5.1.1. Mooring Installat ion
In the concept, the mooring consists of a single vertical
polyester rope connected to the seabed using a vertical
load anchor (VLA).
The Stevmanta VLA allows for single line installation using
the shear pin angle adjuster, see Figure 5.1. During installation,
the installation line is the same polyester line
as the one used for the mooring.
Installation can be performed using one anchor-handling
vessel (AHV). A typical AHV, with around 200 tons of Bollard
Pull, will be able to install and retrieve the anchor.
The typical day rate of a deep-water AHV is in the order of
$80,000 USD, and an additional $20,000 USD will be calculated
for a barge carrying and storing the large volume
of mooring lines and anchors. The mode of the anchor
changes when the shear pin breaks at a load equal to the
required installation load.
For Stevmanta VLA, there is no setup time required.
Therefore, the anchor can be connected to the floating
unit immediately after the installation.
A brief introduction to the required installation steps follows.
Steps
1 Optional: attach the tail to the anchor.
This tail assists in orientation on the seabed.
2 Connect the mooring line to the angle adjuster on the
AHV.
3 Lower the anchor overboard, descend tail first. Please
note that multiple rope elements are required to
obtain the required length.
4 After touchdown, the AHV pays out the line while it
slowly sails away from the anchor.
5 Increase line tension, the anchor will start to embed
into the seabed.
6 The shear pin will fail when the predetermined
installation load has been reached with the AHVs
bollard pull.
7 The anchor is now in normal loading mode; tension can
be increased for proof loading.
8 Attach submerged buoy to the polyester line end and
throw overboard