Shaking tables, also known as wet tables, consist of a sloping deck with a riffled surface. A motor drives a small arm that shakes the table along its length, parallel to the riffle and rifle pattern. This longitudinal shaking motion consists of a slow forward stroke followed by rapid return strike. The riffles are arranged in such a manner that heavy material is trapped and conveyed parallel to the direction of the oscillation. Water is added to the top of the table perpendicular to the table motion. The heaviest and coarsest particles move to one end of the table while the lightest and finest particles tend to wash over the riffles and to the bottom edge. Intermediate points between these extremes provides recovery of the middling (intermediate size and density) particles.
Shaking tables find extensive use in concentrating gold but are also used in the recovery of tin and tungsten minerals.These devices are often used downstream of other gravity concentration equipment such as spirals, reicherts, jigs and centrifugal gravity concentrators for final cleaning prior to refining or sale of product.
The Wilfley Laboratory Concentrating Table, has a capacity of up to 150 lbs per hour on 20 mesh, +200 mesh feed, complete with one interchangeable 18 x 40 right hand molded fiberglass construction tabletop, one sand deck, capacity for complete with motion generator, drive frame, feed, and discharge launder, constant speed drive, adjustable stroke, with 1/2 HP/115 -230 V/1 Ph/60 Hz TEFC motor. Shipped completely assembled on a fabricated steel base.
The Wilfley Shaker Tables are gravity concentrating devices that separate material based upon differing densities ofthe material. They are effective in concentrating high density minerals, such as precious metals, have beenused in metallurgical applications, mineral processing applications, soil remediation and recovering light densityores, such as coal from the heavy density refuse.
The Wilfley Tables have two distinct deck designs available. The sand deck is designed for recovering particlessized from 20 mesh to 200 mesh. The slime deck is designed for recovering fine particles in the rangeof 200 mesh to 325 mesh. The model 13-A is the laboratory sized Wilfley Table and is ideally suited for labor pilot plant test work.
Utilizing the sand deck, a Wilfley Table can concentrate ore in the 20 mesh to +200 mesh particle sizerange. With the slime deck, it will concentrate ore in the 100 mesh to +325 mesh particle size range. Thecapacity for a lab size Wilfley Table (13A) is between 30 and 50 pounds of feed per hour, with lower capacitieswhen using the slimes deck.
The sand deck is efficient in separating high density from low density material (with a difference of 1 SG unit), in the particle size range ranging from 10 mesh to 150 mesh. Slimes decks are used for particles in the 150 to 325 mesh range. However, as one that has used the slime deck, the surface tension of water interferes with recovery in this particle size range. This is probably why 90% of people using the tables use the sand deck.
SHIPPING DIMENSIONS:2440mm Long x 930mm Wide x 1420mmHigh and294kgs FOOTPRINT (IN USE):2350mm x 830mm x 1450mm High DECK DIMENSIONS:Deck surface area of 0.8 m2,Conc Edge 640mm, Tail Edge 1280mm ELECTRICAL SUPPLY:Single phase, 110/230V 50/60Hz.Motor is 0.37kW WATER SUPPLY:Wash Water requirement of 6 to 12 l/min,Feed dilution to ~25-30% w/w solids CAPACITY:Samples: 1-20 Kgs/hour,Continuous: <75Kg/hr
The Wilfley 800 Laboratory table offered provides state of the art separationperformance suited to a wide range of mineral testing, including Tin, tantalum, tungsten, gold, zircon, rutile etc. recovery and concentration applications in Research and University establishments around the world. The drive is self lubricating and run tested in accordance with a fully documented in house QA system.
All steel framework is stainless steel, and the decks (2 x supplied for fine and coarse separations) are gel coated smooth glassfibre construction. Drive is by power connection to speed control inverter, and can be easily adapted tosuit single phase global power supplies. The 0.37kW motor is pre-wired. Single water connection to a manifold provides controlled water flow to feed dilution, wash water bar and water wash down gun. The machine is packed in fully assembled form, ready for positioning and power/water connections. Adjustable rubber pad feet, allow levelling. Manual deck tilt and longitudinal slope by handwheel are possible to optimise testconditions.
The most popular of several similar devices, the Wilfley Shaking Table was developed in the 1890s. It has been in use since and is a common device for concentrating particles in the intermediate range, such as 10-200 mesh (1.65 mm-74 pm) particles for ore and 3-100 mesh (6.7 mm-150 pm) for coal. It is an oblong, shaken deck, typically 1.8- to 4.5-m wide; the deck is partially covered with riffles that taper from right to left. The deck is gently sloped downward in the transverse direction. Feed enters at the upper right and flows over the riffled area, which is continually washed from a water trough along the upper edge of the deck. Heavy particles are concentrated behind the riffles and are transported by a bumping action (of 12-25 mm throw at 200-300 strokes/min) to the left end of the table where flowing film concentration takes place.
Gaudin (1939) identified three principles of operation: hindered- settling, asymmetrical acceleration, and flowing film concentration. The hindered-settling action takes place in the boil behind the riffle. Asymmetrical acceleration, from a spring and from the bumping action supplied by a pitman and toggle arrangement (not unlike that in a Blake-type jaw crusher), not only transports the material behind the riffles but also helps to separate heavy from light materials. Heavy minerals are influenced less by the bumping action than are light ones, and thus the heavier particles have much longer residence times on the deck than do light ones. The bumping action also keeps particles in motion and allows the wash water to remove light particles more thoroughly. Final particle separation is made on the flowing film pan of the deck, which produces a superior heavy mineral concentrate.
The final slope sequence is fine-to-intermediate heavy panicles highest upslope, fine light and intermediate-to-coarse heavy panicles in between, and coarse light panicles furthest downslope. This sequence differs from that of a hindered-settling classifier. Accordingly, it is common practice to have separate shaking tables, each with different settings, treat the various spigot products from a hindered- settling (sorting) classifier.
Whether shaking tables or some other intermediate-to-fine gravity concentration devices are used for roughing, shaking tables are commonly used for cleaning to produce an acceptable concentrate. They are frequently used for upgrading heavy minerals that are not well floated, such as -Win. (6.4 mm) coal particles (as coarse as -10 mm in some instances), small middling streams, and heavy particles to be removed during environmental remediation. The latter is typified by such procedures as removing metal splatter from foundry sands and separating metal grindings from abrasives. In treating relatively coarse -8-mesh (2.4-mm) ore particles, the tables can handle several tons per hour, but for much finer, 150- to 400-mesh (100- to 37-pm) particles, and their capacity may drop to about 0.3 tph. If -10-mm coal is treated, a capacity of 12 tph per deck may be achieved. To clean coal, shaking tables are often stacked two or three decks high, all controlled by the same shaking mechanism.
