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What’s a Dredge Cutter?

A cutter refers back to the type of excavator head corresponding to a basket cutterhead or bucketwheel on a hydraulic pipeline dredge. The cutter houses the suction intake and is used for cutting or agitating the materials which might be being dredged.

Cutters have two fundamental functions:

Loosen and break up supplies from the underside of a waterway into smaller fragments which might be appropriate with the dredge’s pumping system.
Intro the crumbled particles into the high-velocity stream at the suction intake in a prescribed capacity where the supplies will be then pumped and transported via a dredge’s hydraulic pipeline system.

Specialised types of dredger are often of small dimension and output. They include easy jet-lift and air-lift, auger suction, pneumatic and amphibious dredgers.
Jet-lift dredgers use the Venturi impact of a concentrated high-speed stream of water to draw the adjacent water, collectively with bed materials, into a delivery pipe. The jet head has no moving parts so blockage by wires and different dock debris is minimised. These dredgers are comparatively small units and some might be manoeuvred on spuds alone.
Air-lift dredgers are very similar to the jet-lift dredgers however the medium for inducing water and materials flow is high pressure air injected on the mouth of the suction pipe. As with jet-lift dredgers there are no moving parts within the flow system. Hard or other troublesome to loosen materials can’t be dredged.
Augur suction dredgers operate on the identical rules as a cutter suction dredger, besides that the mechanical chopping tool is a rotating Archimedean screw placed at right angles to the suction pipe. The screw dislodges materials, which is fed to the centrally positioned suction pipe. Most units have a shroud over the reducing screw which reduces the spread of the plume of disturbed bed material which usually escapes from all dredgers. The augur suction dredger advances into the slicing face by hauling itself along a wire deployed directly ahead. Very accurate horizontal and vertical dimensions can be achieved.
Pneumatic dredgers work on the ‘evacuator’ principle. A chamber with inlets for bed material is pumped out with the inlets closed. The inlets are then opened and water and materials drawn in. The combination is then pumped out and the cycle repeated. The unit is generally suspended from a crane on land or from a small pontoon or barge. The dredging motion is intermittent and suitable only for easily flowing material.
Amphibious dredgers have the bizarre characteristic of being able to work afloat or elevated clear of the water surface on legs. They are often equipped with grabs, buckets or a shovel installation.
All the above specialist types of dredger (and others) have been developed for specific situations and customarily for small scale work equivalent to narrow canals, industrial lagoons and reservoirs. Some types have been developed to handle contaminated sediments with minimum disturbance. They are not normally employed for big scale upkeep or capital dredging work.
An extra type of dredger is the plough or bed leveller. This consists of a blade or bar which is pulled behind a suitable tug or work-boat. The tactic can be utilized for direct dredging over short distances and for levelling off the bed to the desired depth when a trailer or seize dredger is operating. It could also be used to drag away materials positioned close to quay walls and other places the place a trailer can not reach into a more accessible area. Sometimes the trailer itself operates the leveller if no tug or work-boat is available.

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Types of dredger

Hydraulic Dredger
The principal feature of all dredgers in this category is that the loosened materials is raised from its in-situ state in suspension by way of a pipe system related to a centrifugal pump. Numerous means will be employed to achieve the initial loosening of the material. If it is naturally very loose, suction alone could also be sufficient, however firmer materials may require mechanical loosening or using water jets. Hydraulic dredging is most efficient when working with fine materials, because they will easily be held in suspension. Coarser materials – and even gravel – can be worked however with a greater demand on pump energy and with greater wear on pumps and pipes.

A Suction Dredger is a stationary dredger used to mine for sand. The suction pipe is pushed vertically right into a sand deposit. If necessary water jets assist to bring the sand up. It is loaded into barges or pumped by way of pipeline directly to the reclamation area.

Profile or Plain Suction Dredger
In its most straightforward kind the Profile or Plain Suction Dredger consists of a pontoon able to support a pump and suction pipe and to make the connection to the offloading pipe. More sophisticated vessels have separate suction and delivery pumps, water jets at the suction inlet and articulated suction pipes. While working, a dredger could also be held in position by one or more spuds or, in deeper water, by a fancy system of moorings. Plain suction dredgers are mainly used to win fill material for reclamation, with the material being positioned ashore via a floating pipeline. Very long distances will be pumped by the addition of booster pumps in the line. Materials could alternatively be loaded directly into barges moored alongside. The normal measures of measurement are the diameter of the offloading pipe, which can vary between 100 and 1,000 mm, or the put in horsepower.
One other use of plain suction dredgers – frequent in the USA – is to dredge from the navigation channel of a river and side cast the fabric to nearer the bank by means of a brief pipeline or just by jetting. In this role they are more commonly known as dust-pan dredgers.
Modern suction dredgers can recover material from nice depths and also can extract sand from below a clay overburden. Known as a deep suction dredger, this type presents the potential to recover fill materials from depths up to one hundred m. Production is very dependent upon the permeability of the material dredged and is best in clean sands.

A Cutter Suction Dredger is a stationary dredger which makes use of a cutter head to loosen the fabric to be dredged. It pumps the dredged materials via a pipeline ashore or into barges. While dredging the cutter head describes arcs and is swung across the spud-pole powered by winches. The cutter head could be changed by a number of kinds of suction heads for special functions, similar to environmental dredging.
When the in-situ materials is too compact to be removed by suction action alone, some type of mechanical loosening should be incorporated close to the suction mouth. The commonest methodology is a rotating cutter: the principle function of the cutter suction dredger. This is mounted on the lower finish of the ladder used to help the cutter drive and the suction pipe. The loosened materials then enters the suction mouth, passes by the suction pipe and pump (or pumps) and into the delivery line.
Cutter suction dredgers operate by swinging about a central working spud using moorings leading from the lower end of the ladder to anchors. By pulling on alternate sides the dredger clears an arc of lower, and then moves forward by pushing in opposition to the working spud using a spud carriage. A usually smooth backside might be achieved, and modern instrumentation allows profiles and side slopes to be dredged accurately. A number of the larger cutter suction dredgers are self-propelled to allow easy movement from site to site.
The dimensions of a cutter suction dredger is measured by the diameter of the suction pipe and by the installed machinery power. Pipe diameters are within the range one hundred to 1,500 mm. A contemporary highly automated cutter suction dredger is capable of achieving high outputs over sustained durations and production rates of round 500,000 m³/week are doable under good conditions.
Cutter suction dredgers can be used to deliver by means of a pipe- line or to load barges. They may even be used simply as loosening devices for material to be re-dealt with by one other type of dredger, in which mode offloading is directly over the stern to the sea. Pipeline offloading is commonest but is vulnerable to waves and currents and causes an obstruction to different vessels. To keep away from these problems part of the pipeline may be submerged and laid on the channel-or sea-bed.
Cutter suction dredgers are mainly used for capital dredging, especially when reclamation is associated with the dredging. Smaller vessels might be dismantled into sections and moved by road or rail for work in inland waterways, sludge lagoons, reservoirs and related isolated areas. Massive heavy-duty cutter dredgers are capable of dredging some types of rock which haven’t been pre-treated.
An alternative type of loosening is using a rotating bucket wheel on the suction mouth. Bucket wheel dredgers are most commonly used in mineral extraction operations and so far haven’t found general favour among the many main worldwide dredging contractors.

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