Monday, July 28, 2008

Placer Mining Equipment: the Spiral Wheel Concentrator

No matter how efficient the type of placer mining equipment you employ, there will always be a small percentage of very fine or "micron-sized" flour gold left in your black sand concentrates after you've removed the larger gold pieces (i.e., nuggets, coarse flakes, "pickers," etc.). Often, this very fine gold is nearly invisible to the naked eye and seems to defy any and all attempts to recover it.

One very effective way to accomplish this task is by using a "spiral wheel " concentrator. What's a spiral wheel concentrator? In essence, it is a motorized "automatic" panning system designed specifically for fine gold recovery from black sand concentrates.

How does it work? The spiral wheel concentrator works on the same principle as a gold pan, but is designed and configured to maximize gold recovery far beyond that of a pan by using a specific set of operating parameters or recovery elements, including:

  • optimum recovery angles,
  • adjustable water flow,
  • centrifugal forces,
  • continuous action,
  • double angle riffles,
  • recycling tub, and
  • multi-speed rpm recovery rate (in some models).
The basic components of a spiral wheel concentrator are the spiral wheel (or pan) itself, a 12-volt pump and motor powered by a car battery, an adjustable water flow sprayer or washer, a support stand, a recycling tub, the pan's center recovery "cup," and assorted tubing or hoses.

What are the advantages of a spiral wheel concentrator?

Efficiency (up to 95% gold recovery to about 500 mesh size)
Portability (typically weighs 20-30 pounds and can be broken down, transported, and set up easily)
Running Time (usually 6-8 hours on a full battery charge)
Can Use Recycled Water (the recycling tub uses as little as 3 gallons of water, an asset in dry placer areas)
High Processing Rate (up to 100 pounds of black sand concentrates per hour)
Sturdy and Dependable (if maintained properly)
Ease of Clean Up (most models use a gold recovery "cup" that can be easily removed from the center of the pan or wheel and then replaced after the gold has been removed from the cup)

There aren't many disadvantages to using a spiral wheel concentrator but at least two items should be addressed:

1) Cost (as low as $200.00 on up to $500.00-$700.00 depending on the brand and type of spiral wheel concentrator you are interested in. For someone with good mechanical and fabrication skills, building a spiral wheel concentrator might prove to be a cost-effective and challenging do-it-yourself project)

2) Function (spiral wheels are made for recovering fine gold from black sand concentrates and are not designed for use and abuse as primary pieces of mining equipment like a highbanker or sluice box. Although they can function as such, only small amounts of gold-bearing material can be "fed" into them AFTER it has been screened or "classified" to a very small mesh size first)

There are other effective means of recovering fine gold from black sand concentrates such as mini-sluices and bowl concentrators like the "Blue Bowl," and these may provide the grist for another post later on.

Take care and good luck.

(c)  Jim Rocha (J.R.)  2008

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