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DanAK
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Dredge question ( 05:18:35 SatApr 29 2017 )

Anyone have an idea of how high out of the water a 6" derdge will lift material ? I'm hoping to incorporate a dredge set up on my wash plant to discharge into my trommels hopper that is aproxamatly 8 feet above the water level.

  
Jim_Alaska
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Re: Dredge question ( 13:29:09 SatApr 29 2017 )

Dan, I don't have an exact number regarding how high it will lift. But I will say that the lift won't be too high. I remember years ago Dave McCracken had a project where he needed to lift material out of a pond and over a berm.

After many tries it proved to be impossible. I tried it with a four inch one time and was only lifting about two feet. The flow slowed drastically.

You may want to look at adding a conveyor. You can find small conveyors used to transfer grain at farm auctions or suppliers.



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polekaat
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Re: Dredge question ( 13:52:41 SatApr 29 2017 )

It can be done. You will probably need 1 or 2 more jet logs above the water level. More hp is always a plus. Without the extra pump/s and log/s, The solids would slow, drop to the bottom, stack up, then plug your feed.

Polekaat



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micropedes1
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Re: Dredge question ( 15:17:52 SatApr 29 2017 )

What you need is called a hydraulic elevator. I use one to routinely lift sand and gravel 6 feet into a big boil box. Requires screening though. Big stuff will not pass thru the hydraulic jet.

  
geowizard
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Re: Dredge question ( 16:11:26 SatApr 29 2017 )

The question is;

How far can you suck and blow?

How much force is required?

There ARE dredges that have the "power" needed to exert the required "force" to move thousands of cubic yards hundreds of feet in a day.

What are the numbers?

A suction dredge of ANY DESIGN that is required to suck sand and gravel from a given depth with a given amount of horse power has a limit. It produces a suction with a given efficiency. IF the suction dredge must CONVEY or BLOW then we are NOT talking about a "suction dredge".

Well, Geowizard, What ARE we talking about?

A commercial dredge that BLOWS uses a PUMP. The pump is INLINE with the flow. It is usually mounted on deck, however, some applications use a submersible pump. It's generically referred to as a "trash pump".

Trash pumps CAN suck and blow!

Horsepower is the next question...

Well, we can calculate the horsepower or we can use a process of "estimation".

1. A weed eater engine will operate a very small trash pump. maybe pump the sand out of a fish tank.

2. A 10 HP four cycle Honda engine will run a trash pump that will pump out a stock tank and blow the sand and water maybe five feet.

3. I know from experience, a 4 inch, 23 HP Vanguard centrifugal pump will suck vertically 6 feet above the water line and blow water ten feet horizontally. It's a centrifugal pump.

Considering the gravel, rock, and mud weight in a column of solution being pumped - that added LOAD adds to the FORCE needed and translates to Horsepower demanded.

Using the process of estimation, it is likely that an 8 inch trash pump with a 50 to 100 HP engine will be required to satisfy a lift to a trommel.

There are other - possibly more practical solutions. The trade-offs include added mechanization, maintenance and potential failure modes.

- Geowizard
[1 edits; Last edit by geowizard at 16:16:01 Sat Apr 29 2017]

  
geowizard
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Re: Dredge question ( 16:25:35 SatApr 29 2017 )


My next dredge;

http://www.westerndredge.com/3418436

- Geowizard

  
chickenminer
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Re: Dredge question ( 17:19:44 SatApr 29 2017 )

Dan....
I helped a friend with this trommel/dredge project a couple years ago..



He was using a 6" couple jet for lift. The project worked to a degree but the relevance for your question is he was lifting about 4' above the water level. He had no problems with material that would pass through the 6" hose but I would say from watching the thing work that it was close to the max lift w/o starting to experience lift problems with the heavier cobbles.



