Types of dredging and Components used dredging

Dredging involves taking soil, like sand or gravel, from beneath the water and moving it to a different location. Regular dredging is necessary because, with time, sand and dirt carried by water can accumulate, filling up these areas and making them shallow.

Here are some common dredging methods:

  • Mechanical Dredging: 

This method uses tools such as buckets with mechanical parts to extract material from water. Their internal workings are less complex than hydraulic dredges, making them potentially easier for crews to handle. However, mechanical dredges have some disadvantages. Unlike hydraulic dredges, they often have limited mobility and are not well-suited for challenging environments. Additionally, they tend to be less cost-effective overall.

  • Hydraulic Dredging: 

Hydraulic dredging is a preferred choice in many dredging situations. It offers cost-effectiveness, mobility, reliability, versatility, and adaptability to challenging conditions. In hydraulic dredging, the process involves drawing in water and material from the waterway’s bottom. This is accomplished through a centrifugal pump creating a partial vacuum, where atmospheric pressure and the water’s weight combine to push the water and material through a pipe and into a pump.

  • Trailing Suction Hopper Dredging:

In this method, a ship with Trailing Suction Hopper Dredging equipment drags one or two suction arms from its side while moving slowly. Each suction arm has a drag head at its entrance, which works like a vacuum cleaner to collect soil. For harder soils, like compacted sand, or sticky ones, they use special methods like water jets, blades, or rippers in the drag head.There are more dredging methods like cutter suction using cutter head, bucket dredging, water injection etc.

Components of Dredging: 

  • Dredge Pump: 

Dredge pumps are built to handle tough conditions. They can pump and handle all sorts of materials like slurry, mud, sand, gravel, rocks, and debris. A hydraulic design of a dredge pump  makes the pumps more efficient, with better wear resistance, high reliability, and a longer life cycle.

  • Dredge Value: 

The dredge valve is a part of Cutter Suction Dredges or Trailing Suction Hopper Dredgers. Its purpose is to manage the movement of water and sand in the suction and discharge pipes. Dedge valves generally come in three different variants of 10, 20, and 30 bar. The dredge valve offers real-time feedback on the position of the gate.

  • Gate Value: 

The Dredge Gate Valve is utilized to open and close pipelines for transporting slurry on dredge vessels or ships, with diameters ranging from 250 to 1400mm. It comes in low pressure (8kpa), medium pressure (15kpa), and high pressure (15kpa) variations. This gate valve includes a gate or blade that can be lifted or lowered to manage the flow of materials and water within the pipeline. By altering the gate’s position, operators can control the amount and speed of material discharged during dredging operations.

  • Dredge Ball Joint: 

A dredge ball joint works as a link between two pipes employed for transporting a mixture of water and sand from a dredging vessel to the discharge location.Dredge ball joints are created to offer flexibility to the pipeline in all directions, within a specific angle limit. 

  • Cutter Suction Dredgers (CSD): 

A cutter suction dredge is a special kind of machine used for digging in water. It has a rotating cutter head that pulls in material through a pipe and sends it out through another pipe to a disposal site. These dredges are effective and save money because they pump material directly to where it’s needed. Their sharp blades make them good for various types of soil, including rocky areas. Cutter suction dredges are helpful in places where other types of dredges may not work well. 

  • Drag Head: 

The dredge drag head is a steel framework linked (attached) to the dredging vessel through a suction pipe. Using hydraulic winches and supported by gantries, the dredge drag head and suction pipe are lowered to the seafloor to extract a mixture of water and sand.

  • Booster Station:

Booster stations are equipped with pumps that enhance the efficiency of the dredger’s pumps, enabling the transportation of dredged material over extended distances.Booster stations are useful with both Trailing Suction Hopper Dredgers (TSHD) and Cutter Suction Dredgers (CSD). 

  • Bow Coupling:

The bow coupling establishes the link between the ship and the floating pipeline. It comprises both a female and a male part. The female component is secured to the bend of the discharge pipe, while the detachable male part needs to be attached to the floating hose.

  • Hopper Overflow: 

In instances where the hopper exceeds its capacity, any surplus mixture escapes through the overflow, finding its way back into the water. This overflow of sediment plays an important role in the formation of sediment plumes in the vicinity of the dredging vessel.

Conclusion:

In the past 20 years or so, the dredging industry has grown worldwide. It does a lot of different jobs like getting rid of water blockage, cleaning, excavation, maintenance, and more of such activities. Dredging makes traveling through water easier to travel and easier for fishing, especially in shallow streams. It also cleans up dirty stuff from the water and fixes damaged areas by reclaiming them.When we dredge, it’s important to safely get rid of the stuff we dig up. We should dump it where it won’t harm important land or lives. In certain places, dredging changes the minerals in the water, so we need to be careful and watch for any changes it causes.

FAQ'S

How many methods of dredging are there?

There are three types of dredging methods including mechanical dredging, hydraulic dredging, and airlift dredging.

Typically, dredging is done with machines known as dredges, which are mounted on a barge.

Dredges are machines specifically designed to loosen the sediment at the bottom of the water, using a vacuum pump to remove the undesired debris.

The unwanted material is moved to a disposal site which is safe and does not hurt the land or lives.

It is a dredging component of a Trailing Suction Hopper Dredger (TSHD) or a Cutter Suction Dredger (CSD) that is responsible for controlling the flow of water.