Roll corrugations must be selected according to the materials to be processed and the finished product requirements. Coarser grooving provides longer life and higher capacities but will produce coarse or thicker finished products. Finer corrugations lead to finer products but will reduce capacity and wear out faster. Reviewing roll corrugations as grinding requirements change is an often-overlooked aspect of roll crusher grinding.
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Roll speed differential is the difference in rotational speed between the two rolls in a pair and is one of the biggest reasons roll crushers produce a grind with a lower standard deviation than hammermills. The differential creates a shearing effect between the rolls that cuts the material rather than squishing it. Using a higher differential will reduce the amount of fines produced, improving the standard deviation. The differential ratio is limited by the size of the sheaves that can fit within the guard of the rollermill. Sheaves are the pulleys on the roll shafts that are connected via belts to spin the rolls at the designated speeds. If the pulleys are too large, they will contact either the other pulley on the paired roll shaft or the frame/guard of the machine. The most common roll speed differential in roll crusher grinding is 1.5:1.
To maximize roll life and achieve consistent end-to-end performance, each pair of rolls must be parallel and tram, which means level with each other on a horizontal plane. If the rolls operate out of parallel, they will grind the material fine at one end and coarse at the other and will also wear unevenly. The same is true for rolls out of tram. Normally the tram adjustment will only be set when the operated rolls are changed or in some significant upset condition (such as lost elevator buckets and bolts appearing in the nip of the rolls).
When the rolls are not parallel or tram, material tends to "drift' in the nip of the rolls toward the more open end(s). This excess material may begin to 'pile up' in the nip of the rolls and cause accelerated wear. Trying to make a fine grind when out of parallel or tram may cause the 'close' end (or center of the rolls if out of tram) to make metal to metal contact. You can routinely check the roll parallel by using a feeler gauge when the machine is open or by taking samples from each end of the rolls to compare grind sizes.
In double- or triple-pair machines, it is necessary to balance the work being done between the pairs of rolls to avoid premature wear on one of the roll pairs. When properly managed, each pair of rolls will wear at approximately the same rate. By using a 'staggered' corrugation on the fast and slow rolls (with coarser grooving on the fast roll) all four (or six) rolls will be ready for recorrugation at the same time. Changing all rolls at once is usually the most efficient use of the time and effort required to make a roll change.
Rolls must be operated in a way to avoid having the material pile up in the nip when the mill is running at full capacity. This is not normally a problem when the rolls are in good condition, as the corrugations will easily pull in the material and the motor load will limit the throughput. As the corrugations, in the top rolls especially, become dull, they will lose their effectiveness at pulling the grain in, and material may begin to pile up in the nip. This condition must be avoided since the material slipping in the roll nip will greatly accelerate roll wear. If the mill capacity decreases, or if the motor load does not go up when the feeder speed is increased, it is very likely that the material is not passing through the top pair of rolls. To maximize capacity and extend roll life, open the top pair of rolls slightly and/or reduce the feed rate to eliminate accumulation in the nip of the top rolls. If the finished product is too coarse, close the bottom rolls to obtain the desired finished particle size (Figure 5).
The impact crusher and hammer crusher both use the impact principle to crush materials, and the product has an excellent grain shape. They look similar, but are different in many ways. So, which is better?
This blog will compare them in materials, price, structure, output, grain shape, wear parts, etc.
The impact crusher is designed for the crushing of hard and high-moisture materials. It is very suitable for highway, water conservancy, railway, airport, and other industries.
The hammer crusher is used for the large-scale and high-yield production lines. It is simple and efficient by crushing and forming at one time.
Types Impact crusher Hammer crusher Material hardness Medium-hard materials with low toughness and high brittleness Medium-hard and brittle materials Material with high moisture content ApplicableUnapplicable
(Water content should not exceed 10%)
Compressive strength of materials ' 350 MPa ' 200 MPa Feed size ' 800 mm ' mm Common materials Granite, concrete asphalt, construction waste, gypsum, dolomite, clay, river pebble, etc. Glass recycling, limestone, quartz, slag, coal, etc.Not sure whether your materials can be processed or not? Free Sample Testing!Contact us.
Impact crusher price: $1, 000 (the lowest price).
It is mostly used as the secondary crushing equipment, so a coarse crusher is also needed in the crushing. It crushes small materials that discharge from the jaw crusher.
Hammer crusher price: It has many models with the lowest price of $976. Among them, the heavy hammer crusher has a larger granularity and is sold $5, 000-$180, 000.
Hammer crusher can form a single production line to achieve one-time molding, which can simplify the crushing process and save 40% of the cost.
2 or 3 large crushing cavities.
Advantage: the crushing is more sufficient.
1 small crushing cavity.
Advantage: good sealing, solve dust leakage.
Direction of plate hammer/hammer head The plate hammer moves from the bottom to the top to crush, then it throws material onto the upper impact plate. The hammer head strikes and crushes along the direction in which the material falls. Rotor linkThe plate hammer is fixed on the rotor.
Feature: large speed and kinetic energy.
The hammer head hangs in the air and crushes materials individually.
Are you interested in learning more about hammer mill crusher? Contact us today to secure an expert consultation!
Feature: limited speed and kinetic energy.
Output size adjustmentAdjust the rotor speed;
Adjust the rotor diameter;
Adjust the opening size of the distributor;
Adjust the gap of the grinding chamber.
Adjust the screen gap of the sieve plate.Impact crusher: It is not easy to cause material blockage.
Reasons:
Hammer crusher: It is equipped with a bottom sieve plate, which increases the possibility of material blockage.
: Although the grain shape is more rounded after 2-3 shaping processes, multiple impacts seriously affect the output (productivity).
Hammer crusher: It has a higher output, up to 3 times that of an impact crusher. Therefore, it is often used in large-scale and high-yield production lines.
Impact crusher: The crushing ratio is above 50. The discharge is cubic, with uniform particle size, without tension and cracks. And the fine powder and dust content are low.
So, the impact crusher is the final crusher to produce concrete aggregate for the antiskid pavement of the high-grade highway.
Hammer crusher: The crushing ratio is large (generally 10-25, even to 50). The output size is 25 mm or less. The product contains more needles, flakes, and powders.
Whether for the impact crusher or hammer crusher, the plate hammer and hammer head are the main wear parts.
Impact crusher: It wears little during the crushing, as the wear occurs only appears on the side of the material, and its metal utilization rate can reach 45%-48%.
When crushing limestone, the plate hammer is not seriously worn. However, when crushing granite with high hardness, it needs to be replaced constantly.
Hammer crusher: Due to the hanging state of hammer head, the wear occurs at the top, front, back, and side. Compared with the plate hammer, the hammer head is more seriously worn, and its metal utilization rate is 35%.
Besides, the rotor of hammer mill may also be worn. The bottom screen plate can be severely worn so you need to replace all the grids, which is very complicated.
How to maintain the impact crusher?
How to maintain the hammer crusher?
9 Faults and Solutions of Hammer Crusher
How to choose between the impact crusher and hammer crusher? You should choose according to the actual production situation.
Types Impact crusher Hammer crusher Hard materials ' High requirement for final grain shape ' High demand for output 'Ftmmachinery has been engaged in the production of crushing equipment for nearly 40 years. Contact us to customize your best crushing plant !Contact us
Jordan is the writer of the blog with a broad knowledge of this industry. Most importantly, he hopes to help you in your projects sincerely.
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