Internal Disconnectable Turret (BTM Mooring System)
This system is of a similar principle as the internal
turret system. The system provides large transfer capacity and allows the
FSPO to operate in harsh environmental conditions in medium operation
depths. For this system, the internal
turret is integrated into the forward end of a tanker or barge. A large
collet-type connector connects the turret to a mooring buoy. This has
sufficient buoyancy to support the weight of the chain legs and risers. For
reconnection it is sufficient to pull up the buoy under the ship. This is
done with a wire rope hauled in on a drum winch. When the vessel leaves,
the column remains on location.
The main advantage of this system is that it allows
the FPSO to disconnect itself to avoid any typhoons, hurricanes, icebergs
and other extreme dangers. Years of experience and development has achieved
that nowadays the disconnect-reconnect sequence is very quick, safe and
reliable.
External turret
An external turret is
structural comparable to an internal mooring system. The turret itself is
placed outside the hull through a rigid structure at the bow or at the aft
of the tanker. A disadvantage is the fact that here the amount of risers is
very limited. The building process do not has to be performed on a dry-dock
which reduces cost and delivery time. The weight of the system is also less
than an internal turret which saves on steel. The system is normally
applied to FPSO in shallow waters and small oil or gas fields. There are disconnectable
external turrets as well.
External disconnectable Turret (RTM
Mooring system)
An external disconnectable
turret is mounted on the bow of a vessel. It disconnects automatically in
two stages. During the first stage the risers are being isolated.
Successively the riser column is being disengaged by a large hydraulically
operated collet-type connectors. From the moment the tanker is disconnected
it will sail away, while the column remains on location.