A. The unit is packed with plastic securing ties holding the table deck shaft, onto its support half bearings, and also securing the gearbox cover and ancillary yellow piping. These must be removed before use. B. THERE IS A SMALL WOODEN BLOCK INSERTED BETWEEN THE DRIVE THRUST YOKE (PART 133) AND THE GEARBOX CASING. This is to prevent movement of internal parts during transport and MUST be removed prior to electrical connection and start-up (see photo)
C. Raise the water manifold support after removal from timber crate and securely bolt in upright position. D. Ensure the head motion is filled with SAE 20W/50 oil (Automotive grade) to the correct level as shown in the maintenance section of this manual before running. E. Adjustable feet mountings (FOUR off) are pre-fitted to the base legs. These will require adjustment to level the machine in its location prior to operation.
The machine is mobile for use, with adjustable feet for levelling prior to operation. Position on a flat level surface ideally at a level suitable for the operator to observe separation and provide sufficient room for the operator to walk around the machine.
Connect the water pipe nozzle to a clear water supply using flexible rubber hose. Typical wash water requirement is 5 10 litres/minute. Recommended feed dilution water is 3 parts water to 1 part solid. i.e. 25% Solids w/w A spray gun and hose are provided to assist with washing off the decks, launders and washing products out of the buckets. DO NOT WASH DOWN THE MOTOR.
Connect the single phase mains supply (refer to technical specification for voltage requirements) to the terminals marked L and N, the earth wire must be connected to the Earth terminal marked E (or the earth stud on the heatsink).
Installing a deck is easy. Simply lower the deck onto the half bearings gently and connect up the deck support shaft to the head motion by tightening the M16 nut with a 24mm spanner. Connect up the water supply to the wash water pipe.
Prepare the table feed by mixing the dry solids with water to give a 25% solids by weight mixture. Some feed stocks are Non wetting and will require addition of a wetting agent to assist settling of these particles which would otherwise float to tailings without having been influenced by their gravitational forces.
The feed material will also respond better on the table if the feed has been sized beforehand so that all particles are in a narrow size particle band. This avoids coarse lights reporting with fine heavies (Stokes Law) and therefore gives better separating performance. The degree of sizing will be specific to the material and should be determined by experimentation.
Feed rate is a function of particle size and specific density differences between particles. This can vary from a few kgs/hour upwards. However, as a general rule, the finer and/or more close density the separation between particles the lower the feed rate will be. (Typical max. 70 kg/hour)
The angle of the table from feed to concentrate end can be adjusted using the hand wheel located under the support beam at the concentrate end of the table. This angle can only be optimised by trial and error. However, the higher the concentrate end the longer the material remains on the table.
The wash water should flow evenly over the deck. The quantity of wash water can only be determined by experimentation. Higher wash water volume results in cleaner concentrates and lower recovery and vice versa.
We have set the mid-point (setting 50) to maximum setting on the inverter to coincide with the most useful range of speeds i.e. 200 300 rpm. The instruction leaflet for the AC Inverter is in the control box.
Re fit deck so shaft sits into shaft supports. Ensure there is a washer either side of the Thrust Yoke Tighten the M16 nut to thrust yoke (24mm spanner) The deck concentrate discharge end should rest approx. mid point in the product launder.
The RP-4 shaker table is the most widely used and most successful gold gravity shaking concentrating table worldwide, used by small and large mining operations and the hobbyist. The patented RP-4 is designed for separation of heavy mineral and gemstone concentrate. The RP-4 table can process up to 600 (typically 400) lbs. per hour of black sand magnetite or pulverised rock with little to no losses. The RP-4 uses a unique reverse polarity of rare earth magnets, which will cause the magnetite to rise and be washed off into the tails. This allows the micron gold to be released from the magnetite, letting the gold travelling to the catch. The RP-4 is compact and weighs 60 lbs. With a small generator and water tank, no location is too remote for its use. The RP-4 is a complete, ready to go gold recovery machine. THERE ARE NO SCREEN INCLUDED with the small shaking table. Use was reservoirsgreater than 250 gallon and recycle all your water. Only 400 Watt of power drawn by typical pump. The small RP4 gold shaking has a mini deck of 13wide x 36 long = 3.25 square feet of tabling area. The RP-4 is the best and longest selling small miner shaker table still on the market today. With many 1000s of units sold during the last 10 years! Review the RP-4 Operating Manual and Installation Guide lower on this page.
The RP-4 uses a unique reverse polarity of rare earth magnets which will cause the magnetite to rise and be washed off into the tails and allowing the micron gold to be released from the magnetite leaving the gold travelling to the catch.
When assembling the RP-4, it is very important to set it up correctly to get the best recovery. The unit needs to be bolted preferably to a concrete pad or bedrock when in the field. It can be weighted down with seven or eight large sandbags. Wooden stands will set up harmonics and vibrations in the unit. Vibrations will create a negative effect on the concentrating action of the deck and create a scattering effect on the gold. We would strongly advise getting the optional stand to mount it. See a detailed RP4 Shaker Table review.
Once you have the RP-4 mounted or weighted down, you will want to level it, place a level under the machine on the bar running attached to the two mounting legs. Use washers to get a precise level adjustment. Once mounted and leveled, use the adjustment screw to adjust the horizontal slope of the deck. It took me about 10 minutes of playing with the adjustment till you are satisfied the slope angle was where it needed to be. A general rule for good recovery is less grade for the table deck and as much water as possible without scouring off the fine gold particles.
When the table is set, wet down your black sand concentrates with water and a couple drops of Jet-Dry to help keep any fine gold from floating off the table. You are now ready to start feeding the RP-4.
DO NOT dump material into the feed tray. You want a nice steady feed without overloading the table. Use a scoop and feed it steadily. Watch the back where the small gold should concentrate. If you see fine gold towards the middle, adjust your table angle just a bit at a time till it is where it needs to be.
Run a few buckets of black sand tailings that already panned out just in case there might have been some gold left behind. Its a good thing, too, because I pulled almost three pennyweights of gold out of my waste materials. Thats a pennyweight per bucket!
You could run all of you concentrates over this awesome little RP-4 Gravity Shaker Table. Some ran bottles No. 1 and No. 2 over the table a second time and cleaned it up some more, getting out almost all of the sand in No. 1 and removing more than half the sand from No. 2. It was amazing to see a nice line of fine gold just dancin down the table into the bottle. And, to think you were was about to throw away all of that black sand that still had color in it! This machine is small enough for the prospector and small-scale miner who, like me, wants all of the gold for his or her hard work. The 911MPE-RP-4 Gravity Shaker Table is also big enough to clean up bucket after bucket of concentrates from a big operation! The RP4 people came up with the solution for getting all of the gold!
All RP4 shaker tables operate best when firmly secured to a dense solid mounting base. Wooden stands will set up harmonics and vibrations. Dense concrete or solid bedrock is preferred or a heavy braced steel table sitting on concrete. Mount shaker table to solid bed rock if possible when operating in the field. When that is not an option, six or seven sand bags may also be used if concrete or bedrock is not available for mounting.
Place a level on top of the steel bar that extends between the two bolts down mounting feet.Use flat washers installed under either end of the mounting feet for precise level adjustment in the long axis.
