Weld a flange on the top of the pressure vessel 2

[JuliusChoi]

Hello,

We got the pressure vessel (ss316) with MAWP 15 psi at 347 F.
We are thinking of cutting 26" diameter F&D top head and weld the cut vessel and the top head to class 75 26" flange.
I am wondering how I could get any number to confirm if this is doable. I am worrying that the vessel cannot hold the flange well.
Also what does 75 in class 75 flange mean?

Thank you for your help!

 

[JStephen]

I think that's referred to as a body flange, and should be doable.
If the vessel is built to ASME or other codes, you'd need to evaluate for the change per the code(s) involved. At 15 psi, it may be a non-code vessel,
From a website: "Note: The ASA (now ANSI) terms 300 lb. through 1500 lb. represented working pressures of flanges in elevated temperature service...ANSI has since dropped the previous ASA term "lb." and now refers to flanges by "CLASS"."

 

[saplanti]

please find the dimensions of the flange;

https://www.texasflange.com/product.../ansi-b16-47-series-b-flanges/class-75-ser-b/

And this is for full catalog;

https://www.texasflange.com/wp-content/uploads/2019/06/catalog-c-v5.pdf

 

[Dhurjati Sen]

This is a modification in the design of the existing vessel.

Consult API 510 for the suitability of the same.

DHURJATI SEN
Kolkata, India

 

[JStephen]

One other thing- in my work, 75# is uncommon, 26" size is never ever used, SS is a little harder to find.
So with that combination, you may have trouble finding the flanges in stock.
Coordinate design codes and type/availability of flange- it may work better to use plate flanges, etc. than normal 75# flanges.