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Dick Hammond - Chicken, Alaska
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DanAK
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Re: Dredge question ( 17:42:42 SatApr 29 2017 )

Thanks for the input !
Most of my limited experience with a dredge has been with my Keene 2-1/2" high banker and after it is set up the dredge hose attached to the hopper is about 2 or 3 feet above the water level and I haven't had any luck in making it work very well, it could be my pump isn't large enough to get good suction, I was wondering about a larger size dredge and if it was more efficient than what I had experience with.
The dredge I will build will be a 6" it will clean up the bottom of my diggins which is up to 12 feet deep, the intake side of the hose will be connected to a manifold that will be mounted on my excavator bucket, the manifold itself will be approximately 40" wide and have a slot cut in it on the bottom side closest to the bucket teeth which will allow me to rake the bottom and hopefully suck up the fines left over after removing the gravel and a few feet of bedrock, the intake "slot" should classify off anything larger than an inch in size, the dredge hose will be 50 feet long, I'll add a Venturi ? To create suction, and can add several if needed, I have lots of high pressure pumps available to use for powering the dredge hose, the trommel uses a 6" high pressure 850 gpm pump and I have 2ea 2-1/2" fire pumps that can produce 150 psi each, the preferred would be to discharge into my trommels hopper and use the trommel to screen the material and drop into my existing sluice boxes, I suppose an alternate would be to discharge into a big boil box and later run that material thru the wash plant after dredging is complete.

  
geowizard
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Re: Dredge question ( 20:26:53 SatApr 29 2017 )

Dick brings up an interesting point. It's the problem with suction dredges in general. If you load up the suction hose or any other INLINE section, the party's over!

When the suction hose loads up, the flow slows down and everything stops as the hose loads further. The problem amounts to having hundreds of pounds of rock, sand and gravel that have to be removed.

Pushing a suction dredge to the limit is actually pretty easy to do. For the most part, because there are limits to the horse power you can use in "recreational mining" as well as the suction hose diameter, the limit is defined.

So, if the laws of physics (F=M x A) have any relevance, the Mass part of the equation is the water plus the ambition of the miner! A suction dredge creates the force side of the equation. Suction is measured in pounds and mass is measured in pounds. Acceleration is the capacity to move material at a given rate. You have to compromise on the amount of mass and the rate or capacity of production. A larger motor and a larger pump are the only alternative to more lift and moving a given mass at a given rate.

- Geowizard
[1 edits; Last edit by geowizard at 20:28:27 Sat Apr 29 2017]

  
JOE_S_INDY
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Re: Dredge question ( 21:05:47 SatApr 29 2017 )

Dan,

One thought - dredge the bedrock 'sweepings' up to the surface (1" classification) and then further classify before going into the boil box. Then use a slurry pump to pump the slurry (now less than 1") up to the trommel? The down side - loss of all those larger nuggets. :devil:

Another thought - have a dredge sluice box a little above water level, riding along on the floating trommel's pontoons. If nothing else comes together for trying to get that minus 1" slurry up to that trommel just have two separate recovery systems selectively sharing the same water and pressure. Just feed the dredge sluice with the bedrock cleaner / suction nose and the trommel with the excavator. Select which one gets water and go for it! Pretty much a PIA with two cleanouts - unless the dredge sluice has all Gold. :eeekyellow:

Joe
[2 edits; Last edit by JOE_S_INDY at 04:11:56 Sun Apr 30 2017]



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Wiser Mining Through Endless Personal Mistakes
 
 
Jim_Alaska
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Re: Dredge question ( 04:47:25 SunApr 30 2017 )

Or put a conveyor inline.



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Jim_Alaska
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LipCa
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Re: Dredge question ( 13:39:58 SunApr 30 2017 )

Might be easier to lower trammel?

