A dredger is a machine used for the construction of harbors and canals, land reclamation, in mining projects, as well as in transport construction (including highway construction).
Depending on the purpose, different models of dredgers may differ in some way from each other, but in general we can distinguish the following list of components and assemblies characteristic of this type of machine:
- Frame.
- Papillon piles and pile apparatus.
- Deck superstructure.
- Hydrotransport installation.
Made in the form of pontoons. Serves as a basis for placing all the necessary working mechanisms.
Located at the back of the case. Ensure the movement of the dredger during soil development.
Located on the central pontoon. Includes a control room with all the necessary set of control and measuring equipment.
Placed in the hold of the car. Consists of the following elements:
- soil pump;
- power plant (drive);
- suction slurry pipeline;
- pressure slurry pipeline.
The following can be used as a power plant:
- electric motor;
- diesel-electric installation;
- diesel engine.
The suction slurry line is a pipe connecting the soil pump and the soil intake device.
The soil pumped out by the pump is fed into the pressure slurry pipeline, through which it is transported to the floating slurry pipeline, and then to the onshore one.
The working body of a dredger, with the help of which soil is excavated.
Using the boom, the operator adjusts the development depth and also moves the ripper. The boom is raised and lowered using a winch, for which a steel cable is attached to its head.
Performs an auxiliary function for flushing, cooling and sealing the parts of the soil pump.
Before you start placing an order for a dredger, it’s a good idea to find out what it is like today, what it’s made of, and so on, read about it in our article.
If buying a dredger is too expensive, a good option is to rent it. How this is done and what is needed for this - read, the latest and most relevant information.
Production of dredgers^
The production of a dredger is a complex of works in which the actual production of the machine is only the final stage.
First of all, the customer fills out a questionnaire and draws up a technical specification, in which he describes in as much detail as possible the requirements regarding the future machine, as well as all the features of the planned dredging or reclamation work.
The design department of the manufacturer studies the technical specifications and the questionnaire, and also analyzes information about the type of soil being developed, the current and waves in the operating area of the designed dredger, climatic conditions, navigability, and the distance to unloading the soil.
In addition, the possibilities of transport delivery of dredger modules to the work site are taken into account.
The information obtained serves as the basis for developing a dredger project, in which, first of all, the type of future machine is determined and justified. Depending on the task and working conditions, this may be:
- dredger with rotary ripper: provides high-quality loosening of the soil, but cannot be used on hard rocks.
- dredger with milling ripper: able to work with almost any type of soil. Provides a fairly even bottom profile. Flaw: May interfere with shipping.
- dredger with free suction: instead of a loosening agent, hydraulic erosion of the soil is used, which is then sucked into the slurry pipeline by a soil pump. The best option for developing loose soils.
- dredger on caterpillar tracks: Suitable for all types of soil, except hard rocks or soils containing large stones. If waves and currents are below the pontoons, they have virtually no effect on the operation of this machine. Has extremely high mobility and stability.
- multi-bucket Dredger: The use of this type of dredge is driven by the need to keep the rock being extracted relatively dry. Requires a barge or floating conveyor belt for loading soil. Nowadays, it is most often used for the extraction of minerals: gold, diamonds, tin, etc.
- grab or multi-grab Dredger: The performance of these dredgers depends on the cycle time and bucket volume. Advantages: allows you to mine at great depths and extract large stones, is easy to operate, and has a relatively low cost.
- Backhoe Rod Dredger: Great for hard soil excavation. At the same time, it allows you to quite accurately plan the bottom profile.
When developing a project, engineers determine the required dimensions of the working parts and other components of the dredger, select the type and power of the drive, calculate the required lifting capacity of the winch, etc.
At the production site of the dredger, only partial assembly of the individual components of the machine takes place so that it is transportable.
This point is very important, since an increasing number of projects are being carried out in remote areas with poor navigation. The only way to deliver a dredger to such regions is by car or rail. That is why it is so important at the design stage of the machine to provide for the possibility of delivering it by these modes of transport.
