Crushing Chamber Selection Principle
There are two types of cone crusher: short head type and standard type. The applications of the two types are different, and there are many types of crushing chamber for short head or standard. The standard type is used for two-stage and three-stage crushing, and the particle size of the finished product is generally larger than 25mm. It does not require closed-circuit circulation for two-stage crushing, and the crushing ratio is 4 ~ 6. The short head type is used for three-stage breaking, and the particle size of the finished product is less than 25mm. Closed-loop circulation is required, and the crushing ratio is 3 ~ 5.
1 Breakdown ratio
i = F (80) / P (80).
i: breaking ratio. F (80): 80% of the size of the sieve through which the feed can pass. P (80): the size of the screen hole through which 80% of the output can pass.
2.Feed size and abrasiveness
The tight side feed opening of the crusher cannot be smaller than a very large feed particle size. The inlet should not be too large or too small.
If the inlet is too large:
- The material is mainly concentrated in the lower part of the crushing cavity, which causes excessive wear of the lower part of the lining and low utilization of the lining.
- The crushing ratio decreases, the crushing efficiency is low and it is easy to cause the rotating cone to rotate.
If the inlet is too small:
Material cannot enter the crushing cavity, the production capacity is severely reduced, and the inlet lining is severely worn or even destroyed.
Causes large fluctuations in the crushing force and the jump of the adjustment ring, which causes damage to the pads of the rack seat, accelerates the wear of the lock cylinder seals, and affects the stability of the equipment.
The abrasiveness of the material mainly affects the service life of the broken lining board. An appropriate increase in the manganese content of the lining board (not exceeding 20%) can increase the service life of the lining board. Currently, the most commonly used is a lining board made of ZGMn18Cr2 (XT810).
3. Particle size and shape of the product
The particle size of the product depends on whether the crushing process is open-circuit or closed-circuit. The discharge opening required to obtain a satisfactory product particle size must be clear. The discharge port here refers to an approximate value. Even if the two crushers are the same in the same working condition, the discharge port is not necessarily the same.
Generally speaking, the tight-edge discharge opening of the crusher is equal to the size of the sieve openings or slightly larger than the average particle size of the desired product. As far as the product size is concerned, the short-head type crushing cavity can obtain excellent product size, followed by the standard fine cavity type. The larger the cavity type, the more difficult it is to obtain a good product size. In order to ensure a good product size, the crushing ratio should be controlled to 3 to 3.5.
How to get a better product particle size
Good product particle size should ensure that the ratio of a very large size and smaller size of more than 90% of the product is less than 3 (the smaller the ratio, the better the particle size). The product particle shape is determined by many factors, the main influencing factors are concentrated on the feeding, crushing cavity type, discharge port, crushing equipment and crushing process.
1. Feed correctly
A cone crusher must achieve full cavity feeding. Stable continuous grading feed can avoid the change of crushing power and feed gradation cut-off while maintaining a relatively stable crushing chamber and discharge port.
A wide grading feedstock is better than a narrow grading feedstock. This part of the material that is smaller than the discharge port will increase the squeeze between materials and have a good filling effect in the crushing chamber. Don’t be too thin, the excellence is slightly smaller than or equal to the size of the discharge port, and the ratio should not exceed 20%.
A large discharge port will bring more flaky products, so in order to obtain a good product size, a smaller discharge port is required, and the crushing ratio is controlled to 3 to 3.5. This requires controlling the particle size of the feed, and the excellence should not exceed 50mm. Unreasonable feeding will affect the crusher production capacity and may cause a series of problems such as the jump of the adjustment ring, shortening the service life of the lining board, and poor particle shape of the crushed product.
2. Reasonable choice of crusher and the crushing chamber
Choose reliable cone crushing equipment and crushing chamber type. Power, crushing force and discharge opening are the three major factors that determine the output and particle size of the cone crusher. The method to increase the power is to increase the feed rather than reduce the discharge opening. The excellent crushing power is about 80% of the rated power.
The runout of the adjusting ring represents that the crushing force exceeds the design limit. Once the crushing force appears in the crusher, the discharge opening can be increased by 1mm ~ 2mm. The adjustment ring runout and power peak will add extra stress to the crusher and eventually cause serious damage to the crusher.
3. The closed-circuit and crushing system
The crusher is part of the crushing system, and other equipment will also affect the entire crushing system. The conveying system must have sufficient conveying capacity. Whether the buffer silo is in front of the crusher is very important for the stable crowded feeding of the crusher.
The effect of the screening efficiency on the crushing system is also huge. Insufficient screening, on the one hand, causes too much fine material in the return material, which easily causes the crusher to overload; on the other hand, excessive qualified fine materials are returned to the crusher, which reduces the production capacity of the crushing system.
The non-crushing foreign matter in the crushing system will cause great damage to the crusher. For example, passing iron may cause the burner to burn the copper sleeve, crack the frame, and severely break the main shaft.
Closed-cycle crushing, used in the second stage crushing, can provide accurate feed granularity for fine crushing, avoid excessive fine materials entering the crushing chamber, and achieve the ideal filling effect of the crushing chamber.
4. Material characteristics and product granularity
Generally speaking, the softer the rock, the coarser the crystalline particles of the rock, the coarser the product, and the better the broken grain shape. For example, to get 6 ~ 15mm products. The second stage crushing adopts closed-circuit circulation to break below 50mm, sieve out the materials below 6mm, and ensure that the fine crushing has a stable 6 ~ 50mm continuous grading feed.
A hydraulic cone crusher has great advantages in the field of crushing. A reasonable crushing system, coupled with the correct equipment and cavity selection, as well as standard operating and maintenance habits, can make the performance of the hydraulic cone crusher more effective.
Example of HP400 crushing chamber
Below we will use Metso HP400 as an example to illustrate the effect of different cavity types on materials.
SH Extra Fine
- Max Opening Closed Side 123mm(4.83″)
- Max Opening Open Side 173mm(6.79″)
- Max Setting closed Side 78mm(3.07″)
- Max Opening Closed Side 109mm(4.28″)
- Max Opening Open Side 101mm(6.33″)
- Max Setting closed Side 77mm(3.04″)
- Max Opening Closed Side 137mm(65.41″)
- Max Opening Open Side 186mm(7.32″)
- Max Setting closed Side 77mm(3.04″)
- Max Opening Closed Side 171mm(6.72″)
- Max Opening Open Side 217mm(8.55″)
- Max Setting closed Side 76mm(2.99″)
- Max Opening Closed Side 190mm(7.48″)
- Max Opening Open Side 232mm(9.12″)
- Max Setting closed Side 67mm(2.65″)
- Max Opening Closed Side 251mm(9.88″)
- Max Opening Open Side 291mm(11.45″)
- Max Setting closed Side 66mm(2.58″)
- Max Opening Closed Side 299mm(11.76″)
- Max Opening Open Side 328mm(12.91″)
- Max Setting closed Side 63mm(2.5″)
STD Extra Coarse
- Max Opening Closed Side 314mm(12.36″)
- Max Opening Open Side 344mm(13.55″)
- Max Setting closed Side 63mm(2.5″)