Frantz Operation

II. OPERATION

I. General Description and Principles or Operation In the magnetic barrier field magnetic energy gradient has maximum value at a laminar

isodynamic region extending along the length of the working space at the front of the gap between the forward edges of the poles.

For separating materials according to differences in paramagnetic susceptibility the mixture is fed so that it enters the anadynamic field region, * which is inside the gap and extends along the length of the working space parallel to the laminar isodynamic region. The magnet is oriented so that the chute has a side slope downward towards its outer edge. By convention such a side slope is "positive" . The range of side slopes that is useful for exploiting paramagnetic susceptibilities is large: from +20 to +600. Gravitational force aided by vibration urges the material through the anadynamic field region towards the laminar isodynamic region against increasing magnetic force. Particles baving paramagnetic susceptibility such that the magnetic force exerted on them at the laminar isodynamic region equals or exceeds gravitational force are deflected and move along it down the chute to a point at which they are intercepted by a divider in the middle of the chute with its point at the lower end of the working space. Particles having lower paramagnetic susceptibility and diamagnetic particles pass through the barrier field and out of it on the outer side of the divider.

* An anadynamic region is one in which magnetic energy gradient CHaR/ax) transverse to field direction increases in the direction in wh ich field intensity decreases.

Rev. 7/21 /93

13

For separating materials according to differences in diamagnetic susceptibility the mixture is fed so that it enters the katadynamic field region, * which is outward from the gap and extends along the length of the working space parallel to the laminar isodynamic region. The magnet is oriented so that the chute has a side slope downward towards its inner edge; that is, it is given a "negative" side slope, which may be from -2 to -8 , and sometimes steeper. The mechanism of separation is the same as that described above; magnetic force in the katadynamic region opposes the movement of diamagnetic particles toward the laminar isodynamic region, where it has maximum value. There particles having sufficient diamagnetic susceptibility are deflected, while particles having lower diamagnetic susceptibility and paramagnetic particles pass through it.

Vibration of the chute with the Model LB- l Slope Feed System urges particles down the length of the chute with the magnet oriented so that the chute is horizontal. For most materials, however, orientation of the magnet giving the chute a forward slope downward towards its exit end aids separation. The component of gravitational force urging particles down the chute contributes to dispersion of them on its surface to uniformity of the direction of their motion and to freeing particles that tend to adhere to the chute surface.

2. Model LB-l slope feed system.

2.1 Feed sYstem.

The vibrator and feed hopper are held in vertical alignment over the appropriate receiving compartment of the chute by the adjustable arm mounted on the column of the separator. The hopper has a one inch diameter cylindrical cavity with a 114" diameter orifice and with fitt ings for securing a 5/16" wide movable platfo rm between side walls beneath the orifice. The hopper extension has a conical mouth 1-7 /8" in diameter.

* A katadynamic region is one in which magnetic energy grad ient transverse to field direction increases in the direction in which t1eld intens ity increases. Contiguous katadynamic, isodynamic and anadynamic regions, arrayed in that order. form the barrier field. Figure 1 shows the LB-l magnetic circuit and the location of the barrier field regions.

Rev. 7/21/93

14

For feeding granular material the longer surface of the platform is placed beneath the hopper orifice and set at an angle such that when material falls onto it a pile fonns, blocking further flow out of the hopper. Vibration is supplied to move the material off the discharge end of the platform. The angle of inclination of the platform and the height of the gate at its discharge end may be varied to aid in controlling the rate of feed. The gate should usually be set well above the surface of the platform so that it does not interfere with the movement of material. In that position its function is onJy to prevent spillage when material is poured into the hopper: the plug is inserted between the gate and the platform to block discharge until a pile forms beneath the hopper orifice.

For feeding fme powders the baffle assembly should be mounted on the "e" bar depending from the vibrator, with the baffl e suspended over the hopper orifice. It may be raised or lowered to vary the annular space between its perimeter and the inner wall of the hopper. Fine adjustments of the position of the baffle are made by turning the rod, which is threaded where it passes through the support.

When the hopper is vibrated material falls through the annular space and through the orifice. The motion of the baffle edge tends to break up agglomerates or balls that are formed when fine material is vibrated in constricted space.

The shorter surface of the platform is placed beneath the hopper orifice when powdery material is to be processed. It is set at an angle close to vertical, and the feed gate is extended downward so that there is a small opening between them beneath the hopper orifice. In this position the platform and gate serve to contine and direct the falling stream of powder.

2.2 Inclined chute assembly. At the upper end of the chute there are two receiving compartments divided by a partition. A bracket is provided which may be mounted on the upper end of the chute to hold either the feed trough or the feed blade. Granular material may be fed either directly onto the surface of the chute or into the feed trough. When powdery material is to be processed, the feed blade should be used to aid dispersion of the material. Uses of the feed troughs and feed blade are further discussed below.

A divider in the center of the chute with its point where the gap begins to widen provides two channels for conducting the "magnetic" and "nonmagnetic" fractions separated in the working space out of the field. A hole is cut through the chute floor at the lower end of

15

each channel and a discharge piece is affixed to the underside of the chute to conduct the two fractions into separate containers. The containers are supported under the discharge piece by a

support secured to the chute carriage.

The carriage supporting the chute rests on a mounting plate which is secured beneath the lower core by shoulder bolts which also secure the lower pole piece. Slots in the carriage base plate through which the bolts pass permit movement of the carriage inward or outward in order that the chute may be placed in any desired position with relation to the magnetic barrier. Three hand screws in the mounting plate are tightened to press the carriage plate against the bottom of the magnet core in order to hold it in place.

The surface of the chute must be clean for satisfactory operation. Washing with warm water and a detergent before each use is usually advisable. Avoid touching the chute surface. A fingerprint will cause material to stick to the surface.

Aluminum chutes are supplied with two braces, one held against each side of the chute by 7 screws. The braces improve the performance of the chute under vibration by enhancing rigidity and increasing weight. The screws should be checked for tightness frequently.

2.3 Controls. The controls consist of two on-off switches, two potentiometers, two

push buttons for supplying maximum vibration and two fuses , each in a separate circuit serving

a vibrator.

3. Chute position. The position of the chute is critical both to effective use of the magnetic barrier and to proper operation of the Model LB-l slo[Je feed system. It must be (i) aligned so that material enters the desired region of the magnetic field, encounters the laminar isodynamic region and is intercepted, if it is detl ected along it, by the divider, and (ii) centered in the 3/ 16 inch gap between the opposed faces of the upper and lower poles. Centering of the chute may not be necessary when the system is fi rst assembled since it was centered before shipment. Centering should be checked, however, by passing a 0 .010" feeler gauge along the gap above and below the chute. If the gauge binds either above or below the chute, recenter the chute as described at 3.2 below.

3.1 Chute alignment. The chute is aligned wi th relation to the magnetic barrier by moving the carriage supporting it. To place the chute in the desired alignment, loosen the three hand screws in the mounting plate which press against the carriage plate. The carriage may be

16

moved inward or outward at either end when these screws are loose. There are two basic chute alignments, one for separating materials according to

differences in ferromagnetic or paramagnetic susceptibilities and one for separating materials according to differences in diamagnetic susceptibilities. Characteristics of the mixture to be processed are of importance in selecting an alignment of the chute with relation to the barrier that is optimum for separation. The basic alignments, however, are as follows:

(a) Paramagnetic or ferromagnetic separations. For separating materials according to differences in paramagnetic or ferromagnetic susceptibilities the chute should be aligned so that the fixed center piece between the two receiving compartments is inward from the outer edges of the poles and the tip of the divider at the lower end of the working space is outside the gap.

(b) Diamagnetic separations. For separating materials according to differences in diamagnetic susceptibilities the chute should be aligned so that the center piece between the receiving companments is outward from the outer edges of the poles and the tip of the divider is inside the gap.

(c) Finding and recording chute alignment. Finding the alignment of the chute that is consistent with sensitive separation is best done on the basis of observation of the movement of material in trial passes.

The index marks engraved on the outer corners at each end of the lower core piece of the magnetic circuit of the separator and the scales engraved on the chute carriage provide means for locating the chute with relation to the barrier field. The center line of the chute is aligned with the laminar isodynamic region of the barrier field when the index marks on the core are aligned with the center or zero lines of the scales at each end of the chute carriage.

In operation the center line of the chute should always cross the laminar isodynamic region; for exploiting paramagnetic susceptibility the center line of the chute should be inside the outer edge of the gap at its upper, or entrance, end, and outside the outer edge at its lower, or exit, end. The tip of the divider at the lower end of the separating region is then visible outside the gap. For exploiting diamagnetic susceptibility the center line of the chute should cross in the reverse direction; from outside the outer edge of the gap at its upper end to inside the gap at the lower end of the separating region. The tip of the divider at the lower end of the separating region is then inside the gap.

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When chute alignment for separating a sample has been selected on the basis of trial passes, record it for future reference.

3.2 Centering. The thickness of the chute at the tip of the divider is 0.150 inch. With the chute cover in place and the thumb screws for securi ng the chute to its supporting frame screwed tight the thickness of the chute and cover in the gap is about 0.160 inch . The chute should be centered between the opposed pole faces, which are separated by a gap of 0.190 inch in the working space, so that there is a clearance of at least 0.010 inch between the face of the upper pole and the surface of the plastic chute cover and at least 0.010 inch between the lower pole face and the bottom of the chute.

If the chute is not properly centered, vibration will cause it to strike one or both of the pole faces. Random motion of particles will result, and the chute may be deformed. The fl oor of the chute in the working space is only about 0.040 inch thick. The centering procedure outlined below should be foll owed when operation indicates that the chute is not correctly centered.

To center the chute: (a) Orient the magnet in the horizontal position, with no side or forward slope.