An example of such mobility is the BEAVER dredgers from IHC, individual blocks of which are adapted to international container standards.
The final assembly of the dredger and launching are carried out at the work site.
How to determine the quality of a dredger^
Before signing a contract for the supply of a dredger, experts recommend visiting the production facilities of the manufacturer.
This visit will give you the opportunity to personally verify the quality of the assembly work, check how well the welds are made and with what equipment.
A sign of a good, reliable and durable design is the presence on the body of the machine of the so-called ship set. It is a strong skeleton made of rolled metal beams of angle, tee or strip profile.
Make sure the foundations under the machinery and equipment are secure.
If they are not strong enough, under the influence of engine vibration the entire structure will quickly become loose and you will have to spend a lot of time and effort welding and patching numerous cracks.
It is desirable that the dredger design allows for disassembly into a minimum number of modules that can be conveniently transported.
Do not forget that for proper operation, as well as the possibility of repair, the dredger must be accompanied by comprehensive operational documentation:
- passport (form);
- specification;
- technical description;
- user manual.
If you don’t need a “big” dredger, then you might be interested in a mini dredger. About these units, of different companies and names, for example, Minnow, Crab and others, make the right choice.
Sand is a very important element used in the construction of any structures. As a building material, sand is formed under natural conditions and due to the influence of many natural factors. The methods of its extraction directly depend on the conditions under which sand deposits are formed.
Sand is tiny particles of rock. It can be located both at the bottom of reservoirs and on land, which makes up a considerable part of the surface. And completely different methods are used to extract it.
What is needed for mining
But in order to extract sand from the bowels of the earth, you need not only trucks, dump trucks, a special dredger for sand extraction, but also a license for such activity in a certain place, since without it it is illegal. A license is required for all miners, except for landowners of garden and household plots, as well as enterprises that have launched mining in areas on the border of the allotment of mountainous and geological lands.
Sand mining methods
For each method of sand extraction, specialized equipment and methods are used.
The first method is dry mining. In this approach, sand is extracted from a quarry. Here, characteristic methods and techniques are used for open-pit mining of any minerals. To begin with, they then loosen it with the help of explosives, and only then load it onto trucks and transport it to factories and enterprises.
The second method involves extracting sand from the bottom of a reservoir (lake, river, shallow sea). In this case, a special design is used - a sand dredger. Also, as an option, you can use long-arrow ones with a throw-out bucket. However, such equipment is expensive, which affects the final price of the material.
Mining can also occur in wet conditions using hydraulic scouring. This method does not require blasting or drilling. It has an advantage over competitive methods - the extracted sand is free of impurities.
Sand mining in shallow waters
As noted above, in rivers, lakes and shallow seas, a dredge is used to extract sand. The principle of operation is as follows: a device with pumping equipment sucks in sand that is located at the bottom of the reservoir. Next, it is loaded into the hold of a ship or onto a barge. The most convenient for this method of extraction are dry reservoirs.
The sand dredger has a complex design, which depends on the conditions of use. In particular, a scoop type dredger is used if the soil at the site is harder. The extracted sand is immersed and transported to a place where it undergoes final purification to remove impurities.
Dredger design
A dredger for sand extraction contains a mandatory list of design elements:
- The hull is a necessary part for attaching all the necessary mechanisms; it is also equipped with pontoons.
- The pile apparatus is an important component that ensures the movement of the dredger when extracting sand and soil.
- Deck superstructure - located in the central pontoon, has a deckhouse with the necessary equipment.
- The loosening device is the main part of the soil development complex.
- Installation for soil transportation. It consists of several elements and is usually located in the hold. Main parts: soil pump, suction wire, drive, as a power unit and pressure wire. The drive usually used is a diesel, electric or diesel-electric drive.
- Arrow. It helps the mechanic control the excavation depth and also move the ripper. Thanks to the winch included in its base, the boom is raised and lowered.