At no time should sand or slime be re-circulated back with mill water. Large, calm, surface areas are required to settle slimes. Buckets, barrels or any deep containers with turbulent water will not allow slimes to settle. Tailings should discharge into a tails pond or into a primary holding vessel before entering slime settling ponds. Surface area is more important than depth. A small 10 x 20 ft. settling pond can be installed in about 30 minutes. Shovel a 6 high retainer wall of earth and remove all gravel. Lay a soft bed of sand in the bottom. A small raised wall area (with the top approximately 2 blow water level) should be placed around the pump area. Roll out plastic liner and fill with water. Desert areas require a plastic cover to retard evaporation. Use a 24 wood across pond and lay plastic.
As with ponds, at no time should sand or slime be re-circulated back with mill water. A calm surface is needed in the final two barrels to settle slimes. (In lieu of the last two barrels, the discharge from barrel two may be directed to a settling pond as outlined above.)Turbulent water will not allow slimes to settle. Tailings are discharged into the first container.
A small compact tailings thickener introduces tailings feed at a controlled velocity in a horizontal feed design that eliminates the conventional free settling zone. The feed particles quickly contact previously formed agglomerates. This action promotes further agglomeration and compacting of the solids. Slowly rotating rakes aid in compacting the solids and moving them along to the discharge pipe, these solids are eventually discharged at the bottom of the unit. Under flow from the thickener 60-65% solids are processed through a vacuum filter and a90-95% solids is sent to the tailings area. Tailings thickeners are compact and will replace ponds. A 23 ft. diameter will process flow rates at 800 gpm or 50 tph.
Pine oils and vegetation oils regularly coat the surface of placer gold. Sometimes up to 50% of the smaller gold will float to the surface and into the tails. The pine oil flotation method for floating gold is still in use today. A good wetting agent will aid in the settling and recovery of oil coated gold.
Separation of concentrate from tails Minerals or substances that differ in specific gravity of2.5 or to an appreciable extent, can be separated on shaker tables with substantially complete recovery. A difference in the shape of particles will aid concentration in some instances and losses in others. Generally speaking, flat particles rise to the surface of the feed material while in the presence of rounded particles of the same specific gravity. Particles of the same specific gravity but varying in particle size, can be separated to a certain extent, varying in particle size, can be separated to a certain extent, removing the larger from the smaller, such as washing slime from granular products.
Mill practice has found it advantageous in having the concentrate particles smaller than the tailing product. Small heavy magnetite particles will crowd out larger particles of flat gold making a good concentrate almost impossible with standard gravity concentrating devices. The RP-4 table, using rare earth reverse polarity magnets, overcame this problem by lifting the magnetite out and above the concentrate material thus allowing the magnetite to be washed into the tails. This leaves the non-magnetics in place to separate normally.
No established mathematical relationship exists for the determination of the smallest size of concentrate particle and the largest size of tailing particle that can be treated together. Other factors, such as character of feed material, shape of particles, difference in specific gravity, slope or grade of table dock and volume of cross flow wash water will alter the final concentrate.
Size of feed material will determine the table settings. Pulverized rod mill pulps for gravity recovery tables should not exceed 65-minus to 100-minus 95% except where specific gravity, size, and shape will allow good recovery. Recovery of precious metals can be made when processing slime size particles down to 500-minus, if the accompanying gangue is not so coarse as to require excessive wash water or excessive grade to remove the gangue, (pronounced gang), to the tails. Wetting agents must be used for settling small micron sized gold particles. Once settled, 400-minus to 500 minus gold particles are readily moved and saved by the RP-4shaker table head motion. Oversized feed material will require excess grade to remove the large sized gangue,thus forcing large pieces of gold further down slope and into the middling. Too much grade and the fine gold will lift off the deck and wash into the tailings. Close screening of the concentrate into several sizes requires less grade to remove the gangue and will produce a cleaner product. A more economical method is to screen the head ore to window screen size (16-minus) or smaller and re-run the middling and cons to recover the larger gold. This concept can be used on the RP-4 shaker tables and will recover all the gold with no extra screens. A general rule for good recovery is less grade for the table deck and as much was water as possible without scouring off the fine gold. Re-processing on two tables will yield a clean concentrate without excess screening. Oversized gold that will not pass through window screen size mounted on RP-4 shaker tables, will be saved in the nugget trap. Bending a small 1/4 screen lip at the discharge end of the screen will trap and save the large gold on the screen for hand removal.
On the first run, at least one inch or more of the black concentrate line should be split out and saved into the #2 concentrate bin. This concentrate will be re-run and the clean gold saved into the #1 concentrate pocket. Argentite silver will be gray to dull black in color and many times this product would be lost in the middling if too close of a split is made.
The riffled portion of the RP-4 shaker table separates coarse non-sized feed material better than the un-riffled cleaning portion. Upon entering the non-riffled cleaning plane, small gangue material will crowd out and force the larger pieces of gold further down slope into the middling. Screen or to classify.
The largest feed particles should not exceed 1/16 in size. It is recommended that a 16-minus or smaller screen be used before concentrating on the RP-4 shaker table, eliminating the need for separate screening devices. Perfect screen sizing of feed material is un-economical, almost impossible, and is not recommended below 65-minus.
A classified feed is recommended for maximum recovery, (dredge concentrates, jig concentrates, etc.) The weight of mill opinion is overwhelmingly in favor of classified feed material for close work. Dredge concentrates are rough classified and limiting the upper size of table feed by means of a submerged deck screen or amechanical classifier is all that is necessary. A separate screen for the sand underflow is used for improved recovery when using tables.
Head feed capacity on the RP-4 tables will differ depending on the feed size, pulp mixture and other conditions. Generally speaking, more head feed material may be processed when feeding unclassified, larger screened sized material and correspondingly, less material may be processed when feeding smaller sized classified rod or ball mill pulps. Smaller classified feed material will yield a cleaner concentrate. Ultimately, the shape of the feed material particles and a quick trial test will determine the maximum upper size.
The width between the riffles of the RP-4 table is small and any particle over 1/8 may cause clogging of the bedding material. A few placer operators will pass 1/8 or larger feed material across the RP-4 table, without a screen, with the intent of making a rough concentrate for final clean up at a later date. This method will work, but excess horizontal slope/grade of the table deck must not be used as some losses of the precious metals will occur. Magnetite black sands feed material, passing a 16-minus screen (window screen size if 16-minus + or -) will separate without losses and make a good concentrate at approximately 500 to 600lbs feed per hour for the RP-4. Head feed material must flow onto the RP-4 screen, at a constant even feed rate. An excess of head feed material placed onthe table and screen at a given time will cause some gold to discharge into the tailings nugget trap. Head feed material should be fed at the end of the water bar into the pre-treatment feed sluice. Do not allow dry head feed material to form thick solids. The wash water will not wash and dilate the head feed material properly, thus allowing fine gold to wash into the tails.