(b) Check the clearance between the chute cover surface and the upper pole face with a 0.010 inch feeler gauge. If a feeler gauge is not avail able a piece of writing paper used . The gauge should pa

therefore, both positioning bolts should be turned the same amount in order to center the chute. Operation of the equipment with the surfaces of the positioning bolts at different heights may cause stress and distortion of the chute and irregular vibration patterns.

(d) If the chute cannot be adjusted by turning the positioning bolts so that the gauge does not bind at any place, remove the chute and check it to make sure that it is straight on a surface plate or with a straight edge.

(e) Straighten the chute, if necessary, by bending or twisting it gently on the edge of a table.

(t) Clean all supporting frame surfaces, chute surfaces and the pole faces. (g) Replace the chute on its carriage, and, with the cover in place, tighten the thumb

screws securing it and recheck the tolerances. (h) Turn on the chute vibrator and turn the potentiometer up towards maximum . The

system should be reasonably quiet. If there is noise indicating that surfaces of the chute are striking other surfaces at a potentiometer setting below 7, further fine adjustments of the positioning bolts should be made until vibration at near maximum amplitude without contact noise is obtained .

0) When the chute is centered correctly, tighten the set screws in the positioning bolt blocks. * These set screws are nylon tipped to protect the threads on which they press when tightened . Do not use metal set screws without a plastic pad.

G) Remember to wash and dry the chute well when it has been handled during straightening or centering.

4. Mal:net orientation. A side slope - orientation giving the chute an inclination in a direction transverse to its length - is required for all separations. A forward slope - orientation giving the chute an inclination in the direction parallel to its length and downward towards the discharge' end - aids movement of materials down the chute. Particle size, shape, surface characteristics, density and other physical properties affect movement on the chute in response to vibration and magnetic and gravitational forces. Determining optimum orientation of the magnet for processing a particular mixture consequently involves some trial and error.

*A 3/32" hex key is supplied.

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4.1 Side slope. The side slope controls the component of gravitational force opposing the magnetic force on particles. For separating particles of low magnetic susceptibility the side slope should be moderate. A side slope of 2 is the smallest that has been found to be practica1. Side slopes up to + 60 may be used for separating ferromagnetic or strongly paramagnetic materials. A special feed trough and a special plastic guard are provided for helping to control the movement of material at steep side slopes (see Fig. 4a). *

The following guidelines may be useful for selecting side slopes for processing new samples.

(a) Sequence. In processing a sample consisting of several minerals differing in magnetic susceptibility the usual procedure is to begin by separating the ferromagnetic and most strongly paramagnetic components and proceed with separating the other components in order of declining susceptibility. It follows that:

(1) The first passes of the sample are in most cases made with the magnet oriented and the chute positioned for separation according to differences in ferromagnetic or paramagnetic susceptibil ity . (2) In the usual sequence, accordingly, the side slope is relatively steep for the early passes of the sample and is progressively moderated as the less strongly magnetic components are processed. (3) After component minerals apparently similar in susceptibility have been. concentrated, further concentration can usually be obtained by reprocessing the concentrated fraction with a different magnet orientation. Paramagnetic components concentrated at a moderately steep side slope - say + 15 - can often be further separated and concentrated at a steeper side slope. Relatively pure diamagnetic particles can be best separated from less pure particles of the same mineral or from other diamagnetic minerals by reprocessing a concentration of diamagnetic materials separated at a moderate side slope of say, -3 at slopes increasing by up to one degree fo r successive passes.

The "nonmagnetic" fraction remaining after all diamagnetic materials have been separated usually contains weakly paramagnetic materials with sufficient susceptibilities to be separated when they are reprocessed without the interference with their responses caused by the presence of diamagnetic material.

*See Table A.

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I S I D E

S L 0 P E

S E T T I N G S

FRANTZ MAGNETIC BARRIER LABORATORY SEPARATOR (ModeJ LB-l)

TABLE A

Table showing angles between a line pe!1>Cndicular to the surface of the chute and vertical. Settings on the equipment scale allhe end of (he arm where it joins the coil assembly ("forward slope") and the scale at the base of the arm near the column ("side slope") are shown, respectively, in the top line across and the column at the left . -

FORWARD SLOPE SETTINGS

" II 0 5 10 I 15 20 25 30 35 40 45 50 55 0 0 5 10 15 20 25 30 35 40 45 50 55 5 5 7.07 11.l7 15.79 20.59 25.46 30.38 35.31 40.26 45.22 50.18 55.15 10 10 11.17 14.11 17.96 22.27 26.81 31.47 36.22 41 .03 45.86 50.73 55.61 15 15 15.79 17.96 21.09 24.81 28.70 33.23 37.70 42.27 46.92 51.62 56.36 20 20 20.59 22 .27 24.81 27.99 31 .61 35.53 39.67 43.96 48.36 52.84 57.39 25 25 25.46 26.81 28.70 31.61 34.28 38.29 42.06 46.03 50.14 54.37 58.68 30 30 30.38 31.47 33.23 35.53 38.29 41.41 44.81 48.44 52.24 56.17 60.21 35 35 35.31 36.22 37.70 39.67 42.06 44.81 47.85 51.13 54 .60 58.23 61.98 40 40 40.26 41.03 42.27 43 .96 46.03 48.44 51.13 54.07 57.20 60.50 63 .94 45 45 45.22 45.86 46 .92 48.36 50.14 52.24 54.60 57.20 60.00 62.97 66 .07 50 50 50.18 50.73 51 .62 52.84 54.37 56.17 58.23 60.50 62.97 65.60 68.37 55 55 55.15 55 .61 56.36 57.39 58.68 60.21 61 .98 63.94 66.07 68 .37 70.79 60 60 60.13 60.50 61.12 6 1.78 63 .05 64.34 65.82 67.48 69.30 71 .25 73.33 65 65 65 .10 65.41 65.7 1 66.60 67.48 68.53 69.75 71.11 72.61 74.23 75.97 70 70 70.08 70.3 2 70.71 71 .25 71.94 72.77 73 .73 74.81 76.00 77 .30 78.69 75 75 75.06 75.23 75.52 75 .92 76.43 77.05 77 .76 78.56 79.45 80.42 81.46 80 80 80.04 80.15 80.34 80.61 80.95 81.35 81.82 82.36 82.95 83.59 84.28 85 85 85.02 85.08 85 .17 85.30 85.97 85.67 85.71 86.17 86 .47 86.79 87.13 90 90 90 90 90 90 90 90 90 90 90 90 90

20A

ANCl [

60 60

60.13 60.50 61.)2 61.78 63 .05 64.34 65 .82 67.48 69.30 71.25 73.33 75.52 77.80 80.15 82.56 85.02 87.50

90

/\J '- "~ ,,,,,0

65 70 75 80 85 90 65 70 75 80 85 90

65 .10 70.08 75.06 80.04 85.02 90 65.41 70.32 75.23 80.15 85.08 90 65.71 70.71 75.52 80.34 85 .17 90 66.60 71.25 75.92 80.61 85.30 90 67.48 71.94 76.43 80.95 85.97 90 68.53 72.77 77.05 81.35 85.67 90 69.75 73.73 77.76 81.82 85.71 90 71.11 74.81 78.56 82.36 86. 17 90 72.61 76.00 79.45 82.95 86.47 90 74.23 77.30 80.42 83 .59 86.79 90 75.97 78.69 81.46 84.28 87.13 90 77.80 80.15 82.56 85.02 87.50 90 79.71 81 .69 83.72 85.79 87.87 90 81.69 83 .28 84 .92 86.60 88.29 90 83 .72 84.92 86.16 87.42 88.71 90 85.79 86.60 87.42 88.21 89.13 90 87.87 88.29 88.71 89.13 89.56 90

90 90 90 90 90 90

He v. 5/16/ 95

Processing of some mixtures is expedited by preliminary separation into bulk fractions at relatively fast feed rates and fu rther separations of the bulk fract ions at feed rates consistent with more sensitive separation.

(b) Material characteristics. Optimum side slope for separating a particular material depends in part on physical characteristics of the material other than magnetic susceptibility. A fine powder with high moisture content is likely to move slowly on the chute surface at a moderate side slope; at the same slope spherical part icles may move too fast.

(c) Force relationship. Since it is the relationsh ip between gravitational and magnetic force which provides separation, there exists for many materials an appreciable range of side slopes at which separation can be obtained with proper adj ustment of magnetic force . Experience indicates that as a general rule the relationship should be established nearer to the higher than to the lower end of the range applicable to a particular material . Agglomerations of particles of different susceptibil ities are more likely to come apart under stronger separating fo rces. Effects of the random forces that interfere with separation are in general reduced as the opposed magnetic and gravitational forces are increased.

In its application to ferromagnetic separations, the foregoing guideline requires qualification . For separating materials differing in fer romagneti c propert ies means are provided (with the Low Field Control) for pulsing the field. If it is assumed that two ferromagnetic materials are separable either by us ing a rel at ively steep side slope and an unpulsed fiel d or by using a more moderate side slope and a pulsed fi eld. separation under the latter conditions is likely to be more satisfactory. Pulsing frees entrained particles.

Another consideration in separating ferromagnetic materials is that when two such materials are highly magnetized their responses to magnetic force tend to become alike; the lower the magnetizing field, the more likely are their responses to differ sufficiently for separation. A side slope too steep to permit use of optimum tield intens ity is obviously undesirable.

With these qualifications limiting the fi eld intens ity that is practical for separations accord ing to diffe.rences in ferromagnetic properties, the principl e that a side slope providing high gravitational force is des irable nevertheless holds with respect to such materials .

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4.2 Forward slope. Material characteristics affecting movement on the chute surface are of primary importance in selecting forward slope. For free flowing granular materials forward slopes in the 5- - 15- range give good results. For fine powders forward slopes in the 15- - 30 range are usually needed to avoid sticking of material to the chute surface.

