Show description of plant BY J B FLEMING below is a report together with a brief description of the hoisting plant arill and surface equipment at present under construction st at the nevada hills mine fairview nevada careful experiments made on oil a large scale before the plant was designed proved conclusively that fine crushing in stamp batteries and table concentration followed by sliming in tube mills and final in connection with continuous pulp thickening agitation decantation dilution and filtration delivering the final pregnant solution to continuous zinc dust precipitating presses would yield the best results in metallic extraction as well as economical operation with the plan of treatment determined the most suitable mill site was found to be a west sloping hillside having an inclination of 1712 17 va degrees and immediately adjoining the lower side of the new three compartment shaft just being started near inear the top of the hill the center line of the mill extending through the center of the me shaft ground was broken on the day of last september and work has continued without interruption except for the inclement weather since that da dae e tile the plant and equipment is as follows the hoisting plant the hoister bolster which is located feet east and on a level with the collar of the shaft is a joshua hendy iron works double drum hoist operated by a H P type 1 I form M general electric motor revolutions per minute and equipped most approved type of control the drums are 51 inches diameter inches and each has a capacity of 2000 feet of 78 inch wire rope the maximum duty of the hoist will be to raise a total unbalanced load of pounds in either compartment at an average speed of feet per minute approximately as follows pounds 1000 feet 78 mch inch rope 1200 1 40 cubic feet capacity self dumping vertical ore skip with hood and safety clutch dogs 2000 1 special forged norway iron cage 40 cubic feet ore total hoisting ropes are the tico special being the highest grade of hoisting rope made by the trenton iron company and each has an ultimate strength of thirty five tons and a guaranteed safe working load of seven tons similar equipment is provided for both compartments of the shaft and under normal conditions the ore skips will be operated in balance reducing the power consumption about 40 per cent or from H P to 9 90 0 H P the hoist is housed in a building 40 feet feet which will also contain an in gerroll rand two stage air compressor having a piston displacement of 1350 feet at loo pounds gauge pressure capable of operating about 15 inch drills or their equivalent in other sizes tile the compressor will be belt driven by a H P general electric motor the machine shop and blacksmith shop immediately to the north of the hoist house is 30 feet x 50 feet equipped with lathe drill press shaper emery wheel crane forges etc operated by a 10 H P general electric motor the carpenter shop located just south of the hoist house is also 30 feet x 50 feet and will be equipped with usual wood working machinery electrically driven there is also located in this building a 25 H P electric hoist for operating an inclined tramway extending to the bottom of the mill used for hoisting concentrates lowering supplies etc both buildings are connected to the collar of the shaft by means of an 18 inch gauge track which passes through the center of each shop for convenience in handling timbers machine drills tools etc the new three compartment shaft Is surmounted with a substantial concrete collar 25 feet high which also forms the foundation for the front posts of the on one side and of the bin posts on the other side the steel head frame is 77 feet high weighs 28 tons and is equipped with 2 84 inch bicycle type sheave wheels over the two working compartments of the shaft and 1 48 inch sheave wheel over the service compartment immediately in front or the head frame is a ton bin divided into two compartments one for ore and the other for waste so arranged that one or both of the two ton skips can discharge into either compartment as desired the waste bin is provided with a counterbalanced bottom gate discharging into a car on the same elevation as the collar of the shaft shaf t the ore bin is discharged through a side gate directly into the crusher the bins and crushers are covered by a building 32 f feet x 40 feet the transformer house the transformer house located just north of the mill is 20 feet x 30 feet and is equipped to transform current to the amount of 1000 H P if needed and from volts to volts delivered at the switchboard from where it is distributed to the various light and power circuits throughout the plant current is furnished bythe by the pacific power company with whom a very satisfactory ten year contract exists delivery of current began about june the mill building the mill building adjoining the waste and ore bin on the