mineral classifier inch mm massive tires for

wilfley table

The Wilfley table is a truly remarkable gold concentrating table first built on a preliminary scale in May 1895. The first full-sized table was built by Mr. A. R. Wilfley and was used in his own mill in Kokomo Colo., in May 1896. The first table sold for installation was placed in the Puzzle mill, Breckenridge, Summit County, Colo., in August 1896.

The mill enthusiasts at first hailed it as the cure for all the ills that flesh is heir to in the milling line. A little later it was found to make losses which were serious, and on this account, the table succeeded only to a limited extent in displacing the vanners of the gold-mills. Still later, mill-men in a number of districts throughout the country made special studies of the faults of the machine and devised a number of ways of grouping supplementary machines to overcome as far as possible the losses, and at the same time retain the benefit of the extraordinarily large capacity accompanied by the production of clean concentrates for which the machine has become so justly famous.

I hope to make an exhibit of some of these methods in an appendix to my book on ore-dressing which is now in preparation. These experimenters have not written up the subject, and if they possess all the facts they have not given them out for the benefit of the mining profession at large.

The object of this paper is to obtain the facts and to present them so clearly that their bearing can be seen by all. To this end, two complete series of tests have been planned. One (the present paper), to study the concentration of galena in presence of quartz; the other (to follow shortly), to study the concentration of chalcopyrite in presence of quartz.

Some authorities claim that the table does its best work when treating natural products; by this phrase, I mean products which have been crushed to pass through a limiting sieve, but have had no other preparation whatever; in consequence, they have all sizes of grains of both the heavy valuable mineral and the light waste gangue, ranging from the largest grains that can pass through the sieve down to the finest dust.

Others claim that the ore fed to a Wilfley table should be closely sized before it is fed. That is to say, it should be divided by a series of sieves ranging from coarse to fine into a series of products with sizes of grain ranging from coarse grains to fine grains; and that each of these products, in which the grains of the heavy mineral are of approximately the same diameter as the grains of the light mineral, should be fed to the Wilfley table.

Still, the third group of authorities claims that the ore before being fed to a Wilfley table should be classified by a hydraulic classifier, which divides the crushed ore into a series of products ranging, like the sized products, from coarse grains to fine grains, by carrying it in a water-current over a series of apertures or vertical pipes, called sorting-columns, up through which water-currents are passing. These currents are graded from faster to slower, and therefore allow only the heaviest grains to settle down through the first sorting column and out through the spigot, while lighter smaller grains settle in the second, and still lighter in the third, and so on, diminishing until the last sorting-column and spigot give very small grains, and the overflow has the finest grains of all. The classified products differ greatly from the sized products in that the grains of the heavy mineral is much smaller in diameter than the light grains with which they settle, and therefore behave in a somewhat different way upon the Wilfley table from the sized products. It should be said that the first spigot-product of a classifier differs from the others in having coarse grains of the heavy mineral present also.

The usual division of products upon a Wilfley table is easily and naturally made, as shown in Fig. 1, A being concentrates; B, middlings; C, tailings, and D, slimes. Of these, when natural products are fed, the concentrates, A, are nearly clean heavy mineral, slight contamination of small grains of quartz being present. The middlings, B, carry some large grains and also some small grains of heavy mineral. The tailings, C, carry some very small grains of heavy mineral, and the slimes, D, carry very minute grains of heavy mineral.

I believe that the small grains of heavy mineral in middlings, B, and tailings, C, is of less diameter than the smallest in the concentrates, A, and of greater diameter than the majority in the slimes, D and that they belong in middlings and tailings from the law of their existence. The re-running of such middlings upon the same table is therefore not a wise proceeding, and only admissible as an expedient in small establishments when the quantity of middlings is not sufficient to warrant other provision. So much for the speculation before the investigation was made.

The materials for this test were pure white massive quartz for the light mineral, and crystalline galena, nearly free from blende and other impurities, from Joplin, Mo., for the heavy mineral. The quantities of these impurities were so small as to have little effect on the results. Both minerals were broken down to 2-mm. size, and mixed so as to have approximately 10 percent, of galena and 90 percent, of quartz.

TheWilfley tableused for the tests had a net working surface of 2 ft. by 4 ft. This is the table that has been found very satisfactory for students work at the Massachusetts Institute of Technology. An error is present to a slight extent in the full-sized table, 16 ft. long by 7 ft. wide, and to a serious extent in the small Wilfley testing table, 7 ft. long, found in some of the schools. It is due to tacking tapered riffle-cleats onto a linoleum plane surface, thereby making two planes: first, the roughing- plane over the riffle-cleats, E, Fig. 1; second, the cleaning-plane or part where there are no riffles, F, Fig. 1. These two planes make an angle with each other, or a slight trough, which heaps up the sands deeper than is wise along the line of the tips of the riffle-cleats. This error is completely overcome on the little table here used by cutting the riffles down into the wooden surface of the table. The roughing- and cleaning-planes are therefore one and the same plane. By observing this precaution I believe that this little table is able to do as good work as the full-sized table.

These figures represent the usual range used in practice. Seventeen runs in all were made; Nos. 1 to 5, inclusive, were made upon natural products, the several feed-products being 2 mm. to 0; 1 mm. to 0; 0.5 mm. to 0; 0.25 mm. to 0; and 2 mm. to 0. Run No. 5, although fed with the same size as No. 1, was fed at a different rate. In making these runs no effort was made to re-run the middlings; first, because the concentrates and tailings would both have been contaminated and would not have shown as well; second, because the middlings themselves would have undergone a change in composition. As a consequence of this ruling, the quantities of middlings appear abnormally large.

In these runs, the dividing line between concentrates and middlings was chosen so as to make concentrates nearly clean to the eye. The dividing line between middlings and tailings was chosen so as to keep all the large grains of heavy mineral in the middlings. The four productsconcentrates, middlings, tailings, and slimeswere sized on a series of sieves, and the quartz in them determined by dissolving out the galena in hydrochloric acid. The galena was determined by difference. Runs Nos. 6 to 11, inclusive, were all upon sized products, and the results obtained are given in Table II.