Feed material should disperse quickly and wash down slope at a steady rate, covering all the riffles at the head end,washing and spilling over into the tails trough. A mechanical or wet slurry pump feeder (75% water slurry) is recommended for providing a good steady flow of feed material. This will relieve the mill operator of a tedious chore of a constantly changing concentrate line when hand feeding.
Eight gallons of water per minute is considered minimum for black sands separation/concentration on the RP-4 shaker table. 15 gallons of water per minute is consideredoptimum and will change according to feed material size, feed volume and table grade. A 1 inch hose will pass up to 15 gpm, for good recovery, wash water must completely cover the feed material 1/4 or more on the screen.
The PVC water distribution bar is pre-drilled with individual water volume outlets, supplying a precision water flow. Water volume adjustment can be accomplished by installing a 1 mechanical PVC ball valve for restricting the flow of water to the water distributing holes. Said valve may be attached between the garden hose attachment and water distributing bar.
More water at the head end and less water at the concentrate end is the general rule for precise water flow. More feed material will occupy the head end of the RP-4 shaker table deck in deep troughs and less material will occupy the concentrate end on the cleaning plane. A normal water flow will completely cover the feed material over the entire table and flow with no water turbulence.
A rubber wave cloth is installed to create a water interface and to smooth out all water turbulence. This cloth is installed with holes. Holes allow water to run underneath and over the top of the cloth and upon exiting will create a water interface smoothing out all the water turbulence. Bottom of water cloth must contact the deck.
Avoid excessive slope and shallow turbulent water.For new installations, all horizontal grade/slope adjustments should be calculated measuring from the concentrate end of the steel frame to the mounting base. For fine gold, the deck should be adjusted almost flat.
All head feed must be fed as a 75% water pulp. Clean classified sand size magnetite will feed without too much problem when fed dry. Ground rod or ball mill feed material 65-minus or smaller must be fed wet, (75% water slurry by weight or more) and evenly at a constant rate, spilling over into the tails drain troughat the head end of the table. Feed material without sufficient water will not dilute quickly andwill carry concentrate too far down slope or into the tails. A good wet pulp with a deflocculant and a wetting agent will aid the precious metals to sink and trap within the first riffles, thus moving onto the cleaning plane for film sizing. Round particles of gold will sink instantly and trap within the first riffles. The smaller flat gold particles will be carried further down slope to be trapped in the mid riffles. Potential losses of gold can occur if the table deck is overloaded by force feeding at a faster rate than the smaller flat gold can settle out. Under-feeding will result in the magnetites inability to wash out of the riffles, thus leaving a small amount of magnetiteconcentrated with the gold. A small addition of clean quartz sand added to a black sand concentrate will force the magnetite to the surface and will aid in its removal. Slimes require a separate table operation.
In flotation, surface active substances which have the active constituent in the positive ion. Used to flocculate and to collect minerals that are not flocculated by the reagents, such as oleic acid or soaps, in which the surface active ingredient is the negative ion. Reagents used are chiefly the quaternary ammonium compounds, for example, cetyl trimethyl ammonium bromide.
A substance composed of extremely small particles, ranging from 0.2 micron to 0.005 micron, which when mixed with a liquid will not gravity separate or settle, but remain permanently suspended in solution.
A crusher is a machine designed to reduce large rocks into smaller rocks, gravel, or rock dust. Crushers may be used to reduce the size, or change the form, of waste materials so they can be more easily disposed of or recycled, or to reduce the size of a solid mix of raw materials (as in rock ore), so that pieces of different composition can be differentiated. Crushing is the process of transferring a force amplified by mechanical advantage through a material made of molecules that bond together more strongly, and resist deformation more, than those in the material being crushed do. Crushing devices hold material between two parallel ortangent solid surfaces, and apply sufficient force to bring the surfaces together togenerate enough energy within the material being crushed so that its molecules separate from (fracturing), or change alignment in relation to (deformation), each other. The earliest crushers were hand-held stones, where the weight of the stone provided a boost to muscle power, used against a stone anvil. Querns and mortars are types of these crushing devices.
A basic alkali material, such as sodium carbonate or sodium silicate, used as an electrolyte to disperse and separate non-metallic or metallic particles. Added to Slip to increase fluidity. Used to aid in the beneficiation of ores, to convert into individual very fine particles, creating a state of colloidal suspension in which the individual particles of gold will separate from clay or other particles. This condition being maintained by the attraction of the particles for the dispersing medium, water, purchase at any chemical house.
Manner in which the intensity and direction of an electrical or magnetic field change as a function of time that results from the superposition of two alternating fields, (+/-) that differ in direction and in phase.
The smelting of metallic ores for the recovery of precious metals, requiring a furnace heat. Each milligram of recovered precious metal is gravimetric weighed and reported as one ounce pershort ton. Atomic Absorption (AA finish) is the preferred method for replacing the gravimetric weighing system.
A reagent added to a dispersion of solids in a liquid to bring together the fine particles to form flocs and which thereby promotes settling, especially in clays and soils. For example, lime alters the soil pH and acts as a flocculent in clay soils. Acid reagents and brine are also used as a flocculent.
The method of mineral separation in which a froth created in water with air and by a variety of reagents floats some finely crushed minerals, whereas other minerals sink. Separate concentrates are made possible by the use of suitable depressors and activators.
An igneous oxide of iron, with a specific gravity of 5.2 and having an iron content of 65-70% or more. Limonite crystals, sometimes mistaken for magnetite, occurs with the magnetite and sometimes may contain gold. Vinegar will remove gold locked in limonite coated magnetite.
In materials processing a grinder is a machine for producing fine particle size reduction through attrition and compressive forces at the grain size level. See also CRUSHER for mechanisms producing larger particles. Since the grinding process needs generally a lot of energy, an original experimental way to measure the energy used locally during milling with different machines was proposed recently.
A typical type of fine grinder is the ball mill. A slightly inclined or horizontal rotating cylinder is partially filled with balls, usually stone or metal, which grinds material to the necessary fineness by friction and impact with the tumbling balls. Ball mills normally operate with an approximate ball charge of 30%. Ball mills are characterized by their smaller (comparatively) diameter and longer length, and often have a length 1.5 to 2.5 times the diameter. The feed is at one end of the cylinder and the discharge is at the other. Ball mills are commonly used in the manufacture of Portland cement and finer grinding stages of mineral processing. Industrial ball mills can be as large as 8.5 m (28 ft) in diameter with a 22 MW motor, drawing approximately 0.0011% of the total worlds power. However, small versions of ball mills can be found in laboratories where they are used for grinding sample material for quality assurance.
A rotating drum causes friction and attrition between steel rods and ore particles. But note that the term rod mill is also used as a synonym for a slitting mill, which makes rods of iron or other metal. Rod mills are less common than ball mills for grinding minerals.
