Bolts Values for ASTM A-193 B7 in AD MERK Code

[Calidad]

Dear Colleagues:

I have 9 years of experience designing Pressure vessels but at this moment I have Mental Lakes about values that I need to take in consideration if I use this german Code.

This code in its part B7 uses Z factors as Safety Factors , well, my ethernal doubt is : Must I use K(T) and K20 as Yield Point of bolts directly from values of ASME Section II table Y-3 and introduce them without any modifications?
Could anybody to clarify my big lake?

Thanks in advance.

Jose Luis Gómez R.
Mech Engineer of INTEGASA - Spain.

 

[ijzer]

My interpretation is that indeed K is the yield at temperature without any safety factor S.
Since they use Z here and the Z value is outside the square root in the formula , the final safety factor will be larger than the normal (S=1.5) they use in other formula's.

Question from my side would be : are you allowed to use B7 bolts in AD-Merkblaetter? Usualy only German (DIN or VdTUV)materials are allowed.

 

[Calidad]

Thanks ijzer for your promptly answer.

In this we are talking about CE marking equipments and if we use european approval of material you don't have further problem, AD Merk is only a Design Code and there is no necessity to use only German Materials.

But, I have no doubt about Z factors, I think normal values for Bolts like A-193 Gr B7 are very higher , and I understand that it could report too much many bolts like this or a little bolts, we , designers, always have been a little conservative in this matter but if you have had experience like this and you have used directly Kt and K20 for materials of Bolt, there is not problem to begin to use them.


Best Regards

José Luis Gómez

 

[ijzer]

It is our standard that if we make a design to AD-Merkb. , we always do an additional flange calculation in accordance with ASME VIII-1.
Reason is that AD-Merkbl. flanges are thinner and although the stresses are within acceptable limits they are less reliable on leakage. So perhaps we are also concervative.