How allowable stress is set from the ultimate strength in ASME Section VIII Div.2 Edition 2007? Or UTS/2.4 at room temperature means? Or 2/3 Sy at design temperature?
For example SA 387 GR 11 CL2 at 420 deg centigrade (design temp.) is having allowable stress = 149.8 MPa, How this is calculated?

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Paresh Gujarati
M.TECH (Industrial Process Equipment Design)

The allowable stress calculation basis is given in the asme code

Allowable stress = Min ( UTS/Factor of safety,2/3* yield stress, Creep resistance (Applicable only at the higher temperature))

Regards
Pradeep

Hi Paresh,
The governing allowable stress will be the smaller of the min.UTS/Factor at room temp and 2/3 YS at design temp.

With regards to your example, the allowable stress is selected from yield stress at 420C, you need to intepolate for the value of YS at ASME II part D table Y-1

Gilbert