Dear all,

In our project, we have static equipment designed based on ASME SEC VIII- DIV-1. We have used NozzlePro for nozzle qualification.

We received a comment from client as below :

"The equipment is designed based on ASME SEC VIII- DIV-1. NozzlePro cannot be used when the static equipment is designed based on ASME SEC VIII- DIV-1. Please qualify based on WRC 107/297 as NozzlePro evaluaton is based on ASME SEC VIII- DIV-2."

Is it true?

In this above case, we cant use NozzlePro?

I would understand that your Client says that the vessel is designed according to ASME Section VIII, Division 1, better known as the "design by rule" or "design by formula" approach. Simplifying the discussion means it calls for simple and conservative mechanics formulas together with warnings regarding various effects(as nozzle loads, for example).

Division 2 of Section VIII calls for "design by analysis" as a need to develop pressure vessels that permit higher allowable stresses without compromising the safety. With Div 2 rules, we are able to calculate stresses "everywhere" in the vessel and the allowable is higher because we have confidence in the calculated values of stress.
May the value of the allowable stress be the basis of your Client objections? It is worth to discuss this aspect.

I think a good point in your discussion would be... OK, FEA is "design by analysis" but is WRC 107/297 "design by rule"? For me WRC 107/297 seem to be more "design by analysis" with the tools of '60s than "design by rules", so I think that what your Client says make sense just in case in the contractual specification they made clear they want WRC as basis for nozzle loads.

In the end, a nice article of Mr. Trevor Seipp (TGS4 in http://www.eng-tips.com)
http://becht.com/blog/performing-an-fea-...u-2-g-component

The Paulin group would disagree with your client's assessment. However, if their prerogative is to use WRC, they must accept that your piping must meet better flexibility requirements to meet WRC loads as opposed to NozzlePro loads.

True, Michael. However would it be an inconvenient for Client with a lump sum contract, providing that the supplementary flexibility does not affect the accessibility or maintenance works, does not induce vibrations, etc?

Thank you Mariog & Fletcher for your reply

Same question I send to Paulin group,

what they said " The best approach would be to use ASME Code Case 2695 as jutification for using finite element analysis with Div. 1 allowables."

My doubt is,

Is there any option to select the "ASME Code Case 2695" in the NozzlePRO software.

Or simply, its enough to select the allowables from SECTION VIII-1 in the material tab.

In fact, Nozzle Pro does not calculate the nozzle-repad-shell "according to" ASME Div 1 or 2 or CC 2695, the calculation is developed by FEA in compliance with the methodology written in Div 2. You have to activate Material tab and input the allowable or better to activate Import material from Mat/PRO" and choose the row where is your material (Spec, Grade), Design Code "Section VIII-1", Source (IID, Table), Year, etc.

I am not sure Paulin Group point of view will be agreed by your Client, however you can try to deal with them. The reason is CC 2695 has additional requirements and your Client would say that, for example, their PV is already manufactured and the Code Case 2695 is not shown on the Manufacturer's Data Report, neither the report mentions the nozzle has been designed according to the Code Case 2695 (both seem to be required by CC 2695).

Just for my curiosity, the Pressure Vessel file doesn't say anything about the Nozzles' allowable? In case the file is complete and considered allowable loads based on WRC, I think it would be difficult to force FEA approach trying to increase the allowable loads.

To answer to your original question... WRC is not a chapter of Div 1 and FEA does not axiomatically belong to Div2, I think this is the first step you may try with your Client.

Full disclosure: I'm not too familiar with Div 1.

I would agree that it's ultimately the owner's decision, but you may try to persuade them to allow the use of FEA to qualify the nozzle loads.

And I agree that WRC-107 is not a requirement of Div 1. I think it is only mentioned in a Div 1 nonmandatory appendix as a good practice.

I don't think Div 1 prohibits qualifying the nozzle using FEA. In U-2(g), it states that Div 1 does not contain rules to cover ALL details of design and construction. Other methods that can be shown to be safe may be acceptable. Here's more on that.
https://becht.com/blog/performing-an-fea...u-2-g-component


Anyway, just wondering. Let's say you only calculate the flexibility using Nozzle pro. And then you use it in your Caesar analysis. You get your loads, and then you run WRC-107. Would you pass WRC-107? If so, would that not satisfy the client's requirement?