  
DanAK
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Re: Dredge question ( 18:40:34 SunApr 30 2017 )

LipCa, the trommel would not be easy to lower, here is a picture of the wash plant the dredge will attach to.

https://imageshack.com/i/pn0SgaV1p
[1 edits; Last edit by DanAK at 18:43:09 Sun Apr 30 2017]

  
DanAK
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Re: Dredge question ( 18:49:46 SunApr 30 2017 )


  
geowizard
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Re: Dredge question ( 02:25:45 MonMay 1 2017 )

Dan,

I recommend a bucket-line! :gonetoofar:

- Geowizard

  
LipCa
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Re: Dredge question ( 03:44:34 MonMay 1 2017 )

Yes, it would hard to lower.
A question.... why does it(the dredge) have to feed into the trommel?
Why not just use it like a dredge?
I think if you try to classify to 1" at the "nozzle", it will plug up immediately??

  
Jim_Alaska
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Re: Dredge question ( 04:51:03 MonMay 1 2017 )

Harry, I posted the same thing you did and then deleted it. You have to go back through the whole thread to see what he is trying to do. His classification is at the bucket with bars on it. Then what gets scooped up in the bucket is all one inch or less.

If he were to use it like a dredge he would be dredging blind because the tails drop back into the pool.

I tested the tails from a pond operation in Alaska for the owner. He wanted to see if he was losing anything. It turned out that he wasn't. But he did it with an open bucket and classified the large stuff at the grizzly on top of the trommel, then just let the trommel do the final classification.

It worked real well for him and may work well for Dan too if he chose to go this way.



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Jim_Alaska
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DanAK
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Re: Dredge question ( 06:14:50 MonMay 1 2017 )

The dredge does not have to go into the trommel, I was trying to use my existing sluice for ease of cleanup and it has good recovery, I could use a separate sluice for the dredge.
I think the dredge manifold could plug up easily also but I've got to start somewhere, the bottom of the pond is pretty well cleaned up after I'm done digging and feeding the trommel, I'm hoping the dredge will clean up any lost gold that I've missed on bedrock.
The manifold that attaches to the bucket will have a 1" slot that will act as a nozzle, much like a big shop vac floor sweeper, the 1" slot is a WAG calculation, the bucket is 40" wide if I was to have a 6" opening across the width of the bucket I would doubt the 6" dredge hose would have any suction, I won't be scooping to fill the bucket while dredging, I'll just rake the bottom in hopes to recover any fines that get sucked up with the dredge

  
LipCa
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Re: Dredge question ( 14:28:10 MonMay 1 2017 )

Dan,
I hope it doers work.


Think about your 2.5" dredge nozzle if it were flattened down to a 1/4" slot.....
[1 edits; Last edit by LipCa at 14:31:51 Mon May 1 2017]

  
Honza_Basta
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Re: Dredge question ( 07:22:15 ThuMay 4 2017 )

Quote: chickenminer at 17:19:44 Sat Apr 29 2017

Dan....
I helped a friend with this trommel/dredge project a couple years ago..



He was using a 6" couple jet for lift. The project worked to a degree but the relevance for your question is he was lifting about 4' above the water level. He had no problems with material that would pass through the 6" hose but I would say from watching the thing work that it was close to the max lift w/o starting to experience lift problems with the heavier cobbles.


I think that this is too high... The sluice ends 4" above water level - useless... Even the pipe fom dredge to trommel may be a bit shorter. Little things that pays...

  
Honza_Basta
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Re: Dredge question ( 11:33:17 ThuMay 4 2017 )

And what about this? With this conception the jet log would be some 6" higher than without trommel. Even the trommel could be driven from the pump engine. I have engine and outstanding keene pump, so I can place a pulley there. And belt to a gearbox and than to the drum.


  
LipCa
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Re: Dredge question ( 14:57:01 ThuMay 4 2017 )

Would probably work for someone.
But, DanAk already has a trommel he was trying to feed... see previous posts..

  
Honza_Basta
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Re: Dredge question ( 18:51:38 ThuMay 4 2017 )

Quote: LipCa at 14:57:01 Thu May 4 2017

Would probably work for someone.
But, DanAk already has a trommel he was trying to feed... see previous posts..


