304 vs 304L vs Dual rated 304/L as it applies to ASME code
304 vs 304L vs Dual rated 304/L as it applies to ASME code
(OP)
I have recently performed an ASME code calculation (using software) on a pressure vessel. I thought that it was odd that the vessel would pass for 304 but not for 304L. This of course raised the question of what the difference is between the two at say 1150 degrees F. My question isn't really what the difference between them is, rather what are the properties of the dual rated version, and if there is such a clear dividing line of 0.03% carbon content, how can the material perform the function of both? Also, my purchasing manager has stated that he cannot find pure 304 anywhere, that we must use 304/L or go to a different # stainless, is this true?





RE: 304 vs 304L vs Dual rated 304/L as it applies to ASME code
304/304L dual certified material is readily available if you go to the right stockists/manufacturers. 304 is stronger than 304L. The dual certified material meets the requirements of both material specifications.We have used dual certified plate and pipe material on a recent Project. We did not have much problem sourcing.
RE: 304 vs 304L vs Dual rated 304/L as it applies to ASME code
Dual certified stainless has to be carefully evaluated for service. At low to moderate temperature service, no problem because corrosion resistance is the controlling factor in design application. Once you get above 1000 deg F, there are noticeable differences in creep strength that you must consider in your design (the maximum service temperature permitted for 304L is 1200 deg F, while for 304 is 1500 deg F).
If you have access to ASME B&PV Code, review Section II, Part D. Evaluate the differences in allowable stress values between 304 and 304L.
RE: 304 vs 304L vs Dual rated 304/L as it applies to ASME code
The real issue is creep resistance. The original creep limits for 304 were based on material with some C in it. Even if you have high strength 304L with nitrogen it will not have as high of creep strength.
You need to look at the limitation on your design very carefully.
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RE: 304 vs 304L vs Dual rated 304/L as it applies to ASME code
We also take into account both the High and Low allowable for design with both 304 and 304L, noting that the Low values for 304 and the High values for 304L overlap at the lower temperatures. I'm not sure how this is handled at the present with the dual certified materials.
RE: 304 vs 304L vs Dual rated 304/L as it applies to ASME code