- Water supply equipment. Has an auxiliary role in cooling, flushing and sealing pump parts.
As can be seen from the description, A dredger for sand extraction, the photo of which clearly confirms the complex design of the mechanism, is a whole complex of interconnected systems, the interaction of which greatly facilitates human labor and simplifies the production of material.
Characteristics of dredgers
During operation, dredgers must have certain characteristics that allow them to perform the job as efficiently as possible. For example, installation and dismantling of a dredger should be short and simple. To move quickly, the machine must have a floating base, which can be quickly removed if necessary.
When choosing equipment, you need to pay attention to the dredger's drag coefficient when extracting sand, the type of soil, the extraction method and the capabilities of the mechanism. The main characteristic of a dredger is its performance. This is a device that combines many different functions. When the functions work together, maximum performance will be achieved.
Dredger classification
These mechanisms are divided according to the method of loading and transportation into:
- Suction dredger - loading and moving is carried out due to the pulp.
- Rock crushers - used for loosening rocky soils of varying strength.
- Scoop machines are a type of excavator machine that moves and immerses soil using a scoop.
According to the method of transportation they are divided into:
- Refuler. The clearance coefficient of a refuler dredger when mining sand is an important characteristic that affects the performance of the dredger. Transportation is carried out using a slurry pipeline afloat.
- Shalandovy. Transportation using scows - specialized vessels that load soil into the hold and take it to the port.
- Longucular. A long chute is used to move the soil, sending it to the shore or to a cargo ship.
- Self-pickup. As the name suggests, the dredger loads soil into its hold and transports it away.
- With pulp ejection using a hydromonitor effect. It is used if work is carried out at river mouths, as well as on sea waters during hydrowashing.
According to the method of working movement:
- Anchor - move due to built-in anchors.
- Self-propelled - movement due to the built-in engine.
- Pile - movement occurs on piles.
- Pile-anchor - they use both anchors and piles.
According to the method of work they are divided into:
- Trench - when extracting sand, the dredger forms trenches, moving along the site.
- Papillon - the dredger moves across it when developing a site.
Dredging units are intended for sucking up soil from the bottom of a reservoir (sometimes with preliminary loosening) and moving it along a slurry pipeline to the laying site or for transporting soil from the development site to the laying site. They are used in the construction of canals, deepening and cleaning of canals, sedimentation tanks, rivers, lakes, seas, and reservoirs; for extracting building materials from under water (sand, gravel); for reclamation of dams and dams.
The development of soil by a suction dredger is based on the erosive and dragging ability of water. Centrifugal pump 3 (Fig. 178) creates a flow of water that separates soil particles from the bottom of the reservoir. Through the soil receiver 1, it is carried into the suction pipeline 2, fills the pump housing and is thrown by the impeller into the discharge and transport pipelines 5 and 6, through which it is transported to the installation site. The transport pipeline (slurry pipeline) 6 within the reservoir is laid on pontoons 7. The centrifugal pump is driven by engine 4.
Continuous soil suction is ensured by the constant location of the soil receiver in close proximity to the developed soil. To do this, the soil receiver is moved across and along the layer being removed and the angle of inclination of the suction pipeline in the vertical plane is changed. Piles 8 for controlling the movement of the dredging unit are lifted by winches.
When developing cohesive soils, a mechanical ripper 9 is installed at the soil receiver, which separates soil particles from the mass with knives, and the water flow created by a centrifugal pump captures them and sucks them in suspension into the suction pipeline.
A centrifugal pump installed on dredging units is called a dredger.
Rice. 178. Scheme of operation of the dredging unit:
1 - soil receiver; 2 - suction pipeline; 3
- centrifugal pump; 4
- engine; 5
- discharge pipeline; 6
- transport pipeline;
7 - pontoons; 8
- piles; 9
- mechanical ripper.