The total quantity weighed 33 kg., of which 30 kg. was quartz and 3 kg. was galena. The guiding was done simply to make clean concentrates and tailings. The middlings was in every case re-run until they could not be further reduced without contaminating the concentrates or thetailings. Where a sized ore is free from included grains and from any middleweight mineral, the feeding-back of the middlings on the same table is logically good practice, because the middlings product is simply a mixture of concentrates and tailings; therefore, they could be fed back on the same table and disappear entirely without harm to concentrates or tailings.

Runs Nos. 12 to 17, inclusive, were made upon sorted or classified products. The classifier, Fig. 2, had 12 closed spigots or blind spigots; that is to say, spigots that discharged sand into 2-gallon bottles as fast as it came but discharged no water. The sorting columns were of 0.5-in. pipe, squared at the top and 3 in. long. Expressed in mm. per second, the rising-currents in the successive sorting-columns were: 105, 85, 69, 55, 45, 36, 29, 23, 19, 15, 12, 10, respectively. The 13th spigot had no rising current, and it was simply a safety spigot to prevent any accumulation of sand that was too light to go down in the 12th and too heavy to go over into the overflow. This apparatus gives a set of products beautifully classified.

To define the classified products more completely, a small aliquot part of each was sized, photographed, and analyzed. The photograph, Fig. 3, shows to the eye the distribution of sizes in each spigot. Table III. shows the distribution of quartz and galena in the different sizes of each spigot. Expressed in mm., the sieve-sizes used were: 2.83, 2.49, 2.06,1.63, 1.44,1.27,1.10, 0.97, 0.84, 0.68, 0.57, 0.45, 0.36, 0.28, 0.24, 0.20,0.15,0.12,0.10,0.08. The middlings picked out and weighed for the first four spigots consisted of blende-galena included

grains, with some free blende-grains. Their use here is simply to show how nearly pure the galena was. The settling-ratios are of special interest; for example, at the foot of spigot No. 4 we have the settling-ratio, 3.26, which signifies that in spigot No. 4 the average diameter of the quartz-grains is 3.26 times the average diameter of the galena-grains. The method of computing these ratios is given in my paper, Close Sizing Before Jigging. It was thought wiser to combine the spigots

somewhat instead of making 12 separate runs; accordingly, the 6 runs were fed with products as follows; 1st spigot; 2nd spigot; 3rd and 4th together; 5th and 6th together; 7th, 8th, and 9th together; 10th, 11th, and 12th together.

Comparing the 17 runs as to the quantity of the products without looking at the quality, it will be noticed at once that the concentrates and tailings in runs Nos. 6 to 11 and Nos. 12 to 17 are very much larger in quantity than these products in runs Nos. 1 to 5; while the middlings is very much smaller in quantity.

A comprehensive table of all 17 runs is given in Table VII., which shows the proportions of concentrates, middlings, tailings and slimes in each, and also the percentage of galena and quartz in the various products.

In comparing the analyses of the concentrates of these five runs (Table VIII.), we see a very remarkable similarity in the behavior of the quartz and galena through all five runs. The coarser sizes and the finer sizes are almost clean galena, being nearly free from quartz. At a point somewhere a little below the middle, the quartz rises to a maximum, which in the first run reaches 18.99 percent, of quartz, in the third run reaches 7.38 percent, of quartz, and in the fifth run reaches 13.80 percent, of quartz.

Comparing the different analyses of the middlings (Table IX.), we find the galena among the very largest and smallest grains gives a very high percentage, and down to a little below the middle, the galena runs down to a very low percentage, while the quartz behaves just in the opposite way. This is analogous to the composition of the concentrates.

Comparing the tailings of the five runs (Table X.), we note that the galena appears only to a very slight degree in any of the tailings until we get down to the smaller sizes, and there we have figures that rise to an almost alarming size, the first run giving 17.5 percent, of galena in the finest size; the 2d, 17.8 percent.; the 5th run giving 12.17 percent, in the finest size.

The slimes (Table XI.), which have a serious quantity of material only in the finest size, have also a serious percentage of lead in that finest size. The other percentages of lead are generally much smaller. There are three exceptions, in the 2d, 3d, and 4th runs, where the percentages run high in the larger

Commenting upon runs Nos. 6 to 11 (Table XII.), as compared with runs Nos. 1 to 5, we note immediately that the concentrates all the way through are almost pure galena with scarcely any quartz, and the tailings are almost pure quartz and scarcely any galena. The middlings, as remarked before, are so small in quantity that they affect the runs but little, and when we consider that they can go directly back onto the table in the continuous run, they do not affect the result at all. This set of runs, Nos. 6 to 11, therefore appears to distance runs Nos. 1 to 5 in the competition. There is really no comparison since runs Nos. 1 to 5 are not in the same class with them.

Comparing the concentrates of runs Nos. 12 to 17 (Table XIII), we see in the first place an enormous heaping-up of concentrates in run No. 12. The weight, 49 tons, is more than double the weight of all the other live runs in this set put together. This heaping-up of the great number of concentrates on the table which treats the first spigot of a classifier is one of the prominent features of the use of a classifier in preparation for feeding Wilfley tables. If we look at the total percentage of galena and quartz in the concentrates of run No. 12 we see that they contain 99.26 percent, of galena and 0.74 percent, of quartz. This makes an extremely good showing and one that bids for favorable consideration of the classifier set.

Looking at the water spigots, that is to say, runs Nos. 13 to 17, inclusive, in the analyses, we see that the percentage of quartz looks high in the coarser sizes. This would seem a serious disadvantage if it were not for the fact that these products which have high percentages of quartz are so small in quantity that the quartz cuts scarcely any figure in the final percentage of quartz in the concentrates. Altogether this set

Looking at the middlings (Table XIV.), we see that the quantity is extremely small, and can be made to disappear in a continuous run by feeding them back onto the table without harming either the concentrates or the tailings. They have, however, some very interesting features that are worthy of note. The galena in the 12th run runs high in the coarse and in the fine and very low in the middle sizes, there being a great heaping-up of quartz in this part. This same point is true in the 16th and 17th runs to a very marked degree. It is again true to a less marked degree in the 14th and 15th runs, and it appears not to be true at all in the 13th run.

Looking at the tailings (Table XV.), we see that run No. 12 stands out pre-eminent, having only 0.29 percent, of galena in the whole tailings, and the tailings of runs Nos. 13 to 17 are very low in galena, and would probably pass in any concentrating establishment.

