Hi all,

I’m fairly new to this board, this will be my first post.
The question I’d like to ask deals with dual certified 304. I’ve already google-ed this topic a lot but I cant find a satisfying answer to my question.

Right now, the company I work for (we work in e.g. the (petro-)chemical industry) is making a new pipe spec for 304 material.
We didn’t have any for 304 spec before, so I thought of, while making the new 304 spec, to use dual certified 304, since it’s good available as such, and has almost the same parallels as 316/316L (for which we already had a spec).

Now, the one thing bothering me is that 304L flanges are limited (per ASME B16.5) to 425 deg C, while 304 flanges go up 1500 per ASME B16.5.
If you have dual certified 304/304L flanges, can you then ‘just’ use such dual certified flanges up to and above 425 deg C?

The second question (not that important but still interesting); what would you have to do if you want to use 304/304L piping systems beyond 1000F (~538 deg C)?
What values for stresses do you then use, how do you do the calculations?