The dredge pump (Fig. 179) differs from conventional water centrifugal pumps only in that the body 1 and impeller 2 are designed to pass water with soil containing large rocky inclusions and are made of wear-resistant materials. The impeller (one-way suction) is mounted cantilever on shaft 3, supported by bearing support 4 and connected directly to the electric motor shaft by an elastic coupling, or through a gearbox and friction
Rice. 179. Dredger:
1 - body; 2 - impeller; 3 - shaft; 4 - support; 5 - pressure pipe; 6 - suction pipe.
clutch with an internal combustion engine. The shaft with the impeller is held against axial displacement by a thrust bearing installed at the rear of the bearing support. The impeller hub is located in a stuffing box, which protects it from contact with abrasive particles. To protect the stuffing box seal from slurry, clean water is supplied under pressure between the housing and the impeller on the shaft side. Cleaning and checking the condition of the housing and impeller is carried out through hatches in the housing. Suction pipe 6 attached to the front cover. To suck out air when starting the dredger, there is a hole in the upper part of the body to which a vacuum pump is connected.
The impeller has 3 to 6 blades spiraling from the center to the outer diameter between two end discs. When the impeller rotates, a vacuum is formed at the suction pipe, and the pulp is sucked into the space between the blades, from where it is pushed into the pressure pipe 5 dredger and further into the pipeline.
Dredging units are divided into land-based and floating.
Land installations are manufactured: stationary and mobile on railway, tracked, walking and wheeled; floating - on pontoons.
Stationary dredging units are used for volumes of work that can be performed from one parking lot, and for transporting soil developed by other machines.
Mobile dredging units are used for work when, due to terrain conditions and the volume of work, soil development or transportation from one parking lot cannot be ensured and the unit must be moved towards the face.
Dredging installations intended only for transporting soil are made with a stationary suction part during operation.
In irrigation and drainage work, floating suction suction units - dredgers - are most commonly used. Based on their design, they can be divided into two groups:
- dredgers for reclamation and dredging work, adapted for work on canals, rivers, lakes and ports. These dredgers have their own diesel or diesel-electric power plant and are adapted to work in fast water flows and large waves;
Dredgers for construction purposes and mining with mechanisms driven by electric motors powered by electricity from a stationary or mobile power station. These installations are used in the construction of large canals, pits, cleaning of settling basins and canal heads, reclamation of dams and dams, for the extraction of sand and gravel from under water and in stripping operations.
Diesel and diesel-electric small-sized dredgers are used to clear sediment from canals, ponds, reservoirs, dredge the bottom of small rivers, supply channels of pumping stations, build irrigation and drainage canals, dig pits for reclamation structures and other similar work. They can be divided into dredgers for working on canals and in excavations with a bottom width of over 2.5 m with a capacity of 20-35 m3/h and over 5 m with a capacity of 60-100 m3/h.
Dredgers of the first group (Fig. 180) are manufactured with a combined device for developing and transporting soil. Housing 3 is metal, flat-bottomed, with rectangular contours. In machine room 6, a dredger and a generator are installed in the front part, and an internal combustion engine is installed in the rear part.
Rice. 180. Small-sized floating dredger:
1-rotor ripper; 2 - mixing hopper; 3 - body; 4 - rope; 5 - control panel; 6 - engine room; 7 - piles; 8 - canopy; 9 - winch; 10 - bracket.
The working bodies - the rotary ripper 1 and the suction pipe passing through the mixing hopper 2 - are pivotally connected to the body and suspended on a pulley block to the bracket 10 so that they can be raised and lowered with a winch. The control panel 5 with control devices is located on the deck in the bow of the hull, covered on top by a removable canopy 8. The projectile performs its working movements using piles 7 and two ropes 4, attached to a papillon winch 9.
Most small-sized dredgers have replaceable working equipment - a sucker, a scooping device and a rotary ripper. Sucker is used to develop sands and loose sandy loams; with a scoop device - dense sandy loams, light loams; rotary ripper - viscous silty soils overgrown with vegetation. To replace working equipment
it takes 1.5-2 hours.
