How Do Rotary Unions Work in Hose Reels?

On an offshore hose reel, rotary unions (integrated with electrical slip rings) transfer hydraulic fluid, data and power signals through the reel hose down to subsea equipment. In some applications, pressurized hydraulics, power and data supply remotely operated vehicles (ROVs) allowing the control of subsea tools.
Learn more at www.dsti.com/learn/what-is-a-r...
Applications suitable for DSTI's offshore rotary unions include subsea and topside intervention and workover umbilical reelers / winches, installation and decommissioning operation umbilicals, shallow and deepwater vertical / horizontal completion umbilicals, ROV flying leads and jumper umbilicals, and other subsea tieback and control umbilical hose reel applications.
Source: www.dsti.com/industries/marine...

[@kristofferbeder]

That explained nothing

[@sekharrl2729]

🔌rotary joint animation

[@StevethecavemanLive]

Says what it does.... but not how... need different title for video, did not answer question