We have one feature here which does not and cannot happen in sized runs, Nos. 6 to 11viz., the tailings get richer in galena down to the finer sizes; but when we look at the tonnage we find that there is scarcely any weight of material down in those sizes, and therefore this loss is not serious and does not bring up the percentage of galena in the final tailings to a serious extent.

Fig. 4 is an ideal sketch of what happens at the discharging corner of a Wilfley table. Running from coarse on the lower edge to fine on the upper, A, B, C, D, F, F, G, and H represent the different sizes of galena. It appears that they arrange themselves approximately according to this order on the Wilfley table. In like manner, the quartz-grains arrange themselves approximately in order of size, beginning at the lower edge with the largest grade and running smaller and smaller upwards, as indicated by the letters I, J, K, L, M, N, O, and P. The slimes at once take off the galena (H), and the quartz (P). These finest of all grains have not sufficient weight to hold them up to the upper edge, where mathematical logic would place them. They, therefore, go into the slimes. The. next grade, G (galena), and O (quartz), are not fine enough to

go into the slimes nor coarse enough to stand up against the water-current in the position shown in the sketch. These grains are found, therefore, sprinkled through the concentrates, middling, and tailings. See the heaping-up of galena in the small sizes in Tables VIII., IX., and X.

6 to 11, and 12 to 17, and to see why it is that runs Nos. 6 to 11 and Nos. 12 to 17 are so much better than runs Nos. 1 to 5. Runs Nos. 1 to 5 take the products just as they are shown in Rig. 4 and give galena, C, D, E, F, in the concentrates contaminated by quartz, (N). See the heaping-up of the quartz a little below the middle size in Table VIII., and the middlings that gives quartz, K, L, and M, contaminated by galena, A, B, C, and G. See the heaping-up of galena among the large grains and among the small grains in Table IX., and the tailings have in them the quartz, I, J, and 0, contaminated by galena, G. See the heaping-up of galena in the fine sizes in Table X. Runs Nos. 6 to 11, on the other hand, have put together on the coarse table, quartz, I, and galena, A, which have nothing whatever to do with one another (see Table XII.), and therefore make almost 100 percent, of galena in the concentrates, and almost 100 percent, of quartz in the tailings. The little accidental middling-product, simply being the dividing line between the two products, goes back on the table and disappears. On the second table, we treat quartz, J, and galena, B, with the same result. On the third table, we treat quartz, K, and galena, C, with the same result. On the fourth table quartz, L, and galena, D; on the fifth table quartz, M, and galena, E; on the sixth table quartz, N, and galena, F. There seems no reason logically why these should not turn out 100 percent, of galena in the concentrates and 100 percent, of quartz in the tailings. The probable reason why we did not obtain those figures was that the accidental flat scales and the fine abrasions of galena went where they should not.

Going to the third set of runs, Nos. 12 to 17, we need to bring in an ideal picture of the products of a classifier by means of Fig. 5. Suppose, for example, that we drop into a tall tube of water grains of quartz ranging from our maximum size down to zero, and grains of galena in the same way, and that these grains are of approximately the same shape, then the rate of settling of these grains may be stated in the following terms: the larger grains of a single mineral will settle faster than the smaller grains; and when we compare the two gravities of quartz and galena, the higher gravity will settle faster than the lower gravity for the same size. So definite is this law that if we look for equal-settling particles, we shall find that the grain of quartz which is equal-settling with the grain of galena is about 8 or 4 times the diameter of the grain of galena. See settling ratios in Table III. We may, therefore, construct the ideal diagram, Fig. 5, and we can draw a set of horizontal lines across it, putting the equal-settling grains together, ranging from the heavier grains of the first spigot in the lower part of the diagram up to the lighter grains of the finer spigot at the upper part of the diagram. We see then that spigot 1 contains a large amount of galena ranging from the coarsest size down to one-quarter the diameter of the coarsest quartz, and that the quartz is almost all in the coarse sizes. See spigot 1, Table III. This is exactly what we found in our run Xo. 12. See the heaping-up of galena in the large sizes in Table XIII.

Spigot 2 has small galena and large quartz, but both are a little smaller than those in spigot 1. Spigot 3, again, has small galena and larger quartz, but a little smaller than spigot 2, and so on up the scale with spigot 4, spigot 5, and spigot 6. See the heaping-up of galena in smaller sizes, Table XIII., and of quartz in larger sizes in Table XV.

Looking at our diagram, Fig. 5, to see what will happen when these several spigots are put upon the table, we shall find that run No. 12 receives galena, A, B, C, D, E, F, and F and quartz, I. Logically these have nothing to do with one another, and therefore should make for perfect separation. Spigot 2 fed in run No. 18 would have quartz, J, and galena, F2. Spigot 3 would have quartz, K, and galena, F3, and so on. Spigots 4, 5, and 6 could work their way up, having quartz always larger, and therefore belonging at a lower place on the table, and galena of smaller diameter belonging at a higher place on the table, making for clean separation of concentrates and tailings, with a middling product that can go directly back on the table and disappear. In proof of this, see points of heaping-up of galena and quartz in Tables XIII. and XV.

In the light of Fig. 4, comparing runs 12 to 17 with runs 6 to 11 we see that the natural lines for quartz and galena are farther apart for the classified products than for the sized products. For example, in run 12 the galena lines A to F average farther from the quartz I than does the galena A of run 6. Again, in run 13 the galena F is farther from quartz J than is the galena B from quartz, J in run 7. In like manner we may compare classified runs 14, 15, 16, and 17 with sized runs 8, 9, 10, and 11.

This demonstrates that with perfect classification the work will be better done on the Wilfley table than with sizing, and it also shows that with much middleweight mineral or included grains a good classifier will probably be more efficient than screens.

While the sized-product feed, as shown in Table VII., appears to have done better work than the classifier-product feed, if we give full weight to the great performance of run No. 12, we can agree that this has fully offset the slight falling- off of runs Nos. 13 to 17, and that the classifier-feed work is fully up to the sized-feed work on the Wilfley table, and with a perfect classifier the work will be better done than with screens.

