.

Thus, when boiler vendor is happy to isolate at some terminal point, why do you worry!

regards,

sam

Thanks Sam;

But the problem is the given values for the boiler side seems to be as results of an analysis rather than being allowables. There are three different cases and for both the forces moments and displacements are given. I could not understand how such an analysis is done but I cant understand in such a complex piping like boiler how anyone can calculate the allowables either. Is it possible to cut any model and try if it is OK with the limit values?

Regards;

Ozguristan,

If you can apply the same loads and load cases used in the analysis of boiler piping, you are able to use displacements at the terminal point for the turbine piping analysis. However, you need to iterate your analysis until the forces and moment at the terminal point reach close to the forces and moments which were given at the terminal point of the boiler piping. Watch signs, the moments and forces have to be with opposite signs of given. This can apply for the new piping.

If you are trying to analyze existing piping this may still work. In case you can not find the same forces and moments you need to think about what is causing that. You can find infinite reasons for that. Your job is to screen them and find the possible cause with the information available or the required information may not be available and you need to ask for them.

In case the terminal point is very close to the outlet header of superheater/reheater of the boiler, I suggest you to include the header and its supports into the analysis. Some cases the support of the header can be the SH/RH tube bank support on the walls. Some cases the wall to wall line might have more than one header; this becomes a bit more complicated if you are not familiar with boiler design.

Including the boiler piping into your analysis can make your analysis more complicated due to the determination of neutral thermal lines or elevation on the header side and introduced thermal expansions onto the header by the boiler bank in case HRSGs are concern. Conventional boilers are a bit more complicated than this.

In case the header of boiler SH/RH includes risers from the SH/RH the analysis may become more complex.

If you can attach one or two cross section of boiler piping we may be able to give you better guidance on boiler side if you need.
You can write me on the following address if you need to discuss:

demir@bigpond.net.au


Kind regards,

Ibrahim Demir