How do you handle the selection of the material in PV Elite when your material has dual certification as 304/304L?

Thanks,
Dale

Hello Dale C

I would simply call it up as 304. That is quite legal, because the material does indeed comply with the 304 specification chemically and mechanically. As a vessel engineer, I have been doing that for years.

The documentation that accompanies the design report (calculations), such as the drawing and other design specifications will explain that dual certified material has been used. There is adequate information at the end of the day to detail the material details for the authorized inspector.

I came across this scenario.

in the case of 304 / 304L dual certified material, there is a significant difference in strength of the material (especially at high temperatures). SS 304L has lower allowable strength due to lower percentage of Carbon. A SS304/304L dual certified material would have lower carbon content (equivalent to SS304L requirement i.e. max 0.03%) but still meet the requirement of SS-304 (max. 0.07%).

in order to remain conservative, I used SS304L as the basis for design, since the vessel was in hydrogen service with approx. 500 deg C temperature,

Hello tayyabeme,

I was a vessel engineer for part of my life. The principle for 304L/316L to be dual certified are twofold:

1 That the carbon content meets the requirements for L grade, and,
2 that the mechanical properties meet the requirements for non L grade

Steel makers are able to fine tune the chemical contents or stainless steel, and at the same time get good mechanical values. If you look at an MTR (Material Test Report) for a dual certified material, glance at the mechanical properties.

Carbon controlled stainless steel is has better welding qualities, with less likelihood of forming chromium carbide, which is bad news.