A Look at Gold Mining Equipment
At one time gold mining consisted of miners squatting over streams or river beds, swirling their pans and smiling when those shiny bits of earth separated from the sand. You can still find that today, but like any other industry, gold extraction has become a highly mechanized process accomplished with heavy-duty gold mining equipment. Large-scale gold recovery is a costly endeavor, and many of the heavy-duty machines used for mining projects are designed to be time- and cost-effective. There are numerous machines and equipment used to facilitate successful gold extraction operations: wash plants, trommels, pan feeders, screens, jigs, sluice boxes, and shaking tables—to name just a handful.
Wash Plants and Trommels
Wash plants are engineered to thoroughly wash and recover alluvial gold. Wash plants feature horizontal designs that allow for lower feed heights and more intense cleaning action. Numerous spray bars and nozzles thin and separate gold into nugget traps, sometimes 10-feet long.
Trommels are screened cylinders that separate materials by size and prevent blockage. Screens are constructed from steel or rubber and can be snapped into place. While more expensive, rubber screening media is thought to outlast its steel counterpart by 10 to 15 times.
Pan Feeders and Screens
Feeders are designed for in-line placement to convey material to a screening or washing plant. They can use vibration to transport material, be remote-controlled, or use surge bins. Their capacities can range from 50 TPH to 1,500 TPH. Pan feeders feature screen decks with drive shafts, oversize bearings, and adjustable throw. Research has shown that incline feeders capable of reversal can result in a higher scrubbing action for gold recovery. Variable speed drives allow for adjustment of the feeder or screen. Some feeders are designed with the spray system separate from the vibrating unit to minimize broken spray bars. Screens are used to separate gold from sediment and other minerals or materials. Dewatering screens are useful in gold recovery operations for various reasons:
- They save water by removing it from the sluices or jig tailings. As the dewatering screens remove water from the sand, it becomes packed and can break off in large chunks.
- The high-impact screens are extremely durable and enable the machine to run constantly.
- When combined with a cyclone, the screens remove large amounts of fine sediment from the water. This helps keep sediment buildup to a minimum in the recalculating ponds.
Most jig systems are comprised of a hutch containing water with a screen on top. The material is placed on the screen while a rubber diaphragm at the hutch’s bottom is driven up and down. When driven up, the growing water column dilates the shot bed while differentially sorting the particles based on gravity: heavier particles stay on and nearest to the shot bed, while lighter particles are carried away. On the down stroke, the heavier particles are pulled downwards through the bed and are discharged through a valve in the bottom of the hutch.
Advantages of a Jig System:
- Adding a jig system to a gold recovery operation is said to increase results by five to 40 percent, and most of that recovery is in the 100 to 250 mesh-size range.
- As the jig system is self-cleaning, it is low-maintenance with low operating costs.
- It has low water consumption.
- The jig’s immediate feedback allows for quick analysis of the discharge.
Sluice boxes are known as the most cost-effective gold recovery machine and form the basis of any large-scale gold recovery operation. The boxes are designed in single, double, and triple configuration with riffles staying below three feet in width. If a sluice box is not set up correctly with the perfect water flow, gold can be washed right out. Sluice boxes allow for large amounts of material to be processed, versus the traditional gold panning technique.
Shaking tables, or gold concentration tables, provide the final steps prior to the smelting process. They are designed to wet the separation of minerals based on gravity and are simple to operate. The table uses water that is circulated through pumps, filtered, and reused at precise pressure levels. Shaking tables are invaluable when it comes to extracting fine gold.
From retrieving to cleaning and separating, heavy-duty gold mining equipment is necessary for large-scale gold recovery operations.