Editing Dredging (section)

===Suction dredgers===
[[Image:Pogłębiarka „Sawa”, głowica, Wisła, Saska Kępa, Warszawa 3.jpg|thumb|The [[dredge drag head]] of a suction dredge [[barge]] on the [[Vistula River]] in [[Warsaw, Poland]]]]
[[File:Sudging dredger Tuk87-47-10.jpg|thumb|sudging dredger in the [[Beaufort Sea]] used to build artificial islands for oil prospection]]
[[File:2022-10-06 01 Dredger PROVINCIA DE EL ORO NO I, III & IV.jpg|thumb|Cutter-suction dredger, ''Provincia de el Oro No 1'', in Puerto Bolivar, Ecuador]]
[[Image:Geopotes 14.jpg|thumb|The ''Geopotes 14'' lifting its boom on a canal in The Netherlands. (''gēopotēs'' is Greek for "that which drinks earth")]]
[[File:Berky Dredge King Typ 6780.jpg|thumb|alt=Dredge boat 'Dredge-King'|After collecting, the material can be transported to the shore via tube]]
{{For|suction-type excavation out of water|Suction excavator}}
These operate by sucking through a long tube like some [[vacuum cleaner]]s but on a larger scale.

A plain suction dredger has no tool at the end of the suction pipe to disturb the material.

====Trailing suction====
A trailing suction hopper dredger (TSHD) trails its suction pipe when working. The pipe, which is fitted with a [[dredge drag head]], loads the dredge spoil into one or more hoppers in the vessel.
When the hoppers are full, the TSHD sails to a disposal area and either dumps the material through doors in the hull or pumps the material out of the hoppers. Some dredges also self-offload using drag buckets and conveyors.{{citation needed|date=July 2018}}

{{asof|2008}} the largest trailing suction hopper dredgers in the world were [[Jan De Nul]]'s ''Cristobal Colon'' (launched 4 July 2008<ref>{{cite web|url=http://www.sandandgravel.com/news/article.asp?v1=11114 |title=Jan de Nul's mega trailer Cristóbal Colón launched - Dredging News Online |publisher=Sandandgravel.com |date=7 July 2008 |access-date=14 June 2013}}</ref>) and her sister ship ''Leiv Eriksson'' (launched 4 September 2009<ref>{{cite web|url=http://www.sandandgravel.com/news/article.asp?v1=11221 |title=Keel-laying ceremony for Jan de Nul's Leiv Eiriksson held - Dredging News Online |publisher=Sandandgravel.com |date=1 September 2008 |access-date=14 June 2013}}</ref>). Main design specifications for the ''Cristobal Colon'' and the '' Leiv Eriksson'' are: 46,000&nbsp;cubic metre hopper and a design dredging depth of 155&nbsp;m.<ref>{{cite web|url=http://www.jandenul.com |title=Jan De Nul Group |publisher=Jandenul.com |date=7 June 2013 |access-date=14 June 2013}}</ref> Next largest is ''HAM 318'' ([[Van Oord]]) with its 37,293&nbsp;cubic metre hopper and a maximum dredging depth of 101&nbsp;m.

====Cutter-suction====
A cutter-suction dredger's (CSD) suction tube has a cutting mechanism at the suction inlet. The cutting mechanism loosens the bed material and transports it to the suction mouth. The dredged material is usually sucked up by a wear-resistant centrifugal pump and discharged either through a pipe line or to a barge. Cutter-suction dredgers are most often used in geological areas consisting of hard surface materials (for example gravel deposits or surface bedrock) where a standard suction dredger would be ineffective. They can, if sufficiently powerful, be used instead of underwater blasting.<ref>{{cite web | url=https://www.marinelog.com/index.php?option=com_k2&view=item&id=25244:deme-orders-worlds-most-powerful-cutter-suction-dredge&Itemid=257 | title=DEME orders world's most powerful cutter suction dredge | publisher=Marine Log | date=1 March 2017 | access-date=13 November 2018}}</ref>

{{As of|2024}}, the most powerful cutter-suction dredger in the world is [[DEME]]'s [[Spartacus (ship)|''Spartacus'']], which entered service in 2021.<ref>{{cite web | url=https://www.deme-group.com/news/deme-takes-delivery-spartacus-most-powerful-and-innovative-cutter-suction-dredger-world | title=DEME Takes Delivery of 'Spartacus' – The Most Powerful and Innovative Cutter Suction Dredger in the World | date=4 August 2021}}</ref>

====Auger suction====
The '''auger dredge system''' functions like a cutter suction dredger, but the cutting tool is a rotating [[Archimedean screw]] set at right angles to the suction pipe. Mud Cat invented the auger dredge in the 1970s.<ref>{{Cite web|url=http://www.mudcatdredge.com/our-history/|title = Mud Cat Dredges - Careers & Job Opportunities with Mud Cat}}</ref>

====Jet-lift====
These use the [[Venturi effect]] of a concentrated high-speed stream of water to pull the nearby water, together with bed material, into a pipe.

====Air-lift====
An [[Airlift (dredging device)|airlift]] is a type of small suction dredge. It is sometimes used like other dredges. At other times, an airlift is handheld underwater by a [[underwater diving|diver]].<ref name=RRR4672>{{cite book |author=Robbins, R |chapter=USAP Surface-Supplied Diving |editor=Lang, MA |editor2=Smith, NE |title=Proceedings of Advanced Scientific Diving Workshop |publisher=Smithsonian Institution |location=Washington, DC |year=2006 |chapter-url=http://archive.rubicon-foundation.org/4672 |access-date=5 April 2013 |archive-date=26 May 2014 |archive-url=https://web.archive.org/web/20140526013827/http://archive.rubicon-foundation.org/xmlui/handle/123456789/4672 |url-status=dead }}</ref> It works by blowing air into the pipe, and that air, being lighter than water, rises inside the pipe, dragging water with it.