OCR

The changes made in 1963, however, converted the secondary-tertiary crushing-screening building to tertiary crushing, and added a new building between the primary and tertiary buildings for secondary crushing. The single 7-ft. crusher was relocated in the new secondary crushing building, and a second 7-ft. crusher was purchased and paired with the original crusher unit in the original secondary-tertiary crushing building. Then between the secondary and tertiary buildings, conveyors were placed to build and reclaim from an outdoor surge stockpile. The flow of ore through the crushing section now proceeds as follows: ore is still delivered to the primary crusher surge bin, and then the chain feeder draws it over the grizzly to feed the jaw crusher. The 54-in. conveyor then carries the minus 7-in. ore to a 5 x 2 ft. vibrating grizzly set at 4 in. The plus 4-in. ore passes to a 7-ft. crusher for a secondary crushing. The crushed ore, now minus 4 in. , is combined the orginal undersize, and is carried on a 36 - in. conveyor 292 ft. long to the stockpile area. This conveyor has a 63-ft. lift, and the stockpile is designed for 8,000 tons of live storage and 20,000 tons of dead storage. Ore from the stockpile is reclaimed by two 42 x 72-in. feeders and fed to a 36-in. reclaim belt conveyor that has a 65 ft. 9-in. lift. This 305-ft. belt delivers the ore to the two double-deck screens that still operate in the tertiary crushing building. Here, after closed circuit screening and final crushing to minus 1/2-in., the ore is carried to the original fine ore conveyor system and distributed in the mill storage bin. Dust collection in the crushing section has been revised purchasing a new dust collector for the tertiary crushing building, and relocating the type N Rotoclone at the new secondary crushing building. In the mill, duplicate grinding facilities were installed, four 10-cell banks of rougher-scavenger flotation cells, and one 10-cell cleaner flotation machine were added. To make room for this additional, equipment, the building-was extended 80 ft. on the south side. Ore from the mill storage bins was formerly fed by two belts under each bin to a single collector belt feeding the ore rod mill. With a com¬plete duplication of grinding facilities, conveyors under the storage bins were revised so that the two feeder belts under each bin now feed to two separate collecting belts--one belt feeding each of the rod mills. The original 10 x 13-ft. rod mill was increased by adding a. 3-ft. ring to the discharge end. A new 10 x 16-ft. rod mill was then purchased for the new grinding section along with two 10-1/2 x 13-ft. ball mills--matching the units in the original circuit. Cyclone classification (three 2G-in. cyclones for each ball mill) was also duplicated for the new grinding section.