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Higher Allowable Stresses for Low temps in Division 2

Higher Allowable Stresses for Low temps in Division 2

(OP)
Hi,

I'm trying to figure out what value for maximum allowable stress to use for division 2, it is a vessel for liquid nitrogen storage, hence working temperature of -196°C.

On ASME II - D:

For Division 1 we have a maximum allowable stress of 115 MPa (-30 to 40°C) (Table 1A)
For Division 2 we also have a maximum allowable stress of 115 MPa (-30 to 40°C)

However, on Division 1 we have Part ULT, that is specific for Low temperature applications where it give us a value of 23.6 ksi = 162.7 MPa.

So I ask, is there any part on Division 2 that can increase my allowable stress the same way Part ULT does on Division 1?

Regards

RE: Higher Allowable Stresses for Low temps in Division 2

ASME Vessels codes are very limited when it comes to low temperature.

ASME VIII-2 Section 3-A specifies that the tables in ASME II Part D shall be used to find allowable stress (with what appears to be no exceptions).

The tables in ASME II Part D are not applicable to your application as they only cater for a temperature down to -30°C.

Therefore consider looking at ASME II Mandatory Appendix 2 to manually calculate allowable stress. This appendix does suggest that for below room temperature, room temperature properties shall be used (in which case the tables look to be applicable).

RE: Higher Allowable Stresses for Low temps in Division 2

There is no equivalent to ULT in Division 2.

RE: Higher Allowable Stresses for Low temps in Division 2

(OP)
MrPDes,
That is exactly as I thought, thanks for making it clearer. I was hoping that since division 1 allows higher stresses, division 2 would also provide something similar.

TGS4,
I was afraid of that. So, in your opinion, for this application, is it more cost-effective to design it using division 1? Or there are other better ways?

Thanks

RE: Higher Allowable Stresses for Low temps in Division 2

Division 2 doesn't have a provision akin to ULT. However, the Code Committees are dynamic volunteer groups, and if the right person came along recommending/offering to assist in incorporating ULT into Division 2, I know that they would be receptive.

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