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Wheel Trencher
"SUBTRENCH TWO"
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Page updated
2010/06/23 |
Introduction
to "SUBTRENCH TWO"
Based on our experiences from the development
of our first Sub sea wheel trencher, JD-Contractor A/S has developed
a new heavy wheel trencher ROV for pre-trenching in hard soils,
such as clay, chalk and stone reefs.
SUBTRENCH TWO is mainly suited for making trenches for larger power
cables and pipes in depths up to 100 meters. The unit is built for
trenching before laying the cable, but it can also be fitted with
tracking devices for following an existing cable, which can then
be moved into the trench. It grinds a narrow trench, which protects
the cable well against dragged objects such as trawls and anchors.
On our first mission with SUBTRENCH TWO, it trenched a distance
of 6300 m. in the Great Belt.
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Method of trenching
The trenching unit is placed on the seabed,
and grinds a trench 60 cm wide, and 80, 100 or 115 cm deep
depending on the customer's requirements.
The material is pressed into the wheel, and taken up over
the seabed, where it is taken away by the suction system,
and scattered over the seabed besides the trench.
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The machine operator can follow the process on TV screens
showing pictures from cameras placed at several key positions
on the machine.
SUBTRENCH TWO digs trenches with very even and vertical sides.
They become half filled with light materials that act as the
first protection for the cable when the cable is jetted down.
The cable will not be covered further, but light material
will over time settle in the trench and protect the cable.
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Environmental effects
The machine makes a narrow trench compared to
digging from a barge on the surface.
The material is scattered in a thin layer, and hereby does not have
a heavy influence on the environment near the trench. |
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On the multibeam below, the difference between making trenches with
a traditional surface controlled excavator and the trenching wheel
can be seen. On the right side of the scan the trench has been made
with a mechanical excavator placed on an excavator vessel. Here
you can see the trench is very wide, and the debris from the excavation
is visible next to the trench. On the left side the trench has been
made with the trenching wheel, and consequently the trench is much
narrower. There is very little debris on the side of the trench.
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Click to enlarge photo
Summary
The wheel trencher, SUBTRENCH TWO:
 is very efficient where the seabed consists of clay, chalk and other
hard materials.
makes a narrow deep trench that protects the cable well.
is friendly to the environment due to a narrow trench.
is little influenced by weather.
operates at large depths.
is not hindered by large stones.
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Link to video of SUBTRENCH TWO: |
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Related link: Connecting East and West Denmark for the first time
ever |
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Nybovej 8-9