Dispersion of materials on the chute surface tends to improve as forward slope is increased, and this aids separation. The length of time during which separating forces are exerted on material increases, on the other hand, as forward slope is reduced. A forward slope that is moderate but sufficient to provide steady movement down the chute should be used for processing materials of low susceptibil ity.

4.3 Coordinatinl: settines . Feed and movement down the chute must be coordinated. When a new sample is to be processed trial passes should be made to find the effects of magnet orientation, feed mechanism settings, vibration amplitude for feed and for travel down the chute, and alignment of the chute with relation to the barrier. Selecting an orientation of the magnet and an alignment of the chute for trial in separating the strongly magnetic components of the sample are the first steps. Adjusting the feed mechanism is the next step.

5. Feed. The rate of feed of granular material is controlled by the angle at which the longer surface of the platform is set beneath the hopper orifice and by the amplitude of vibration.

The rate of feed of powdery material is controlled by the position of the feed baffle inside the hopper and by the amplitude of vibration.

5.1 Hopper position. When the magnet bas been oriented, adjust the arm holding the hopper arid vibrator so that they are in vertical alignment over the appropriate compartment of the chute, with the bottom of the hopper cl ear of all parts of the chute, the feed trough or the feed blade.

Place the hopper so that it discharges into the receiving compartment near the inner edge of the chute, towards the coils , for separations according to differences in paramagnetic susceptibility. Place it to discharge into the outer compartment for separations according to differences in diamagnetic susceptibility.

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For feeding granular materials the discharge end of the platform should be close to the surface of the chute to reduce bouncing of particles, or, if the feed trough is used, close to the surfaces of its angled wings. For feeding powdery material the discharge should be close to the surface of the feed blade, and the feed blade should be set at an angle close to vertical. Hopper dispositions are further explained below and iJlustrated in Figures 3 and 5.

5.2 Settings for free 00\\,ln2 material. For feed ing free flowing granular material the long surface of the platform hould be beneath the hopper orifice. Set the platform at a slight inclination from horizontal. Loosen the collar of the hopper and turn the hopper so that the discharge end of the platform is towards the rear of the chute, away from the magnet (see Fig. 3). This orientation of the hopper is preferable whether material is to be fed directly onto the floor of the chute or into the feed trough.

With the platform set at an angle such that with no vibration material falling on it from the hopper forms a pile and comes to rest, stopping the fl ow, the rate of feed is controlled by the feed vibrator. In most cases the feed gate need not be used for controlling the rate of feed . It may be set at a height above the surface of the platform that permits free flow of material and will not cause plugging of the opening by large grains. When the gate is in that position , the feed plug may be inserted in the opening to keep material from sp illlng off the platfo rm when the hopper is being fi lled. A platform setting such that at low vibration a single layer of particles moves slowly to the end of the platfo rm and falls to the chute surface is consistent

with good control of feed rates within the range that is practical for all but the maximum rates . For very high feed rates it may be necessary to increase the angle of inel ination of the platform.

For processing a new sample start with a moderate incl ination and increase it if faster feed rates are required. Note that the feed system is not completely isolated from the chute vibrator; vibration transmitted through the separator may be enough to start the feed if the platform is given too steep an inclination .

The baffl e should not be used when granular material is processed. Grains are likely to stick between it and the hopper wal l. It is needed only for control of the feeding of fine powders.

Three feed troughs, shown in Figs . 4, 4a, and 4b. are provided fo r aiding the feed and flow of granul ar materials. Each can be set at a su itable inclination, with its discharge end

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directed into the part of the magnetic field which should receive the material and with a tilt that inclines its floor with respect to, or disposes it in a position parallel with, the chute surface.

The feed troughs are particularly useful for feeding at higher rates. When material is fed at high rates directly onto the floor of the chute, the stream may spread toward the edge of the chute and some particles may not move through the regions of the barrier field as required for separation. The feed troughs aid in introducing a stream of particles in such manner that they move through the regions of the barrier field as required for separation.

The feed troughs (and the feed blade described below) are secured by tightening the set screws in the clamp. *

5.3 Settings for fine powders . For feeding fine powders the short surface of the platform should be beneath the hopper orifice. Set the platform at a steep angle so that there is a small opening between it and the gate with the gate all the way down. (See Fig. 5.) In this position the platform and gate serve to confine and direct the falling stream of powder.

Set the feed blade over the appropriate receiving compartment so that its lower edge is below the upper edge of the fixed center piece and in the space which will receive the feed. Set the blade at an angle close to vertical, with an inclination opposite to that of the chute**. The curved end of the blade should always be toward the magnetic field, with the curve pointing upward. Loosen the hopper collar and turn the hopper so that the hopper orifice is above the inel ined surface of the blade. Material should be fed as near to the clamp holding the blade as is practicable.

* A 1116" hex key is supplied. **When material is fed into the inner feed compartment for exploiting paramagnetic susceptibility, the feed blade is inclined so that its upper edge is nearer to and its lower edge is away from the operator. When material is fed into the outer teed compartment for exploiting diamagnetic susceptibility, the indination of the feed blade is reversed, so that its upper edge is away from the operator.

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Loosen the wing bolt which clamps the baffle support arm and the bolt in the arm which holds the rod attached to the baffle. Screw the rod to extend it downward full y. Lower the support arm so that the baffle is centered and rests on the concave inner surface of the hopper. Clamp the support arm in place by tightening the wing bolt. Enter the sample. Then rum the rod to raise the baffle to provide a large enough annular opening between it and the hopper wal l so that materi al will be discharged at a suitable rate when vibration is supplied. Tighten the bolt in the support arm to hold the rod in place. *

Rates of feed of fine powders are contro lled by the height of the haffle and the ampl itude of vibration. The platform and gate should be used only to direct the feed not to control the feed rate. If the opening between platform and gate is too small, powder accumulates in the space below the hopper orifi ce and tends to agg lomerate and ball up under vibration.

When powder is fed so that it fall s out of the hopper directly onto the floor of the chute, some of it sticks and layers build up until dots are shaken loose by chute ibration. The clots are not well dispersed by vibration as they move down the chute.

When the stream of powder is directed so that it falls on a sloped side of the feed blade, the formation of layers and clots of material is largely avo ided. and dispersion of the material on the chute is substantially imp roved .

6. Vihration . The vibrators attached to the feed and chute assemblies are adjusted to provide the range of amplitude of vibration useful fo r normal operation. Push buttons which by-pass resistors provide greater amplitude for clearing residues of material out of the feed system arid the chute.

* A 1/8" hex key is supplied.

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6.1 The chute should always be vibrating when feeding is commenced. If the feed vibrator is turned on first, material accumulates in the receiving compartment and when chute vibration is started it moves into the working space in a mass that cannot be effectively separated.

6.2 Observe the movement of particles on the chute carefully when feed is started or when feed rate is increased. When processing rates are to be increased chute vibration should usually be increased before the feed rate is increased.

6.3 Observe the movement of material along the entire length of the chute from time to time during processing . It should be fairly uniform in response to vibration. Marked acceleration or deceleration as material passes over any part of the chute - except in response to magnetic or gravitational forces - may ind icate that the thumb screws securing it should be tightened, that centering should be checked, that surfaces should be cleaned or that it has been twisted or bowed.

6.4 The adjustment made before shipment permits the moving armature of each vibrator to strike the stationary core when resistors are by-passed by pressing the surge button. Press the button only for short bursts of a few seconds to clear material out of the hopper or off the chute at the end of a separation. Operation for longer periods with the armature hitting the core will damage the vibrator.

6.5 The stray field of the Separator increases the amplitude of vibration of the chute vibrator substantially as current to the main coils of the separator is increased. If the Low F ield Control is used with the Separator, amplitude of vibration will increase with increase of current when the current reversing switch is in the + position and decrease when the switch is in the - position. To maintain a substantially constant rate of travel on the chute, the potentiometer controlling chute vibration accordingly should be turned to a lower setting when current to the separator is increased.

If the effect of increasing current to the separator is to reduce amplitude of vibration, either the Low Field Control reversing switch is in the - pos ition or the separator coils are incorrectly wired. In the latter case the leads to the separator coils should be reversed.

The stray field does not substantially affect the feed vibrator.

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7. Isodvnamic Separator reference material.

A substantial body of information has been published concerning separations performed with the Frantz Isodynamic~ Magnetic Separator (Model L- I), wh ich has been standard equipment for mineral investigation for many years. Much of the information in the publications about the L- l is useful fo r operating the LB- 1. Diffe rences in principles of design of the two separators which should be kept in mind by the operator of the LB- l are as follows:

7.1. Direction of mal:netic force. The direction of magnetic force in the working space of the LB-l is the reverse of that in the L-l. In the L-l field magnetic force urges paramagnetic materials towards the outer edge of the chute and diamagnetic materials towards its inner edge. Consequent! y a side slope downwards towards the inner edge of the chute is used for separations according to differences in paramagnetic susceptibility and a side slope downwards towards the outer edge of the chute is used for separations according to differences in diamagnetic susceptibility.

In the barrier field magnetic fo rce is exerted on paramagnetic materials in the direction toward the inner edge of the chute and on diamagnetic materials in the direction toward its outer edge. The side slopes used for separations according to differences in paramagnetic and diamagnetic susceptibilities accordingly are the reverse of those used with the L-l.

7.2 Use of force. With the L-l magnetic force is used to urge particles across the chute against a component of gravitational fo rce. The isodynamic shape of the pole pieces provides constant force across the width of the working space in order that particles of like susceptibility will be subject to like force wherever they are in that space.

With the LB-l a component of gravitational force is used to move material across the working space against magnetic force increasing to maximum value at the laminar isodynarnic field region. Particles having susceptib ilities such that magnetic fo rce on them at the laminar isodynamic region equals or exceeds gravi tational force are prevented from crossing the barrier, while particles having lower susceptib il ities pass through it.

