The shovel-scoop cutter head operates as a shovel which pivots to open as the dredge yaws from side to side. This also shows the shovel-scoop cutter head on the end of the suction pipe. In fact the operating costs are so low it might make it feasible to re-mine tailings of past generations of miners.įigure 2 shows the major components of a 15-inch dredge.
Handling the gravel only once substantially lowers the operating cost of placer mining. The feed gravel is only picked up once, the gold and other heavy minerals are stripped out in the concentrator-classifiers, and down the tail chute to the pond floor in only seconds. No more of the surging and purging associated with conventional placer mining. Suction dredges’ continuous feed rate is many times more than of the largest excavator and the feed is much more consistent. (Compare to a bucketline dredge and typical heavy equipment placer mines.) There is no repetitive feeding by excavators endlessly cycling bucketfuls into a hopper, then pushing the tailings away from the plant and finally reclaimed. Suction dredges can continuously move material from the earth to the processing equipment and dump onto the tailings pile in one non-stop motion using a minimum of moving parts and machinery. The cleanup equipment is even onboard.įloating suction dredges are the most efficient way to mine unconsolidated sediments ever developed.
This dredge has a high tech undercurrent concentrator-classifier recovery system (figure 4) that is excellent at fine gold recovery. It generates 500 kW which runs the pump, concentrators and other electrical controls. The dredge can process up 400 cubic yards an hour. The pump motor is 300 horsepower and can pump 4000 gallons per minute. This Shell 15-inch dredge has an overall length of 123 feet from the nozzle tip to the tail race. Figure 1 shows the largest suction dredge in Alaska. Richard Shell has been manufacturing very large suction dredges for over forty years.
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