[edwin16]

“On block valves”!??

Not on block valves…I never mentioned block valves.
They pipelines are connected to valve blocks. I mean (connection-) blocks where valves/servos etc are mounted to. It is partly visible on one of the photos.
This is very common in the hydraulic industry.

I’ve never encountered these “types” of flanges before

Neither have I.
Normally we use 3000/6000 psi square or SAE flanges (AVIT and/or STAUFF make) in the hydraulic industry but I’ve never seen these before.

…with a “normal” type of flange

Define “normal”. You mean “normal” DIN or ASME flanges? That’s very uncommon in the hydraulic industry.