goosespear65's Sovren Profile

https://www.octalflange.com/slip-on-flange/ , also called SO flange. It's a kind of flange slides over the pipe with internal design is slightly larger than the pipe.

Slip On Flange Specifications and Dimensions - Octal Flange

Slip on flange (SO Flange) internal diameter is bit larger than pipe OD, so it can slide over the pipe and directly welded to other equipment.