Gravity Separation & Concentration Methods

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Dredging Bucket (20 replies)

Dizzy Flores
2 years ago
Dizzy Flores 2 years ago

Could a Dredging Bucket be used for alluvial mining? I suppose it is an accessory that replaces a bucket of an excavator. Cutter head and slurry pump moved by the hydraulic. Has anyone known or worked it?

Sugar Watkins
2 years ago
Sugar Watkins 2 years ago

A few years ago I visited a processing plant for diamonds and gold. It was mounted on a large raft and fueled by a dredging bucket that was digging the gravel up to 18 meters deep. This equipment was composed of several links (like a treadmill of a bulldozer) each with a bucket of 400 liters capacity. The rotational movement was through a powerful electric motor and a hydraulic pump by lifting.

Ace Levy
2 years ago
Ace Levy 2 years ago

Perhaps the following will give you an idea: Traditionally it's a large vessel mounted bucket dredge. The engaging tool is an inclined level elevated rotating set of buckets that articulate from side to side whilst activated in a forward motion in tandem with a cutting action against the material being excavated. The cutter buckets excavate at the front and escalate to the rear discharging its load into a rear mounted hopper feeding a processing plant housed inside and behind the distributor inside the vessel house. Processing is (depending on the mineral and material extracted) by the following means:

1. Either by traditional sluice (usually for gold) or

2. Stationary primary followed by downstream secondary and clean jigs (can be utilise for gold combined industrial minerals) or gold alone. Also by adjustments in cam stroke on Jig for diaphragm pulsation they can be set for gems followed by downstream gem clean up (a set of different apparatus where certain static lubricants (grease is the catalyst for capture) the latter is more advanced over traditional alone.

Capability of depth and manoeuvrability along with capacity is usually engineered for the purpose it's meant to perform. Limitations are usually attributed to the environment it's located to extract in. Depth being one of them followed by the type of material under excavation. It requires knowledge of; Particle distribution (both minerals being extracted and boulder/pebble size of gravels along with the density of the consolidated/unconsolidated nature of the resource).

Marshal Dienes
2 years ago
Marshal Dienes 2 years ago

Are you talking about a bucket line dredge popular around the turn of the century?

Jean Rasczak
2 years ago
Jean Rasczak 2 years ago

I can send you pictures. Being involved in alluvial mining I visited and seen a couple operating in Brazil (in the Jequitinhonha river, for diamonds and gold for Mineração Tejucana) and Portugal (for tin). Huge machines, high volume, low unit cost, low recovery.

Carl Jenkins
2 years ago
Carl Jenkins 2 years ago

Please clarify if you are proposing bucket ladder dredging or modern suction dredging? The former is nearly extinct. The Tweet family still operate a small dredge for alluvial gold in Western Alaska (http://alaskamininghalloffame.org/inductees/tweet.php), and there are operations for mineral sands, tin, and gold in Brazil and Indonesia. See Robin Grayson's page (http://www.mine.mn/WPJ8_1_gold_dredges.pdf). It's been disappearing rapidly. Three types of suction dredging exist - trailing, cutter head, and backhoe. The Bering Sea Gold tv show highlighted a small barge and backhoe operation on the offshore beach placers in Nome. This New Zealand type dredge is very popular on land as well - mining and reclaiming simultaneously, saving costs of re-handling material. Dredging and pumping costs need to be compared with dry mining alternatives. Scale, availability, and costs of the latter can be competitive depending on the deposit.

Carmen Ibanz
2 years ago
Carmen Ibanz 2 years ago

Congratulations to all for the comments on this subject. I also visited Mineração Tejucana processing plants in the Jequitinhonha river in 1990 and I think it is appropriate to comment on low production of these equipment: The reasons were using a trommel as a classifier which is not as efficient as a vibrating screen and the most aggravating was the excessive speed operating above the ideal, or be, up than 45 to 50% of the critical speed and consequently lots of smaller grain including lots of diamonds was expelled along together with the oversize. Another problem that also contributed to considerable losses was the type of jigs (trapezoidal) used on that project which are not suitable for the recovery of diamonds and with a feed in disagreement with the jigging area capacity. The real purpose of these comments is only to clarify that the inefficiency was not the dredging system but yes the equipment used in the minerals classification and concentration.

Dizzy Flores
2 years ago
Dizzy Flores 2 years ago

Thanks for your clever collaboration. You are describing the same equipment but I'm seeking a different one, handling and cheap too. Sure with less performance. This part replaces a bucket on boom and works a cutting rotatory head and a slurry pump too. One excavator operating like a dredge.

