Dear Richard & Dave,

My question is related to CAESAR II Application Guide about Modelling Trunnion.
Why in the example method doesn't explain what density to be used?
We usually use zero density, but maybe some other will use fluid density.
If it depend on the judgment of the engineer then, still you have to explain it.
Many technique to modelling trunnion, some company i see also use Avarge design Temp. + Amb. Temp. as their trunnion temp., and it is still can be understand, but if you use fluid density for the trunnion, how can you explain these?
Thanks.

NB: btw when the CAESAR II Exam for certificate will be open?

Regards
Dee

Zero density. There is no fluid inside trunnion.

Or is an unintentional error or maybe it was considered as not having influence on the results so it was ignored.

If you want that your model is accurate, use zero density.

Regards,

Thanks danb,
i just want to clarify. Like i said above we ussualy use zero, that is for correct result, and not put sif there beacuse we don't cut hole to attach the trunnion with the run pipe. If we want to check local stress we use our spreadsheet.

I just check some calculation from one of EPC Company that quiet famous, where they modeled the trunnion with the density, and then the force they got from CAESAR II based on that calculation with fluid density they use to calculate the local stress in their spreadsheet, and well the local stress is pass, but that is because they applied the fluid density in the trunnion, how about if the trunnion have zero density that make it more on carry the weight of the run pipe and the system behaviour, do it steel passed?
I questioned this to myself...still i got to check again...

There are many topics that cover this subject, one of these you can see below:

http://65.57.255.42/ubbthreads/ubbthreads.php?ubb=showflat&Number=39233

There are different methods for checking the trunnions (e.g. Kellog, ASME Code Case N-392-3, TR- 107453, SIF, FEA and so on) with pluses and minuses.

Regarding the other aspect, all companies, including the famous ones, have human beings as employees. You can ask them why they did not changed the density to zero. They will answer that it was unintentional error or maybe that it was considered as not having influence on the results so it was ignored. I expect that it is not a critical issue.

Regards,

Thanks Danb, idon't quote for SIF question for trunnion, but for density, especially this density is the density of water (1000 kg/m3) not a gas or vapour, that offcourse if it is vapour or gas i will considered there will be no significant issue.
As i check they spreadsheet they put into the Radial Load, Circumferential Load and Longt.load from Load they got from CAESAR, so from this point of view offcourse density will make the different, i just check until 8"trunnion (12" run pipe) between with and without density, the local stess increase with trunnion with zero density than trunnion with the water density density (Offcourse!!), now the problem is when does this will be a critical issue, is it above 12" or above? that this density of water should be ignore and put as zero.
I will talk to them, and back to you if i found something to share.
Just for info, this company is the one that make one of the method you mentioned, so i think they know what they are doing, i will discuss with them.

Thanks Danb.

One thing is for sure. In reality, there is no water inside the trunnion.

But I really want to know their answer.

Regards,