Screening is the separation of solid materials of different sizes by causing one component to remain on a surface provided with apertures through which the other component passes. Screen size is determined by the number of openings per running inch. Wire size will affect size of openings. -500=500 openings per inch is maximum for gravity operations due to having a solid disperse phase.
Long established in concentration of sands or finely crushed ores by gravity. Plane, rhombohedra deck is mounted horizontally and can be sloped about its axis by a tilting screw. Deck is molded of ABS plastic, and has longitudinal riffles dying a discharge end to a smooth cleaning area. An eccentric is used to create a gentle forward motion, compounded to full speed and a rapid return motion of table longitudinally. This instant reverse motion moves the sands along, while they are exposed to the sweeping and scouring action of a film of water flowingdown slope into a launder trough and concentrates are moved along to be discharged at the opposite end of the deck.
A material of extremely fine particle size encountered in ore treatment, containing valuable ore in particles so fine, as to be carried in suspension by water. De-slime in hydrocyclones before concentrating for maximum recovery of precious metals.
A mixture of finely divided, micron/colloidal particles in a liquid. The particles are so small that they do not settle, but are kept in suspension by the motion of molecules of the liquid. Not amenable to gravity separation. (Bureau of Mines)
Flotation process practiced on a shaking table. Pulverized ore is de-slimed, conditioned with flotation reagents and fed to table as a slurry. Air is introduced into the water system and floatable particles become glom rules, held together by minute air bubbles and positive charged edge adhesion. Generated froth can be discharged into the tailings launder trough or concentrates.
The parts, or a part of any incoherent or fluid material separated as refuse, or separately treated as inferior in quality or value. The gangue or valueless refuse material resulting from the washing, concentration or treatment of pulverized head ore. Tailings from metalliferous mines will appear as sandy soil and will contain no large rock, not to be confused with dumps.
A substance that lowers the surface tension of water and thus enables it to mix more readily with head ore. Foreign substances, such as natural occurring pine oils, vegetation oils and mill grease prevent surface wetting and cause gold to float. Addition agents, such as detergents, (dawn), wetting out is a preliminary step in deflocculating for retarding gold losses.
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Global mining solutions warrants that all mining equipment manufactured will be as specified and will be free from defects in material and workmanship for a period of one year for the RP-4. Providing that the buyer heeds the cautions listed herein and does not alter, modify or disassemble the product, gms liability under this warranty shall be limited to the repair or replacement upon return to gms if found to be defective at any time during the warranty. In no event shall the warranty extend later than the date specified in the warranty from the date of shipment of product by GMS. Repair or replacement, less freight, shall be made by gms at the factory in Prineville, Oregon, USA.
All bearings are sealed and no grease maintenance is required. Do not use paint thinners, or ketones to clean your deck. A small amount of grease should be applied to the adjustable handle which is used for the changing the slope of the deck.
Do not allow the RP-4 to stand in direct sunlight without water. Always keep covered and out of the sun when not in use. Heat may cause the deck to warp. Do not lift or pull on the abs plastic top, always lift using the steel frame. Do not attach anything to the abs plastic top. Do not attach PVC pipe to concentrate discharge tubes, constant vibration from the excess weight will cause stress failure of the plastic.
A Gold Shaking Table are basically low-capacity machines used as last step in the gold upgrading process. Theshakingtable is a thin film, shear flow process equipment, that separatesparticlegrains of its feed material based on thedifferences in their specific gravity, density, size and shape. Mineral rich particles, from light to heavy and fine to coarse will be sorted by net effective weight. Finely crushed or ground ore material goes as feed mixed with water to form a pulp (mud) andfed as slurry of an average about 2025% of solids by weight onto the highest point of the table deck. The gold tables deck hasa reciprocal movement along its main axis that is given using a vibrator or an eccentric head motion. The table surface is manufactured and fitted with several tapered strips called riffles or grooves, often made with of yellow pine (way back in time that is), low-density polythene or aluminum surfacing.Shaking tables and other thin film separating plant recover finely divided gold under conditions of subcritical laminar and supercritical laminar regimes of flow, which may occur only where there is a very thin depth of fluid.
Agold shaking tables riffles taper downwards in elevation in the direction the gold (and all heavies), precious metals concentrate discharge end of the table. This facilitates the ease with which mineral particles can move transversal to the tables axis or shaker-line, therefore helpingseparation over the complete tablelength. Riffle heights and pattern designs are selected based on the desired and required duty/function expected.
Preparing several size fractions for tabling is usually achieved in a hydrosizer. Ifgold is present in both coarse and finely divided sizings at least three, or perhapsfour separate size fractions must be treated, each under a different set of operatingconditions. Tables operate most efficiently with a closely sized feed. The slurry fansout across a smooth section of the surface until it reaches the riffles. The lighterand very fine particles are washed over the riffles and moved along the riffles by thereciprocating motion imparted to the deck while the heavier particles are held back. The concentrates of heavy mineral and gold are discharged over the end of thedeck. Tailings are washed over the lower edge and a middlings fraction is taken offbetween the lower edge of the concentrate strip and the higher edge of the tailingstrip.
Wash water usage is dependent upon the particle diameter and varies from aslow as 0.7 m/t/h of solids for slime decks, up to 56 m/t/h for coarse solidsseparation. Coarse fractions are usually treated at feed rates of up to 1 t/h using approximately 15 to 20 mm stroke lengths at around 280 rpm (Wilfley table data). Thestroke lengths of finer fractions are reduced to 915 mm with increased speeds ofup to 325 rpm but, because of the corresponding lower film, thickness capacitiesmay fall to around 0.25 t/h. The inclination of the deck is adjusted during operationusing a hand-operated tilting device. It is important following each adjustment toallow the table operation to settle down before making a fresh adjustment. The correct inclination is reached when the ribbon of concentrates is clearly defined andremains steady.
The extreme sensitivity of water depths and corresponding current depths to obtain F = 1, and the use of stationary tables as primary concentrating units, was probably the main reason for the consistently low (R.E. 6065%) gold recoveries of early dredgers. For such table types, the fluid forces are applied to the stream-beds as a whole and ripples form, which keep the sand in orbital motion and provide for the denser particles to sink to the bed. Deposition is most favoured by anti-dune conditions produced by free-surface flow at or near the supercritical state. Such bed forms are in phase with the water surface and are produced in the rapid flow conditions of Froude Number F = 1. In this state of flow, the bed forms of the upper flow regime are stable. Below F = 1 the flow is tranquil and shear forces are reduced. In reviewing recovery distributions of certaindredgers it wasnoted that some coarse gold reported with the tailing after passing through two stages of tabling and that fine gold did not concentrate noticeably down the line.
I consider the gold shaker table to be a shaking sluice box OR self cleaning sluice as they both essentially are classifiers used as heavy gold concentrating devices. Apart from nuggets; generally the valuable minerals like heavy precious metals like platinumandpalladium thatcan berecovered by tables and sluices, are found in one size range (generally the finest) and the waste minerals in another. On agold sluice, large particles (gravel) travel by sliding and rolling over the riffles, with finer particles travelling by saltation. Sand travels by a combination of modes described earlier with some saltation over the riffles.Very fine particles are maintained in suspension by turbulent and inter-particle collision.
