Review of Cabling Techniques and Environmental Effects Applicable

Review of Cabling Techniques and Environmental Effects Applicable to the Offshore Wind
Farm Industry – Technical Report
Table 3.5: Overview of Cable Burial Machines
36
Burial Machine
Type
Cable Burial
Ploughs
Tracked Cable
Burial Machines
Free Swimming
ROVs with Cable
Burial Capability
OVERVIEW OF CABLE BURIAL MACHINES
Burial Machine Options Mode of Operation
Cable ploughs are available in
varying types:
● Conventional narrow share
cable ploughs
● Advanced cable ploughs
● Modular cable ploughs
● Rock ripping ploughs
● Vibrating share ploughs
Tracked cable burial machines can
be equipped with the following
burial tools:
● Jetting systems
● Rock wheel cutters
● Chain excavators
● Dredging systems
Free swimming ROVs can be
equipped with the following burial
tools:
● Jetting systems
● Dredging systems
Burial Sleds Burial sleds can be equipped with
the following burial tools:
● Jetting systems
● Rock wheel cutters
● Chain excavators
● Dredging systems
Cable ploughs are towed from the host vessel with
sufficient bollard pull to ensure continuous progress
through the seabed with the cable being simultaneously
buried as part of the lay process. The plough lifts a
wedge of soil and places the cable at the base of the
trench before the wedge of soil then naturally (via
gravity) backfills over the cable. Cable ploughs are
capable of working in a wide range of soils and are
typically deployed where longer lengths of cable burial
are required. Ploughs can operate in shallow water and
in water depths up to 1500m.
Tracked cable burial vehicles are usually operated and
controlled from a host vessel such as a Dive Support
Vessel (DSV) or a barge, have subsea power packs, and
are controlled via an umbilical cable back to the host
vessel. They usually operate in post lay burial mode
(although one machine, the LT1, simultaneously lays
cable from a reel mounted in the vehicle) and they
are equipped with either jetting tools or mechanical
cutting tools depending on the seabed conditions which
are anticipated. The tracked cable burial vehicles are
typically used on shorter lengths of cable burial work.
Divers are often required to assist in the loading and
unloading of cable into and out of the vehicle in the
shallow water machines. However, some vehicles have
fully automated cable loading/in-loading equipment.
Some vehicles track over cables and straddle the cable
with jetting forks. Tracked cable burial machines can
be operated in shallow waters (providing motors and
power packs can be cooled) and in water depths to
2000m.
Free swimming ROVs are operated and controlled
from a host vessel such as a DSV or a barge. They will
always operate in post lay burial mode and use either
jetting or dredging system to bury subsea cables.
Their range of application is limited to sands and clays
(performance in clay will be directly related to available
jetting power). ROVs are typically used on shorter
lengths of subsea cable and can operate in water
depths of 10m to 2500m.
Burial sleds are usually operated in shallow waters for
work in ports, estuaries, river crossings and shore-ends
for cable systems. They are often deployed from barges
or jack-ups and either have subsea power or utilise
power systems which are mounted on the host vessel.
The range of burial tools allows the varying types of
burial sled to work in most seabed conditions from
sands, gravels, clays and softer rock.