Design Strength, AD2000 Merkblatt code 1

[victorpbr]

Hello,

I`m studying the AD2000 code, However I`m having difficulty setting the design strength stress for my calculations.

Let me show an example with a simple calculation. From part B1 we have that the minimum thickness for a cylindrical shell is given by:

s = (Da*p / (20*K/S*v+p)) + c1 + c2 , Being s the thickness, Da, the outside diameter, K the design strength at design temperature , S being the safety factor at design temperature,v being weld efficiency , p design pressure and c1 and c2 allowances.

Now, I`m trying for my studies to design a cryogenic vessel for liquid nitrogen storage, this vessel would be made of SA-240-304L, which in the Europe is referenced as material no 1.4306, on Part B0, item 8.1 it says that for Rolled Plates the safety factor S is 1.5 at the design temperature and 1.05 for test pressure (Can someone please help on the meaning of this value when on test pressure? I think this means that when on hidrostatic pressure, the safety factor will be of only 5%, is that correct?)

On Part W10 (Materials for low temperatures; ferrous materials), it says the material 1.4306 is able to withstand temperatures as low as -270 C, which is good since I`ll have a working temperature of around -190 C. However it does not states nothing about the value of K (my design strength). Should I use on K the value of the yield strength of the material I found online? Or it has in some place the value I should use, as in Part 2 of the ASME BPVC code, when it says the allowable stresses for div 1 and div 2?

Can someone with experience on this code, please give me some advice?

Kind Regards,

Victor

 

[XL83NL]

Im not very experienced in AD2000, but Ill give this a try.
[ol 1]
[li]Im not sure what AD2000 requires when you use materials not listed in AD2000 (e.g. A240 316L as you mentioned). After a quick read of the W-series there's no detailed guidance on that.[/li]
[li]

Can someone please help on the meaning of this value when on test pressure? I think this means that when on hidrostatic pressure, the safety factor will be of only 5%, is that correct?

For testing conditions, when you check if the design can handle the test pressure, you can use S=1.05 rather than S=1.5 to verify if your design has adequate strength against your test pressure. 1.5/1.05 = approx. 1.43, which is the same value the PED uses for test condtions.[/li]
[li]

Should I use on K the value of the yield strength of the material I found online? Or it has in some place the value I should use, as in Part 2 of the ASME BPVC code, when it says the allowable stresses for div 1 and div 2?

Im not sure if you can/may use the BPV II-D values. I wouldnt do it regardless. I think that for the K-value at design minimum temp (i.e. -190 C) you need to use the value of K at ambient temperature. Typically these are the same - that's how most codes deal with design strength or allowable stress at temperatures lower than those listed in the codes. Dont use yield, as the design strenght are typically based on percentage of yield and percentage of tensile whichever is lower.[/li]
[/ol]

Hope this helps.

 

[victorpbr]

Hi XL83NL, thank you for your reply.

Well, the material is listed on part W of the AD Code as material no 1.4306 , which has the similar requirements of the SA 240 304L, that I was intending to use.

Thank you for your reply on the test pressure safety factor, it is clear to me now.

Regarding the design strength, I do not want to use the values from BPVC II-D, I'd like to use the values from AD 2000, however I do not find them anywhere for this material at my design temperature (I can not find it even in ambient temperature), thats my issue.

Curious thing is that using softwares such as Lv-Soft it has an internal library that can give me these values, for example for these conditions it says that my design strength if of 240 MPa, which is even higher than the yield strength of this material that is of 180MPa, according to

http://cdna.terasrenki.com/ds/1.4306_X2CrNi19-11_AISI-304L_SS-2352_SUS304L_Datasheet_2.pdf

. So where does the software take these values from?

 

[MGZmechanical]

Hi, just one question, hasn't it been superseceded by EN 13445? I don't think AD is harmonized standard under PED.

 

[victorpbr]

Hi, ManoloGalarraga.

Yes it has been superseced by EN 13445 as an harmonized standard, However it is still used in some places outside Europe and in cases the AD is accepted and the requirements of EN 13445 are not needed, so in this case it would be cheaper.

 

[EdClymer]

Victorpbr

I recognised the heading Merkblatt AD-2000 code description in your question.

My copy (purchased and paid for), dated May 2006, is called AD2000-Merkblatt with title Pressure vessels in glass fibre reinforced thermosetting plastics (what USA calls FRP and we call GRP).

It was produced by the Germans, because they wanted to avoid using BS4994 and particularly the new EN13121-3 (both entitled GRP tanks and vessels for use above ground).

But your question appears to be about strength of a particular grade of steel.

Surely there can't be two AD-2000 codes?

Regards

Ed

Ed Clymer
Resinfab & Associates
England

 

[XL83NL]

AD2000, or AD Merkblätter, has subsets ('blätter' as the German call them, hence the name). The subsets are A, B, G, HP, N, S and W (at least, those are the ones we have). The subset N is for non-metallic materials, which also covers pressure vessels in GRP. So you probably own a part of AD2000

 

[victorpbr]

EdClymer,

It is exactly what XL83NL said, your reffered part is part N1, which is only a small part of AD 2000.

 

[EdClymer]

Greetings all

My copy of AD2000 - Merkblatt does indeed have a sub marking of N1.

Thanks to those who replied; I am now slightly wiser.

And, is there anyone out there using EN13121-3 for design of GRP (FRP) tanks and vessels?


Regards

Ed

Ed Clymer
Resinfab & Associates
England

 

[ijzer]

If you work per AD 2000 you have to use materials approved per AD 2000. So in your case if you have to use a SS type 304L than go to AD 2000 par. W2 and select the required material from the list of approved standards. In case of a plate this would mean that you have to use material per (DIN) EN 10028-7 . You will find the yield at temperature in this EN 10028-7 under the applicable material type ( e.g. 1.4306)