Dredging Vessel Jobs
Dredger or Dredging
vessel involves in dredging which
is an excavation jobs generally done underwater in shallow sea areas or in rivers
for the objective of collecting up underneath sediments and dumping them at another
site. Dredging is usually done
to retain waterways navigable. It is also used as a method to restock sand on 
various
public beaches where sand has been removed because of coastal erosion. Dredging
is also used as a practice for fishing for some species of edible clams and crabs.
Without
the numerous and nearly uninterrupted dredging operations throughout the world,
the world's trade would be greatly lost, generally only within a few months
because to a large extent the world's freight is transported by sea through ship, and require to clear harbours
or seas through channels.
The most
of maritime dredging operations and the dumping of the dredged substances will need
proper licences which are obtained from the related regulatory authorities
and dredging activity is generally carried out by or for harbour companies or subsequent
government organizations.
Suction
Dredger
The suction dredging is conducted through a long sucking pipe similar
to certain vacuum
cleaners but to a greater extent. In plain suction dredger no machinery at the inlet
of the suction pipe is used to disrupt the bottom. This is usually the most
commonly used method of dredging.
Trailing
Suction
Dredger
The trailing
suction hopper dredger-TSHD trails its suction pipe while dredging. The pipe
which is fixed with a dredge drag head dumps the dredge materials into one or
more hoppers in the Dredging vessel. When the hoppers are filled the TSHD proceeds
to a dumping location and either dispose the load through flaps in the hull or
pumps the substance out of the hoppers. There are also dredges which are self offloading
by means of drag buckets and conveyors.
Trailing Suction Hopper Dredger
(TSHD) is generally used for dredging loose and soft soils such as sand, silt,
clay or gravel. One or two suction pipes, fitted with a drag head, are lowered
on the sea bottom and the drag head is trailed over the sea floor. A pump arrangement
sucks up a combination of or soil, sand and water and releases it in the hopper
or hold of the dredger vessel.
The substances can be dumped on the
seafloor via underneath gates, or reclaimed by means of the ‘rainbowing’ method.
The material can also be offloaded through a floating pipeline to shore and which
may be used for reclaiming ground.
The
biggest trailing suction hopper dredgers in the world are presently Jan De Nul's Cristobal Colon deployed on 4 July
2008 and its sister ship Leiv Eriksson
deployed on 4 September 2009.
Cutter Suction Dredger
The
cutter-suction dredger's-CSD suction pipe has a cutting machinery at the
suction end. The cutting mechanism softens the sea bottom soil and transfers it
to the suction opening. The dredged material is typically sucked up by a wear resistant
centrifugal pump and release either through a pipe line or to a material barge
alongside.
Cutter-suction
dredgers are mainly utilised in geological regions which are of hard surface substances
like gravel deposits or surface bedrock where a typical suction dredger would
be unsuccessful. In recent years, dredgers with higher powered cutters have
been built consecutively to excavate harder rock with no require of blasting.
The cutter suction
dredger-CSD is outfitted with a revolving cutter head, for cutting and splintering
tough soils. The mud is sucked up by the help of dredge pumps and released through
a floating pipeline and pipes on to the shore to an accumulating location. Otherwise
the matter is offloaded into split hopper barge which is moored alongside of the
cutter suction dredger. These split hopper barges discharges the mud at the disposal
site.
During dredging a CSD is
a standstill dredger, i.e. it does not sail while dredging. All through dredging
the dredger hang about on one position, secured by a spud lowered in the seafloor
by the help of winches and anchors. The dredger swings sideways and the cutter
head cuts and take outs the earth. Larger CSD are self propelled which facilitates
the dredger to navigate by its own engines to a new dredging site.
Backhoe
or Dipper Dredger
The
backhoe or dipper dredger has a backhoe like on some excavators. A rough and ready but utilisable
backhoe dredger can be prepared by mounting a land type backhoe excavator on a
pontoon. The backhoe dredger is fitted with a half open shell. The shell is
crammed by shifting it in the direction of the machine. Generally dredged
material is offloaded in cargo barges. This type of machine is mostly used in
harbors and other shallow waters.
The backhoe
dredger-BHD is mainly a pontoon fitted with a
hydraulic excavator. To keep the
pontoon steady and fix firmly, three spuds are settled down. The excavator will
excavate the sand and soil and offload it into a split hopper barge which is
moored alongside the pontoon. The split hopper barge discharges the mud at the dumping
location.
hydraulic excavator. To keep the
pontoon steady and fix firmly, three spuds are settled down. The excavator will
excavate the sand and soil and offload it into a split hopper barge which is
moored alongside the pontoon. The split hopper barge discharges the mud at the dumping
location.