With both separators a component of gravitational fo rce is used to urge material down the chute .

Rev. 7/21 /93

27

7.3 Range of force. The range of fieJd intensity provided by the two separators is substantially the same: from zero (when the Low Field Control ** is used to eliminate residual magnetization of the circuit) approximately to 20,000 Gauss. With the regulated power supply* maximum field intensity of 20,000 Gauss can be maintained for extended periods of operation. At any field intensity selected, however, the effective force provided by the LB-l is about three times greater than the effective force provided by the L-l. A small adjustment of current to the LB-l consequently results in substantially greater change in effective force than the change in force which results from a comparable adjustment of current to the L-l. Separation of materials which differ slightly in susceptibility is imprOVed with the LB-l .

The range of materials that respond to magnetic force sufficiently for separation is also extended. Responses of highly magnetized ferromagnetic materials in a magnetic field tend to be similar. Effective force on material in the barrier field of the LB-l is equivalent to effective force on the same material in the isodynamic field of the L-l when field intensity values in the barrier field are about one third those of the broad isodynamic field. It follows that conditions for separating ferromagnetic materials are provided with the LB-l at field intensities very much lower than those required with the L-l, and that, being much less highly magnetized, their responses to separating forces are more likely to be dissimilar.

At high field intensities magnetic force in the barrier field of the LB-l is sufficient for separating weakly paramagnetic and weakly diamagnetic materials that cannot be separated with the L-l.

*TIle regulated power supply provides linked regulation of voltage and current, so that as resistance increases with hearing of the coils, voltage is automatically increased sufficiently to maintain the selected current. The power supply is installed so as to by-pass the electrical parts in the base of the separator.

**1be conditions for separating ferromagnetic materials are established with an accessory device, the Frantz Low Field Control (Model LFC-2). It provides means for reversing the direction of the current to the separator's coils, for sensing a zero field condition, for regulating and monitoring current from zero to about 90 milliamperes and for pulsing the current at selected frequencies between selected values. Pulsing the current pulses the magnetic field; it may be pulsed through the zero field value to reverse the polarization of the particles with each pulse. This causes chains of ferromagnetic particles to collapse and release entrained particles. Separate operating instructions are furnished with the LFC-2.

Rev. 10/11/95

28

8. The "effective magnetic barrier"; some practical guidelines for operation.

8.1 The "effective magnetic harrier!! . Observation of barrier separations and analysis which takes into consideration factors other than magnetic and gravitational forces indicates that there is an "effective magnetic barrier" for any separation according to susceptibility which has a certain width in the symmetry plane in the direction transverse to the lengthwise axis of the gap. It may be thought of as a band with the laminar isodynamic region at its center, bordered on either side by portions of the katadynamic and anadynamic regions approximately equal in width. The band extends along the length of the barrier field in the region of and paral lel with the outer edges of the opposed faces of the poles .

In the processing of any mixture the particles undergoing separation move along the length of the barr ier field in somewhat erratic paths . Particles traveling more or less in single fil e along the barrier on the surface of the vibrating chute at a very slow rate of feed and a moderate rate of travel deviate from the paths they would fo llow if those paths were determined by magnetic and grav itational for es only. The fract ion deflected as magnet ic may cross and recross the isodynamic plane several times , but it is contained within a band of which the outer edges lie, respectively, in the katadynanlic and anadynamic regions.

Friction, adhesion and other interactive surface fo rces vary widely depending on the nature of tbe surfaces in contact with each other and other particle characteristics. Probably each surface of a grain is in contact with the chute several times as it travels down the chute, sliding, turning, rolling and bouncing . The direction given to a grain by each vibration impulse probably diverges somewhat from the axial direction of the vibratory motion as a resul t of the many changes in interactive surface forces and in the magnitude and direction of impacts th at occur, as well as complex factors such as position of the center of mass of each particle with relation to whichever of its surfaces is in contact with the chute surface or with a surface of another particle. Relationships among random facto rs affecting the paths of particles are too complex for detail ed discussion here.

When the di rection given to a grain by a vibratory impulse diverges toward alignment with the component of gravitat ional fo rce opposed to magnetic force. the effect may be to increase Significantly the nonmagnetic force tending to move the grain through the laminar isodynamic region. Observation ind icates that this typically occurs several times during the

29

travel of a particle along the barrier. Concatenated effects of random forces may urge grains

so far beyond the laminar isodynamic region that magnetic force is overcome.

It follows that in order to deflect particles of like susceptibility in a barrier field the magnetic force at the laminar isodynamic region must be greater than that required to balance

opposed gravitational fOfce. Were it not, random responses to vibratory impulses would move

most or all of the particles through the region and through portions of the adjoining anadynamic or katadynamic region where magnetic force is high. Yet the margin by which

magnetic force on particles of like susceptibility at the laminar isodynamic region exceeds the

opposed gravitational force must be small if they are to be separated from components of the

mixrure slightly lower in susceptibility.

As feed rates are increased above minimum, material travels through the barrier field

as a continuous stream. The width of the deflected stream varies with the rate of feed, the

composition of the mixture, the characteristics of the material and the relationship between

magnetic and gravitational forces that is established. Although increasing the rate of travel

down the chute tends to disperse particles and reduce the width of the stream, the deflected

magnetic stream will have appreciable width, for example, when a mixture is processed at a

relatively fast feed rate to make an initial concentration. Obstruction by the magnetic stream of

the movement of the "nonmagnetic" components of the mixture through the barrier increases.

For some part icles of "nonmagnetic" material the magnetic stream becomes a mechanical

barrier which prevents separation.

Collisions also occur which drive across the barrier particles of a susceptibility such

that magnetic force would otherwise be sufficient to deflect them. There is, thus, entrainment

by both the nonmagnetic and the magnetic stream which, for any mixrure, increases as feed

fate is increased.

Rev. 7/21 /93

30

8.2 Practical guidelines for operation. Persons who have operated the Model L-I are likely to be familiar with "Notes on Operation of Frantz Tsodynamic Separator", a paper by the late Professor H. H. Hess of Princeton University, which is appended to these instructions, as Appendix A. The guidelines set forth in that paper for operation of the Model L-I are in many respects applicable to operation of the Barrier Separator. The differences between the LB- l and the Isodynamic Separator outlined in section 7 of these instructions, beginning at page 29, should, of course, be kept in mind.

(a) Preparation of sample. The part icle size range given by Professor Hess - 30 to 400 mesh - is indicative of the range for convenient processing with the Barrier Separator. The LB- l has proven capable of good separations of both tiner and coarser material : samples containing much material of submicron size (e.g., laterite, tal , calcined alumina); and coarsely ground ores (e.g., kimberlite, quartz) averaging 1-2 mm. in particle size.

Washing of samples to remove dust, as Hess recommends, is advisable when that is feasible. Washing with the aid of ultra-sonic vibration is the most effective way of removing dust. A coating of paramagnetic dust on a diamagnetic particle can make it respond as paramagnetic. Dust accumulating on the chute interferes with the movement of particles in response to magnetic and gravitational forces.

Hess warns that magnetite and iron fil ings will stick to the pole pieces or the chute and block the free flow of material. He advises that they should be removed by combing the sample with a hand magnet. Hess also describes a method for separating magnetite from complex iron ores or rocks (at page 5) . These methods are useful if the Low Field Control (LFC-2) is not available. Separation and concentration of ferromagnetic materials with the Low Field Control, if one is available, is always preferable. Either of the methods recommended by Hess will result in removal of strongly paramagnetic grains, such as ilmenite, with the ferromagnetic particles. Neither of the methods recommended by Hess will remove all fine ferromagnetic particles. Rev . 7/21/93

31

(b) Instrument settin~s. (i) Orientation. The orientations of the LB-l magnetic system with respect to side

slope (inclination transverse to the length of the gap) which are practical and effective differ markedly from those recommended by Professor Hess for operation of the Isodynamic Separator. The improved ratio of magnetic force to field intensity in the barrier field is consistent with use of greater opposed gravitational force for separations over virtually the entire range of susceptibilities.

The maximum side slope that is practical with the LB-I is + 60. Relatively steep side slopes usually are effective for separating the more strongly paramagnetic minerals from each other, which include those listed below:

Ilmenite Biotite Allanite Garnet Perovskite Tourmaline Chromite Euxenite Epidote Columbite Hornblende Gahnite Chlorite Pyroxene Monazite

Xenotime

When the maximum side slope of + 60 is used. a forward slope setting (inclination parall el to the length of the gap) of at least 20 must be used. The chute vibrator will not clear the column of the base of the separator at lower forward slopes. The minimum forward slope setting of 20 is in any event required for satisfactory travel of material down the chute when maximum side slope of + 60 is used .*

* 20 as shown on the scale at the end of the arm, where it joins the magnetic circuit, is the minimum instrument scale reading. Actual forward slope at 20 scale reading with a 60 side slope is 9.847.

Rev. 7/21 /93

32

As a general rule use of a large gravitational force component is also the correct method for separating ferromagnetic materials . The side slope that is practical for separating ferromagnet ic materials may, however, be less than maximum. Even when a relatively weak fie ld - established with the Low Field Control - is pulsed, it may cause all ferromagnetic materials to respond alike, or it may cause particles to adhere to the surface of the chute or its plastic cover. If reducing the field intensity results in magnetic force insufficient to deflect the ferromagnetic component to be separated against a large gravitational force component, side slope should be reduced . Satisfactory orientations are often best determined by trial and error.

(ii) Feed, travel rates. The data given in the Hess paper as to feed and flow rates that are practical for the Isodynamic Separator are generally inapposite to separations with the LB-I because of the major differences in equ ipment des ign. For example, very good concentrations of strongly paramagnetic components of a mixture can be obtained with the LB-J at feed rates of 10 grams per minute and higher .