Dredgers of the second group (Fig. 181) are manufactured with a non-dismountable body 10 and a body 10 that can be dismounted into two parts. The working parts - milling ripper 1 and suction pipe - are mounted on a frame 11, which is pivotally connected to the body 10 by the fifth, and the head is suspended on a pulley. The ripper is rotated by a motor 12 installed on the platform at the heel of the frame. Papillon winches 2 are located on the bow deck, and pile lifting winches 7 are located on the rear deck of the hull. Dredger 3, priming pump 4, internal combustion engine 5 and diesel generator b are located in the hold of the machine room. The piles are attached to the rear of the body by 8 guide brackets. The floating slurry line 9 is connected to the discharge pipe of the dredger using a flexible hose or a ball joint.
Electric dredgers(Fig. 182), intended for the mechanization of excavation work at large hydraulic facilities and stripping operations, as well as for the extraction of building materials, are produced with a capacity of 100, 300, 500 and 1000 m3/h, weighing from 64 to 650 tons. They have essentially the same the same design as small-sized diesel-electric projectiles, but they do not have their own source of electricity (diesel generator). 
Rice. 181. Dredger with diesel-electric drive:
1 - milling ripper - 2 - papillon winch; 5 - dredger; 4 - filling pump; 5 - internal combustion engine; 6 - diesel generator; 7 - winch for lifting piles; 8 - pile apparatus; 9 - pulp pipe; 10 - body; 11 - frame; 12 - ripper drive electric motor.
Rice. 182. Dredger with electric drive:
1 - cutter; 2 - rope to the anchor; 3 - frame: 4 - body; 5 above-deck superstructure; 6 - dredger; 7 - electric motor; 8- piles; 9 - winches; 10 - floating slurry line.
The body 4 of the dredger is divided into water-permeable compartments. The above-deck superstructure 5 is equipped with papillon winches and a control panel. The dredger 6, connected by an elastic coupling to the electric motor 7, a centrifugal pump for filling the dredger and supplying water to its seal, and a vacuum pump are located in the middle compartment of the hull hold. Piles 8 are lifted by winches 9 located on the deck of the rear part of the hull. The floating slurry line 10 is connected to the pressure pipe of the dredger by a ball joint. The frame 3 of the ripper is attached on two hinges in the cutout of the body and suspended on a chain hoist. Ropes 2 from the papillon winches to the anchors go through guide blocks mounted on the ripper frame. Ripper 1 is driven into rotation by an electric motor through a gearbox. The electrical devices of modern dredgers are very complex and consist of a high-voltage flexible power cable for connection to coastal networks (usually laid along the pontoons of a floating slurry line), starting and protective equipment, a transformer substation, a high-voltage and low-voltage internal network, a blocking and secondary switching system and a centralized control panel .
Electrically driven dredgers use milling, rotary
Rice. 183. Papillonage scheme for a conventional pile move:
/, // - winches; 1-4
- layers of soil.
Rice. 184. Papillonage scheme for rotary pile driving:
1-III- dredger position; 1,2 - ropes.
and hydraulic rippers. The last two species are almost not widespread. For the working movements of dredgers, two types of pile passes are used: two piles, each of which is attached in guides to the dredger body (see Fig. 180), and two piles passing in the guides of the rotary cage (rotary pile drive) installed at the rear of the body, so that it can rotate about a vertical axis (pressure rotary pile drive).
With the first type of pile drive, the movement of the dredger during soil development is performed by alternately turning the projectile around one of the piles (Fig. 183). Pile A under the influence of its own weight it sinks and sinks into the ground. Winding the cable onto the winch / and loosening the winch cable //, turn the projectile around the pile A to the position shown by the dotted line. At the same time, the working body removes a layer of soil /. Then the pile A rises and the pile B falls. Winding the cable onto the winch // and loosening the winch cable /, turn the projectile around the pile B, removing a layer of soil 2. By repeating such operations, the layers are removed until the anchors need to be repositioned. Having moved the anchors to a new place, further development is carried out in the same way.
