304L vs. 304H

[Dlynch85]

I was faced with what I though was a simple question at first, but now I am not satisfied with what I have found. Our shop is fabricating a piping system made of 304H stainless steel. The piping has a 825 degree Fahrenheit operating temperature and falls under B31.3. They are running out of pipe and wanted to know if they could use 304L in its place. After researching the code and internet the only facts I have found are in sec II part A under sa-312/sa-312m 1.2 304H is intended for high temperature service, their tinsels are 5000 ksi different and the minimum carbon for 304h is .04-0.10 where as the 304L has a maximum carbon content of .035. Online on a different forum I noticed that someone wrote that 304L is only used up to 800 degrees Fahrenheit, I have not located where that is written. My question is then, can 304L be used in place of 304H? Why or why not? Where is this information located? Thank you.

Dlynch85

 

[metengr]

You will not be able to substitute the 304H for 304L. Look at the allowable stress lines in Appendix A-1 of B31.3. You can possibly use 304.

 

[moltenmetal]

Ditto what metengr said, but I think he confused matters by swapping the two grades. You might be able to use 304/L dual grade, or 304 straight grade, but you cannot use 304L as a substitute for 304H in a high temperature service.

 

[metengr]

Yes, sorry about that. Senior moment.