The approach recommended by Professor Hess, however, of making trial runs of material is obviously sound, and the visib ility of material moving on the barrier chute increases the useful ness of trial runs. Trial separations provide, for example, info rmation as to ranges of side and forward slopes consistent with satisfactory movement of material on the chute, as to practical ranges of rates of feed and travel at selected orientations, and as to the effects of various current settings.

(c) Processing sequences. The "Examples Illustrating Use of Separator" on pages 2 and 3 of the Hess paper are applicable to processing with the LB- l.

Rev . 7/21/93

33

The sequence of current adjustments given in example 1 for obtaining a pure concentration of a mineral illustrates the method which best serves that purpose. Such a sequence tried at several different magnet orientations also provides guidance as to the orientation at which separation is likely to be most sensitive to slight differences in susceptib il ity .

As removal of the more strongly paramagnetic minerals proceeds and the proportion of diamagnetic to paramagnetic material remaining in the sample increases, mechanical entrainment of paramagnetic material by the "nonmagnetic" stream increases. Such entrainment interferes significantly with the concentration of quite strongly paramagnetic materials, such as monazite when diamagnetic material constitutes a substantial proportion of the original sample. Concentration of paramagnetic materials, particularly those having susceptibilities near the lower end of the range, may therefore be carried out faster and more effectively after most of the diamagnetic material has been removed. *

(d) Trial diamagnetic separations. The equipment adjustments required for diamagnetic separations are conveniently made in the following order:

(i) Set side and forward slopes at zero. (ii) Loosen the three hand screws clamping the chute carriage and align the chute so that the fixed center piece between the chute receiving compartments is outward - towards the operator - from the barrier and the chute divider at the discharge end of the separating region is inward - towards the coils - from the barrier. Tighten the handscrews. Further guidelines for positioning the chute are outlined below.

*It will be apparent that entrainment by the "nonmagnetic" streams occurs to some degree in any separation at reiatively fast rates of feed and travel , roughly in proportiOii ~G the quantity of material that is "nonmagnetic" at the equipment settings. It usually interferes much less with separation of strongly paramagnetic material , such as ilmenite, than with more weakly magnetic material .

Rev . 7/21 /93

34

(iii) Adjust the magnet orientation to provide a side slope of -2 to _4 and a forward slope of 10 for granular material . Orientation at steeper side and forward slopes is usually required for satisfactory movement of powdery material.

(iv) Adjust the feed assembl y so that the hopper is suspended over the outer receiving compartment of the chute. If a substantial quantity of material remains to be tried and most of it is granular, either the "movabl e feed trough " (Fig. 4) or the "diamagnetic feed trough" (Fig . 4b) is useful for directing the stream. The feed blade should be used whenever most of the material is powdery.

(v) Turn the current to maximum.

Separation of diamagnetic fractions is most effectivel y made in reverse order from

separation of paramagnetic fractions: a rough concentration of most of the diamagnetic material is made at a moderate side slope as the first step, and this diamagnetic concentration is then further processed with the magnet orientation adjusted for successive trials to provide increased gravitational force. Strongly diamagnetic material can be concentrated at side slopes up to 10 or more.

The "nonmagnetic" fraction resulting fro m rough concentration of most of the

diamagnetic material usually contains both paramagnetic and diamagnet ic grains of low

susceptibility. Reprocessing of th is fraction with the magnet oriented at a side slope of 2 to 3 should concentrate remaining weakly diamagnetic material . Reprocessing of the residue to exploit paramagnetic susceptibility usually concentrates weakly paramagnetic material.

Trial separations carried through all of the stages mentioned above provide preliminary concentrations that in most cases should be retained. There is little purp se in remixing separated fractions, except that two or more fractions which are substantially alike in susceptib ility may be combined fo r further process ing. Concentration of paramagnetic

fractions proceeds much faster when most of the diamagnetic material has been removed, since mechanical entrainment is reduced.

Revised 7/21193

35

r ---

Variations of the procedure outl ined above which are indicated by particular processing objectives will be evident to the operator. If certain paramagnetic minerals are of primary interest, for example, removal of diamagnetic minerals after separation of ferromagnetic and strongly paramagnetic components expedites processing. This should generally not be attempted until paramagnetic fractions separable at currents up to 0.5 Amps have been removed, since the high field intensity required for separating diamagnetic material may cause strongly paramagnetic grains to stick on the chute.

Equipment adjustments that are consistent with effective separation will be indicated by observation of the responses of the material during the trial separations. Adjustments which are of particular importance are noted below.

(e) Chute alienment. The chute should be aligned with relation to the barrier field so that material is guided into the tield and collected at the mechanical divider in a manner that is consistent with effective separation. The center line of the chute, in the working space between the receiving compartment and the mechanical divider, should transect the laminar isodynamic region so that particles deflected by magnetic force will be intercepted by the mechanical divider.

The angle at which the center line transects the isodynamic lamina may be varied to suit the behav ior of the material. An angle such that the tips of both the feed compartment center piece and the divider are 118 inch or more away from the isodynamic lamina is helpful for processing material at relatively fast rates of feed and travel. For separation at slow feed and travel rates both the center piece and the divider may be closer to the lamina. A stream of material fed into the field at a fast rate 118 inch or more away from the lamina is better dispersed when it encounters it than would be the case if it were fed nearer to the lamina.

The divider should always be far enough away from the laminar isodynamic region so that it intercepts all of the material deflected as magnetic; mechanical division of the magnetic stream remixes part of it with the "nonmagnetics" if the divider is placed too close to the lamina. The feed rate should not exceed that at which separation of the magnetic stream is seen to be substantially complete in the working space above the divider, with none or very few of the "nonmagnetic" particles crossing the barrier near the tip of the divider.

Rev. 7121193

36

(t) Hopper, trough. blade and baffle adjustment. Adjustments of feed hopper and feed trough positions to provide optimum flow and direction of material may be indicated as trial runs are observed. All parts of the feed hopper should be clear of the feed trough, but the hopper should be as low as possible to reduce bouncing . Material should be fed near to the clamped tail of the feed trough, but not so close that particles falloff the back end.

The floor of the feed trough may be slightly above and approximately parallel with the surface of the chute, or angled slightly downward towards its discharge end to aid dispersion of material. The tip of the feed trough may be in contact with the chute surface, but should not be pressed against it. The trough may be angled toward the barrier, but it should be clear of the fixed center piece between the feed compartments to avoid erratic vi bration effects . To maintain feed trough position, secure it tightly with the thumb wheel and set screws, and screw the thumb screw holding the feed bracket tight. If the feed trough rattles at high chute vibration, adjustments should be made.

When the feed blade is used, it and the hopper should be adjusted so that the entire stream of powder falls on the blade near where it is clamped and near to its upper edge. The angle of the blade should be as close to vertical as interception of the stream of powder will allow. There should be no contact between the feed blade and any part of the chute even at high chute vibration.

The baffle should be placed in the hopper at a height such that powder passes its edges with minimum agglomeration. If material falling on the feed blade includes lumps or balls, lower the baffl e to reduce the annular space between its perimeter and the hopper wall. Increase in the amplitude of hopper vibration may then be necessary to maintain a steady flow. Separation will not be satisfactory if material is agglomerated or balled when it reaches the chute surface.

(g) Trouble shootint:. Feed svstem. The feed system of the LB-l provides means for feeding granular

material at rates from a few grains to 25 grams or more per minute. The upper limit of the range for feeding powders is in general lower than that for feeding granular material. When the equipment is adjusted correctly to provide a selected feed rate, the rate is maintained without substantial variation over long periods - 12 hours or mo re - of continuous operation.

Rev . 7/21193

37

When feeding nears the finish and only a small pile of grains remains on the feed platfonn, or only a small accumulation of powder is held on the feed baffle, increase in feed vibration may be required to discharge the material. Press the feed vibrator surge button for intervals of a few seconds or turn up the potentiometer, but do not allow the vibrator to operate continuously with the armature striking the core.

If the rate of feed increases or falls off markedly, the cause may be apparent upon inspection during operation. Interruption or decrease of feed rate may result from jamming of grains between the hopper platform and the gate if the gate is too low, or from occlusion of the space between the baffle perimeter and the hopper wall by lumps of powder. Feed rate increases may occur if the position of the fixed element controlling the rate - the platform under the hopper orifice for granular material or the baffle for powder - is not securely set and changes under vibration.

Erratic motion of the feed trough or feed blade results either from contact with the chute surface or from looseness in the clamp set screws, the thumb wheel or the thumb screw.

Such problems with feeding are usually easy to detect and correct because the erratic motion is visible, or because contact of a part with the chute is audible ..

Chute. Travel of material on the surface of the chute can be provided and maintained at rates consistent with feed rates from a few grains to 25 or more grams per minute. Changes in the velocity of movement of particles on the chute occur in response to the differing force relationships which they encounter as they move through the barrier field: particles having susceptibility such that magnet ic force opposes their movement under gravitational force are slowed and part icles of opposite susceptibility are accelerated as they approach the barrier. Acceleration of granular material which has passed through the barrier may appear to be

unchecked at high chute vibration settings, while grains deflected along the barrier or in contact with surfaces of the feed trough, divider or side wall travel at much slower rates. Small changes in velocity of travel on the chute occur as material moves away from or approaches a spring assembly . These effects are to be expected.

Even when a granular sample is free of fine powder and dust, some grains usual ly adhere to the chute surface. Electrostatic charges are often the cause of sticking, but mechanical interactive forces may also be a cause. With correct equipment adjustment,

Rev . 7/21/93

38

however, particles should not stick to the chute in sufficient quantity to interfere unduly with separation. Building up of deposits of material on the chute surface indicates, however, that equipment adjustment is required.