Riffles function properly only if in the space between them and the slurry is sufficiently live (turbulent) to reject the lighter particles, but not so lively that the gold cannot settle. On a gold shaker table, those particles are allowed to settle as they will get transported to the other end by the vibrating/shaking back-and-forth motion. Lower grade, light pieces, will be able to escape the table a the riffles becomes shorter along the tables length.Once the particle has started to move, the coefficient of friction changes to a dynamic coefficient of friction. In fact, because the fluid push on the particles is larger at the top of the particle than at the bottom, the particle rolls, largely according to the shape of the particle and according to the speed. At low speeds, the effective friction is the relatively large coefficient of dynamic sliding friction, and at high speeds it is the lower coefficient of rolling friction. The change probably takes place partly continuously and partly discontinuously. As a first approximation, the dynamic coefficient of friction may, however, be regarded as constant.
In a sluice box, the settling of heavy minerals between the riffles requires frequent stirring to prevent the riffle spaces from blinding. This also disturbs the gold, which then moves progressively down-sluice. Frequent clean-ups are needed to avoid excessive loss. Boxes may be used in parallel to avoid loss of production time. One box is kept in operation while cleaning up in the other.
Effect of Deck Roughness: The foregoing analysis is based on the postulate that the deck is perfectly smooth. If the deck is rough, i.e., if it has at its surface some recesses capable of partly shielding fine particles from the rub of the fluid, the slope required to move the particles by either rolling or sliding will be increased. At the same time such an effect, while present also for large particles, may be so much smaller for them as to be imperceptible. The relationship of critical angle to size obtained above will therefore not hold for rough surfaces. The problem is analytically complex and it is nevertheless a problem that might well be explored further if a full insight is desired into the mechanism of flowing-film concentration.
Adjustments are provided in all tables for the amount of wash water, the cross tilt, the speed, and the length of the stroke. The speed of the table ranges usually from 180 to 270 strokes per minute, and the strokes are from 1/2 to 1 1/2 long.
Variations in character of feed require variations in operation. The operators duty is to take care of them by adjusting the tilt, the wash water, and the position of the splitters that control discharge of table into concentrate, middling, and tailing launders. One man may look after 10 to 100 tables, depending upon the regularity of the feed and the difficulty of the task assigned to the table.
A coarse feed can be treated in larger amounts than a fine feed. It would seem that the treatable tonnage increases at least as the square of the average size (theory indicates that it increases as the cube of the particle size).
A roughing operation is preferably conducted on a fully riffled deck. These decks have a greater capacity because the particles are treated throughout the deck in the form of a teetering suspension many particles deep instead of as a restive layer one particle deep. Such decks do not provide flowing-film concentration but some sort of jigging. On the other hand, a cleaning operation is preferably performed on a partly riffled deck.
It is clear that minerals of different specific gravity must be present the greater the spread in specific gravity between minerals, the greater the capacity since that sort of condition permits crowding without considerable penalty.
The effect of locked particles on capacity of tables should also be recognized. These particles behave in a fashion intermediate between that of pure particles of their constituent minerals. It is as if a three-product separation were sought in which one of the products would guide-in specific gravity between the two other.
Table capacity may be as high as 200 tons per 24 hr. on a fully riffled deck 4 by 12 ft. treating minus 3-mm. sulphide ore having a specific gravity of about 3.0 (roughing duty), or 500 tons per 24 hr. But table capacity may be as low as 5 tons per 24 hr., or even less, for fine ore (minus 0.3 mm.) if there is only a small specific-gravity differential between minerals.
Operating a shaking table is cheap as power requirement per table are typically low. Most of the energy is expended to move the deck, which must therefore be as light as is consistent with rigidity. Laboratory gold shaking table testingreport.
There are a few steps that need to be taken in order to get yourgold shaker table to work efficiently. The first step that aspiring gold miners must take would be to make sure that all four corners of the table are level from forward to back. It is very important to anchor the bolts so that the shaking of the gold goes to the table and not through the frame. After you begin running your table, you may need to adjust your table from side to side to maintain an even flow of materials on both sides of the table.
A gold shaker table contains a water access point where you can fill it with clean water, which can be seen right under the control area. Alternatively you can directly fill the tank of the shaker table with clean water. The water access point allows you to connect a clean water system through a garden hose. The valve that is right behind the tank is then turned off and the pump system is not running during the process of running fresh water. When clean washing water is distributed at the top of the table at right angles, particles are moved diagonally across the deck and separate from each other according to their size and density. During the fast shaking process, you will gradually begin to see the separation of materials. For example, when you have dirt and rocks that contain materials like lead, sulfides and gold, because of the varying weights of these different materials, you will see these materials venture off in different directions on the shaker table. The lead and the sulfides will be carried over to the right side of the table while the pure gold will be carried over to the far left side of the table.
There is one term to remember when professional gold miners describe the actions of a gold shaker table. When professional gold miners say that small particles of gold are being carried through the grooves, they are referring to the ripples that you can plainly see on the shaker table. When they say that there is an overflow of materials like Black Pyrrhotite, White Quartz, silver and gold on the grooves, then this is a good thing.
When materials are washed by the clean water they are supposed to drop into 3 hoppers/launders underneath the table. There is a centre launderthat will gather the purest portions of gold while the two outside launders will gather some gold, though not as much.
It is crucial to remember to plug the cable of your shaker table into a GFCI (Ground Fault Circuit Interrupter) outlet. Most shaker tables will not work if they are plugged into any other kind of outlet.
In aPercussion Gold Shaker Table,the work of keeping the pulp in a state of agitation, done by the rakes or brushes in the German and Cornish buddies described above, is affected by sudden blows or bumps imparted sideways or endways to the table. The table is made of wood or sheet metal, the surface being either smooth or riffled.
End-bump tables are hung by chains or in some similar manner, so as to be capable of limited movement, and receive a number of blows delivered on the upper end. These blows are given by cams acting through rods, or else the table is pushed forward against the action of strong springs by cams on a revolving shaft, and then being suddenly released is thrown back violently by the springs against a fixed horizontal beam. The movement of the pulp depends on the inertia of the particles, which are thrown backward up the inclined table by the blow given to the table, the amount of movement varying with their mass, and depending, therefore, both on their size and density. The vibrations produced by the percussion also perform the work of the rakes in destroying the cohesion between the particles, and a stream of water washes them down. The result is that the larger and heavier particles may be made to travel up the table in the direction in which theyare thrown by the blow, by regulating the quantity of water, while the smaller and lighter particles are carried down. These machines yield only two classes of material, headings and tailings. One such machine, the Gilpin County Gilt Edge Concentrator was devised in Colorado, and has displaced the blanket sluices atalmost all the mills at Blackhawk. It consists (Fig. 46) essentially of a cast-iron or copper table, 7 feet long and 3 feet wide, divided into two equal sections by a 4-inch square bumping-beam. The table has raised edges, and its inclination is about 4 inches in 5 feet at its lower end, the remaining 1 feet at the head having a somewhat steeper grade. The table is hung by iron rods to an iron frame, the length of the rods being altered by screw threads, so as to regulate the inclination to the required amount. A shaft with double cams, A, making 65 revolutions per minute, enables 130 blows per minute to be given to the table in the following manner; onbeing released by the cam, the table is forced forward by the strong spring, B, so that its head strikes against the solid beam,C, which is firmly united to the rest of the frame.