The above paper, dealt with the behavior of a small Wilfley table when concentrating galena from quartz, the table being fed with natural products, with sized products, and with classified products. Since galena, having a specific gravity of 7.5, is among the heaviest minerals ordinarily concentrated by Wilfley table, it was desirable that a similar set of tests upon a mineral of lighter weight should be made. Chalcopyrite, of specific gravity of 4, would have been the best mineral for this purpose, on account of its great importance as an economic mineral, but in carrying out the test I was obliged to content myself with cupriferous pyrite, the specific gravity of which was 4.68 and the content in copper 8.80 percent. Through the kindness of H. o. Cummins, this material was obtained from Shasta, Cal. in a very pure, clean, homogeneous condition. It was broken by rolls to 2 mm. in size, taking care to make a minimum of slimes. The quartz used to mix with it was pure, white, New England quartz, broken in the same way to the same size.

In studying the accompanying tables, it should be borne in mind that the material concentrated was of low copper content, and in many cases, the quantity fed to the machine was 1 kg. or less. As a consequence of the smallness of the quantity treated it was very difficult to adjust the table and get it in condition to do its best work before the feed became exhausted, and for this reason, many results were obtained which appear irregular.

The material concentrated on the Wilfley table was a mixture of quartz and cupriferous pyrite; 16 test-runs were made. Runs Nos. 1 to 4 were on natural products of the following sizes: 2 mm. to 0,1 mm. to 0, 0.5 mm. to 0, and 0.25 mm. to 0, respectively. Runs Nos. 5 to 10 were on sized products.

A comparison of the results of a sized and classified feed with those of an unsized product (natural feed) is of interest. Table V. shows that both sized feed and classified feed give better results than natural feed in the percentage of copper which is easily and quickly saved in the concentrates. Furthermore, the tailings from the sized product are decidedly better than those from the classified product, although the latter does not carry a large percentage of the copper, and the tailings from both of these classes are better than those from the natural feed.

A comparison of Tables VIII. and XIII. shows that the percentage of values increases in the fine sizes of the natural-feed tailings and in the classifier-feed tailings just as it did in the tests with galena, but since the natural-feed tailings have tonsof products, while the classifier tailings have only a few pounds, the classifier again is more satisfactory than the natural feed.

Fig. 4 of my first paper. This sketch shows that sizing by sieves would send together to the first table, grains, J, quartz, and heavy mineral, A ; to the second table, grains, J, quartz, and heavy mineral, B, and so on. On the other hand, the perfect classifier would put together for the first table perhaps grains, I, quartz, and heavy mineral, A, B, C; for the second table, grains, J, quartz, and heavy mineral, D, and so on. The first table of the classifier set will then have no more difficult separation to make than the first table of the sized set, because the grains, I, and A, have their natural tendency to be the same distance apart in both cases. On the other hand, on the finer tables we see that the sized feed puts together grains, J, quartz, and heavy mineral, B, while the classified feed puts together grains, J, quartz, and heavy mineral, D. The natural distance apart of the two minerals, then, is much greater in the case of the classified feed than in the case of the sized feed. There remains only to design classifiers sufficiently perfect to realize this natural advantage of classified feed oversized feed as applied to the Wilfley table.

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is a fat tire bike easier to ride? read more and find out rock the outdoor life

Seeing a fat bike for the first time is often bewildering, mainly because it looks like a child bike with very fat tires. Unlike standard tires, the fat bike tires are usually between 3.8 inches to 5 inches or more. The distinguishing factor between mountain bikes and fat-tire bikes is that you can use the fat bikes on almost all terrains. This is because the bikes have very high suspension thanks to the low-pressure tires that allow them to float even on soft surfaces.

But how are fat tire bikes to ride? Well as you may have guessed from there wide tires they are harder to pedal. Most fat tire bikes will be about 15% to 20% harder to pedal then other bikes. But do to the extra-wide tires they are easier to balance on and alow them to go were other bikes cant.

The wideness of the fat bike tires gives them better traction on the most unstable terrains. This is because the low pressure allows them to cruise at relatively lower speeds compared to other bikes. The stability of the fat bikes is incomparable to any other bike cycle. Thats why there preferred by novice riders.

Whether you want to ride on the regular ground or even on the most impassable terrains, this bike should be your go-to. Besides, the wide tires give the bike better balance compared to other bikes with narrow tires.

It would seem impossible to go through sand or even snow coverd ground using standard bikes because they tend to sink in the soft fields. However, the thick tires give your bike cycle a larger surface area that enables you to remain afloat.

Its an undeniable fact that riding a fat bike requires much more muscle for pushing. You can, therefore, expect to use more energy riding a fat bike compared to other bikes. This is because the low pressure on the tires creates extra traction that makes it harder to get the tires moving.

Riding the bike on rough grounds, however, becomes more comfortable than on smoother terrains because the bikes are designed for these grounds. On the flip side, though, it can help you with your workouts because you lose more calories riding a fat bike than a standard bike. You even get to work out during the winter season because it can climb up the snow mountains without a hitch.

However, as you ride a fat bike on slippery grounds such as snow or sand, you can expect increased resistance requiring you to use a lot of energy to pedal. This is because the increased traction and low speeds do not give you the required momentum for a smooth ride.

The weight of the bike often determines how hard it is to pedal. The more massive a bike is, the more energy thats required to move it. Well, the good news is that you can get a relatively light fat bike that could make your cycling more comfortable. All you need to have is the right combination of tires and rims. If rims and tires are light, it makes cycling smooth.

Luckily these days, inventors have come up with carbon fiber rims and frames that are super light. However, these modifications come at an extra cost the lighter fat bikes cost more than the heavy ones. Of course, not everyone can afford them but they are well worth the investment.

Not everyone can afford to have a bike for every season and terrain. The fat bike is designed such that it can cruise on all these landscapes. Besides, a fat bike is relatively pricier compared to other narrow bikes. Therefore, the fact that it can be used anywhere makes it the ideal bike for all-season usage.

It is no wonder that these days you find so many fat bikes outside grocery stores and in the malls. However, if you love speed on the road, you might not achieve that with the fat bike. It may be slower, especially if you dont have the strength to pedal faster. The slow speed is due to the low pressure in the tires and deep treads meant for off-road landscapes. However, if you arent in a race with your friends, then you can use the bike to run your daily errands without a problem.

One way you can improve the speed of your fat bike while on the road is to increase the pressure of the tires. It isnt recommended that you put the pressure above 25 psi in the tire because it could create an imbalance with your bike.

If you want a faster bike, then opt for a mountain bike because the fat bike has a lot of rolling resistance. This implies that you have to use a lot of energy to pedal and also, when going uphill, the pedaling can be tedious.

