Fatigue analysis - ASME and EN 13445

[kurtz]

I am working on pressure vessel based on Div.1 citeria, but I also have to perform fatigue analysis.
Vessel will be manufactured in Europe so I need CE stamp and I need meet PED requirements.

Do you think that I can calculated the whole vessel by ASME VIII Div.1 and perform fagigue analysis acc. to EN 13445-3 ?
I am workink on VVD softwere and I don't have Div.2 standard, so do you think I can mixing those standards?

 

[MGZmechanical]

I do not think you will have trouble with calculations; If you need third party design inspection they use to accept ASME without problem. Even more in this case where the design according ASME VIII Div 1 will be just a "first approach" because, probably, the calculation according EN 13445-3 for fatigue will be more restrictive.
The problem, in my experience, is with manufacturing. Do not forget to use EN certified materials for pressure vessels; EN WPS, WPQR and certified welders. And also use welding details included the EN 13445 Annexes and NDT levels.

Best regards

 

[XL83NL]

As Manolo says, you wont have trouble with the calcs, and the NoBo may find this good as well (they usualy do as, in my experience, thet never check any calculation).
But be very careful. Id almost advocate not to do it. Youre mixing codes. The design basis in both codes are different, e.g. stress allowables, and basic calculations for shell thickness. You need to resort to Div 2 or a code case for this. Im sure others can give a much more detailed answer as to how this route should look like in ASME Section VIII, but Im pretty sure it's not best done using EN 13445 as an extension to VIII-1, based on aforementioned reasons.

 

[kurtz]

Do you think I can use Div.1 and perform fatigue analysis by Div.2? For me it's also mixing, because Div.1 has different stress allowable. Div.1 + Div.2 it's similar to Div. 1 + EN13445.

The only way is to calculating all by Div.2. What do You think?

 

[kurtz]

I read that:
"Fatigue design according to ASME Div. VIII Sec. 2 Appendix 5 for welded regions is considered to be non-conservative in comparison with procedures in major European pressure vessel codes (e.g. EN 13445, AD-Merkblatt3, PD 55004) and the underlying experimental results. Thus, ASME fatigue design for these regions is not considered to meet the requirements of PED Annex I. Taking this into account, the results of alternative design procedures may be required for fatigue evaluation, i.e. re-assessment of the fatigue life using a European approach would be desirable in practice"

Does anyone know why ASME Div.2 App.5 does not meet the requirements of the PED Annex I?

 

[TGS4]

FYI - your reference to "Division 2 Appendix 5" is now approaching 12 years out of date. Division 2 was completely re-written in 2007 and has been revised ever since. The newest Edition - 2017 was just made mandatory January 2018. I have not heard of anything regarding non-acceptance of the new Division 2 fatigue methods for PED.

Also, Division 1 with Division 2 fatigue analysis is very common. Since there are no fatigue methods in Division 1, this approach is actually the preferred and recommended way to do things.

 

[kurtz]

Thanks.
Could you recommend any software for fatique analysis by Div.2 which cover calculations for the whole vessel?
PV elite it's only for nozzles. I think Nozzle Pro also.
I have Visual Vessel Design, but it doesn't have Div.2

 

[TGS4]

No such "canned" program exists. You, typically, need to perform finite element analysis. And by you, I mean an expert in the field with substantial expertise and experience.

 

[kurtz]

Thanks, so I can't do it by Div.2.

Is it allowed to use a different code to perform fatigue analysis?
I would like to do calculations the whole vessel acc. to Div.1, then repeat the whole calculations acc. to EN13445 and perform fatigue analysis.

Is there a paragraph in Div.1 that allows such procedure?
I know it does not make sense, but the client wants to have a main calculation acc. to ASME. Fatigue analysis it's only for safety and Notified Body.

 

[XL83NL]

Fatigue analysis it's only for safety and Notified Body.

Well, if its for safety (which is very trivial - why else do we do pressure vessel calcs?), then why is it so hard to get an understanding on the background of this issue, and find out (e.g. using an engineering assessment) what would be a safe and sound (engineered) solution, within the scope of your design code? TGS4 has given a good advice - I recommend you follow that. If you cant do a Div 1 design supplemented with a Div 2 assessment for fatigue, I suggest you leave this up for an experienced expert who can do this.

 

[kurtz]

but it's only 5 bar design pressure (70 psig) - I don't want to perform very complicated FEA analysis, if I can do it by EN 13445

 

[TGS4]

There are so many things wrong with you have written since your 14 Feb 18 10:59 post, I don't even know where to begin.

Perhaps I will start with an example:
Process: Delayed coking thermal cracking
Equipment: Coke Drum
Service: Cyclic in temperature and pressure
Fluid: Gas, hot oil, solid coke (carbon), steam, water (in that order)
Design conditions: 50 psig (at top) @ 875°F - 29.5 psig of static pressure at the bottom
Size: Range between 20' diameter and 35' diameter and 50' to 100' tan-to-tan
Situation: Many drums in this service are designed using the ASME Section VIII, Division 1 rules for pressure only. These typically last ~4 years before developing leaking cracks. Leaking cracks of hot hydrocarbon leads to fires. Those drums that are designed for the fatigue/cyclic service generally last 10-25 years before leaking cracks, but the fatigue analyses generally shows the operator where to look proactively and how often, so that they can repair the cracks before they become catastrophic.

Need I go on?

If you are unable to do the fatigue analysis requested by your client, then find someone who can. Also understand that if the fatigue analysis will govern the design of the vessel (i.e. result in a thickness or design details that wouldn't otherwise be necessary for pressure-only), then there will be a whole host of additional fabrication requirements. For example, have you given any thought to controlling the out-of-roundness/weld peaking? The Code-required value for pressure-only generally results in a fatigue life of the longitudinal seam ~1/10th that of the base cylinder. I could go on and on.

I'll finish with the same advice that I gave in another recent thread:

Find an expert. Engage them. Pay them.

 

[kurtz]

I am from Europe and every day I am using EN 13445.
I can't perform FEA analysis by Div.2, but I am able to design safety vessel by EN 13445-3.
I am aware about weld peaking and out-of-roundness, because they are a significant factor in the calculation by 13445-3 p.17

My question is:
Is it allowed by Div.1 to use a different code to perform fatigue analysis?

 

[TGS4]

Asked and answered.

Also, Division 1 with Division 2 fatigue analysis is very common. Since there are no fatigue methods in Division 1, this approach is actually the preferred and recommended way to do things.

See U-2(g).

 

[kurtz]

Thank you.

 

[MrPDes]

Pressure design and Fatigue design have next to nothing to do with each other and therefore can be conducted using different codes.

For vessels designed within the USA, it is logical to use the American ASME Div 2 fatigue method. If something went wrong during operation, I would expect you would need to justify why you didn't use Div 2. However strictly speaking, I understand that even in the US it is only "recommended" to use the div 2 fatigue method with Div 1, and that any fatigue method can be used. ASME PTB-4 says that a fatigue method is "provided" in Part 5 Div 2, however doesn't specify it as being mandatory.

In Europe, pressure equipment needs to be designed to PED regulations. PED allows any recognised design methods to be used (although EN 13445 is Harmonised to the PED). In Europe, The pressure design of a vessel can be done to ASME VIII Div 1 and the fatigue design to PD 5500 Appendix C (or any other fatigue assessment method) without any issues.

From a European regulatory point of view, using ASME VIII Div 1 for pressure vessel design and EN 13445 for fatigue is more "appropriate" than using Div 2 for fatigue, as EN 13445 is Harmonised to the PED.