Stress Ratio definition

[nicorvp]

Question:

Which is the meaning of "nominal pressure stress (based on minimum pipe wall thickness ..." in ASME B31.3 Fig.323.2.2B (a)-(1)?

I have a ASTM A333 Gr.1 pipe at 15 barg (217,5 psig) and -46°C (-50.8°F). How can I calculate the stress ratio?

Thanks for your help

 

[hokie96]

nicorvp,

To calculate the stress ratio for Figure 323.2.2B, go back to the basic design formula for straight pipe (304.1.2) and solve for "S" using the minimum pipe thickness less any allowances (usually 0.875*thickness listed in your pipe schedule less any thread and/or corrosion allowance) as t. This "S" is your nominal pressure stress.

Divide this nominal pressure stress ("S&quot by the code S from Table A-1 for the stress ratio.

Don't forget to look at notes (a)(2) and (a)(3) as well.

Good Luck.