European Code us Asme Code 5

[Inki]

Hello everybody!

i am concerned about the difference between European Code (EN13445) and ASME VIII, when calculating Spherical heads. My results shows a difference from 2 mm (diamter = 4000 mm) to almost 5mm (diameter = 10000 mm)in the required thickness of the spherical head. My question is if anybody has experience designing with european code and what this difference imply? Is the European code safe comparing with ASME? Is ASME too conservative? In other parts of the vessels (cylinder, conical,etc) the differences are much lower.

Thanks in advance.

 

[dig1]

Hi Inki,

I'm assuming that you are sing Div 1 of the ASME code and not Div 2.

For most materials, EN 13445 has a lower design margin on material physical properties than ASME Section VIII, Division 1. But there are also additional requirements (testing, fabrication tolerances (see Part IV of EN), and perhaps more engineering calcultions that need to be performed depending upon the application.

If all the rules of both Codes are followed, I would not consider one to be "safer" than another. Even though EN is relatively new as a code, older European national codes had similar thicknesses as EN.

The new Div 2 is closer to EN in terms of thickness and has more engineering, fabrication, etc requirements than Div. 1. I recently spoke with a member of the ASME Section VIII design committe and he told me that a Div 1 vessel and a Div 2 vessel are supposed to be "equally safe". Thinner sections with the trade-offs listed above.

I don't know why the differences between EN 13445 and Div 1 would be much lower in other parts of the vessel. The basic formulas (cylinder, cone) are essentially the same (hoop stress is hoop stress) with the major difference being the allowable stress value. Cone to cyliner junctions are also treated differently in EN (no stiffening rings for internal pressure).

It is really impossible for someone here to give you a definitive answer to your question without all information. I suggest that you contact someone who is has knowledge with the codes to review your work if you are not familar with one or the other of them to make sure you are covering not only the design but also the fabrication/testing requirements.

 

[Inki]

Many thanks dig1 for your answer,

you are right, i am design as per Div1. I see that there is a linear relation between the thickness required in ASME Div1 and EN-13445, when you are designing spherical heads. When the diameter of the spheric is higher, the difference in thickness grow. The differences are minimals for diameter lowers than 2 meters.

I am doing this comparission with carbon steels (SA-516 Gr60 for ASME and P265GH for EN).

Is there someone who can explain me how to quantify those additional requirements (testing, engineering, fabrication tolerances,etc)? I just don't want to ask to a workshop because this is an study just to take a decission in my company (but no yet to order an equipment).

Thanks in advance.

Rgards

 

[dig1]

Do you have all the parts to EN 13445 (at least parts 2, 3, 4,and 5)? Part 4 covers fabrication and part 5 testing. The engineering portion is in Part 3. part 2 has several issues including how to prevent brittle fracture.

If you go through these it will help. Give yourself a couple of days to do that to become familiar with the basic requirements.

I would not go to a shop who does not have expericence with EN just as I would not go to a shop that does not have ASME experience.

There was a study done a few years ago for the EU on a cost comparison between EN 13445 & ASME Section VIII. Depending on a variety of factors, sometimes the EN was less expensive and sometimes it was ASME.

Do you have a requirement to construct to EN or ASME? I know some countries will accept a vessel designed and constructed to an internationally recognized code.

 

[Inki]

Hi again dig1!

Yes, i have all the parts of EN13445, but is really hard and timeconsuming to read all. I use some software in the calculations, which take into account the DBF (not the DBA). And i see how many differences exits in spherical ends required thickness. I think it is weird, because in other components there is no such differences.

I have been searching on the internet and i have some information about the comparison, but i want to get (if it is possible free )the "Comparison of Pressure Vessel Codes Asme Section VIII and EN13445". Do you have it? The study for the EU what you say, well, i have it, but the results are stange because its said that there is more difference between several workshop than between several codes (Div 1 Div2, DBF or DBA). I see it very theorethical.

In my company, the used to design vessels as per ASME VIII, but EN13445 its claim to be less conservative, more technical advance, etc what i mean is that if EN allows less thickness it will mean less costs. But it could imply others hidden things like more cost in fabrication (tolerances, quality, etc). This is what i'm afraid of.

 

[insult2injury]

My two cents....there's no substitute for reading and comprehending the codes.

I2I

 

[Raaden]

Here is the link for the comparison:

http://ec.europa.eu/enterprise/pres...isation/Comparative_Study_Summary_07_2004.pdf

The following site might also be useful:

http://www.unm.fr/en/general/en13445/#information

It contains interpretations of different parts of EN 13445 and also a very interesting pdf-book called:
EN 13445 "Unfired pressure vessels" - Background to the rules in Part 3 Design

 

[Konrad]

The study for the EU what you say, well, i have it, but the results are stange because its said that there is more difference between several workshop than between several codes (Div 1 Div2, DBF or DBA). I see it very theorethical.


I see it very deeply true. I can spend more time on designing, using my experience and knowledge of various loopholes in the code. The result will be a pressure device that is lighter or simplier to fabricate. But my work might be more expensive than material savings. Or testing/examination savings.
Now go to China- they would be happy to spend more engineering time to save on titanium material. Go to UK- nobody would give a penny for hardcore designing, particularilly if the material of construction would be a cheap mild steel.
Can you now see the difference? Maybe you didn't have a chance to feel in reality, but believe me, the approaches do vary from place to place.