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Dredging Equipment

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Mining Equipment

A dredge floats on a barge in the middle of a harbour.
Dredging equipment
or a dredge is a piece of equipment used for excavation in underwater applications. It employs a mechanism that scrapes and sucks sediment from the seabed. A dredger is a ship or boat equipped with a dredge.

The term dredging can also refer to digging, gathering, and pulling out material. It is commonly used for maintaining and deepening waterways and creating docks and harbors. Dredging equipment is the most important component of port construction and reclamation projects.[1]

Contents

[edit] History

Like many forms of excavation, digging, and earthmoving, the first methods of dredging were completed by hand. Workers gathered in groups to "drag" river bottoms in preparation of building accessible waterways.

It was the establishment of ports that prompted the need for early dredging equipment. Dredging was first used for navigational purposes. The growing ports around coastlines in the 1800s led to the need to create ports and docks. In order to construct these ports, dredging equipment was needed. Eventually, dredging equipment was also used to keep the portside free of mud and silt.[2] The first dredger was a floating dredger, which consisted of a bucket chain and was driven by either manpower or animals. The earliest recorded dredging machine appeared in 1796.

Some of the earliest dredging equipment is associated with boats. The Bertha, constructed in 1844 in the United Kingdom, is one such boat that used a dredge. Although it was technically referred to as a drag boat rather than a dredger, it employed a blade that, when submerged into the water, scraped the sea bottom and removed sediment.

The oldest steam-driven vessel in the world, Bertha was used to control the accumulation of mud and silt around the dock where she was stationed. Using a chain, Bertha lowered a blade mounted on a sliding pole and dragged the blade on the ground.[3]

The cutting and suction provided by a steam-driven device, such as a suction hopper dredger, enabled anything from minimal to massive excavation, to the preparation and maintenance of port construction.

Dredging equipment, while still closely associated with boats, eventually came into its own. Norbert Degelman and Harold Morgan invented the first original auger dredge, known as the Mud Cat, in 1962. They set out to build a portable machine, operated by two men, with a roto-tiller. Their first attempt didn’t float but it did successfully manage a dredging mechanism. Three years later, they found some investors to assist them and they established their first company. They launched the Mud Cat and built four more shortly afterwards. Today, the Mud Cat dredge is one of the best-selling dredge products.[4]

One of the biggest current projects to require dredging equipment is the 8.5 mile- (13.7 km-) long undersea railway tunnel, also known as the Marmaray Project located on the Bosphorous Strait. Due to be completed in 2012, dredging equipment will aid in the construction of an Immersed Tube Tunnel (IMT). Dredgers will clear 1.3 million cubic yards (1 million m3) of earth in order to dig a trench deep enough for the tunnel. A variety of dredgers are being used, including a clamshell dredger (CSD) and a trailer suction hopper dredger (TSHD)

Today, dredging is used for a variety of purposes, such as:

  • Mining sand, clay, or rock for construction or reclamation projects
  • Mining for gold and other valuables
  • Reclaiming areas damaged by oil spills and storms
  • Cleaning up trash on sea beds
  • Maintaining depth of ports and harbors for safe navigation
  • Providing materials for beaches that have been eroded [5]

[edit] Features

Dredging equipment and dredgers require many mechanical components in order to work effectively and efficiently. Today dredging equipment is mostly mechanical and fitted with a number of implements such as basic augers, hoes, cutterheads, and chain ladders.

Dredging equipment can come in many different sizes, made suitable for a range of applications.[6]

[edit] How it Works/Types

There are many types of dredgers, including:

[edit] Hopper Dredger

The hopper dredger is a boat that collects sediment and loads it into an area called a hopper.

[edit] Trailer Suction Hopper Dredger (TSHD)

This dredger is attached to a self-propelled ship that travels a designated path. The hopper is usually used in open waters such as rivers, canals, and the open sea. It is equipped with trailing suction pipes that lift material through the pipes by a series of one or more pumps for deposit into a hopper. The TSHD is similar to that of a floating vacuum cleaner, which hovers over the area to be dredged.

[edit] Clamshell Dredger

This type of dredger operates with a type of clamshell bucket used on many other types of earthmoving equipment, such as crawler loaders and hydraulic excavators. The bucket can dump materials directly into a hopper or barge for removal.

[edit] Cutter Suction Dredger

This type of dredger is used for heavy-duty construction applications and is designed for continuous and simultaneous use. It is a stationary dredger that loosens material and pumps it via pipeline.

[edit] Submersible Dredge Pump

A hydraulic or electric-driven pump, it provides different types of suction heads to suit different dredging applications. [7]

[edit] Hydraulic Dredger

These types raise loosened material in-situ—where they are suspended—by a pipe connected to a centrifugal pump.

[edit] Suction Dredger

This type is stationary and used for mining sand. It uses a suction pump that vertically drives sand into the dredger for deposit into barges or to be pumped by pipeline to a reclamation area.

[edit] Reclamation Dredger

This is a stationary dredger, which is used to empty hopper barges via suction pipe.

[edit] Barge Unloading Dredger

This dredger transfers material from hopper barges to shore for the purpose of reclamation. [8]

[edit] Common Manufacturers

  • Damen Dredging Equipment
  • DEME (Belgium)
  • Jan De Nul (Belgium)
  • Royal Boskalis Westminster (Netherlands)
  • Van Oord Dredging and Marine Contractors (Netherlands)

[edit] References

  1. Dredging. Science Direct. 2008-10-29.
  2. Dredge and Spoil. Dredging and Spoil Disposal Policy. 2008-10-29.
  3. Bertha. World of Boats. 2008-10-29.
  4. History. Mud Cat. 2008-10-29.
  5. Coasts and Marine. Department of Sustainability and Environment. 2008-10-29.
  6. Hopper Dredger. Dredge Source. 2008-10-29.
  7. Damen. Mining Technology. 2008-10-29.
  8. Dredging Info. European-dredging. 2008-10-29.