With such a pile drive, the dredger, making working movements, rotates relative to different axes. Due to this, the working body passes part of the way along the mined-out section, and leaves part of the section undeveloped. When developing heavy cohesive soils, this disadvantage reduces productivity.
The rotary pile drive ensures the excavation of soil in regular concentric strips with slight overlap (Fig. 184) due to the fact that the pile on which the rotation occurs is each time fixed to the axis of the slot. To start work, the dredger is set to position /. A pile is fixed into the ground, installed with a guide clip along the axis of the projectile body. Winding the rope / onto the winch drum and loosening the rope 2 the dredger rotates around the lowered pile to position //. Then, using a special mechanism, the guide holder with piles rotates until the raised pile moves forward and aligns with the axis of the slot. Simultaneously with the rotation of the raised pile, the same mechanism moves the dredger forward to the /// position. By the tension of the rope 2 with the rope weakened, the dredger rotates relative to the newly lowered pile and removes the next strip of soil. So, by turning the dredger relative to the piles lowered one after another and moving forward, the soil is removed before repositioning the anchors.
The pulp from the dredger to the shore is pumped through a floating pipeline - a slurry line, and then through pipes laid on the ground or special supports.
A floating slurry pipeline is a chain of pontoons (barrels), hingedly connected to each other, with pipes laid along them. Some pontoons are equipped with hand winches, with the help of which the slurry line is secured with anchors from being displaced by water flow and wind.
To transfer anchors within a reservoir, a boat or boat is attached to the dredgers, and floating cranes are used to connect the floating slurry pipeline to the shore one.
Float level gauges are installed on tanks for storing liquid and bulk substances.
The composition of dredgers operating on the inland waterways of Russia is determined by the properties of the soils being mined, the conditions for their extraction and disposal, hydrological and other factors of the work sites.
Depending on the listed and other factors, dredgers are divided into types according to the following criteria:
A method for separating and lifting soil from the bottom of a reservoir and removing it beyond the boundaries of the slot being developed;
The mode of working movements of dredgers in the process of extracting and removing soil;
Type of power plant;
The method of moving the dredger from one job to another;
Hull structures.
Individual types of dredgers are distinguished by their hourly productivity, expressed in cubic meters of excavated soil.
Based on the method of separating soil from the bottom and lifting it above the surface of the water, a distinction is made between dredgers and scoops.
Dredgers (Fig. 1, a) suck up soil along with water using a subsoil pump that has a suction pipe immersed below the bottom surface. The water entering the pipe erodes and captures the soil. The mixture of water and soil is called pulp. The latter, through the suction pipe, enters the soil pump, and then into the pressure soil pipeline of the dredger body connected to the pump, to which is connected a floating soil pipeline intended for moving soil to the place where it is laid. The process of moving pulp through a pipeline is called refilling. All types of soil can be refilled, but gravelly and rocky soils are mostly impractical to move in this way due to the fact that the soil pump and soil pipeline wear out greatly.
Soil pipelines can be floating or onshore, i.e., refueled soil can be transported both into the water and onto the shore. There are dredgers in which the soil pipeline, suspended on a special boom, goes away from the projectile. On low-capacity dredgers, the pulp can move away from the projectile in the form of a jet (Fig. 1, b) ejected through a special nozzle.
To develop cohesive clay soils, dredgers with a mechanical loosening agent, which is a milling cutter with knives, are used (Fig. 1, V), which separate soil in the form of shavings from the bottom of the reservoir. The end of the suction pipe goes inside the cutter so that the soil chips are carried into the suction pipe by the sucked stream of water.
To improve the absorption of sandy and gravelly soils, hydraulic loosening agents are used, which are devices that emit one or more jets of water under pressure, loosening the soil. This increases the productivity of dredgers and improves the cleanliness of the excavation - it reduces bottom unevenness formed after the dredger operates.
Scoop shells come in multi-scoop and single-scoop types. The latter are divided into rod and grab. For multi-bucket projectiles (Fig. 1, d), the main working device is an endless scoop chain moving along the scoop frame.
