#Gold mining dredge how to#

However, it is more expensive and mechanically complex than the cutter suction dredge. It is better at excavating harder materials, has better digging characteristics at the bottom of the cut, and traps heavy minerals such as gold or tin that might fall away from the standard cutter. The bucket-wheel dredge is identical to the cutter suction dredge except that a wheel excavator is used in place of the rotary cutter. The cutter suction dredge is most suitable for mining softer deposits where the material is of a relatively low specific gravity or fine particle size-for example, in sand and gravel pits, phosphate mines, and various salt deposits. The dredge is then moved ahead and the process repeated. Winches and wire ropes are used to swing the dredge in an arc around the spud until all the material in the arc has been removed. Normally, the dredge is held in place during cutting by a pile called a spud. The material falls downward to the mouth of a centrifugal pump, and this transports the slurry (containing 20 to 25 percent solids) to the processing plant. The cutter suction dredge has a rotary cutting head or other excavating tool for loosening and mixing soil at the face of the mine. The digging power of hydraulic systems has been greatly increased by the addition of underwater cutting heads. Hydraulic dredging has also been applied to the mining of deposits containing diamonds, tin, tungsten, niobium- tantalum, titanium, monazite, and rare earths. They are best suited to digging relatively small-sized loose material such as sand and gravel, marine shell deposits, mill tailings, and unconsolidated overburden. In pure hydraulic dredging systems, the digging and lifting force is either pure suction, suction with hydrojet assistance, or entirely hydrojet. Although it can operate in deeper water than other systems and handles large particles and trash well, it has the disadvantage of being a discontinuous, batch-type system, taking approximately one bite per minute. The clamshell dredge, another mechanical system, is characterized by a large single bucket operating at the end of cables. After the valuable material has been removed by the treatment plant, waste is dumped off the back end of the dredge. The filled buckets, supported by rollers, are pulled up the ladder and dump their load into the hopper. The chain of buckets passes around the upper end of the ladder at a drive sprocket (called the upper tumbler) and loops downward to an idler sprocket (the lower tumbler) at the bottom. The lower end of the ladder rests on the mine face-that is, the bottom of the pond where excavation takes place-and the top end is located near the centre of the dredge, at the feed hopper of the treatment plant.

The excavation equipment consists of an endless chain of open buckets that travel around a truss or ladder. It consists of a single hull supporting an excavating and lifting mechanism, beneficiation circuits, and waste-disposal systems. The bucket-ladder, or bucket-line, dredge has been the traditional placer-mining tool, and it is still the most flexible method for dredging under varying conditions. Dredging systems are classified as mechanical or hydraulic, depending on the method of material transport. SpaceNext50 Britannica presents SpaceNext50, From the race to the Moon to space stewardship, we explore a wide range of subjects that feed our curiosity about space!ĭredging is the underwater excavation of a placer deposit by floating equipment.

Learn about the major environmental problems facing our planet and what can be done about them! Saving Earth Britannica Presents Earth’s To-Do List for the 21st Century.Britannica Beyond We’ve created a new place where questions are at the center of learning.100 Women Britannica celebrates the centennial of the Nineteenth Amendment, highlighting suffragists and history-making politicians.

#Gold mining dredge how to#

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