spiral classifier calculator

spiral classifiers

spiral classifiers

The Spiral Classifier is available with spiral diameters up to 120. These classifiers are built in three models with 100%, 125% and 150% spiral submergence with straight side tanks or modified flared or full flared tanks. All sizes and models are available with single-, double- or triple-pitch spirals.

The tank is heavy plate with strong structural base. The extra heavy shaft has an improved submerged bearing. The greatest improvements, however, are found in the drive-unit which has been strengthened and improved over all other classifiers. A specially designed classifier reducer eliminates the over hang or cantilevered load normally found where the reducer shaft carries the pinion. The Classifier Reducer has an outboard bearing integral with the reducer base which provides positive alignment of the bevel gears.

The gears themselves are greatly improved as they are cast from metal patterns which have cut teeth. The accuracy of the patterns and the quality gear castings result in a cast-tooth gear of cut-tooth quality. The gears mesh smoothly, have greatly increased capacity and are noticeably more quiet than other spiral classifiers.

Spiral Classifiers are available in sizes up to 120 diameter, three tank styles, single, double and triple pitch spirals, three degrees of spiral submergence flexibility to provide a unit built for your job. Write for detailed recommendation on the correct size and type of Spiral Classifier to do your job economically and profitably.

This is the best method of determining the required pool area. However, if settling tests have not been made and it is inconvenient to make tests, the following procedure, which has been proved to be entirely satisfactory, may be used.

Example: Assume it is desired to overflow 100 tons of dry solids per 24 hours at 65 mesh in a pulp of 20 % solids. Table I shows that 6.43 tons will overflow per sq. ft. of effective pool area. Therefore, to overflow 100 tons in 24 hours, a classifier with 15.5 sq. ft. (100 divided by 6.43) effective pool area would be required.

For a 65 mesh separation it is preferable to set the classifier at 3 slope. Table II shows that at 3 slope the 30 Cross-Flow Classifier has an effective pool area from 12.9 to 16.4 sq. ft. depending on the height at which the weir is set. Therefore the 30 classifier would be the proper size for the overflow capacity desired.

Table III shows that at 65 mesh a peripheral speed of 44 ft. per min. is recommended, which on the 30 classifier corresponds to 5.6 R.P.M. At this speed the 30 classifier will convey 275 tons of solids per 24 hours, which then is ample for this job. Therefore, this size Cross-Flow Classifier will satisfy all the requirements of this problem.

But, suppose the circulating load required was 300% instead of 250% specified above. The amount of sand to be raked would be 300 tons per 24 hours. In this case it would be necessary to speed up the conveyor of the 30 classifier above the normal speed of 5.6 R.P.M. in order to handle the 300 tons of sand. In speeding up the conveyor more agitation is produced in the tank and settling is interfered with, resulting in a slightly coarser overflow. In this case it might be necessary to provide a 36 classifier.

If the classifier is to be used in open circuit it may be the shortest standard length made in that particular size. For installation in a closed grinding circuit the classifier length must be pre-determined to assure that it will close circuit with the ball mill. This is entirely a mechanical problem and the correct length is determined by making a ball mill-classifier layout to scale.

The pool area varies with the slope and since capacity at a required mesh depends on pool area, the slope cannot arbitrarily be changed to accomplish a closed circuit. With the classifier size and slope established it is necessary to make the classifier of sufficient length to close the circuit.

In general the classifier should be installed with a slope of from 3 to 4 in 1 ft. The steeper the slope the less the pool area of a given size classifier. The less the pool area the less the capacity. The maximum capacity for any mesh separation is obtained at a slope of about 3 in 1 ft. But, for very coarse separations it may be necessary to increase the slope and thus decrease the pool area so as not to cause overloading.

65 to 150 mesh3 per ft. 48 to 100 mesh3 per ft. 35 to 65 mesh..3 per ft. 28 to 48 mesh..3 per ft. 14 to 35 mesh4 per ft.

The launder from ball mill discharge to the classifier should have a slope of about 1 per ft. depending on fineness of grind and pulp density. The launder from sand discharge of the classifier to the ball mill scoop box should have a slope of from 4 to 6 per ft.

The speed of the conveyor should be just sufficient to handle the sands to be removed. The slower the speed the less the agitation in the pool and the finer the overflow. The lower the speed the longer the life of the classifier and all wearing parts.

Most efficient grinding is effected by removal of material from the ball mill as soon as it has been reduced to the required size. This eliminates over-grinding and permits utilizing all of the power applied to the ball mill in actually grinding the oversize material. This may be accomplished by using the Cross-Flow Classifier in closed circuit. The entire ball mill discharge goes to the classifier which separates the material ground to the desired size; returning the oversize material to the ball mill.

