FEA of Nozzle per Table 5.3 of ASME Div.2 Load Case Combinations & Allowable Stresses for an Ela 1

[PressureVesselEngineer]

Hello Everyone

We are performing FEA of nozzle by NOZZPRO software as per ASME SEC VIII DIV.2 4.1.5 Design Basis which states that,
4.1.5.1 Design Thickness. The design thickness of the vessel part shall be determined using the design-by-rule
methods of Part 4 with the load and load case combinations specified in 4.1.5.3. Alternatively, the design thickness
may be established using the design-by-analysis procedures in Part 5, even if this thickness is less than that established
using Part 4 design-by-rule methods.

Now as per Table 5.3 of ASME Div.2 Load Case Combinations & Allowable Stresses for an Elastic, we need to consider all the loads and its combination during FEA.

Normally, we used to perform nozzle FEA for internal pressure and external nozzle loadings.

But our client interested to perform FEA of nozzle for pressure, wind, earthquake, external loads, etc.

As per Table 5.3, yes. It shall be perform. But can anyone highlight requirement to perform all loads combination.
Also in NOZ Pro we cannot add wind or seismic load for nozzle FEA.

Waiting for your valuable feedback/advise.

Regards

 

[TGS4]

Not sure what your question is. All load case combinations must be considered, including having some of the loads equal to zero. The wind and seismic are mandatory.

 

[jte]

Maybe you should consider getting some FEA software which can do the job. It would seem that your current selection is not capable.

But allow me to ask another question: When you get your results, do you use Stress Intensity (Tresca) or von Mises stresses when comparing against your allowable stresses? What is your basis?

 

[PressureVesselEngineer]

Dear TGS4 and JTE

I am performing shell nozzle junction analysis with NOZ PRO for Div.2 Vessel.

I am using loads as internal pressure and nozzle external loads. Later I am evaluating Von Mises stress with ASME allowable.

But as this vessel is Div.2 and I am using FEA (Design By Analysis). Client ask me to use all loads for shell nozzle junction FEA from Table 5.3 of Div. 2 which includes wind and seismic also.

Now I want to know that " Is it really required to perform FEA of shell nozzle junction for wind and seismic loads.

I hope I am enough clear to my question.

Regards

 

[TGS4]

To answer your question: yes, it is required. Why would you think it would not be?

 

[jte]

Why would you think it would not be?

Well, if the software can't evaluate these loads, then it must not be "...really required to perform..."



But PressureVesselEngineer, perhaps I'm feeling generous enough to expand a bit on what I think TGS4 is trying to tell you. Perhaps the better approach is to use alternative methods to evaluate the loads. As I suggested above, FEA software which is fully capable of adding external loads is available, and I don't have tremendous respect for your chosen package when it is used beyond its limits (as I all too often see). Note that TGS4 never said that these loads must be analyzed using your chosen software. Remember, "consider" and "evaluate" can include using other methods and even engineering judgment.

 

[PressureVesselEngineer]

Dear JTE and TGS4

Thank you for reply.

I do agree that applying all Table 5.3 of Div.2 loads in commercial FEA software's are available in market.

But here I would like highlight again that analysis focus area is shell nozzle junction not whole vessel.
In order to evaluate stresses and asses shell nozzle junction, contribution of internal pressure and piping loads will be more than wind/Seismic.
Also for wind/Seismic design by formulae method available in Div.2. Accordingly I have performed design by formulae method for whole vessel.

Only for shell nozzle junction I would like to use Design by Analysis method.

So I think it is not necessary to consider again wind/Seismic in design by Analysis method as it is already covered in Design by Formulae.

Also for most of shell nozzle junction FEA, wind/Seismic loads are not considered by many vendor and it was approved by end user also.

But this time client is commenting to add wind/Seismic load in FEA.

I want to know Technical requirement behind this.

Regards

 

[NRP99]

Perhaps you should look into getting piping/nozzle loads that are derived from pipe stress analysis(Ceaser/Autopipe) considering all the load cases and load case combinations, if your nozzle loads do not contain these loads and load case combinations. What load/load cases is considered for deriving nozzle loads? Are you using piping size based nozzle loads?

I think that is what the client is suggesting.

 

[PressureVesselEngineer]

Dear NRP99

Note that even though Piping loads might include seismic/wind loads, these loads are applied only to piping attached to the vessel (amongst another loads), they are additional and independent to the combination of Pressure + Wind/Earthquake loads sustained by the vessel itself, clearly indicated as separated loads in Table 5.1

Means piping loads derived from wind,seimic,dead weight,etc are based piping layout, not for vessel.

Regards

 

[TGS4]

PVE - your logic in excluding occasional loads because it's "only a nozzle connection" is faulty. It's a pressure vessel component that requires rigorous evaluation like any other. There is no exception granted in the Code, based on such (il)logic.

How many different ways do you need to hear the same answer (even though it's not the one you want to hear)?

 

[PressureVesselEngineer]

Dear TGS4

Thank you for reply.

I am here to discuss different ways/views on one problem.

So requesting to keep discuss healthy than closing this topic quickly.

Thank you.

Regards

 

[TGS4]

PressureVesselEngineer - I see that you are new here. Welcome to eng-tips and the Boiler and Pressure Vessel forum in particular. I hope that you continue to visit and contribute.

One of the excellent features in this community is that we award each other (true peer review) "stars" when we provide good and helpful answers. We then accumulated these stars and this forms the basis for an MVP list (

http://www.eng-tips.com/tipmasters.cfm?pid=794).

Two of the people replying to you are in the top three of this list, and constitute almost 50 years of combined experience, including almost 30 years combined experience in ASME Codes and Standards writing. So you're not just getting some random advice, but advice from a deep well of experience and expertise.

I guess what I'm trying to say is that I'm not so much shutting down a discussion, but explaining to you from my perspective that you seriously need to rethink your perspective. Nevertheless, if you disagree with me (here), then I would highly recommend that you submit an inquiry to the ASME Code Committee through the formal channels as described in the Code book, and then you can get their (my) opinion there. But the opinions will be consistent, that I can assure you.

 

[PressureVesselEngineer]

Dear TGS4

Thank you for welcoming me.

I really appropriated all members views and those are valuable to me.

I understand that in my past experience ( though its very small compared to all members here), i saw normally shell-nozzle analysis considers only internal pressure and nozzle loads. This is the reason i got stuck in applying W&E on shell-nozzle analysis.

Yes. As per code if UDS specified such requirement, regardless of significance of W&E loads on nozzle shell junction, all loads to be applied.

Thank you again for presenting your valuable views and feedback.

Regards

 

[racookpe1978]

Note.

Your nozzle and its attachment welds WILL SEE the actual stresses that are forced on them by the attached pipes under the real world conditions of ice, snow, wind, stuck support springs, twisted metal, thermal movement and hydrostatic fluid loads and dynamic fluid loads, regardless of whether you think they will or not.

Your analysis and your opinions about the unknown future loads are not only irrelevent, but can never really be verified. You can only make prudent assumptions, then apply prudent (and Code-approved) design factors to minimize the likelihood of failure under the assumed future loadings. What these more experienced forum members are telling you is that the assumptions you are using are not prudent and your analysis software is "elegant" and fancy at what it does, but it is not completely capable of analyzing all of the actual loads present, and - worse - and is (very likely) analyzing only partial loads that you have chosen to assume are going to be present.

Thus, your software selections and your analysis process are not approximating the real world loads. You have not recognized this, and your nozzle is thus more likely to fail. Your client seems to be aware of this, by the way. Don't let your client be the one to tell your boss this failure.

 

[PressureVesselEngineer]

Noted and Thank you.