The mountain bike, on the other hand, has thinner tires that make riding faster and easier. However, if you want comfort and fun, then the fat bikes make a better choice. The thick tires and rims offer better shock absorption especially when going through rough paths.

If youre a newbie rider, the fat bike is a good option because it gives you the stability, comfort, and fun of riding all year round, albeit the slow speed. The mountain bike despite being fast has lower suspension and shock absorption which makes riding a little bumpy especially on rough surfaces.

The first thing to consider should be the floatation of your bike. The thickness of the tires and rims determines how well your bike can float on soft surfaces. If you want a bike to use on rough, sandy, or snowy terrains then get one with the widest tires that you can get. However, if you want a bike to use around your home, then you dont need the fat tire bikes with extra width on the tires.

The rims of the bike also affect floatation depending on their thickness. Ideally, the rims should fit well in the fat tires to avoid deformation of the tire shape, which could lead to instability. For instance, a 3.8-4 inch tire can fit a rim between 65-80 mm wide. All rims have widths ranging between 65 mm to 105 mm. As such, its upon you to identify one that perfectly fits into your tires.

The frame of a fat bike cannot sustain a conventional braking system. Therefore, most fat bikes use mechanical disc brakes that are harder to service and maintain. Some manufacturers also use of hydraulic brakes.

Hydraulic brakes are, however not suitable for all regions especially if the brakes make use of mineral oil. Mineral oil tends to have a high operating temperature and can quickly freeze in cold temperatures.

Depending on your weight and height, you have to choose a bike that suits your needs. Most fat-tire bicycles have rigid frames that make your standover height rise. The carbon fiber frames come in about 4 sizes to choose from. The other heavier fat bikes also come in many different sizes that allow you to choose one that gives you maximum comfort.

Gears are an essential component of a fat bike. Ideally, you should get a bike with a range of gears. Its near impossible to get started in a high gearing because of the increased traction from the wide tires. Therefore, ensure that the bike has low gears to improve comfort as you pedal.

The suspension of a fat bike is vital, especially if the bike is meant for harsh landscapes. Most fat bicycles have a rigid suspension that makes it comfortable to use when going over rough surfaces such as tree stumps or rocks.

However, there still exist some front and full suspension bikes in the market. Depending on where you want to use your bike, choose accordingly. Its also worth noting that suspension in the fat bikes leads to the increased weight of the bike as well as the need for maintenance.

Most fat bike frames are made of steel, titanium, or carbon fiber. The steel frames are most preferred, especially if you need to use it in your location on specialized pathways. The steel frames can be easily repaired even in your location. The titanium framed fat bikes are rare but still exist. Titanium frames are light in weight making them ideal for smooth terrains.

Most bike companies have now started producing carbon fiber frames for fat bikes. The carbon gives the bike little weight which is easier to handle especially when going uphill. Depending on where you want to ride the bike, make sure to choose one with an ideal frame.

Fat bikes are not just a trend but bicycles that you can use at any time of the year due to their versatility. The bikes are relatively slower than mountain bikes and require more muscle to pedal. However, the thick tires and rims give the bike better traction which makes it ideal for rough surfaces. Most importantly, fat bikes are fun and comfortable to ride since they have better shock absorption mechanisms.

You decided to take up a new hobby and you have it narrowed down to either kayaking or paddle boarding. There both good hobbies. Both get you outside and both get you out on the water as well as...

Hi and welcome to RockTheOutdoorLife.com. My name is Jayson and Ive long been a outdoor enthusiast, I love being outside weather it biking, kayaking of just going on a hike. Im not someone that likes to spend me free time in the house. Even if Im home Im outside doing something like cook on the grill. So I started this site to share all Ive learned over the years and some things Im still learning. I hope you find the information on my site helpful.

Hi and welcome to RockTheOutdoorLife.com. My name is Jayson and Ive long been a outdoor enthusiast, I love being outside weather it biking, kayaking of just going on a hike. Im not someone that likes to spend me free time in the house. Even if Im home Im outside doing something like cook on the grill. So I started this site to share all Ive learned over the years and some things Im still learning. I hope you find the information on my site helpful.

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This site is owned and operated by Jayson C. RockTheOutdoorLife.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com. This site also participates in other affiliate programs and is compensated for referring traffic and business to these companies.

double roll crusher

For sale with its 8 inch by 3 inch rolls, the 911MPERC8C is the finest laboratory double roll crusherChina has. It is massive and of top quality!Crushing by the Double-Roll Crusher is primarily accomplished by compression andconsist of two heavy metal rolls of equal diameter placed horizontally which are rotated towards each other at same or at different speeds. The rolls are mounted on heavy shafts. One of the rolls is motor driven while the other roll rotates due to friction. The gap between the two rolls is adjustable because of two reasonsthe product size is determined by the size of the gap between the rolls and to compensate for wear. The rolls have narrow faces and are large in diameter so that they can squeeze sharply (nip) the large lumps. The roll surfaces of the Double-Roll Crusher are smooth. The materials to be crushed are fed from the top. As the rolls rotate they are nipped between them and get crushed by compression, and are discharged from the bottom. Compression crushing is extremely efficient, as energy is only used to crush those particles larger than the gap between the rolls. Fines are minimised because already crushed materials pass freely through the crusher with no further size reduction. The speed of rolls can vary but is fixed on this model. These machines give a reduction ratio of 4 to 1 with few fines. The double-roll crushers accept feed sizes up to 10 mm, though larger feed can be effectively handled in certain applications. The machine is protected against damage due to unbreakable materials like nut or bolts, by spring mounting at least one of the rolls. It retracts instantly when an unbreakable is encountered, then reverts to its original position once the unbreakable passes through the crushing chamber with no stoppage of the crusher. Advantages of this double roll crusher:

roll crusher - an overview | sciencedirect topics

Roll crushers are generally not used as primary crushers for hard ores. Even for softer ores, such as chalcocite and chalcopyrite, they have been used as secondary crushers. Choke feeding is not advisable as it tends to produce particles of irregular size. Both open and closed circuit crushing is employed. For close circuit the product is screened with a mesh size much less than the set.

Figure6.4 is a typical set-up where ores crushed in primary and secondary crushers are further reduced in size by a rough roll crusher in an open circuit followed by finer size reduction in a closed circuit by a roll crusher. Such circuits are chosen as the feed size to standard roll crushers normally does not exceed 50mm.

