Dredgers


Sand Mining, deepening of rivers and reservoirs, as well as land reclamation today are carried out mainly by the use of dredgers, which ensure high efficiency and low cost of implemetation. (Clich here)

Depending on the method of extraction of sand and soil, two types of dredging are distinguished.

Dredging with submersible pumps

The first method is dredging with a submersible pump. This is when the extraction of sand is carried out by a pump, which lies directly on the bottom of a river or pond. Dredging directly from it, the water-sand mixture is then transported ashore or in the hold. Such dredgers have a high efficiency and low fuel consumption, which is the main overhead in the cost of sand-mining. In addition, such dredges are twice as effective in terms of productivity and in depth of development – up to 40 meters.

 

However, when the dredgers are operated with a submersible pump, difficulties arise due to the need for highly skilled personnel, since its submersible pump can be easily filled with extracted sand, in cases where, during the extraction of sand, a funnel-shaped depression is formed, which can fill the pump itself, which damage may require half the cost of such a dredger.This approach also requires special technology for its deployment.

Dredger of classical type – with a submersible pipe

The second approach is submersible dredging. This is when the pump is installed on board the dredger, and mining is carried out by lowering the bottom of the submersible pipe, through which the suction of sand and soil occurs and feeding it to the shore or into the hold.

Dredgers of this type are considered classic and much easier to maintain and operate. They are the most commonly used everywhere without any restrictions.

 

Highlights of hydraulic flushing

In addition to the existing types of dredging, it is also necessary to know that the productivity of the dredgers is directly dependent on the depth of extraction and the range of transportation of the water-soil mixture.

In other words, the greater the depth of sand deposition and the range of its transportation, the less the productivity of the dredger in the extracted sand, since for a large pumping the percentage of sand will be substantially less.

In classical dredges with a depth of up to 5-7 meters and a transport distance of up to 500 meters, the sand content in the pulp is up to 20%. With greater depth and longer range, it will be about 10%.

Proceeding from this, clients should not get carried away by the great depth of extraction of sand or the long distance of its transportation.

Although, if necessary, the range of transportation can be more than a kilometer or two kilometers. But for this purpose, special booster stations are used, these being water pumps, which increase the pressure and range of pumping. However, these are at additional costs, which will substantially increase the cost of the sand to be pumped.

Dredger with a slurry pipeline with floats

For transportation of sand from dredgers to the shore, pipelines are used that are equipped with floats and are located on the surface of the water – to ensure greater productivity of the dredgers. Sometimes, with a small depth of development and a small distance from the shore, pipes without floats can be used, which are located directly on the bottom of the reservoir depending on the designated areas for mining activities and the relief to accomodate the pipe, which will have large angles of elevation. with this method, the volume of extracted sand will not be large. This also needs to be understood when organizing the work related to the use of dredgers.

MAIN WORKS ON HYDRAULIC WASH

  – dredges are used for two main tasks:

1.Dredging.

2.Hydraulic deposition (reclamation) of land and Mining of sand.

What is their difference and essence?

  1. Dredging

 These works are very important in the areas of navigable rivers and in the water areas of ports. Because water constantly carries soil and sand into rivers. This often leads to the fact that the rivers become shallow. Their depth decreases reducing the overall capacities of these water bodies.

Self-propelled dredger ships for deepening the seabed in water-bodies and ports

To maintain the required depth, it is necessary to use special equipment. For this purpose, special types of dredgers have been developed that do not simply deepen the bottom, sucking out excess sand and soil, but they also accumulate the sand in their own holds or wash it onto trailer barges as the extracted soil must be banked to prevent it returning to the water body to avoid further depth reduction.

 the banked soil is accumulated and taken to shore, where it is used for different purposes. For example, sold for the production of concrete.

Dredgers used for dredging are the most complex and expensive. It should be noted that they are self-propelled ships with their own propulsion system, capable of sustaining long terms away from the coast.

