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rings are stacked atop of each other to provide multiple independent flow paths.

The inner and outer ring concentricity is maintained by triple race roller bearings.

Seals around the periphery of the interface between the inner and the outer rings

prevent leakage of the working fluid.

The swivel design is based upon the following guiding principles:

Flow re-routing as back mode of operation

Swivel redundancy

Ease of maintenance with minimum intervention

Maximum use of field proven designs

The driving arrangement for the swivel stack is an integral part of the

overhead framework structure. An individual driving ring is supported at two

opposite sides by a fork arrangement. Each swivel unit is therefore driven on both

sides of the outer ring simultaneously resulting in a pure driving torque with no net
shear being applied on the piping flanges.

The swivel sealing system incorporates double seal sets in each module. A
leak detection system and recuperation system is built-in between the seals which

collects any product fluid and returns it to the production flow.
The gas swivel sealing principle is based upon an over-pressurised back-up

fluid that serves as a barrier between the gas to be sealed and the environment.

This is achieved by using three seals on each side of the gas chamber. In order to

assure the absolute gas tightness, the pressure on the back-up fluid is always

maintained higher than the gas pressure. This is achieved through a simple

accumulator.

6.1.4 Marine Systems

Inert Gas and Tank Venting System

To avoid the presence of an explosive mixture in the cargo tanks above the

oil an inert gas is installed to provide a slight overpressure gas blanket at the top of

the cargo tanks and slop tanks.

The inert gas system is designed to comply with the SOLAS 1974/1978
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