A distinct class of roll crushers is referred to as sizers. These are more heavily constructed units with slower rotation, and direct drive of the rolls rather than belt drives. They have a lower profile, allowing material to be easily fed by loaders, and are a good choice for portable crushers at the mine that reduce the coal in size for conveying to the preparation plant. An example of these units is shown in Fig.9.4.

9.4. (a) Primary sizer with attached feeder. The large motors and gearboxes drive the relatively low-speed toothed rolls that break the coal. (b) Haulage truck dumping coal directly into the feed hopper for a primary sizer, which discharges onto a product belt. (c) Tertiary sizer for crushing coal to the desired size for a preparation plant.

Their lower speeds are claimed to reduce fines generation, while lending themselves to high throughput applications. Sizers can either have the rolls rotate towards each other to carry feed between the rolls to be broken, or can be constructed as tertiary sizers with the rolls rotating away from each other. With tertiary sizers, feed coal is added between the rolls, and much of the fine material falls through. The coarser material is then carried to the outside to be broken against fixed sizing combs. This design increases the capacity by producing two main product streams instead of one, and also minimizes overcrushing by removing a large fraction of the fines. Tertiary sizer capacities range from 440 tons/h (400 metric tons/h) for 2448 inch (61122cm) rolls producing a 2-inch (5cm) product, up to 3968 tons/h (3600 metric tons/h) for 2096 inch (51244cm) rolls producing a 10-inch (25cm) product (Alderman and Edmiston, 2010).

A typical coal handling package using sizers would comprise a dump pocket discharging to a primary sizer discharging to a product belt, as shown in Fig.9.4b. This product belt would then feed a secondary or tertiary sizer, such as is shown in Fig.9.4c, which may include intermediate screening to remove product prior to subsequent stages of breakage. Typical size ranges would start with run-of-mine coal feeding to the primary sizer at 2000mm, and reducing to 350mm. The secondary sizer would receive this coal and discharge at a nominal 125mm, followed by a tertiary sizer/screen combination to generate a 50mm topsize preparation plant feed (FLSmidth, 2011).

The intermediate crushing in the cut roll crusher is mainly used for the crushing of brittle materials like concrete and clay sintered bricks, along with the compression of rough materials like wood and fabric (to avoid being too small in size) after the coarse (primary) crushing. The selective crushing in this process is good for the separation of impurities. Impact crushers are commonly applied in intermediate crushing. However, when used in crushing of mixed C&D waste, the wood and fabric materials will be broken and mixed in recycled aggregate materials by the high-speed operating rotors and are difficult to be separated.

Although not widely used in the minerals industry, roll crushers can be effective in handling friable, sticky, frozen, and less abrasive feeds, such as limestone, coal, chalk, gypsum, phosphate, and soft iron ores.

Roll crusher operation is fairly straightforward: the standard spring rolls consist of two horizontal cylinders that revolve toward each other (Figure 6.14(a)). The gap (closest distance between the rolls) is determined by shims which cause the spring-loaded roll to be held back from the fixed roll. Unlike jaw and gyratory crushers, where reduction is progressive by repeated nipping action as the material passes down to the discharge, the crushing process in rolls is one of single pressure.

Roll crushers are also manufactured with only one rotating cylinder (Figure 6.14(b)), which revolves toward a fixed plate. Other roll crushers use three, four, or six cylinders, although machines with more than two rolls are rare today. In some crushers the diameters and speeds of the rolls may differ. The rolls may be gear driven, but this limits the distance adjustment between the rolls. Modern rolls are driven by V-belts from separate motors.

The disadvantage of roll crushers is that, in order for reasonable reduction ratios to be achieved, very large rolls are required in relation to the size of the feed particles. They therefore have the highest capital cost of all crushers for a given throughput and reduction ratio.

The action of a roll crusher, compared to the other crushers, is amenable to a level of analysis. Consider a spherical particle of radius r, being crushed by a pair of rolls of radius R, the gap between the rolls being 2a (Figure 6.15). If is the coefficient of friction between the rolls and the particle, is the angle formed by the tangents to the roll surfaces at their points of contact with the particle (the angle of nip), and C is the compressive force exerted by the rolls acting from the roll centers through the particle center, then for a particle to be just gripped by the rolls, equating vertically, we derive:

The coefficient of friction between steel and most ore particles is in the range 0.20.3, so that the value of the angle of nip should never exceed about 30, or the particle will slip. It should also be noted that the value of the coefficient of friction decreases with speed, so that the speed of the rolls depends on the angle of nip, and the type of material being crushed. The larger the angle of nip (i.e., the coarser the feed), the slower the peripheral speed needs to be to allow the particle to be nipped. For smaller angles of nip (finer feeds), the roll speed can be increased, thereby increasing the capacity. Peripheral speeds vary between about 1ms1 for small rolls, up to about 15ms1 for the largest sizes of 1,800mm diameter upwards.

Equation 6.6 can be used to determine the maximum size of rock gripped in relation to roll diameter and the reduction ratio (r/a) required. Table 6.1 gives example values for 1,000mm roll diameter where the angle of nip should be less than 20 in order for the particles to be gripped (in most practical cases the angle of nip should not exceed about 25).

Unless very large diameter rolls are used, the angle of nip limits the reduction ratio of the crusher, and since reduction ratios greater than 4:1 are rare, a flowsheet may require coarse crushing rolls to be followed by fine rolls.

Smooth-surfaced rolls are usually used for fine crushing, whereas coarse crushing is often performed in rolls having corrugated surfaces, or with stub teeth arranged to present a chequered surface pattern. Sledging or slugger rolls have a series of intermeshing teeth, or slugs, protruding from the roll surfaces. These dig into the rock so that the action is a combination of compression and ripping, and large pieces in relation to the roll diameter can be handled. Toothed crushing rolls (Figure 6.16) are typically used for coarse crushing of soft or sticky iron ores, friable limestone or coal, where rolls of ca. 1m diameter are used to crush material of top size of ca. 400mm.

Wear on the roll surfaces is high and they often have a manganese steel tire, which can be replaced when worn. The feed must be spread uniformly over the whole width of the rolls in order to give even wear. One simple method is to use a flat feed belt of the same width as the rolls.