The pulp coming from the copper plates is fed on to the table near its upper end by a distributing box, D, and is spread out and kept in agitation by the rapid blows. Thesulphides settle to the bottom of the pulp, and are thrown forward by the shock, and eventually discharged over the head of the table at the left hand of the figure, while the gangue is carried down by the water and discharged at the other end. One machine is enough to concentrate the pulp from five stamps. If the table consists of amalgamated copper plates, it is of some use for catching free gold also, treating about 8 cwts. of ore per hour. This machine is not so effective in saving slimed pyrites as the Wilfley table or the vanners.
Gold shaker tables are environmentally friendly (chemical free) for recovering pure gold as they can play an important part in reducing the use of mercury by gold miners. With gold shaker tables miners dont need to resort to mercury amalgamation or cyanide to recover gold. The filter will constantly need to be removed and cleaned as it will get dirty even after using the table a few times.
Miners can design and construct a basic shaking table out of cheap materials that are affordable in local stores, including a drive mechanism that contains bicycle gears, chains and rubber bands that are made from car tire inner tubes. The drive mechanism for a gold shaker table can be a hand crank or it can contain parts of a motorcycle frame and engine. If one prefers to use a motor for his or her table, either an electric motor or a motor that runs on diesel fuel would be the ideal options.
It is important to keep in mind that there is no one specific way to create your own gold shaker table system. Many professional gold mining organizations will create tables of different shapes and sizes to cater to the needs of their customers. Some shaker table systems will feature machines that can crush hard rocks, which are referred to as jaw crushers. The speeds of shaker table systems will vary as they can shake from hundreds to thousands of pounds of materials per hour.
Concentration of grains from 10 to 30 mm. is effected by hydraulic jigs with two compartments, and in the case of the smaller grains down to 2 mm. by jigs with five compartments.The construction of the jigs is the same in both cases. Fig. 3 gives the details of a jig with two compartments; it is formed of three cast-iron plates which support the bearings of the eccentric shaft, joined by a wooden casing or wooden walls so as to form two communicating chambers for pistons and screens. This construction has no special advantage beyond facilitating the transportation and mounting of the jigs. But in some details the Monteponi jig differs greatly from those in general use.
The eccentrics have a variable stroke. A first eccentric fixed to the shaft is surrounded by a moving eccentric; the first has a flange which partly covers the second at the side, and both have holes through which the bolt is passed to hold them together. The holes being at a different distance in the two eccentrics, the combination forms a kind of vernier caliper, which allows variation in the eccentricity.
With five holes in each partial eccentric, 25 combinations of different strokes can be obtained between the two extremes. The superiority of the system consists in the facility with which the eccentricity can be regulated, and in the assurance that this eccentricity cannot vary during the work of the jig. This eccentric is shown in Fig. 4.
The discharge of the concentrated material is made by pipe for the coarser grains; by pipe and suction through the sieve into the hutch beneath for the sands. The pipe varies in diameter from 13 to 51 mm., according to the classes treated. It is placed, slightly inclined towards the outside, and transversely to the screen, at about half the height of the layer of grains. On the bottom of the pipe, in the middle of the screen, a hole is bored, through which the grains with the water rise through the pipe and flow away.
The jig separates the grains in layers of different density. The pipe gives an outlet to the layer of valuable mineral as fast as it rises on the screen. The discharge is made at intervals, especially for the small grains, and is stopped when waste is found mixed with the ores.
In jigs treating grains larger than 10 mm., the ore falls on sorting-tables of perforated iron sheets. The jigs have two discharge-pipes, one for each compartment, and the division between the compartments is raised only as high as the pipe, to allow free movement to the upper layer. The first pipe discharges principally a mixture of galena, barite, and cerussite; the second discharges smithsonite and calamine. Sorting on the outside tables gives finished products.
The jigs with five compartments, for sands between 2 and 10 mm., discharge at the same time by pipe-discharge and hutch. A bed of iron disksthe waste from punching-machines spread on the screen gives the resistance necessary for the separation of the sands and secures the continuous production, above the bed, of a layer of ore, which is forced out through the pipe-discharge as it is formed. To close the spigot, a stopper of some sort is employed, or else a bend, which can be turned upwards when it is desirable to stop the outflow. The screens have perforations larger in diameter than the maximum diameter of the sands, and the products from the pipe and from the hutch of the same compartment have nearly the same composition.Table II. shows the principal features of the jigs in use at Monteponi.
All these jigs are directly fed by the vibrating-screens, and perform continuous work. The mixed products from the jigs for sandfor instance, the mixtures of galena, barite, cerussite, and smithsoniteare separated by closed jigs, with one compartment of 0.45 by 1.20 m. free surface of screen, giving beds of different ores, which can be removed by hand at intervals.
For sands below 2 mm. to 0.05 mm. the Shaking table has been in use since 1898. This apparatus is well known also in other countries, since the Fried. Krupp Grusonwerk bought the patent and introduced it into almost all mining regions.
The Shaking-table is built in two types: one for fine sands below 2 to 0.5 mm., the other for sands of 0.5 down to 0.05 mm. They are identical in principle. The former is shown in Fig. 5. A rectangular table is placed horizontally in the direction of the movement, and slightly inclined in the other direction. It rests on six inclined springs, and receives an Shaking motion from an eccentric, exactly like the vibrating- screens; the table is covered with linoleum. Its inclination may be regulated during the progress of the work by wedges placed between the table and the frame, which rests on the springs. The mixture of water and sand from the hydraulic
classifier is distributed by a short longitudinal hopper to the upper angle at the side of the eccentric, while the water flows away transversely. The grains are discharged on the table, running in parabolic lines, according as their specific gravity is greater and their diameter smaller. The spray-pipe placed at the upper side of the table pours out a slender stream of water which holds the grains suspended. Lengthwise grooves depressed in the linoleum prevent a too rapid fall of the heavy grains (without stopping the fall of the waste), and force them under the short spray-pipes placed at the end opposite to the hopper, where they are divided into groups of different character and specific gravity, and pushed towards the outlet.
