5.1.3. Platform Transportat ion and Installat ion
The chosen spar buoy concept for the platform is not
equipped with self-propulsion, which would only be required
for transportation to the destination location. For
that reason, the platform must be transported by other
vessels. Two options are considered.
Tugboats
Usually used for low to medium distance transport, tugs
are relatively broadly available and widely used; therefore,
they might be economically more feasible than using
a heavy transport vessel. Tugboat sailing speeds are
slightly lower than that of a transport vessel. The image
below shows an example. Please note that the dimensions
of spars shown in this section are larger than the
collecting platform concept. The illustrated spars are
used for offshore oil and gas development projects.
Semi-submersible heavy transport vessel
Depending on the availability, a heavy transport vessel
can be economical as well. The vessel submerges by filling
the ballast tanks. In submerged position it can sail underneath
the spar. It is lifted again and can then be transported
by the supporting vessel. The company Dockwise
is a leader in transport using this method. Cruise speeds
of 12 knots and over are realizable.
Figure 5.3 Spar buoy tugged Figure 5.4 Spar transport using a heavy transport vessel
Installat ion
Installation depends on the actual transport price:
1 In case of the semi-submersible transport vessel the
draft is increased, after which the vessel floats away
from the barge again.
2 The spar is put in upright position by filling its ballast
tanks with sea water.
3 Mooring is applied as described in section 5.1.1.
Multiple polyester ropes are connected to the spar
instead of the single vertical line for the booms. The
lines are in taut configuration to minimize the rope
length.