That’s a Blind Flange
What is it used for?
A blind flange is used to seal/close off the end of a pipe, valve, or vessel.
Instead of letting fluid flow through, it blocks it.
Main uses:
1. Pressure testing - To cap a line during hydrotest
2. Future expansion - Close a nozzle on a vessel/pipe that may be used later
3. Maintenance isolation - Block flow in a section of pipeline
4. End termination - Seal the end of a piping run
Details I can see from your photo:
• Type: Blind Flange - solid face, no bore in the center
• Bolt holes: 8 holes - looks like 150# / PN16 drilling pattern