Cone crushers are exclusively used for secondary and tertiary crushing. The cone crusher operates in much the same way as the gyratory crusher except it operates at a higher speed. It has a flatter crushing chamber designed to give higher capacity and reduction ratio. The aim is to increase retention time of material in the crushing chamber or to reduce the velocity of material through the crushing chamber to allow multiple impacts to occur (higher reduction ratio).
The two most common types of cone crushers used in metal mining in North America are the CS cone crushers manufactured by Nordberg and the Hydrocone crushers manufactured by Boliden-Allis (formerly Allis Chalmers). There are several other types manufactured throughout the world; the information contained here, however, is based on data from Nordberg and Allis Chalmers.
DEFINITION OF TERMS.
Crusher Sizing—Nordberg designates the crusher sizes by the mantle diameter measured in feet. At present, crushers ranging in size from 0.6 to 3 m (2 to 10 ft) are manufactured. Nordberg’s descriptions of CS cone crushers in general are vague but understood by the industry through common usage. Allis Chalmers’ designations are a little more specific. These define both the feed opening and mantle diameter in inches. For example,
Model 10-84 means a crusher with 254-mm (10-in.) feed opening and 2134-mm (84-in.) mantle diameter.
Cone Crusher DESCRIPTIONS.
CS Cone Crushers—Nordberg has two major types of cone crushers, a standard cone crusher that is used for secondary crushing applications and a short-head cone crusher that is used for tertiary crushing applications. Both types are made in sizes ranging from 0.6 to 3 m (2 to 10 ft). Over 1000 2-m (7-ft) crushers are in operation, but the 3-m (10-ft) crusher has found only limited application and is now being superseded by a high-capacity smaller unit (MP 1000).
The major difference between standard and short-head cone crushers is the shape of the crushing cavities.
Standard cone crushers are designed to make a product ranging from 12.5 mm (1/2 in.) to more than 63.5 mm (2-1/2 in.) in both open and closed circuits. They may be furnished with fine, medium, coarse, or extra coarse cavities to meet variations in feed and end product size.
Short-head crushers as shown in Fig. 188.8.131.52 have a steeper head angle and a more parallel crushing cavity than standard machines. They are designed to produce a crushed product ranging from 3.2 mm (1/8 in.) to 19.0 mm (3/4 in.) in closed circuit with the appropriate screens. They may also be furnished with fine, medium, coarse, or extra coarse crushing cavities to meet variations in feed size and desired product size.
Nordberg also produces three other series of cone crushers:
Omnicone, Gyrodisc, and WaterflushTM Wet Cone (Fig.184.108.40.206) crushers. Omnicone requires less headroom and is available in sizes 940 to 1524 mm (37 to 60 in.) (note the change in measuring mantle diameter in inches instead of feet). Omnicone crushers should be considered as an alternative for mobile plants and low-tonnage plants. Gyrodisc is a fine-product crushing machine and is capable of crushing hard, clean material down to –4.76 mm (4 mesh). It could, therefore, be a potential replacement for rod mills in a conventional crushing and grinding flowsheet. In the Gyrodisc crusher, crushing is achieved by a combination of impact and attrition. It will not handle wet sticky material nor will it handle material with excessive fines. Gyrodisc crushers are available from 914 to 2134 mm (36 to 84 in.).
Wet Cone crushers (WF Series) use WaterflushTM technology in which water is added to the crusher to flush fines through the crushing cavity. It is claimed that flushing produces a significant amount of flaky, shaped particles that break easily during ball milling. This results in elimination of the rod mill and a major reduction in overall comminution power requirements.
All Nordberg cone crushers are driven through a pinion mounted on a countershaft. The pinion drives the gear, which rotates the eccentric. The eccentric causes the main shaft head and mantle liner to gyrate, opening and closing the gap with the stationary bowl liner. The main shaft and head are supported on a spherical bronze socket liner. All assemblies except for the
countershaft are removed from the top of the machine. The crusher setting is adjusted by rotating the bowl, which has external threads that are screwed into a matching set of
internal threads on the adjustment ring mounted on the main frame. On current models, the bowl is rotated by hydraulic rams mounted on the main frame. Tramp iron entering the crusher
causes a spring release system to enlarge the crushing gap, allowing the tramp iron to pass. If the crusher becomes jammed, clearing jacks powered by a portable hydraulic raise the pack
adjustment ring and bowl permitting noncrushable material to pass. The Omnicone has no springs, and protection is provided by a nitrogen/hydraulic accumulator system.
Approximate capacities for the standard and short-head crusher models are given in Tables 220.127.116.11 and 18.104.22.168. The capacities shown are neither maximum nor minimum and are based on results secured in actual practice. The figures are in short tons and apply to materials weighing 1602 kg/m3 (100 lb/ ft3) and are based on a properly graded feed.
screen analyses of crusher product at different crusher settings are listed in Table 22.214.171.124. It will be noted that for average ore, the tables are based on 70% of the product being finer than
the constant closed-side setting. For hard ore, the tables are based on 60% passing the losed-side setting.
ALLIS CHALMERS HYDROCONE CRUSHERS:
Allis Chalmers does not distinguish between a standard and short-head design but uses the same basic crusher for both secondary and tertiary crushing. The appropriate crusher is selected for each service by changing the crushing chamber design. Up to six different chamber designs are available for the 2134 mm (84 in.) (mantle diameter) model, which is the largest crusher in the series; fewer alternatives are available in the smaller sizes.
Allis Chalmers offers six sizes of crushers. Approximate open circuit capacities are shown in Table 126.96.36.199. Qualifications listed in the table should be noted.