A common cause of sticking is moisture, oil or other foreign matter on the chute surface. Even a light touch of a finger may leave a film that causes particles to stick. Wiping the surface with a clean, absorbent cloth or paper may reduce the problem . If material continues to stick unduly, remove the chute and wash it in warm water and detergent. Rinse and dry it thoroughly . Use compressed air if it is avail able; if not press absorbent towels against all surfaces and into holes and grooves until no moisture is detected . Avoid rubbing the chute to dry it, as increased electrostatic charges may be induced .

Looseness of connections may cause mater ial to build up on the ~hute surface or move in aberrant paths. The three hand screws in the mounting plate under the chute carriage should be tight, so that the carriage is pressed against the core of the magnet and immobile. The set screws in the blocks beneath the chute holding the chute positioning bolts and the three thumb screws securing the chute and the discharge piece shou ld all be tight.

Strongly magnetic material held on the chute su rface inside the gap divens particles from normal paths. Such material is best removed with the tield at zero condition, but it may be possible to remove most of it by turning the current off, wiping it toward the discharge end of the chute and supplying strong vibration.

Material spilled on the plastic chute cover may get caught between it and the upper pole piece. Particles wedged between chute and pole piece have a damping effect on chute vibration, and may cause erratic particle motion.

Positioning the chute otherwise than centered between and approximately parallel with the opposed surfaces of the pole pieces is likely to affect partic le motion adversel y, particularly if any part of the chute is vibrated against a pole piece surface. When that occurs a metallic contact sound usual ly warns of the problem, but if a part of the chute surface is pressed tightl y against a pole piece surface there may be little change in the sound of vibration. Slide a 0.010 feeler gauge or a piece of writing paper between chute and pole piece - both above and below the chute to find where contact is occurr ing , and then recenter the chute, following the procedure outlined at section 3.2

Rev. 7/21193

39

9. Maintenance. CAlITlON: HAZARDOUS VOLTAGES ARE PRESENT IN THE EQUJPMENT;

AVOID DAMAGE TO COILS, CORDS AND OTHER EXPOSED ELECTRICAL COMPONENTS. DISCONNECT A.C. POWER BEFORE EXPOSING ANY BARE CONDUCTORS.

DO NOT DISCONNECT ENERGIZED COILS. INDUCTIVE ENERGY MAY CAUSE SHOCK AND FIRE HAZARDS.

9. 1 Preventive Maintenance: At least annually inspect coils, cords and connectors for damaged insulation. Repair or replace as needed.

All surfaces touched by the mineral samples and all surfaces where there are sliding fits should be kept clean. They may be cleaned with a suitable solvent. It is important that no oil be used on these parts, since even a thin film of oil will cause grains to stick and either impair the separation or cause cutting of the sliding parts.

Bolted connections of the chute carriage are tightened with a torque wrench to a tension of 30 inch-pounds at the factory. They should be retightened periodically with a torque wrench. If they are allowed to become loose, the blocks holding the chute positioning bolts are likely to move. The blocks and bolts are carefully leveled so that the surfaces of the bolts are in a horizontal plane before the equipment is shipped.

The position of the bolts can be checked and corrected, if necessary, by placing the chute carriage on a surface plate and using a height gauge. It is important that the surfaces of the positioning bolts be within .002" of a horizontal plane. If they are not, when the chute is tightened in place stresses will occur which distort it and cause erratic vibration.

If the rod supporting the feed baffle appears to be bent, remove the finger knob and the two small nuts which secure it, and remove the rod from the support. Roll the rod on a surface plate and bend it gently until it is straight. Reinsert the rod into the support arm. Then turn the small nuts tightly against the knob, one below and the other above it.

Magnet Coils: Resistance of the coils of the Magnetic Barrier Laboratory Separator (Model LB-l) connected in series should be between 58 and 68 Ohms. Disconnect the coil

Rev. 4/24/95

40

cord of units with serial numbers 343 and higher and measure resistance from pin 13 to pin 14. On older units resistance should be measured across the two coil leads with the coil cord disconnected. To check the resistance of each coil, disconnect the coils from each other and measure the resistance across each set of coil leads. It should be between 29 and 34 Ohms.

Vihrator control unit: A circuit diagram for the control unit for the feed and chute vibrators appears as Fig. 6. The diagram should enable a quali fi ed electrical technician to determine the cause of malfunction of the vibrator controls .

9.2 Electrical malfunction: The manufacturer of the power supply, Electronic Measurements, Inc., does not author ize users of the equipment to perform service on its products. Should electrical malfunction occur, report it to S. G. Frantz Co . Inc. An attempt by user to perform service on the power supply may damage it and is likely to result in voiding any warranty that would otherwise be app licable.

9.3 Vibrator adjustment: The gap between the core of the chute vibrator and the armature is correctly adjusted when it is just sufficient so that the armature does not strike the core at the maximum setting of 10 of the potentiometer when the current to the Separator is off. Greater length of the gap results in reduced amplitude of vibration and overheating of the vibrator coil .

To adjust the gap distance of the chute vibrator proceed as follows: (a) Turn the current to the separator coils off. (b) Loosen the lock nut securing the vibrator core. * (c) Screw the core in (clockwise) to reduce the gap, or out

to lengthen it, as required. Find the core position at which the armatu re just strikes it with the potentiometer set at 10, and then increase the gap slightly until there is no contact. Tighten the lock nut.

* An open end wrench for the lock nut is provided .

Rev . 4/24/95

41

To adjust the feed vibrator, check the set screw on the shaft at the bottom of the vibrator. It should be tight on the flat of the shaft. Check for excessive looseness of the vibrator on its shaft. Turn the vibrator on. As vibration is increased listen for the harsh metallic impact sound of the armature hitting the pole. This condition impairs uniform particle feeding. If the condition occurs at a low vibrator setting (below about 7 on the potentiometer scale) or if maximum vibration is weak, the vibrator should be adjusted . The adjustment procedure is as follows:

(a) Remove the vibrator from the feed assembly. (b) Connect a 0-100 milliamperes A. C. meter in series with the vibrator . (c) Remove the cover. (d) Loosen the black knurled nylon nut at the front 112 tum while holding

the slotted rear of the vibrator shaft with a screwdriver. Turn the current on. During the adjustment procedure current should be below 80 milliamperes to prevent overheating.

(e) Adjust the white nylon nut at the back so that at a vibration setting of about 8.0 the armature and pole just miss. The slotted back end of the vibrator shaft must again be held with a screwdriver during this adjustment.

(f) Adjust th e black knurled nylon nut until minimum axial clearance of the armature is obtained without decreasing vibration amplitude.

(g) Adjust the black knurled nylon nut until minimum axial clearance of the armature is obtained without decreasing vibration amplitude.

(h) Remove the milliammeter. Replace the cover and mount the vibrator on the feed assembly.

Rev . 2/18/94

42

MOTES ON OPERA TlON FRANTZ ISODYNAMIC MAGNETI C

H. H. He .. P,inceton Un;"ersity

OF SEPARATOR

'1INTfD IN USA NOVUMtt , ...

More thon twenty years aga, Mr. Samuel G. Frantl saw the types of magnetic separators we wen using in ,he Cepartmen, of Geology and concluded that 0 greatly impro"ed seporolor cauld be mode by designing one, which at ony g!ven curren', hod 0 magnetic pull of uniform strength in ,he orea in which the Sl 'porolion was to be performed. This resulted in conl,ruclion of 0 pilol model of ,he Isodynom ic separator which was lried out ot Princeton ond proved 10 be high ly suceessful. Sinee Ihen, 0 Fron'1 separator h05 been in olmOSI eon'InUOV5 use in Ihi5 deport men' ond 'en5 of ,hausands of seporolions hove been mode.

While il takes little more thon eommon sense 10 operote ,his instrumen', Ihere are 0 few 'rick s leorned over ,he course of yeors whieh are perhops worlh possing on. Furlhermore,l 'his occounl will indieo'e ,he vorie,y of uses '0 whieh the instrumenl hos been put. PREPARATION OF SAMPLE FOR SEPARATION. In general, ,he sompie should be ot least roughly siled. Ordinorily, separations are mode in the range -80 '0 ... 100 or -100 to ... 120 mesh, Thirty mesh is obovt ,he lorgest sile on whieh sepo rotlons are eonvenien' ond *400 mesh obout the smollest, Wi,h ,he finer siles, diffieulties moy be encountered from eleclrostotic charge on Ihe porticles ond eonsequent "bolling vp". If, however, ,he sompie eon be disoggregoted. good separations con be mod: '0 perhops 400 mesh. For routine separations neor, for exomple, 100 mesh, it is odvisoble 10 wosh the scomple before treatment in order 10 remave dust odhering to Ihe grains. Thil is ordinorily done by stirring ,he somple in 0 beoker of woler, ollowing it 10 senle for 20 s.eonds ond deconting ,he WOler severol times. If ,he grains are dust eooted, the quolity of the separation is often mOle,iolly reduced.

Magnetite or iran filings, from previous erushing in on iran mortor, must be removed wi,h 0 hand magnet before Ihe sompie il ploced in ,he separator. Ei,her of ,hese will stie~ :, . ,L !Jole pieces of Ihe mognel ond moy block free flow of the sompie down Ihe chule. !~: ... Hli ' ~\o should be r.moved before woshing Ihe sompie 10 ovoid s,oinin9 of ,he grains by iran oxide. A smoll olnieo magnet, wropped in pC'per cornbt.d 'hrough ,he sompie un,il no more magnetite o. iran il pieked up, is sOlisfoclory fo r this :>-.. JiminoJry step.

