Extruded EPDM 4-TPI Sawtooth Mat Redesign

[Johnedoe]

Great article Dragline.
I can't wait to see the new mats.

Jim....
Nice new forum. I had to re-register to get in here but I'm back.
The old me was WmA.

[Jim_Alaska]

Welcome back WmA. glad to have you back with us.

[GoldMember]

Dragline.Very good info on screening i too agree that this is of utmost importance.Unfortunately clean ups for most commercial ops involve only screening our concentrates.I have found that clean ups with my vortex sluice is always
affected by reducing or screening the cons.We have alot of 100-350 mesh fine gold.If for example the circle in the vortex gets a bit worn from say,running too much larger unproperly classified material.Then we have found that bubbles collect around dull edge of alum vortex thus carring away fine gold.I have seen this happen with cube,different mats that you mentioned have been sold as of late.So i believe the sawtooth would be no exception.Again classify to get the fine gold.This is also important for the type of gold that likes to walk for many different reasons.Laminar flow or not.Question:do you have any info on how your matts would work with heavy
garnet laden material.I remember the old posts about your matts ,great on you for your sticktoitness!

[dragline]

GoldMember, no, I haven't specifically tested the Sawtooth mat with heavy garnet laden sands, but I can guess you're having troubles separating flaky gold and similar mesh garnet sands. I probably won't be telling you anything you don't already know, but here again screening to increasingly narrow particle sizes is how I'd go about it.

Take a look at my previously posted illustrations for the 4-TPI, 8-TPI and 16-TPI. You'll notice that I've illustrated the largest mesh size that can safely be nested within the riffles of the mat as follows:
4-TPI: 14 mesh
8-TPI: 25 mesh
16-TPI: 50 mesh

My thinking is that once you've recovered the larger easy to capture gold you might try screening the remaining material down to 50 mesh and use a fine geometry mat such as your Vortex or try using my 16-TPI Sawtooth Mat. I don't personally like using the Vortex mat because it has a tendency to grab the micro air bubble from the slurry, as you mention, and it is time consuming to clean up.

You're right, at a specific gravity at up to 7.5 g/cc garnet sands are going to be a challenge separating from your gold if both are of a similar mesh size. I assume you've tried screening both upper a lower limits of of your material to decreasingly sized fractions of 50-100 mesh, 100-200 mesh, 200 mesh minus and then running each separately under differing conditions tuned specifically for that mesh range? My tinkering suggests that the slurry velocity, and therefore sluice slope and flow volume, should be reduced as screened particle size decreases.

[Johnedoe]

Hey Dragline.

I got to thinking about your 16 TPI.
I think for any practical purposes that is just too small.
I think the 8 TPI would be small enough.
I have some square rib mat that is about 1/16th and it is just about useless..... It works as a low flow cleanup mat but in the sluice it just washed out... Held nothing.

I agree with you about the vortex matting. you really have to prep it and get all the air bubbles out of it.. Also it really traps vegetable matter which also interrupts the efficiency of the mat.

Of course you know I will be happy to do some testing for you... I already have the 4 TPI panels for the gold cube and sections for the 16" wide sluice as well as a 12" wide so we have that covered.
The 4 TPI works very well in the cube and in the 16" wide sluice.

[Geowizard]

Hi Guys,

I like the fact that dragline offers three different sizes. It's incumbent that EVERY application take into account the requirement for screening and velocity and then - appropriate TPI matting.

I have a Keene Mini-6 Suction Dredge at my mine at Ophir. It has the original 3-Stage sluice with three sections that recover GOLD at three size ranges. It uses "standard ribbed matting" in ALL THREE sections.

Keene standard ribbed matting;

http://www.keeneeng.com/mm5/merchant.mv ... t_Code=RM1

Note: This mat is fiber!

Each section has a different design... and... each section has the SAME ribbed mat at the bottom.

The point is that the 3 stage covers three sizes of gold - not based on the bottom ribbed mat - but because the riffles and screen are different in each stage. Small gold drops out in each stage. It stays in the ribbed mat.

The semantics of SIZE, in terms of TPI matters depending on the smallest gold that is expected.

The reality is that properly classified GOLD will blow through any size ribbed rubber mat if velocity is too great. So, it can be expected that 4 TPI will catch micron GOLD at reduced velocity as well as 16 TPI.

In my experience, a miner has to be pretty inept to run fine GOLD at high velocity. We must also keep in mind, that economics of recovery play a part in having FUN or making a PROFIT. By definition, REDUCED velocity means reduced production in terms of cubic yards per hour at 15 percent solids in slurry.

There are very few GOLD mines that make a living on micron GOLD. High velocity is NOT compatible with catching fine GOLD. Reduced velocity is a show stopper for HIGH production.

In summary, it is all about velocity. Are we having FUN or making a PROFIT?

- Geowizard

[dragline]

Geowizard,

You're right about the slower slurry velocities potentially being a showstopper for major mining operations. But when there is an abundance of extreme fine gold the miner has no choice but to tailor the processes in the direction of profit optimal recovery. I've seen several examples attempting to optimize recovery for extreme fine gold. Take the Snake River, for example. Or certain tributaries of the Amazon for another. Some New Zealand beach placers as well. All of these can and often to require very specific operations targeting extreme fine gold recovery. In a lot of these situations miners have resorted to shallow slope angles and very wide sluices, sometime 4, 8 or even 16 feet wide, so as to allow full productivity at slow slurry velocities down to sometimes 3 feet per second... and sometimes less. But your typical coarse gold placer operation might be running slurry velocities of 5 to 8 feet per second.