The Cross-Flow Classifier is ideal for this closed-circuit work. Its exclusive Cross-Flow principle of operation results in an extremely accurate separation. Various lengths of this classifier and variation in slope make it possible to fit the classifier to the circuit without use of expensive, troublesome equipment such as elevators, pumps, etc.

In closed grinding circuit separations are easily and efficiently made at from 20 to 100 mesh sizes. Normally, it is considered best practice to use a Hydroclassifier for separations at 100 mesh and finer. Efficiency of separation in fine mesh range requires a very large pool area. Thus, the Hydroclassifier, with its large surface area gives more efficient classification, more economically, than is possible with a spiral classifier.

Usually such separations are made on dilute pulps with a relatively small amount of slimes. Under these conditions a mechanical classifier can make efficient separations at a much finer mesh than in a closed grinding circuit where there is a higher density pulp and larger percentage of fines. The Cross-Flow Classifier will efficiently handle sand- slime separations in the range from 150 to 325 mesh, with a minimum amount of dilution water.

The Cross-Flow Classifier provides an efficient means of dewatering sands and concentrates or other granular material. A common application in this work is when the granular material is difficult to handle in a thickener. Also in many cases, where tonnage is not large, classifiers are considerably more economical than a thickener-filter installation lower in first cost lower in operating and maintenance costs require practically no attention.

A very common application of classifiers is in washing granular material to remove reagents, liquors, etc. Classifiers have the same advantage on small tonnage as in the case of dewatering lower initial and operating costs and less attention required. The particles to be washed pass successively up the inclined tanks of several classifiers, while the wash passes through the classifiers in the opposite direction. In each classifier the pulp is diluted, mixed and rabbled, the particles washed, and the liquid removed resulting in a thoroughly washed and cleaned final product.

STAND: For convenience in installing, these smaller sizes are provided with steel legs. The stand is made to give the most commonly used slope of 3 inches per foot. SHAFT: Solid, square steel. FLIGHTS: Hard, cast iron; made in short segments which fit over the square shaft. Flights may be placed on shaft so that blades form a continuous spiral, or may be staggered to obtain an interrupted spiral. DRIVE: Enclosed worm-gear speed reducer driven by motor through V-belts; cone pulleys are used to permit speed variations desirable in experimental laboratory or pilot plant work.

SHAFT: Heavy steel pipe. FLIGHTS: Hard, cast iron; made in short sections; bolted to cast iron arms which are carried on the shaft. Easily replaceable without draining tank. DRIVE: Bevel gear driven by gearmotor through sprocket and chain. Speed of drive is determined by the requirements of each installation. A variable speed drive may be furnished, at extra cost, if desired.

SHAFT: Heavy steel pipe with steel reinforcing sleeve at the lower bearing. FLIGHTS: Steel plate; bolted to cage which is carried by steel pipe shaft. Hard, cast iron wearing shoes, made in short sections, are bolted to the steel flights and are easily replaceable without draining the tank. DRIVE: Cast steel bevel gear and bevel pinion driven from a countershaft through spur gears; gearmotor and V-belts to countershaft. Speed of drive is determined by requirements of each installation. Variable speed drive may be furnished, at extra cost,if desired.

SHAFTS: Same as for corresponding sizes of simplex classifiers. FLIGHTS: Same as for corresponding sizes of simplex classifiers. DRIVE: Heavy cast steel bevel gears and bevel pinions, driven from countershaft through heavy spur gears; gearmotor and V-belt or chain drive. LIFTING DEVICE: Same as for corresponding sizes of simplex classifiers. CONVEYOR ROTATION: The two helical conveyor flights rotate in opposite directions, thus conveying the sands up the center of the tank giving free drainage back along both sides of tank.

classification - sciencedirect

classification - sciencedirect

Design features of the commonly used classifiers such as the spiral, rake, cone, bowl are described. Descriptions and design of centrifugal classifiers, such as the hydrocyclone, are given in some details. The mathematical aspects of designs that are related to operation of these classifiers and the theory behind the design and operation are discussed and explained in some detail. Mathematical correlation of variables that help to better understand the efficient operation of each process is derived and their use is explained using practical examples and solutions of common problems encountered in industry.

an operational model for a spiral classifier - sciencedirect

an operational model for a spiral classifier - sciencedirect

Wash water addition and concentrate port openings are used to tune spiral operation.There is no mathematical model describing the action of wash water and concentrate ports on spiral performances.A semi-empirical model is proposed to account for these operating variables.

Spirals are gravity concentrators used for the valorization of coal and heavy minerals. Coarse hematite iron ores in Canada are usually concentrated by spirals. Spirals classify the particles according to their size and specific gravity. Several mathematical models were proposed to simulate the operation of spirals using a balance between the various forces acting on particles. However few models provide a method to account for wash water addition and the opening of concentrate ports that are two strategic variables for the operation of spiral classifiers. This paper proposes a model to incorporate these variables in a simulation scheme and validates the model with pilot plant data.

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