The scoops are emptied over a soil well, from which the soil flows into special vessels - scows, adapted for quick release of soil. In scows, soil can be transported to any distance. In cases where emptying scows into the water is unacceptable due to shipping conditions or when soil must be unloaded onto the shore, scow unloaders are used. The latter have devices for extracting soil from scows and transporting it to the shore.
The soil extracted by multi-bucket projectiles can also be removed via a floating soil pipeline, but for this it is necessary to have a soil pump with a motor on the projectile. Such shells are not built in the USSR; instead, more economical dredgers with mechanical rippers are used.
Rice. 1. Main types of dredgers:
A- dredger; b- dredger with jet discharge; c - dredger with mechanical loosening agent; g - multi-bucket projectile; d - rod projectile; e - grab projectile
Low-capacity multi-scoop projectiles can remove soil away from the projectile along a long inclined tray called a longcouloir.
There are multi-scoop projectiles of small capacity (for small rivers), which remove soil away from the projectile along a conveyor, which is a rubberized belt (chevron - with ribs) moving along rollers. A conveyor can move soils (except highly liquefied ones) not only in a horizontal direction, but also with some elevation.
On a barbell (Fig. 1, d) the scoop is attached to a rod, one end of which is hinged to a special boom. The other end of the rod is held in place by a cable. The scoop is lowered to the required depth. When removing the cable, the scoop grabs the soil. After the scoop is filled with soil, it is raised, the boom is turned and the scoop is emptied above the scow or at some distance from the projectile.
On a grab tool (Fig. 1, e), soil is removed using a bucket consisting of two or more doors. The bucket is suspended on a cable from the boom. To extract soil, a bucket with open doors is lowered to the bottom (released). When the bucket is lifted, the flaps automatically close, capturing the soil. The bucket is emptied above the scow or at some distance from the projectile (for example, on the shore).
The soil-collecting devices of the dredger are small in size, therefore, during dredging operations, the projectiles are moved across or along the slots (deepened areas). When the projectile moves transversely relative to the longitudinal axis of the slot being developed, called papillonage, narrow shavings of soil are removed along the entire width of the slot. When moving longitudinally, the slot is developed in the form of a trench; Trenching of slots is possible on sandy soils. Trench work is based on the fact that when the suction device is immersed a certain amount into sandy soil, a funnel is formed; When the dredger moves along the slot, a trench is formed at the bottom. To deepen the slot along the entire width, a series of parallel trenches are developed.
Dredgers work using the trench method without mechanical loosening agents. Dredgers with loosening agents and dredgers equipped with special tips work by papillonage. In accordance with the above, depending on the method of working movements, papillon and trench dredgers are distinguished.
According to the type of power plant that drives the device for extracting and moving soil, dredgers are: with internal combustion engines - diesel, diesel-electric, in which internal combustion engines drive electric generators that generate electricity to drive the electric motors of individual units of the projectiles, steam-electric, where electric generators are driven by steam engines.
Modern dredgers are built with diesel and diesel-electric power plants and electrified mechanisms. The cost and maintenance of such projectiles is lower than with steam power plants, which must have steam boilers, large coal bunkers or fuel oil tanks. This increases the size of the projectile bodies, requires more maintenance personnel and increases the cost of soil extraction by 25-30%. However, the dredging fleet still contains steam-powered shells built in previous years.
Based on the method of moving dredgers from one job to another, a distinction is made between self-propelled and non-self-propelled dredgers.
Self-propelled dredgers have propulsors (mainly screws) driven by power units designed to extract soil, or independent. The latter are found on electrified dredgers, where the main engine drives a generator that produces electrical energy, and electric motors are installed to operate individual mechanisms. The power of the dredger's propellers must be sufficient to move it and the service vessels attached to it. Non-self-propelled dredgers are moved from one job to another by towing motor ships.