Since there is no provision for the swelling of broken ore in the crushing chamber, roll crushers must be starvation fed if they are to be prevented from choking. Although the floating roll should only yield to an uncrushable body, choked crushing causes so much pressure that the springs are continually activated during crushing, and some oversize escapes. Rolls should therefore be used in closed circuit with screens. Choked crushing also causes inter-particle comminution, which leads to the production of material finer than the gap of the crusher.

The objective of sample preparation is to prepare test samples from a parent sample or individual primary increments, Fig.5.19 for analysis. Sample preparation includes all procedures that a sample is subjected to in order to produce a reduced mass of sample (analysis sample) that is representative of the parent sample and from which subsamples of relatively small mass can be used directly for analysis. Samples for general analysis (proximate, ultimate, calorific value, total sulphur, etc.) are typically milled samples with 95% passing 0.212mm. Standard AS4264.1 stipulates that the minimum mass required for general analysis is 30g.

However, some laboratory analyses will require larger sample masses. Some examples from AS 4264.1 include Hardgrove grindability index (AS 1038.20) which requires 1kg at 4.75mm top size, and total moisture (AS 1038.1 Method A and B) 300g at 4mm. However, the principles of preparing a representative analysis sample from the original coal sample are the same.

Taking the ash determination as an example: 1g of coal is used in a single ash determination, and that 1g has to be representative of the coal sample. At a top size of 0.212mm the sampling constant, Ks, for most coals will be very small and this constant combined with a 1g mass of coal enables the variance contribution from the IH of the analysis sample to be almost insignificant and therefore a high level of precision can be expected.

Apart from exploration samples, most samples received by laboratories are from mechanical sampling systems at coal handling facilities at mine sites, ports or power stations. In some areas where coal is being sold across land boarders such as the MongolianChinese border, most samples will be extracted directly from haulage trucks. Many samples, such as ship loading samples and some coal preparation plant samples, are produced by multistage mechanical sampling systems. Other samples may be produced from single-stage samplers. As a result, laboratories can receive samples in a wide range of conditions, most importantly sample mass, moisture content and particle size distributions. Sample preparation procedures have to be tailored to suit the samples and the proposed testing and analyses procedures that the sample has been collected for.

In some instances the particle size reduction may be omitted before sample subdivision, for example at the first stage after collection of the primary increment. However, generally before subdivision (subsampling) the particle size should be reduced.

In each case at every stage, the process recognises the relationships between the number of increments, sample mass and particle size to sampling variance, as each stage is a standalone sampling exercise.

Hammers mills comprise a set of swinging hammers attached to a rotating shaft (Fig.5.22). Typically, they are fed a 4mm top size coal to produce analysis samples with >95% passing 0.212mm. They have a device for feeding the coal into the mill. This is often a screw-type feeder. They also usually have a screen on the outlet to ensure that the entire sample achieves a specific top size. Hammer mills tend to generate excessive fines and should not be used in some instances, such as preparation of samples for petrographic analysis and Hardgrove grindability index determination.

Ring mills comprise a cylindrical canister and lid, a steel ring, and a smaller steel cylinder that fits inside the canister (Fig.5.23). The coal is placed in the canister with the ring and the cylinder, and the lid is attached. This is then placed in a jig that moves the canister in a circular motion. The movement of the various metal components within the canister crushes the coal. There is some concern that these mills can become heated and that this may affect the coal quality, particularly CSN values. This type of mill is particularly useful for crushing low mass samples as sample loss is kept to a minimum. Automated ring mills have been in use in laboratories handling large sample volumes to ensure consistent milling and improved productivity.

Roll crushers are comprised of two steel cylinders (Fig.5.24). The coal is crushed as it passes between the cylinders. This type of crusher is useful when preparing samples with a minimum of fines generation.

Incremental division is a manual method of subdivision that can provide precise subsamples. This method requires that the coal is well mixed prior to division. The coal is spread onto a flat surface in the form of a rectangle in a thickness approximately three times the nominal top size of the sample. A grid pattern is marked out on the sample (usually composed of at least 20 rectangles in a 54 grid) and a single increment is obtained from each square. The increment is removed from the sample using a suitable scoop and bump plate to prevent the increment from falling out of the scoop. Incremental division is used almost exclusively in obtaining the final (0.212mm) laboratory sample after the hammer mill operation, because of excessive dust losses by other methods.

Rotary sample division (rsd) is the most common method for subdivision of large samples in coal laboratories. The rotary sample divider (Fig.5.25) comprises a feed hopper, a device for feeding the coal at a constant rate (usually a vibratory feeder) and a number of sector-shaped canisters formed into a cylinder on a rotating platform. The uniform coal stream produces a falling stream of coal that is collected in the rotating canisters, dividing the sample into representative parts.

As the coal particles move through the feed hopper there is a high potential that some segregation and grouping will occur. To counter the effect that this may having on sample preparation variance it is advisable to ensure that each canister cuts the falling stream at least 20 times, i.e. there are at least twenty rotations of the turntable as the coal flows into the canisters. Additionally, it is a good practice to combine material collected in two or more canisters to form the divided increment or subsample. When doing so, canisters that are opposite each other in the rotary sample divider should be selected for recombination. The machine pictured in Fig.5.25 is set to divide a sample into eight divisions. If the requirement was to extract a quarter of the sample for analysis, two of the 1/8th divisions would be recombined.

Riffles (Fig.5.26) are less regularly used in laboratories. Riffles divide the coal into halves by allowing the coal to fall through a set of parallel slots of uniform width. Adjacent slots feed opposite containers. The width of the slots should be at least three times the nominal top size of the coal. There should be at least eight slots for each half of the riffle.

Fractional shovelling may be used for subsampling when a large rotary sample divider is not available. In this process, the coal is formed into a conical heap. Successive shovels of coal are removed from the base of the heap and are placed into daughter heaps. The shovels of coal should be allocated consecutively and systematically to each daughter heap.

Shredding rubber waste reduces the volume of used tires. Generally, the cost of shredding increases with the need to obtain pieces as small as possible. For grinding, rubber wastes are initially processed through mechanical cutters, roll crushers and screw shredders. To obtain finer particles, shear crushers and granulators are used. The final processing of rubber wastes is with high-temperature shredding equipment, such as rotary shredders, where degradation occurs during compression simultaneously with shear and wear (Mikulionok, 2015). In the initial phase, shredding rubber wastes results in dimensions of approximately 7.6210.16cm. These pieces are then placed in cutters that reduce the size to 0.630.63cm (Rafique, 2012).