Marshal Meru
2 years ago
Marshal Meru 2 years ago

I do think that you are talking about Nessie which is manufactured by the Keene Engineering company out of Los Angeles Calif. Check their web page and see it the pics are what you are looking for because you are describing it perfectly.

Zander Barcalow
2 years ago
Zander Barcalow 2 years ago

I think that you are looking for a cutter suction dredge. Go to this site to download specification sheets on their dredges:http://www.boskalis.com/about-us/downloads.html

Boskalis also has a mining division that may be able to help you find the right dredge.

Bill Rico
2 years ago
Bill Rico 2 years ago

Sounds like you are looking more for a cutter dredge type setup than a bucket line dredge. Cutter dredges use rotating teeth on the head assembly to cut through compacted and/or cemented material and if underwater usually best to deliver to surface through various pumping or suction devices which can get very expensive. I have used similar cutter heads on excavators, but only in dry conditions or on banks above the water table would have to use in conjunction with a suction dredge or bucket on another excavator if underwater. May be an option for you if you already own your own excavators.

Ace Levy
2 years ago
Ace Levy 2 years ago

On the website below you can find several movies of hydraulic cutter dredger

http://www.ihcbeaverdredgers.com/en/media/films/

it will give a good impression about the dredger itself, how it operates, transportability and main components.

Mining dredgers are in general equipped with a wheel, in order to generate a more constant feed towards the plant and a spud carriage in order to have a higher efficiency.

Hopefully this link will give you more information about modern dredging equipment.

Jean Rasczak
2 years ago
Jean Rasczak 2 years ago

I have been in the mineral sand dredge mining game for 26 years and agree with Willem a bucket wheel dredger or cutter suction dredger depending on the size of aggregate and feed rate required. The alternative you seem to be aiming at is a dredging attachment on an excavator or alternatively a jet pump attachment with and cutter.

Marshal Meru
2 years ago
Marshal Meru 2 years ago

In this operation most of the gold goes out in the clay phase of the operation due its encapsulation in the clay matrix, plus the coating in sand s these are all evident in this type of operation the clays hold micron size gold because of the strong affinity to the silica in the clay s usually the micron size is 35 microns and is held in ...place under a field 100 x power microscope and you can see this.. Without proper design the enormous amount of water has a tendency to wash away just values... it all deals with size of particles especially gold, plus the water used for operation.

Zander Barcalow
2 years ago
Zander Barcalow 2 years ago

I have seen, studied and visited a bucket line dredge operation and I am familiar with their operation along with both there good and bad aspects for gold recovery.

Marshal Dienes
2 years ago
Marshal Dienes 2 years ago

I worked with the fleet of bucket line dredges that recovered gold from gravels in the Klondike area of the Yukon Territory. The gravels were very coarse and we dug several metres of soft bedrock that also contained a lot of gold.

I don't there was an alternative mining method for that kind of situation. Dredging is very cheap provided you have cheap power. Many bucket line dredges were designed around the beginning of the 20th century and simply re-built when they fell apart or were moved. Casting technology dictated the maximum size of bucket that could be made at reasonable cost. This restriction is longer present so we could build bucket line dredges with enormous capacity that would dig round very cheaply. The problem is the ability to evaluate the ground with an acceptable degree of precision. I don't know what the environmentalists would have to say!

Sugar Watkins
2 years ago
Sugar Watkins 2 years ago

I agree, you're talking about bucket wheel dredge Nessie - I own one in Brazil.

Depending of what you need and what conditions - this is the state of art; in wrong conditions might be you hell in life. It’s an incredible dredge - with limitations - operating up to 150m³/hour.

Bill Rico
2 years ago
Bill Rico 2 years ago

There is a clip on Youtube of Yuba dredge #17 that is still operating in California; it is one of the last ones in North America. These big dredges were built at Natoma, and exported all over the world. Their history is described in Gold Mines of California by Jack Wagner, published by Howell North Books. The large tailings fields they left can still be seen in many places.

Dizzy Flores
2 years ago
Dizzy Flores 2 years ago

I was surprised to learn a bucket line dredge is still running in California. Bucket wheel dredge have their place but I can well imagine the operating problems - including maintenance - when the ground is not quite what was expected.

Carl Jenkins
2 years ago
Carl Jenkins 2 years ago

Yes, Dredge #17 is operated by Yuba Industries near Marysville in the Yuba River dredge-field; there was another Yuba dredge that sank in 2003

Carmen Ibanz
2 years ago
Carmen Ibanz 2 years ago

Glad to learn the craft of dredging has yet to be classified as an extinct procedure of interest to archaeologists.

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