Gyratory, jaw and roll sizers have all been installed underground to act as primary crushers prior to the transportation of the ore to the surface. There are a few gyratory crusher installations in hard rock mines (the latest, 1998, being Phelps Dodge Henderson mine 1,371 mm x 1,880 mm [54 ft x 74 in] in Colorado) but the greatest percentage of crushers working underground are jaw crushers . Until a few years ago, double toggle crushers were the underground crushing choice, however, these are now being replaced with more efficient and less expensive single toggle crushers.
FINE CRUSHING (Secondary, Tertiary and Quaternary)
Fine crushing circuits can be more challenging to design than primary crusher installations. There are more equipment options, and each has different installation and maintenance requirements. The process flowsheet dictates the expected performance of the items in the flow stream. The designer must configure the equipment and structures into a balanced, economical plant design. Screens, feeders, stockpiles, bins, conveyors and crushers must all be interfaced with the most economical supporting structures and buildings.
An open-circuit crusher is easier to design and lay out than a closed-circuit design, since it has fewer equipment items and structures. Figures 13, 14, and 15 show some typical secondary crusher open circuit layouts. Figure 16 shows some typical open circuit secondary and tertiary crushers. Provisions should be made for possible future conversion of an open-circuit plant to a closed-circuit version.
Cone crushers remain the choice for most secondary and tertiary operations, with some gyradisc and vertical-impact crushers also utilized on certain ore types. Water-flush cone crushers have been introduced in secondary and tertiary installation, which requires careful design of the water systems to and from the crusher.
Most open-circuit secondary and tertiary crushers include scalping screens to remove fine material prior to the secondary crushers. Closed-circuit crushers use tertiary screens to control the final product size. In some larger installations, the secondary and tertiary crushers are located in one plant area and the screens in another. Crushers and screens in these plants have common bins feeding to the multiple crushers or screens. Most plants now have the screen feeding the fine crusher, providing for easier access to service the screens. As with primary crushers, fine crushers must meet the design parameters listed above. Design details that are helpful to fine crusher plant layout area listed in the sections that follow.
Feed to Screens or Direct to Secondary Crusher
The conveyor or feeder transporting ore directly to a secondary crusher should be retractable (or tilt at the head end) to permit crane access to the crusher.
• The conveyor feed chute to a secondary screen should have sufficient height to allow the material to feed to the total width of the screen as rapidly as possible. This is especially critical when feeding from a conveyor to the new wider banana screens.
• The installation of a bin feeding to a single secondary crusher or screen can allow for the future installation of an additional secondary crusher and screen.
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Underground Crushers,FINE CRUSHING (Secondary, Tertiary and Quaternary)
Gyratory, jaw and roll sizers have all been installed underground to act as primary crushers prior to the transportation of the ore to the surface. There are a few gyratory crusher installations in hard rock mines (the latest, 1998, being Phelps Dodge Henderson mine 1,371 mm x 1,880 mm [54 ft x 74 in] in Colorado) but the greatest percentage of crushers working underground are jaw crushers . Until a few years ago, double toggle crushers were the underground crushing choice, however, these are now being replaced with more efficient and less expensive single toggle crushers.
FINE CRUSHING (Secondary, Tertiary and Quaternary)
Fine crushing circuits can be more challenging to design than primary crusher installations. There are more equipment options, and each has different installation and maintenance requirements. The process flowsheet dictates the expected performance of the items in the flow stream. The designer must configure the equipment and structures into a balanced, economical plant design. Screens, feeders, stockpiles, bins, conveyors and crushers must all be interfaced with the most economical supporting structures and buildings.
An open-circuit crusher is easier to design and lay out than a closed-circuit design, since it has fewer equipment items and structures. Figures 13, 14, and 15 show some typical secondary crusher open circuit layouts. Figure 16 shows some typical open circuit secondary and tertiary crushers. Provisions should be made for possible future conversion of an open-circuit plant to a closed-circuit version.
Cone crushers remain the choice for most secondary and tertiary operations, with some gyradisc and vertical-impact crushers also utilized on certain ore types. Water-flush cone crushers have been introduced in secondary and tertiary installation, which requires careful design of the water systems to and from the crusher.
Most open-circuit secondary and tertiary crushers include scalping screens to remove fine material prior to the secondary crushers. Closed-circuit crushers use tertiary screens to control the final product size. In some larger installations, the secondary and tertiary crushers are located in one plant area and the screens in another. Crushers and screens in these plants have common bins feeding to the multiple crushers or screens. Most plants now have the screen feeding the fine crusher, providing for easier access to service the screens. As with primary crushers, fine crushers must meet the design parameters listed above. Design details that are helpful to fine crusher plant layout area listed in the sections that follow.
Feed to Screens or Direct to Secondary Crusher
The conveyor or feeder transporting ore directly to a secondary crusher should be retractable (or tilt at the head end) to permit crane access to the crusher.
• The conveyor feed chute to a secondary screen should have sufficient height to allow the material to feed to the total width of the screen as rapidly as possible. This is especially critical when feeding from a conveyor to the new wider banana screens.
• The installation of a bin feeding to a single secondary crusher or screen can allow for the future installation of an additional secondary crusher and screen.