Granulators are used in the second step of the recycling process, where pieces of waste tyres are grinded in the large-sized granulators to produce a large quantity of granules. The use of pulverises can reduce the rubber granulated material into fine powder. The rubber particles size can range from a few micrometres up to centimetres.

Rotary Breakers (Fig. 1). The rotary breaker serves two functionsnamely, reduction in top size of ROM and rejection of oversize rock. It is an autogenous size-reduction device in which the feed material acts as crushing media.

Roll Crusher. For a given reduction ratio, single-roll crushers are capable of reducing ROM material to a product with a top size in the range of 20018mm in a single pass, depending upon the top size of the feed coal. Double-roll crushers consist of two rolls that rotate in opposite directions. Normally, one roll is fixed while the other roll is movable against spring pressure. This permits the passage of tramp material without damage to the unit. The drive units are normally equipped with shear pins for overload protection.

Process is designed to reduce the size of large pieces with minimum production of dust. Two main types of breakers are used in Great Britain, viz. (a) Pick Breaker and (b) Bradford Breaker. Other crushers commonly used are jaw crushers, roll crushers, disc crushers, cone crushers and hammer crushers.

Pick breakerdesigned to imitate the action of miners' picks. Strong pick blades are mounted rigidly on a solid steel frame moving slowly up and down. Coal passes under the picks on a slowly moving horizontal plate conveyor belt. The amount of breakage is roughly controlled by the height to which picks are raisedupper limit is 0.5 m Typical performances: 450 ton/hr with a 2-m-wide machine. Size reduction from 500 mm to 300 mm. Several machines may be placed in series, with screens in between to remove fines. Main advantageminimum production of fines can be achieved. Fines production is controlled by the diameter and spacing of picks. Reduction in diameter and increase in spacing, decrease the proportion of fines.

Bradford breakerScreens break and removes large pieces of accidental material, e.g. pit props, chains or tramp iron, in one operation. Consists essentially of a massive cylindrical screen or Trommel, with fins fitted longitudinally inside the screen. These raise the lumps of coal as the cylinder rotates, until they fall, break, and are screened. Unbroken material passes out of the end of the cylinder. Production of fines is also small. Capacity of machine: up to 600 ton/hr.

Blake jaw crusher. Consists of a heavy corrugated crushing plate, mounted vertically in a hollow rectangular frame. A similar moving plate (moving jaw) is attached at a suitable angle to a swinging lever, arranged so that the reciprocating movement opens and closes the gap between the plates, the greater movement being at the top. The machine is available with top opening up to 2 2.7 m. Usual capacity up to 300 ton/hr. Horsepower required: up to 150.

Corrugated and toothed roll crushers. Two heavily toothed, or corrugated, cylindrical rollers (Fig. 10.1) are mounted horizontally and revolve in opposite directions. (Towards each other at the top side or nip, one being spring loaded.) Alternatively, a single roll may revolve against a breaker plate. Capacity of a 1.5 m-long machine with a 300 mm opening and roll speed 40 r.p.m. is about 350 ton/hr, with a power consumption of about 200 h.p. Best results are obtained by the use of several rolls in series, with screens between.

Run-of-mine coal produced by mechanized mining operations contains particles as small as fine powder and as large as several hundred millimeters. Particles too large to pass into the plant are crushed to an appropriate upper size or rejected where insufficient recoverable coal is present in the coarse size fractions. Rotary breakers, jaw crushers, roll crushers, or sizers are used to achieve particle size reduction. Crushing may also improve the cleanability of the coal by liberating impurities locked within composite particles (called middlings) containing both organic and inorganic matter. The crushed material is then segregated into groups having well-defined maximum and minimum sizes. The sizing is achieved using various types of equipment including screens, sieves, and classifying cyclones. Screens are typically employed for sizing coarser particles, while various combinations of fine coal sieves and classifying cyclones are used for sizing finer particles. Figure 2 shows the typical sizes of particles that can be produced by common types of industrial sizing equipment.

The sponge masses as produced by vacuum distillation have to be prepared before melting. The nine ton mass of sponge has to be crushed to about 12mm size pieces. The sponge in contact with retort wall and the push plates have a high likelihood of contamination with iron and nickel since these metals are soluble in titanium. The top of the mass may also have some contamination of iron and nickel from reaction with the radiation shield and substoichiometeric chlorides. To remove this contamination the outer skin of the sponge mass is removed by use of powered chisels. This material is downgraded from aerospace use and used in less critical applications. The sponge mass then is sliced radially to one to 5cm sections with a large guillotine or similar blade. The bottom section of the mass is removed first as this likely has the most amount of iron incorporated into the sponge. The sponge mass is removed from the working table, so this material can be segregated from the balance of the mass. At this point the mass is placed back on the table, sliced and then sent to a crushing circuit. Titanium sponge is malleable material, thus traditional mineral processing equipment such as roll or jaw crushers are not as effective as high shear shredding machines such as rotary shears or single rotor/anvil shears in preparing sponge with limited very fine particle generation.

Dust generation in the crushing process is a very important aspect of operation. Control of the dust by collection and washing of equipment on a periodic basis is very important to reduce the risks of fire in the processing of sponge. Care has to be taken to avoid working on equipment when dust present as titanium metal fires are difficult to extinguish; a class D extinguisher or rock salt are used to suppress the first. The high temperature of the fire and the low melting point of iron-titanium eutectic can result in melting of equipment, supports or piping in these plants if a fire does occur.

The core of the sponge mass has the lowest level of metal contamination. To harvest the material for applications that need low iron and low nickel levels, it is necessary to core the mass. This is done in several ways; the mass can be upended and the guillotine blade can be used to remove thick layers of outer skin, or chisels can be used to remove the outer layers. Control of the lot by separation during the crushing campaign is used to separate the high-purity products from the normal grades of sponge. Control of the nickel level in the magnesium used in the reduction is also important. Removal of as much stainless steel in piping, retorts and metal reservoirs is also important, as nickel in the magnesium will be incorporated into the sponge. Small concentrations of nickel in magnesium can take a long time to be purged from the process. Control of the quality of magnesium used for make up in the VDP process is as important, as some magnesium can be contaminated with nickel during production. Iron is not as significant an issue as its solubility in magnesium is low.