Slip rings for marine mooring swivels & FPSO turrets

Turret-moored FPSOs and floating platforms weathervane around a fixed mooring, so power, signals, fibre and fluids must pass through a swivel stack at the turret. Voltages reach medium or high voltage, hazardous-area certification is mandatory, and the design must run continuously for decades offshore. Floating wind adds subsea high-voltage swivels.

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What the slip ring has to handle

Medium- and high-voltage power swivels (tens of kV)
Low-voltage electrical swivels for power and signals
Fibre optic swivels with many passes
Hazardous-area certification (flameproof, pressurised, increased safety, intrinsic safety)
Large hollow bores (metres) for fluid swivel stacks
IP66-IP68 marine sealing
Classification-society verification and long life

Typical figures

Voltage	72.5 kV rated (66 kV operating) HV swivel example
Bore	1.4-2.5 m hollow bore (LV swivel example)
Fibre	Up to 52 passes singlemode/multimode
Fluid pressure	Up to 15,000 psi (1030 bar) fluid swivels
Ingress protection	IP66 standard, IP68 to 20 m option; subsea IP68
Temperature	-20 C to +60 C (LV swivel example)
Size weight	HV swivel example 2,300 mm high, 2,510 mm diameter, about 5,280 kg

Example figures from the published sources listed below. Your requirement may differ; an engineer will confirm against your duty cycle.

Recommended slip ring types

Marine and subsea slip rings Large-diameter slip rings High-current slip rings Fibre optic rotary joints Rotary unions and hybrid joints

Standards to consider

ATEX / IECEx - hazardous-area certification
DNV - independent verification of swivel technology
IEC codes for high-voltage design

The complete system

A slip ring rarely works alone. For marine mooring swivels & FPSO turrets it is usually specified together with:

fluid swivel stack
turret bearing
junction boxes
fibre optic swivel
encoder
purge controller

Specifying these together avoids mismatched connectors, cable routes and feedback interfaces, and gives you one point of contact for the whole axis.

Common problems to design out

Insulation breakdown on high-voltage passes
Ingress of seawater or moisture
Fibre attenuation or loss
Hazardous-area seal failure

Frequently asked questions

What voltage can an FPSO swivel carry?

High-voltage swivels rated at 72.5 kV (66 kV operating) are on the market for floating production and floating wind. Low- and medium-voltage swivels sit in the same turret stack for ship services and signals.

Do turret swivels need hazardous-area certification?

Yes. Swivels are certified for hazardous areas using flameproof, pressurised, increased safety or intrinsic safety protection to ATEX or IECEx.

Can fibre pass through an FPSO swivel stack?

Yes. Fibre optic swivels offer up to 52 passes, singlemode, multimode or a mix, mounted in the turret stack alongside electrical and fluid swivels.

Sources

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Like-for-like and better-fit alternatives

Standard, modified and custom options