The second type, or small Shaking table for sands finer than 0.5 mm., is trapezoidal in form, and has no spray-pipe at the outlet; and the hopper at the entrance is replaced by a screen placed a few centimeters above the table, with which it oscillates. The purpose of this screen is to remove the excessively large grains, and to deliver the material evenly. This delivery is made first upon a raised section (A., Fig. 6), less inclined than the rest of the table, B, so as to hold the grains, while the accompanying water flows away transversely. The two sections, A and B, carry semicircular grooves, which diminish in depth towards the side of the outlet. The grooved area is limited by a parabolic line, as shown in Fig. 6.
In all old mills, sands of 1 to 2 mm., and even below 1 mm., are treated by hydraulic jigs with suction. The defects of this system are numerous. In the first place, sizing on screens, and still more by trommels, of grains smaller than 2 mm., is difficult and far from exact; and the work of the machines for classification is costly and delicate. Suction-jigs for fine sands never give well-finished products; for below 2 mm. the pipe-outlet which serves to regulate the thickness of the bed, while maintaining on the screen of the jig a constant layer of ores of the same composition as that which sifts through the screen, cannot be used. The metallic value, or average specific gravity, of the ore which sifts gradually diminishes from one end of the jig to the other, without any sharp separation between the ores of different quality. The shaking-table has the additional advantage of using less power in order to obtain better products, as can be seen by comparing the results of the two systems:
When we consider that half of the products of the suction- jig are submitted to an extra concentration or separation, we see that the advantages of the oscillating-table are increased to about 50 per cent., and, apart from the best results in work, there is also considerable economy in installation.
When argillaceous ores are treated, there are found in the last products from the hydraulic classifiers very fine ores, which run over the tables without sinking into the grooves. These fines have a diameter below 0.02 mm., and would go to enrich the slimes in the settling-ponds if there were no way to separate them. The method employed for this purpose serves, also, to recover the useful ores which might be drawn away by the water accompanying the products of the tables and jigs. It consists of a rubber belt, slightly inclined transversely, 0.60 m. wide, stretched over two drums, of which one serves to give the motion and the other the necessary tension. Every 60 cm. it is supported by rollers with regulated inclination, so as to have the belt almost horizontal at the side of the entrance of the slimes, while the inclination is progressively increased at the side of the outflow of the products. Fig. 7 shows such a belt.
The pulp, reaching the belt through a rubber pipe, with almost no velocity, flows out on the belt, on which it deposits the solid particles, leaving the clear water to flow away. The motion of the belt carries the deposits to the water-sprays, which force them to the edge of the belt, making the lighter portion flow out with the water. The results are different products, some finished and some middlings, which can be treated on a second belt.
The force necessary to operate the slime-belt is merely that required to turn the belt on the pulleys without a load. A belt 4 m. in length treats 40 liters of slime, and requires 60 liters of clear water per minute.
According to the degree of concentration of the slime, more or less material can be treated on the belt, up to a maximum of 240 kg. of dry material per hour. The average is 100 kg., for, generally, concentration of the slime is avoided, so as to prevent losses by being carried away.
As observed in connection with the hydraulic jigs for coarse grains, the mixtures of the first class are separated by stratification on the closed hydraulic jigs with one compartment, removing the products by hand, and layer by layer, as soon as stratified.
Separation of the mixtures of the second class begins with crushing, more or less extreme, according to the nature of the material. The machines for crushing used in Sardinia are the stone-breaker, the rolls and the ball-mill. Of the first two types in Sardinia there is nothing special to be said.
Ferraris Mill.The Ferraris wet ball-mill possesses the advantages of great simplicity of mounting and small requirements of space and power for the same capacity. The steel plates which form the lining do not need to be adjusted, being held in place by the lateral steel walls and the sand formed by the crushing of the ores. There being no central shaft, large lumps of ore can be introduced into the mill, and workmen can easily enter for repairing and cleaning.
The mill is made in two forms: one for coarse grinding (from 5 to 15 mm.), the other for fine grinding (from 0.5 to 5 mm.). The following description of the first form may serve for both, except as to the differences mentioned below.
The mill consists of a drum supported on four carrier-wheels and driven by a spur-gear securely fixed to the drum, which engages with a spur-pinion keyed to the counter-shaft. The drum is divided by an annular perforated partition into two compartments. The larger or crushing-compartment is 61 3/8 in. in diameter by 30 in. long. It is lined with manganese-steel plates with projecting ribs, and contains about 1,000 lb. of forged steel balls 4 in. and 6 in. in diameter. The smaller or screening-compartment, about 10 in. in length, is divided into a series of pockets by means of a cone projecting into the crushing-compartment, and a series of radial partitions extending therefrom. The periphery of this compartment is open, and is surrounded by a screen of the desired mesh. The material passing through the screen falls into a housing surrounding the lower half of the screening-compartment.
The ore to be crushed is fed into the crushing-compartment with the water, and, when reduced to pieces smaller than the holes in the annular partition, passes through into the screening- compartment, where the material which is fine enough passes out through the screen, and the oversize is elevated by the radial partitions until it slides back on the surface of the cone into the crushing-compartment, where it undergoes further crushing.
In this type, the peripheral plates are detached from the inner walls of the drum, leaving between them and the projecting bars a space of 12 mm., through which the water carries into the sizing-compartment the grains below 12 mm. In the second or fine-grinding form (Fig. 8), the peripheral steel plates are close
to the inner walls of the drum, and the water with grains below 10 mm. runs out through holes in the walls which divide the ball-chamber from the sizing-chamber. In both forms the screen is placed at the periphery of the sizing-chamber, and the material rejected by the screen is raised by the radial partitions to the point where it can slip over the exterior surface of the cone and return to the crushing-chamber.
A Ferraris ball-mill requires 7 h.p., with 20 rev. per min., and 80 liters of water per min. The quantity crushed per hr. depends on the quality of the ore and the size. In general, the product is greater from brittle ores like quartz than from tough minerals like diabase. A quartzite mineral in large pieces is crushed to 3 mm. at the rate of 4 tons in 3 hr., or 1.33 tons per hr. If the ore has been broken beforehand to 50 mm., 1.5 tons per hr. can be crushed to an average size of 1.5 millimeters.
The broken ore is sent to the separating-machines after having been sized, if a screen of more than 2 mm. in size is used. In this case the sizing is accomplished by the vibrating-screen. If the crushing is pressed below 2 mm., hydraulic classifiers are applied to the pipe which carries the water and sand, as described above.
At the Rosas mine, there are five ball-mills forming five sections. The ball-mills receive the material which has been broken by the stone-breaker to 2 in. and crush it to 2 mm., at the rate of 1.5 tons per hr. per mill. But diabase impregnated with blende and galena is found to be very difficult to crush.
Each section is composed of one ball-mill, two jigs and three shaking-tables. There is one special section, composed of a distributing-trunk, a classifying-pipe, and eight shaking-tables, to treat the middlings from the five crushing-sections.
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The Amish Shaker Leg Dining Table allows functionality and style to blend perfectly to create a beautiful, simplistic, strongly-built dining room table. Contact DutchCrafters to speak with a knowledgeable furniture specialist today to begin creating the perfect dining table for your home.
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