LHSTRU"EH_Lj];n!HGL!,OR~ :~"~~IL~l'j WITH THE CHUTE~ In diseussing in~1rument settings, 1h~ dirt.-ction at fighl ongles 10 Ihe length of the chute v.' ill be eolled lide Ilope ond parallel to the I:mgth, forward slope. Norrnolly, 0 lide slope o~ C'I-'?roxi-motely 20 0 is v,ed ond 0 forward 110"" nt.o, 30 0 ,. Alleeper forward Ilope moy couse the ijroins 10 bounee when eoaTser grain Si1,, '; (re being leparoted whereos tao smol! 0 Ilop. witf, finer grain liles will impede free flow Ol ;he Iampie down the ehute. A sotilfoetory setting c"" .as i Iy be determined by trio I ond e. (or. $mo 11., 1 ide slopes (2 0 _ 1 0 0) are used tc s',,...oro'. the minerols wilh very Imoll mognetie suscep'ibilities whieh would separate on ,he n(nmognetic lide of the chute 01 0 20 D side slope ond maximum curren'

vol ...... 0'. not 01 oll c"ticol. for .... a.d .. Iop ....

Mon.,. o,h er lobe.Ola .... " ho ... b " ", ... d 01 P,incefon. ,h 10 c ,0 ISO "d ... Iop ond .... 011.,

APPENDIX A

- 2 -

Rate of flow i. confroll.d by screwinv Ih. input funnel up or down. TIt. proper rot. of 110 ... of ,he sompl. down fh. chut. CO" b. judged by .ye oft.r CI littl. proc'ic. . Uain9 CI -100 mes h C-+ 120 muh powd.r, CI rot. of 1 102 ce per minute wauld b. normal for CI JOGfotward ,Iope. Rap id "--initiol separations such os th. removal of 90"0 quortt plus f.ldspor Irom CI rock in which i' is desir.cI 10 concentrot. CI magnetic minerol presen' in small omount, CO" be mode af CI rot. of 5 ce per minute. F i"ol purificotion of Ihe desir.cI mineral wauld b. mode 01 perhops 0.3 ce per minute. Finer powd.r, will flo .... 01 some ..... hot lido ..... e, rotes ond eClots., of foster. Th. ,hicknes. of ,he streom of po ..... d., .hauld be kept ,he some os it wos in Ih. cose of Ihe 100 mesh powder for the rates given ahove. Simi!arly 0 sleeper for .... ord stope will increase rOle of flo .... or 0 gentier slope decrease it. A 1 cc -100 mesh 120 muh somple can he prepared and pass.d through ,he seI'-arotor .... ith 0 30 for .... ord slope at variovs rotes to hecome fomilior .... ith the optimvm stream thicknesses. Once hoy,ng ohseryed ,he proper streoIT' thic\.:ness, there is no difficulty in adjuI'-jng Ihe Ho .... for ony gro,n sile or Ilope to conform 10 this thickness.

EXAMPLES ILLUSTRATING USE OF SEPARATOR

1. SEPA.RA. TlON OF ONE MINERA.L FROM A. GROUP OF MINERA.LS OF A.N ICNEOUS ROCK. The eommenest use 'e .... hlch .... e heye pul ,he separotor is 10 iselote one or mere minerals from on ign eous re ck for ehem,cal analysis of 'hot mineral or minerals. It is usually necessary '0 oh-tain 0 eancentra'e beller ,hon 99.5OC pure. For 0 yery slo .... ly cooled rock {plvtenie ) lhe minerals will erdinorily hoye 0 yery small ronge of composition voriatien and henee 0 smell range of mag-netie susceptibility yarietien. For ropidly coaled recks, the 10ning or composition variation is likely '0 he much greoter and Ihe megnetic susceptibili'y ronges of ,he minereIs .... il1 he propar lionolly lorger so ,hot clean seporolions become more diHicult.

Let us suppose 0 roc k contains minerols A. B, C ond 0 in erder of deereosing mognetic suseep' tibili'Y. It is desired 10 meke 0 pure seporalion of mineral C. A smoll sampie, perhops 1 cc of Ihe po .... der. is used for 0 ,rial separation. The sompie is rvn through the separotor r.p.atedly, increasing the CUTTent by smoll inerements on eoch run until C first oppears in the magnetic con centrote. The CUTTen! is fvrther increosed vnli! no more of C oppeors on the nonmognetic side . This eltoblishes the ronge of mognetic suseeptihilily of the desired mineral. Let us suppose thot Ihe minerol first oppeors on ,he mognetie side ot 0.64 Amps ond that it disoppeored entirely hom the non.mognel ic side 01 0.72 Amps or 0 range fr om 0.64 to 0.72 Amps. AI 0 rule, Ihe ex tremes of the range represent grains .... ith inclusions or comhined grains. A :a.;porotion is ,he" ottempted hy removing Ihe magne,ic fraetion ot 0.66 Amps ond the nenmogn.tic hoc'ion ot 0.70 Amps . The magnetic eoncentrole from Ihe lost separolion shovld .... ilh ruck b. pure mineral C. If 0 minute omoun' of impurity is present. Ihe last t .... o separations ore repeoted seyerol firnes 01 o very slo .... rote of He .... through Ihe seporolor. If Ihe concentrote is still nol sufficiently pure. it is crulhed te 0 some .... hot smol'er groin sile ond Ihe mognetic separotions repeoled.

2. SEPARATION OF THE CONSTITUENTS OF A ROCK TO DETERMINE THE QUANTITIES OF THE VA.RIOUS CONSTITUENTS.

Under favorable conditiens, .... here 0 clean seporotio" ef Ihe yorious phosel presenl is possible, the .... eight per cents of Ihe eonstituents con be determ ined after mognetic seporotions. After crushing, the sampie musl he split in hoctions by screening ond eoeh froctien seporoted inde pendently . It il imporlonl 10 run Ihe finest froclien, Ihe "dust", through os ..... 11 os Ihe coarser froctions. Inosmvch os seme minerals .... ill erush mere eesily ,hen others, oll lile froelie"s mv sI be seperoted ond .... eighed if the 'rue proportions in ,he rock are 10 be fovnd. The p'-ecision of such on analysis is not yery hi9h hut it ohen con be oceemplished more ropidly thon other forms ef velumetrie onolysis ond so moy be yery useful .... here such 0 degree of preeision is oeeeptobie. ("

- 3 -

3. SEPARATION OF MINERALS IN HEAVY MINERAL COHCEHTRATES OF SANDS OR ROCKS AHO INSOLUBLE RESIOUES OF LIMESTOHES.

If it is desired 10 separaTe 0 pellicular mineral or minerals cleonly frorn 0 heavy mineral conce" Irote or on Insoluble resldue, Ihe procedure ;5 Ihe same os in co se 1, Ihe seporation of 0 mineral from on igneous rock. As 0 ruhe, ,his is more difflcult 10 occomplish Ihon in cose I, because Ihe minerol grotns have pTobobly been derlved /rom 0 number of different sourees ond conse Quenlly ore likely 10 have Q Wi der range of compOSl'lons ond k enee 01 mognetic susceptibili'les.

In ,hiS loborotory, heovy mineral tanCenHafe:; Ofe olwoys split Inlo S.X mognetic froctions 10 enhonce rap id ,denld,callon. Mony ~Olrs of m'l"Ierols wh,eh eould eos.ly be eOl"llused by mere oOl,eol eXC","'OI'OI"l foll 11"110 diHerel"l1 magnel,e !rOCl'OI"l", For exomole, greel"l ehlofltold moy eosd y be m'Slokel"l for hornblel"lde or ehlollle. But, ehlofllo.d of In,s color, olmost ,nvoflobly folls 11"10 more mognel,e froet,ol"l Ihon Ihe other 1 .... 0.

A 11000' oi one m,ner'J l moy moke ,I eid/,cult 10 I.l"Id ,he a lher m,nerols oresenl "'I the SUite. ~ognel'c seporct,on so Ihot most, ,I nOI oll, 01 Ih,s m,"ercl ,s . ,solol ee i" one magneTic Iroelio", mokes ,I eos y 10 I'Md oll o ther m,nerols 'n the su,le excepl those in the one /roel,on conloining Ihe lIood. Teble 1 wos mode up from lang expeflence ,n observ,ng the d,str,butlon 01 minerols .n ,he mognel le /roe:,on5 of seooroted heovy m,nerol co"centrotes. The toble IS nOl in follible bul g,ves Ihe normo l POSitions of common mll"le.o Js ,n ,he mogneTlc !roCI,ons.

In c e. lo,n geolog,col slud.es, ,I IS somellmes .equlfed 10 dele.mine whelher 0 certo,n minerol ' s oreseMI or nOl ,n Ihe sude even Ihough the mlne.ol moy be present In the cencenl.ote to the ex tenl 01 on ly OMe g'oln ," 10,000. Sy exom,n,ng 0 certOIn limit ed mognetic /roct'on, coneenTre Ilon 01 the deslfed mlne.ol 100 fold moy ohen be otto.ned. Wh,le 1 groln in 10,000 mey eosi ly be ove.looked, 1 gro,n ," 100 wo!lolmost eertol"ly be lound .

... MAGHETIC CONCEHTRATES FROM SANDS A"'D SEOIMEHTARY ROCKS. In Slrotlgroph'e 51udy 01 sediments, heovy m,"erol eoneeMtroles moy be exomlned to determine Ihe souree or Sourtes of Ihe SI:dimenls. Heovy liquid seporotlons require on hour or more 10 moke so thol it moy be prohibll.ve in time 10 study lorg e numbers of somples in this monner. Almost 011 01 Ihe informot,on requlfed eon u5uolly be obtoined by s'ud y 01 the mognetic conee'" trote from Ihe rocks. Routine seoorolion of Ihe mognetie eeneenlrole split into d froetions con ord lnordy be done ," 5 m,nute .. ond thus mokes study of lorge numbers of .. "mples quite leosible. 5. OIAMAGNETIC SEPARATION USING THE IHCLlNEO CHUTE. I! the side sloDe 's .eversed fra m the usuol sett.ng se thot It slonls forword 2=or 3~ fother then bockward, diomognel lc seeo.otions eon be mode. Th,s wos tried on 0 zirton h.:och sand concen Irote, 01 1.2 Amp .. w,lh 0 2 r slope qUOrtl ond 0 li ftle lireon sepofol ..