lower side is f feet long by 56 feet wide on the crushing and concentrating floors 84 feet wide on the tube mill floor and feet wide in the cyanide department there is a total fall of feet from the crusher floor to the sump floor divided into eight different levels as ag follows first floor crusher and elevator second floor mill bin bill and stamp batteries third floor classifiers and concentrators fourth floor tube mills fifth floor collecting and thickening tanks sixth floor dilution and decanting tanks seventh floor treatment tank and filters eighth floor heating plant sumps bumps etc the foundations and retaining walls are of reinforced concrete and the building as are all the others mentioned above is built of steel throughout and covered with asbestos lined corrugated iron making them easily warmed in the winter and cool in the summer and lire proof they are further safeguarded by a number of hydrants distributed about the plant which are connected by a pipe line to a gallon fire tank located on a hill southeast of the shaft the entire plant is laid out with a view to the highest economy in labor and the greatest convenience of operation whilst the treatment chart embodies the latest proven methods for the treatment of gold bearing silver ores flow sheet and equipment the treatment scheme decided upon and the machinery equipment are as follows the ore delivered to the mine ore bin by two two ton self duming skips in balance is drawn from the bin over a grizzly into a inch hercules crusher which can easily crush enough ore in eight hours to supply the mill for twenty four hours a 12 inch continuous bucket elevator delivers the ore to the top of the mill from where it descends by gravity through an automatic sampling plant and an automatic weighing machine into a ton steel frame ore bin above the stamp batteries the sampling plant is equipped with a hercules crusher a set of rolls 3 vezin samplers a sample grinder and a 4 inch belt and bucket elevator to deliver the rejected portion of the sample to the top of the mill where it joins the main stream of ore just before it enters the weighing machine which automatically weighs and records all ore passing through it each twenty four hours from the ore bin the ore is drawn into four hutchinson feeders which automatically serve the four five stamp batteries of 1250 lb stamps which are arranged in two sections of ten stamps each separately driven by two 35 h p motors which are belted to cam pulleys located in the center of each ten stamp battery the four mortar boxes weigh lbs ibs each and are of the low heavy duty type specially designed throughout and made with very narrow boxes for rapid discharge they are securely anchored to a massive reinforced concrete foundation by seven lm l m in bolts each which are easily removable in case of breakage without interrupting the operation of the battery the entire hattery is specially designed for heavy duty and provided with chrome steel fittings all bolts are of best norway iron crushing through twenty mesh screens is followed by classification and concentration over six no 2 delster deister sand tables and four no 3 deister slime tables tailings discharging to two 45 in akins classifiers overflow to thickening tanks and sands to two 18 ft x 5 ft tube mills discharging into two 12 in belt and bucket elevators delivering to a 36 in hydraulic classifier from which the overflow goes to the thickening tanks and slimes to four no 3 delster deister slime concentrators for final concentration the tailings again return to the akins classi class fiers the overflow to thickening tanks and the coarse sands if any returned to the tube mills thus making a closed circuit from which escape is impossible until all the ore is reduced to the proper fineness each tube mill is separately driven by a 3 bearing 75 h p general electric motor the scheme of concentration may be varied to suit the ore without interruption of operation inasmuch as concentration when preceding dg of silver ores is being abandoned in a great many cases it might be well to state that there is a large tonnage of oxidized ores conta containing inin appreciable quantities of manganese dioxide chemically combined with the silver making a combination which does not yield its values to raw cyanide treatment and concentration must be adopted to recover these values when the oxidized ores are exhausted concentration can undoubtedly be abandoned from the tube mills the finished product flows to two 34 ft dia x 12 ft stave continuous thickening tanks supplied with overflow launders and heavy dorr thickeners the thickened pulp flows to a mixing box where the proper amount of lime water is added passing on to nine 12 ft dia x 32 ft stave agitation or treatment tanks the clear overflow from the thickening tanks being returned by a 6 in x 8 in goulds triplex pump to a gallon tank located