A swivel is a rotary joint which allows fluid to pass through it’s rigid body. It is a hydraulic version of an electric Slip Ring.
A Rotary Union is a Swivel that can transfer various media besides fluid – gas, electric current or bus ( digital data lines )
Repairing and Rebuilding Hydraulic Center Swivel Center Post on Haas Tl-2 CNC Lathe
https://www.youtube.com/watch?v=__DhbYYzukE
Manufacturers
- RotarX joints
https://www.youtube.com/watch?v=bADVKJlvvGc
https://www.rotarx.com/en/slip-rings/rotary-joint/ - Superswivels USA
Great for side loads, inline and angled
https://www.superswivels.com