Magnetite

Pyrrhotite

- 4 -

Toble

COMMON HEAVY MINERALS IN S~DI~ENTARY ROC~S A~~AHf!~~!t'~_~ROUPS BAS~O OH MASS MA~~ETIC S~~CEPTI~!LlT-L..:..

S i d e

B ",ogn.tic

ot O.~ ""'P'

Ilmenite

Gornet

Olivine

Chromite

Chloritoid

S I p ~ 1 0 0

C mogn~lic

01 0.8 ""'ps.

Hornblende

Hy per sthene

Augite

Actinolite

Stourol ile

Epidote

Biotite

Chlorite

T ourmoline

(dark)

o magnelic

al 1.2 "mps

Oiopside

Trel'lolite

Enslotile

Spinel

Stourolite

(light)

Muscovile

Zoisite

Clinozoisite

T ourmoline

(light)

S i d e

E lT'o9n~lic

01 1.2 "mps

Sphene

LeuCOJlene

Apatite

Andalusite

Manolite

Xenotine

Siope 5 ._-------

F nonmagnelic al 1.2 .mps .~~ -~-_.~~

Z ircon

Rutile

Anatase

Arooki'e

Pyri fe

Corundum

TopoI

Fluorite

Kyanite

Sillimonite

Anhydrite

Beryl

F moy b. further suLdi,,jd.d by d.cr.asin9 Ih. ,id. slope or rever,ing it 10 ,.porot. diolllogn.tic min.rah

Ino.",uch 01 mine,ols "0" confld .. obly ,n co"'pa.Uion. ,he, 01.0 "0', con,id.,obl, ,n ",09n,"C fu,c,p',bil,.y. An, 9',,n ""n .. ol mo, b. lound In ,0"" 9'OuP o,h ... hon ,,,,.d ,n ,h. lable. Th. 'able n ,el, ,nd,ca lel ,he IUl c ep"bilrly wh ich i.

uluolly lound .

- 5 -

7. SEPARA TlOtoiSo BY VERTICAL FREE FALL. Th e fr ee la ll 5el u p ' s a dvo n'o g e ous w h er e mo re rapid separallOfH or separatIons of lorger qUO"' ttl,es 01 mal e nal Ofl!' de sl re d. F ihy pounds on heu t moy be run through ,h e mogn et lC fl e ld. It 1$ 0150 pOrllculorly us e h.l lot d,omogn e tlc seporollons. The magnet 15 rctat e d 10 Ih e ve rlicol po ' SITlon emd glven CI 2:10 SCslooe forward ond downword. Fo, CI dlomognet,c se paration, Ih e lun-ne l '5 ,nserleC In Ihe forward hole 01 Ihe COfrier end odjusled 11'1 posiTIon 1.11'11.1 ;1 15 apprOXllnole ' Iy In Ih e plone of the forward loce of Ihe mognet poles. Suppes!!' 0 canc e nHaf e 01 llfcon, rulde end monoZlte Ofe 10 be s e parOlea. A high f,eld strength should be us e d (1.2 Amps . ) Th e d,o' magn e tit llfton w,ll be Inro .... n lorword os Illolls. Ihe rulde moy be ex pe cl e d 10 foll almost ver-I,colly. ond Ihe sllghtl y mognellC monozlle w.ll be ollrOCled bock lowo rds Ihe pole pr e ces. By oo ,usIl"1enl of Ihe pos"'on 01 Ine d,v,der below Ihe nognel, VOIIOUS CUIS moy be mode os desHe~ hom Ine lo li, ng SI'eom. For ony porr,cuior seDorOI,on. some 1"01 exoeflmenTOI,on 'n Ih e OOIUSI--erT cf Ine ::OOS"lon oi Ihe feed lunne . obove and d,Vlder below ' s ne cessoly. F ree fall does 1'101 g,"'e os cleon \eoorOl,ons os does '''e ' "cl,ned chule. I! 's olten C01'1ve"l,enl 10 moke::o !ree 1011, '00'0, l,rSI concer"rO le :rorr. 0 ia.;e somoi e . Tne concenfrOle con then be .eflned by Ihe nc i ,ned chule melhoO.

8, SE PAR ATI ON OF MA GNETITE F ROM COMPLE X IR ON ORES OR ROC KS. The ..,ognel 110 seI '1'1 Ihe "'erl,c:::d 005"'01'1 ond slonl",g steeoly downward ond forward. A piece of W'coo,ng cooe, '5 foslened over the s loplng sudace wo!h Scolch top e 01 d mony such s e aolo' "01'15 ore 10 be mode, on olum'l'Ium shee t tooeled 01 Ihe bollom 10 0 funnel ,s so oHix e d. The magnetite .:onlOln,ng sOr"'ole 's POUII!'~ :lown the sloDlng surface w,lr> 0 small curr e n! IIow1ng throug" !he mag"e!. The 1"10gnelile sllCo

i; , ,

- 6 -

FRANTZ ISODYNAMIC SEPARATOR MODEL L _ I

.:.c -:

9 , ,-7~ .--'

,

2-

EQU,o:I.TIO'\.

[XAMPU:

". . 20

~ -

'0 . ,

K 3e

." ~ . '0 .

,u,~c .

'0 _Iio

-.

' .0 .9 ., .7

.,

2

.,

.09

.00

.07 ~ .OG

.O~

:G"=o

z

" ~ u

NOMOGRAM - SIDE SLOPE - CURRENT - MASS SUSCEPTIBILITY

. OS

.2

. .,

.,

.l' . ,

.,

.9 '.0

.. ,

~ 2

~ 2.' l " , , 5 .,

" , -

8 9 >

" i;

' 5 ,

2C -~

25 ,'. e ",

lO < , l5 40 ,

< .e

'0 '0 '0 ge ' ce

-,---

..

..

.. 2::= -,

-or;-

F

,

)

Rev. 3/23/93

-------------- -

Aj--r--

FIG. P-2 t:~ AC SEM8LY F--DHOpo_" _

- ---

I G:

--J./ F

d B Appen ~x _ ;_ :"0/:; '?5'/, _

E

D

I ~JJJ

o

f----{ .K

Gi

c Gi

M

FIG. P-3

FOR STAW/.ESS STEEL d AWHIAiUJ.A CHUTtz:. ~NL Y

F=.=C HOPPER SUPPORT PI'Ff!S

Appendix B

Rev. 6 / 30 / 93

FIG. P-4 MOUNT/NG PLATE ASSE'vfE ' Y

FIG. NO. PAAT LETTER PART NAME PART NUMBER QUANT "MACH. P4 A MQUNTING PLATE 60 16 1 P4 B MQUNTING BOlT 6020 2 P4 e HAND SCREW ASSY. 56662 3 P4 0 NYLON SPACER BOL T 2 P4 E lOCATING PIN P4 F PAO 3

Appendix B

)

N()llftALLY ~t.."-eXccrr "x,-PIJ/i! ,ALVHIA/VH C#~ ONL..'(

FIG. P-5

CARRIAGE PLA TE ASSEMBLY

Appendix B

K E D e E

..

..

'1\ J

" "

F ' - ,

, _ .. ,-

\ \ ---_...-:-\.:-[]

.' .' H ~ .' r- " 0 0

L

0 ~- 0

~ Il -

== @ @ FIG. p- 6

BASE cf YOKE AS:;=M c ' v

Re v . 6/ 27 / 95 Appendix 3

Appendix B Rev. 10/11/95

Magnetic Barrier Laboratory Separator (Model LB-ll Chute Carriaae Assernblv

Assemblv and adiustment (References are to parts list drawing P-5)

The chute carriage assecbly serves to support the chute, the chute vibrator and the COnta1ners for receiving separated frae~~ons of mater~al. The chute is seeured tO the earriaqe by two thumb se=ews .... hich are screwed into the two posi tioning bol ts ( L 1. The pos1tioning ~olts and the blocks into which they are serewed t R J are at~ac~ec to alurninum spr1ng plates t J, MJ which are j01neC ~o matchec leaf spring assemblies. The vibrator is seeured to a Y shaped support member (Al, and its armature is attached to a sp=~ng

~lla 1:e ( H).

These chu1:e car=iage parts should be carefully assembled ana tiah1:1v secured so t.hat when the chute is attached it will be relat:..vely

fr~e of tors~on and will vibrate in a manner consistent with eont=olled oovement of particles on its sur:aee. The position of the chute 1n the gap is critical; its surface shou1d be at the midplane bet'",een the opposeci faces of the pole pieces. If it is not 50 placed the vibrat:..on amplitude that can be supplied without caus1ng a sur:aee of the chute tO strike a pole face is likely to ~e severely restr:..cted. Magnetic and gravitational force effeets may also be distorted.

The ree ommended procedure ~o= assembling the ?arts is as :ollows:

1. Connect the Y shaped vibrator support tAl to the uppe~ end of the carriage plate. The upper end of the carriage plate is mac~~ned to angle the vibrator support and vi~rator at an at~:..tude such ~hat the direetion of vibration impulses is upward at an angle of 20 to the surface of the chute. Connect the carr1age plate extension (C l to the carriage plate. Tighten the serews so that they hold the parts in place. Note, however, that minor adjust~ent of the pos~t:..on of parts is likely to be required tO complete the assembly procedure (See step 51. As a ~inal step, when the asser.'.::'ly is adjusted, all screws should be tightened with a torque wrenc:-. (See step 61.

2. Assemble the leaf springs (HJ with spr:'ng plates tJ , MI. Note ~hat there