When it comes to the Gold Cube the most common flow example of the recommended 900 to 1100 GPH at a fixed 15° slope. I'm not completely sure what this translates to in regards to feet per second but I'm guessing its well over 5 feet per second. Some Gold Cube operators boast about increasing their productivity by running upwards of 2000 GPH! Ouch! Whether these miners have extreme fine gold to recover or not, they're likely blowing out any they might otherwise be recovering. One of my Sawtooth users states that he runs the 4-TPI Sawtooth mat at no more than 500 GPH when he's targeting finer fine gold. He learned the hard way that running the stock 1100 GPH pump on his Gold Cube was pushing a lot of his fines to tails.

The problem with the Gold Cube and extreme fine gold recovery is that the slope is fixed to about 14° or 15° which makes it difficult to slow the slurry velocity while maintaining flow volume and productivity. When you think about it, you can slow the slurry velocity in one of two ways. You can decrease the flow volume, i.e. GPH, or you can decrease the slope. Of course decreasing the slope decreases velocity while maintaining flow volume, i.e. productivity. The problem with slowing the velocity is that you'll have a more difficult time clearing the riffles for optimal recovery. That's where tighter bulk material screening down to 50 mesh or 100 mesh minus helps riffle clearing at the slower velocities need for extreme fine gold.

The basic operating principle here is to make multiple runs by cutting the screen size in half each time while optimizing each run's sluice slope, flow volume and velocity for the specific screen size.

dragline

[Geowizard]

Beach GOLD 250 miles inland;

I run a Maxi-Banker Wash plant. The sluice box is 36" wide, 6" high on the sides and 8 feet long... The sluice box has a two inch per foot drop = 9.6 degrees... The pump is a Vanguard 23 HP V-twin that pushes 600 Gallons per minute.

This combination with 2" of water running at 300 GPM works out to a velocity of 1.3 feet per second.

That's about one third of your recommended minimum velocity for the 4 TPI.

I use a Bausch & Lomb x7-32 binocular microscope with a micron ruler to measure fine GOLD down to 10 - 50 microns. I'm not even working to get this small GOLD. I run 1" expanded over Commercial Astro-turf in the box. I think I'm running way too fast.

My interest is running ribbed mat under elevated 1/4 inch punch plate. Ideas?

Yes, I am having FUN.

- Geowizard

[Johnedoe]

Here is the system the Gold Cube is based on.
Trev, a beach miner from NZ ... He did a bit of research and found that the old beach miners used a similar set up. He rebuilt it and of course used modern materials.
An important part of what he found was that the angle and waterspeed were an important factor. the angle was 15 deg.

Gold cube contacted Trev and ask if they could use his design and info to build from. Permission was given and today we have the modern version of Trev's boil box gravity well sluice in a folded stack.

Here is a link to the PDF on treasure net forum...... It is the only way I could figure out how to post the file here. http://www.treasurenet.com/forums/sluic ... ost6053674

Ultimately what I am trying to add here is that water flow and angle are important factors in the recovery of fine gold.
I think I mentioned earlier that I used some of Draglines 4 TPI in a cleanup sluice as well as my beach sluice.Angle was important for the recovery..... The cleanup sluice was 8" wide x 24" long. Water volume was right around 750-850 GPH and the angle was about 15 deg.

[dragline]

Geowizard,

Since you're adjusting your operating parameters for micron gold, i.e. down to as small as 10 to 50 microns, you're dealing with something that is perhaps quite a bit smaller than I've personally worked with. Either that or I have worked with it but was blowing it to tails while not realizing it.

Your stated slurry velocity of 1.3 feet per second at a 9.6° slope sounds very exciting to me because you are obviously pushing your systems to the extreme limits of what micron gold recovery via gravitational technologies are capable. My only question about what you're saying regards your slurry flow velocity of 1.3 fps and whether you have directly measured that velocity by dropping floaters into the slurry and timing the distance traveled, or whether you calculated your velocity based upon slurry depth, width and GPM. I personally prefer the direct measurement of slurry velocity with multiple trials with a stopwatch. Ask a miner if they've measured their slurry velocity and 95% of the time you'll get the deer in the headlights look in response despite the fact that all other operating parameters basically boil down to this one metric.

Can you tell me if you have done a microscopic analysis of your gold shape characteristics, i.e. in the range between spherical and flat flake? Since I believe you stated that you were dealing with milled ore can you tell me how many and which mesh size of screenings you are processing? Since you mentioned you are dealing with 10 to 50 micron gold, theoretically, you'd optimally want to be performing multiple screenings while processing each with a sluice that is specifically configured for the characteristics of the gold that falls between those screenings. I think I have a 400 mesh Fisher Scientific screen kicking around here someplace although I've not had an occasion to actually use it for my gold screenings.

Here is a calculated US Mesh Size chart that includes micron gold for your handy reference.



dragline