Historically, swivels for floating production, storage and offloading (FPSO) units were not designed to be opened offshore. The tight quarters typical of FPSOs mean the required 10 inches or so of space between the swivel and bolts that would allow specialists to open swivels in the field did not exist.
In a perfect world, there would be no need to get inside the swivel, which connects the FPSO and riser and allows the FPSO to weathervane.