Yes, maybe this picture wold be better fit to the thread "Rethinking of large dredge"

  
JOE_S_INDY
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Re: Dredge question ( 23:27:05 ThuMay 4 2017 )

OK, another pea brained idea.

Cup your left hand with the curled palm ending upward. That is your excavator bucket about at full curl.

Attach your pickup, slotted, dredge intake (with flexible hoses), somehow' to your knuckles. Make the discharge from the slotted dredge intake go to that 40" wide bucket and dredge your classified slurry into that 40" wide ""container"" --- and then bucket the captured 'sweepings' into the trommel's hopper. It would need a little careful work with those motor skills - but it certainly could be done.

If the "dredging head" could be a detachable add-on to the bucket, you could pick up the 'vacuum', turn it on, vacuum the bedrock into the bucket (emptying the 'sweepings' whenever needed) and when done, park the 'vacuum attachment' on the deck and just go back to bucketing again.

Joe




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Wiser Mining Through Endless Personal Mistakes
 
 
DanAK
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Re: Dredge question ( 01:01:38 FriMay 5 2017 )

Joe,
That's in line with the idea I had, I plan to dig for a day with the excavator feeding the trommel, after the daily cut is done and to start the next day attach the dredge and clean up the bottom of the pond before continuing to dig, dumping the excess or spill over into the trommel hopper is a good idea.

  
DanAK
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Re: Dredge question ( 01:04:39 FriMay 5 2017 )

Honza,
That looks like a great idea for a floating dredge !

  
chickenminer
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Re: Dredge question ( 01:09:33 FriMay 5 2017 )

Quote: Honza_Basta at [unixtime

1493882535[/unixtime ]

I think that this is too high... The sluice ends 4" above water level - useless... Even the pipe fom dredge to trommel may be a bit shorter. Little things that pays...


Many options were tried. When the dredge/trommel was running the end of the box was at water level. If you shortened the pipe the angle becomes steeper. That was tried with negative results.
It was a prototype ... needed a lot of work.



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Dick Hammond - Chicken, Alaska
Chicken / Stonehouse Creek Mining
Chickenminer.com
 
 
geowizard
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Re: Dredge question ( 15:39:52 SunMay 7 2017 )


I'm not sure what is being fixed.

The concept of the suction dredge doesn't need to be fixed. it isn't broke!

The laws of physics prevail. Lift requires energy. It doesn't matter if you lift at 10 degrees for half a mile or 45 degrees for 10 feet. The same amount of energy is required.

When drop is needed in a sluice box - it defines and equal amount of LIFT. If you need 24 inches of drop - you need 24 inches of LIFT. If you need another 24 inches of drop from the feed end of a trommel - that requires 24 inches of lift.

ALL of the variations require LIFT. Beginning at the suction tip of the suction hose. Lifting water below the water line doesn't require lift. Every inch above the water line, the weight of the water column requires an equal amount of force to lift just the water. Add MORE weight in the form of rocks and the amount of force (energy) needed goes up proportionally.

Bucket line dredges were large. They used more power. The conveyed more water and rock. Any intermediate design will absolutely require an equal or slightly greater amount of power than the amount of weight the operation is required to lift over the amount of time required to do the work of lifting.

I hope this helps.

- Geowizard

  
LipCa
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Re: Dredge question ( 22:40:11 SunMay 7 2017 )

assuming you are in a pond.....

  
geowizard
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Re: Dredge question ( 23:09:50 SunMay 7 2017 )


"Pumping" a column of water in a hose or any conduit, pipe, etc is limited by the amount of power available to do the work.

A suction dredge is designed to create suction. It has limited capacity to lift above the water line. A suction dredge is not a pump! So, it isn't reasonable to expect a suction dredge to provide vertical lift above the water line. Since the weight of sand and gravel increase the load, the percent slurry should be kept at a limit of 15 percent.

If it is intended that the dredge have elevated lift above the water line it will need a pump. The pump is required to have positive displacement. Anything less than 100 percent positive displacement reduces the efficiency in lifting a slurry.

- Geowizard

  

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