fatigue analysis on sa-414 g 2

[nhtien]

Hi to all,

We want to use the plate SA-414 Gr. G in a pressure vessel under cyclic reaction due to pressure. The vessel will be done according to ASME Section VIII div. 1. To meet UG-22 (e) requirement, we will do a design based on fatigue analysis according to ASME Section VIII div. 2, Appendix 5 Because we cannot meet the conditions described in paragraph AD-160. But According to Section II part D table 2A, we cannot have a Sm value for the SA-414 Gr. G. Is this mean that we cannot use the SA-414 Gr. G under cyclic Reaction due to pressure?

Thanks.

 

[hjulien]

It's true! I can't find the Sm value of the SA-414 Gr. G in the table 2A of Section II part A edition 2004 Addenda 2006.

I have the same worry related with the following report found on the ABSA (Alberta) web site :

http://www.absa.ca/IBIndex/IB06-003.pdf

The tanks manufacturer mentionned in this report are normally making the dryer towers from SA-414 Gr. G materials and these tanks are working at around 1 000 000 cycles/10 years of full pressure variation (110 PSIG to 0 PSIG and 0 PSIG to 110 PSIG).

Somebody knows the answer?

 

[zjliang]

nhtien & hjulien,

Firstly, I think SA-414 Gr.G shall be a ASME material, and I did find it from the table.

Secondly, if design based on stress analysis will be used to evaluate fatigue, please remember Div 2 allowable shall apply. So, even though you could not find the Sm for some materials, some recommended allowable stress calculation for carbon steel like Min(1/3 UTS, 2/3Sy) can be used.

Finally, the fatigue curve referenced in App 5 of Div 2 Code can actually be applied not just for ASME approved materials. The curves are related only to the UTS.

Thx.

 

[doct9960]

nhtien,
SA-414-G is a SHEET, not a plate.

zjliang,
According to ASME Section II, Part D, Mandatory Appendix 2:
"The values in Tables 2A, 2B, 3 and 4 are established by the Committee only."
Therefore, you can't just use "some recommended allowable stress calculation for carbon steel like Min(1/3 UTS, 2/3Sy" as you have stated.

 

[Xianglu]

1. You should realy pay attention to the welds and weld affected zones where failure (crack) will start. The base material is not a real concern.

2. My experience is that the designer should take into account the following factors: 1]. alternating stress level; 2]. SCF (such as type of joints); 3]. Weld quality or joint efficiency; 4]. Material quality; and 5]. PWHT.

3. You may also want to compare PD 5500 with ASME VIII D2.

Good luck.