Material under ASME BPVC Section II Part D Table 1A SA-240 304L Note G 1

[abbver98]

Material under ASME BPVC Section II Part D Table 1A SA-240 304L, we 02 different values of allowable stress - one under notes G5 & G42 and the other under G42. The one under G5 has a high allowable stress. Note G5 is'nt clear; they speak about greater deformation (stress between 66.6 to 90% of yield strength). Risk of permanent strain. To avoid this we should use Tables Y-2 and Y-1.
In my opinion this is not very clear ! If I have a small vessel welded (no flange and no risk of leakage) do I had to apply Y-2 and Y-1 ?

 

[unclesyd]

Can you describe you PV a little more?

If a little deformation isn't problem then you can use the higher stress values. If you are designing say a flange where deformation would be detrimental to the function of the component you should use the lower values to prevent this from happening. The designer normally determines what values he needs to insure the function of design.
With the current price of materials this question is being asked a lot more.

 

[abbver98]

Diameter 2"1/2
thk 0.05"
It's very small ! but big quantities !

 

[unclesyd]

Very interesting!

This information puts your stress values in a different light as it may not be possible to design it under the ASME per se.
If possible can you provide more information on the physical description and operating conditions of the PV?

When you get into very thin walls your stress values will normally fall out the range of the ASME. Depending on how the material is manufactured and formed the allowable stress values can be extremely high by several orders of magnitude.

 

[metengr]

The code committee was deliberate in using two different stress lines for the same material. Note G5 is rather clear, if the design of the vessel permits some permanent deformation under temperature, the higher allowable stresses may be used. If you want to tolerate either no permanent strain, you can use stress line 6 (no permanent strain) or a lower permanent strain in comparison to the stresses in line 5, use the multiplying factor from Table Y-2 and apply it to the yield strength in Table Y-1 for 304L that will provide an allowable stress value for x% strain. The designer sets the boundary conditions.

 

[panduru]

Thank you metengr, may your tribe increase!

 

[abbver98]

unclesyd,
I had to use a good practice,ASME BPVC VIII-1 is one.

metengr,
Thank you

According to analysis the vessel could work but with permanent strain of 10% ! I make also a burst test and I have an idea about the MAWP that comply to analytical calculation.