The strength of the hulls depends on the area of operation of the dredgers. According to this feature, they can be river, lake and sea. To work on large reservoirs, dredgers with lake-type bodies are built.
The main production indicator of a dredging projectile is its technical performance, given by the projectile in optimal soil and other conditions. Each type of dredger has its own most favorable conditions. For example, dredgers without disintegrants provide the greatest productivity on medium-sized sands; multi-bucket shells - on silty and sandy-gravel soils of medium density, completely filling the scoops and falling out of them well; single-scoop rod projectiles - on coarse gravel. In addition to the physical properties of the soil, the technical productivity is affected by the thickness of the removed layer and the depth of soil extraction. The greatest productivity can be achieved starting with a specific layer for each dredger and the calculated depth of soil extraction. On dredgers, technical performance corresponds to certain values of the length of the soil pipeline and the height of soil refilling.
Technical performance is established in the process of extensive production and thermal testing. It is determined by the volume of the recess (developed slot). To do this, calculate the volume of excavated soil and divide it by the number of hours of clean (minus all downtime) operation of the dredger.
If there are several soil intake or soil disposal devices, the technical productivity is determined for each device: for dredgers - with trench and papillon tips, for working with and without baking powder; for multi-scoop shells - when working on scows and longcouloirs, etc.
The design capacity is the performance assigned to the dredger for specific conditions for the extraction and removal of certain soil; actual - the productivity that the dredger gives in the process of performing this work.
The ratio of actual productivity to technical productivity is called the utilization rate of technical productivity. For example, if the actual productivity is 400, and the technical one is 500 m3/hour, then this coefficient is KP = 0.80.
The working time utilization factor HF is the ratio of the number of hours spent on soil extraction to the time the dredger is at work or on the reach. For example, if with a working period of 3600 hours, 3000 hours are spent on soil extraction, then CV = 0.83.
The product of the considered coefficients is called the operating coefficient
Today, such work is in great demand, through which earth or soil is extracted from reservoirs, as well as reservoirs. Such measures are necessary when they are deepened. In this case, the work is impossible without the use of special equipment. We are talking about machines such as dredgers.
The machine by which such work is carried out has its full name - dredger. Such a unit, while on the water, collects soil directly from the bottom of the reservoir. are based on equipping the unit with the following main components:
Catamaran hull;
- soil intake frame;
- technical water supply system;
- slurry pipeline;
- frame-lifting device;
- suction pipeline;
- papillon winches;
Pressure pipeline;
- baggermeister cabin;
- a set of power equipment;
- diesel generator set under the superstructure.
Design and principle of operation of the dredger are in some way similar to the design and principle of operation of an excavator equipped with a hydraulic drive. 
Let's pay attention to how the dredger works.
A special pump-type bucket collects soil from the bottom of a pond or reservoir. All the time that the soil is located directly in the bucket container, it undergoes a process of thorough grinding. This process is carried out using special grinding knives, which are located directly at the entrance to the pump. Thanks to this grinding, it becomes possible to prevent clogging of the pump, which in turn increases the service life of the unit. Also in the design of the dredger there are special rakes, through which all vegetation adhering to the ground is separated. This measure helps prevent unnecessary particles (debris) from entering the pump mouth.
Design and principle of operation of the dredger almost the same for all modifications of this technique. It is also worth noting that today quite often there are models of dredgers that are made in a special way. It is due to the unique nature of such units that it becomes possible not only to collect soil from the bottom of a reservoir or reservoir, but also to almost immediately remove all the pumped out garbage, as well as waste, to the places where they will be disposed of. This approach to work has a very positive impact on the environment.
The main soil that is processed by the dredger is gravel and sand. These types of soil are loose and have a structure in which there are practically no large fractions.
As for the design of the dredger, it can be represented by two modifications. The first is represented by machines that run on electricity. The second is units powered by a diesel-electric drive. A hose (slurry line) works in tandem with the pump. It can be made of steel material, or be rubber-fabric. To improve ease of use, today such hoses are equipped with several sections during the production process.
