Impact Crushers: This division is represented chiefly by the various styles of hammermill; also by the cage type disintegrator. Combination Impact and Sledging Crushers. In this class we have the single or double sledging roll crushers. An example of the former is the Fairmount crusher, of the latter, the Edison roll crusher.
Some further subdividing and qualification might be applied to these general classifications, but these, for the most part, are not of particular importance. Pressure crushers, for example, may be divided into two subclasses: the reciprocating, and the continuous-pressure, types. The gyratory and jaw crushers come under the first category, the crushing rolls under the second. Strictly speaking, the gyratory motion is not a reciprocating one, but it is so with respect to any vertical radial plane through the crushing chamber; therefore it is convenient to view it in that light. Some roll crushers, notably the light coal crushing type, have more of a tearing action, as contrasted to the heavy sledging performance of such machines as the Fairmount crusher.
During the same years wherein the industry was concerned with development of larger and still larger primary crushers,another member of the family was born: the single, sledging- roll crusher. The Allis-Chalmers Co. entered this field in 1911, building two sets of 36 dia. x 60 face single-roll crushers, flux limestone plant. Taking the name of its proving ground, this machine was christened the Fairmount crusher. The machine quickly achieved a high degree of popularity, and although its field of application is relatively limited, quite a number of them were in-stalled for primary crushing service. The line was expanded to include smaller sizes, as well as the big 60- x 84-in. machine.
Development of concentration and cyanidation in the mining industry called for finer crushing than was feasible in the gyratory or jaw crushers then available. This requirement was met for a number of years by the double smooth-face crushing rolls, originally known as Cornish rolls. As the mining industry during the period we are discussing was a very active one, the development in this type of crusher had reached a fairly high stage before the end of the century, and some excellent heavy-duty roils were available at that time. That this machine was not used to any considerable extent in the commercial crushing plants of that period was due simply to the fact that there was no demand for the smaller sizes of crushed stone, at least not any more than could be taken care of by the crushing methods then in vogue in such plants. This brings us to the rather significant fact that, while all of the interesting and rather remarkable development we have outlined was going on, very little, if anything, was being done to develop special crushers for secondary and fine-reduction work, other than the work on crushing rolls just described.
a jaw, b cone, c mushroom, d hammer, e roller; 1 fixed cheek with the rotation axis; 2 a movable cheek; 3, 4 the eccentric shaft; 5 rod; 6 hinged rear bearing spacer cheeks; 7 spring; 8, 9 width adjustment mechanism of the discharge gap; 10 pull the lock device; 11 bed; 12 still cone; 13 cone moving; 14 traverse; 15 hinge suspension rolling cone; 16 cone of the shaft; 17 drive shaft; 18 eccentric; 19 amortization spring; 20 foot ring ;21 regulating ring; 22 thrust bearing cone; 23 rotor; 24 liner plates; 25 grate; 26 hammer; 27 main frame; 28 crushing rolls.
Selecting an appropriate crusher, or indeed any piece of processing equipment, is important in every quarry operation. Understanding what each crusher type is used for and knowing some general efficiency tips and the proper way to feed these machines will lead to the best results for any given site. Each type of crusher is different and each is used to achieve a particular result. Likewise, to obtain a specific output, each type of crusher requires different maintenance tasks to keep it running efficiently. Operators who can achieve this, along with a consistent feed to the crusher, will be the most efficient and, more importantly, the most profitable.
A jaw crusher is a compression type of crusher. Feed material is reduced by squeezing it between a moving piece of steel and a stationary piece of steel, with the discharge size controlled by the gap setting, ie the space between those two pieces of steel. The tighter the setting, the smaller the output size and the lower the throughput capacity.
Jaw crushers are mainly used in primary crushing stages and are rarely used for secondary crushing. As a compression crusher, this type of machine generally produces the coarsest material because it breaks the rock along its natural lines of weakness. Jaw crushers are an excellent primary stage solution to prepare rock for subsequent processing stages, such as washing, classifying or secondary crushing.
Jaw crushers are routinely choke fed to maximize production capacity and ensure that particles are uniformly broken. This promotes stone-on-stone crushing, which breaks up flaky or slabbier particles. Those seeking fewer fines should try trickle feeding material into the jaw crusher. Keep in mind, however, that this will have an adverse effect on particle shape and will also reduce throughput capacity, hindering the crushers efficiency. Ideally, the feed rate should not be switched from choke to non-choke, as this can cause problems downstream at the secondary processing plant. In practice, many jaw crushers are fed in this intermittent fashion due to gaps in the delivery of feed material from the quarry. Jaw crusher feed should be pre-screened using a grizzly prior to crushing to remove any material finer than the closed-side setting.
Cone crushers and gyratory crushers are also compression-type machines that crush material between a moving piece of steel and a stationary piece. The output is controlled by the setting between the two pieces of steel. Though the chamber is round in shape, the moving piece of steel is not meant to rotate. Instead, a wedge is driven around to create compression on one side of the chamber and a discharge opening on the opposite side. Cone crushers are used in secondary and tertiary roles as an alternative to impact crushers when product shape is an important requirement but the proportion of fines produced needs to be minimized. Even though the reduction in fines produced may only be a few percentage points, this could represent a significant amount of material in a large operation and, ultimately, increase a companys bottom line and profitability.
Uniform distribution of feed material around the cone crusher inlet is good practice. This allows production of a consistent product as well as efficient, reliable operation of the crusher. Choke feeding is important for b to maintain approximately 1015% of material finer than the closed-side setting in the feed to assist the crushing action. More than 1015% will likely cause ring bounce due to the pressures in the chamber.
An impact crusher uses mass and velocity to break down feed material. First, the feed material is reduced as it enters the crusher and makes contact with the rotating blow bars or hammers in the rotor. Secondary breakage then occurs as the material is accelerated into the stationary aprons or breaker plates. Impact crushers tend to be used where shape is a critical requirement and the feed material is not very abrasive. The crushing action of an impact crusher breaks a rock along its natural cleavage planes, giving rise to better product quality in terms of shape. The quality of these products makes them ideal for use in highly specified roadstone and concrete aggregateapplications.
Size reduction in an impact crusher relies on energy being conveyed into the rock from the rotor, and it begins with the feed. The initial impact is responsible for more than 60% of the crushing action, with the remainder being made up of impact against an adjustable breaker bar and a small amount of inter-particle collision. This is why it is vitally important that the feed arrangement to an impact crusher ensures an even distribution of feed material across the full width of the rotor. This will allow for even distribution of energy into the feed material and uniform wear patterns, ensuring consistent product gradation and power consumption.
Remember, when selecting the correct crusher to best suit a particular operation, it is important to understand the requirements for each stage of crushing and how to properly feed each crusher. During the primary crushing stage, the aim is to get the material to a size that conveyors and other aggregate processing machines can handle. Generally, jaw crushers are installed at this crushing stage. Some operations will need further crushing in secondary and tertiary crushing stages. These stages are used to better control and size the output. Impact crushers and cone crushers tend to be used during these stages to better control particle size and shape. Understanding how to best match the type of crusher to the right crushing stage, as well as working with a manufacturer to properly size the crusher, will ensure crushing and feeding efficiency throughout an operation and, ultimately, overall profitability.Get in Touch with Mechanic