2. Hydraulic deposition of territories and sand

The most widespread use of dredgers has been obtained by reclamation or extraction of sand for territorial expansion.

For such purposes, relatively inexpensive dredgers of non-self-propelling type are used. They can not move independently over significant distances and the composition of their equipment includes basically only a pump for sucking and pumping out sand from the bottom of rivers and reservoirs and transporting them ashore. To move these dredgers, special piles are often used, between which a cable is pulled and with the help of low-power engines, these dredgers move along the cable between the piles. This distance is enough to accomplish the work of extracting sand and delivering it ashore.

But the reclamation of territories (land) and the extraction of sand are somewhat different functions, which differ from each other.

  1. a) Hydraulic deposition of territories. Reclamation.

For this purpose, dredgers of high productivity are used. As a rule – not less than 2000 meters of cubic water-sand mixture (pulp). The depth of development is taken as standard – up to 15 meters. Necessities to wash up soil from the higher depths are as a rule, discouraged.

But in the course of the work, it is necessary, in parallel with the reclamation, to roll up the washed up sand, usually bulldozers and earth moving equipment. within the processes, the mined sand must be secured in order to prevent it from shifting. This is especially important for subsequent construction in such a territory. Technically fastening reclaimed areas is done by driving of concrete piles or bored piles field forming piles that as nails, fastened to the existing soil reclaimed area.

Only then is it possible to safely build the capital buildings and structures.

  1. b) Sand hydraulic wastewater (extraction)

For traditional mined sand and its use in construction and production of concrete, dredgers are used with relatively low productivity. Usually up to 2400 meters of cubic water-sand mixture (pulp).

The depth of development of such dredgers is up to 15 meters at a range of pumping – 500 – 750 meters.

And here, in contrast to the reclamation of territories, there are certain nuances. They concern here is not the method of reclamation, but the issues of storage.

As for the hydraulic alleviation of the land, the storage of washed sand does not have a significant value – since the storage area is large.

When mining sand for construction work and for the production of concrete, its delivery is required for consumers. Here, the storage of sand is a very significant factor. Since if sand is washed in one place, a significant part of it will drain back into the water or spread out on the sides, rather than concentrate in the mound.

To do this, there is need to equip special areas, which are called maps. These sites are a territory along the perimeter of which special mounds are made in the form of a scape of sand. It is in the middle of such dumped cards that the sand is poured.

Taking into account that not more than 20% of the water-sand mixture of real sand is included in the composition, the dredgers are also selected in order to avoid washing away of the border (fence) of the reclamation card. Otherwise, the sand will spread and it will be difficult to load it into trucks in the future.

When one such card is filled in, then go on to fill the other one. From the first, with the use of front loaders and excavators, the extracted sand is loaded into trucks.

These are the main methods and technologies for the use of dredgers.

SUMMARY

The financial and industrial company NAFTA GAS SERVICE, which is one of the official partners of UNIG HOLDINGS, has two non-self-propelled dredgers LS-27-1600 (for more details, see here) and LS-27-2200 (see more here)  with a reclamation capacity of 1600 and 2200 Cubic meters of water-sand mixture, respectively. These machines are absolutely effective in the extraction of sand on the reclamation cards and its further use in construction and production of concrete. The total volume of sand extraction, depending on the depth of development and the range of transportation, is up to 600 cubic meters per hour.

They are also able to carry out small deposits of land areas (reclamation), because of their characteristics.

The official partner (click here) another partner of UNIG HOLDING is the Ukrainian company SPETSTEHNIKA, (click here) which occupies a leading position in the production of non-self-propelled dredgers in Eastern and Central Europe. (Click here)

where required, the company is able to produce dredgers of any capacity and performance, at the request of the customer.

regarding the ratio of price / quality, the company “SPETSTEHNIKA” is included in the TOP companies of the world.

At the same time, its dredgers are well known in African countries in general, and in Nigeria in particular. (See Presentation SPETSTEKHNIKA)