near the top of the mill standardized solution is added in the first treatment tank the entire number arranged in series for continuous agitation the ore is under treatment for forty two hours from the time it enters the first tank until it is discharged from the last one in the series air for agitation and aeration is supplied by a 13 in x 10 in duplex low pressure ingersoll rand compressor driven by a 50 h p motor from the last treatment tank the ore passes through three dilution tanks 34 ft dia x 12 ft stave supplied with overflow launders and dorr thickeners arranged in steps so that the overflow from one tank is discharged into the next one below barren solution from the zinc presses is added in the upper tank and thoroughly mixed through it by the action of the dorr thickener diluting the solution in the proportion of 3 to 1 the clear overflow is discharged into the next tank which undergoes the same treatment this treatment of the ore is automatic and continuous through the three tanks at the same time the thickened pulp is being automatically drawn off at the hotto botto urn m and transferred in the opposite direction through the three tanks by diaphragm pumps the ore from the last tank deprived of about 95 per cent of its value by this dilution is discharged into a stock tank 30 ft dia x 12 ft stave equipped with a trent agitator the rich solution overflowing from the last tank in the series is passed through two 36 in 40 frame perrin clarifying presses into three precipitation tanks 15 ft dia x 8 ft stave and the necessary amount of zinc dust automatically added by a merrill zinc dust feeder two 4 in x 6 in goulds triplex pumps deliver the rich solution to two merrill precipitation presses of tons capacity each located in the refinery building the barren solution from the precipitation presses flows to two solution tanks 30 ft dia x 10 ft stave from where it is drawn off and standardized as needed in a tank 34 ft dia x 12 ft stave conveniently located in the mill building from the stock tank the pulp flows by gravity to two oliver continuous filters 11 ft 6 in dia 12 ft face which remove the remaining values discharging the filtered and washed residues continuous to a 14 in belt conveyor tailing stacker ft long placed at an inclination of 2031 20 vacuum for the filters is maintained by two 14 in x 14 in gould belt driven vacuum pumps the machinery for the cyanide plant is driven by a h p general electric motor the mill is heated and the solutions maintained at the proper temperature by two 80 h p oil burning boilers which also furnish steam to operate an auxiliary electric plant of h p to be used to operate mine pumps in case of interruption or temporary suspension of service by the power company the refinery building the refinery building 28 ft x 70 ft is located at the top of the hill and on the same elevation as the shaft collar it is of fireproof fire proof construction throughout and contains two 52 in x 16 frame merril presses four fabre du fauer melting furnaces one fireproof vault one platform scale four steam drying cars together with the usual equipment required for preparing five tons of silver bullion for market each month the concentrates produced will be reground in a 5 ft continuous grinding pan amalgamated and discharged alternately into two filter bottom tanks 6 ft wide by 3 it deep by 20 ft long thence to a steam drier then sacked for shipment water for milling operations will be furnished from the mine by two 41 in x 8 in goulds triplex pumps each having a capacity of gallons per minute aga against dinst a 1000 ft head and direct connected to 40 h p general electric motors these are now on the ground and one is installed on oil the eighth level of the mine to be used for keeping the mine as soon as current is supplied by the power company two gallon tanks are located near the top of the hill one to be used for mine water and the other for water recovered from mill operations the entire plant is carefully designed and substantially built with a constant view to economy in operation and containing a number of valuable features which are not all combined in any one plant at present in operation the following firms furnished the building material machinery etc joshua hendy iron works electric hoist and mill machinery pacific tank pipe company cyanide tanks merrill metallurgical company zinc dust precipitating equipment oliver continuous filter company continuous filters general electric company electrical machinery ingersoll rand company air compressors goulds manufacturing company pumps booth kelly keily lumber company lumber colorado portland cement company cement pacific hardware steel company hardware james J burke co structural steel for all buildings and head frame J B FLEMING note mr J B fleming had entire charge of the construction of the nevada hills mill and other mine equipment editor |