![]() The Bond’ Crushing Work Index is common to calculate the power needed to crush rocks from a given F80 size to a resulted P80 product size. This techniques allows for a rock-to-rock relative comparison. The Compressive Strength of rocks is measured by crushing cylinder shaped (drill core) ore samples of 2″ x 2″ (51mm X 51mm). The resulting Ai is used to predict crusher liner wear rates. ![]() The most common abrasion test however, is the Bond method where a 76x25圆mm (3x1x0.25″) piece of 500 Brinell SAE 4325 chrome-nickel-molybdenum steel rotates in a falling stream of rocks under standard predetermined conditions to measure its weight loss. There are several ways or test methods at your disposition to obtain this number including the Angeles Abrasion Test and the Deval Abrasion test. The (Ai) Abrasion Index measures the abrasivity of rocks during its crushing. Such high abrasion/high silica impact/hammer crusher operation see extremely high maintenance costs having to be endured.Ĭommon work index terms you need to review and understand as they relate to crushing: The only reason why you would use an impact mill/crusher or a hammer mill on a high-silica rock is because it might be sticky in nature and rich in clay. Impact crushers are commonly used to crush rocks with a silica contain under 5% such as coal, limestone, and phosphate. Not mentioned so far it the fact that because of the ‘no nipping angle restriction’ impactors and hammermills produce a much greater size reduction ratio. Soft and low abrasion rocks are offered a large selection of crushing machines to choose from. Since there are not that many small SAG mill operations of under 2000 TPD, and most sub-2000 TPD mills are built with rod mills and/or ball mills only the upstream crusher plant needs to have sufficient crushing power to provide a P80 to grinding of typically 2,000 to 200,000 TPD using semi-autogenous mills only require primary crushing and are selected as well as designed based on: The more you crusher, the less grinding power and the smaller the grinding mills you will need. As gravity pulls the rock down from the top of the crushing chamber (feed) to the discharge (close-side-setting), all rocks undergo multiple impacts causing them to get crushed.Īfter TNT explosives, crusher are the most effective or efficiency rock size reduction hammer the mineral processing industry has. Too large an angle will not grip the rock presented, while to small an angle will reduce the use of the potential size reduction that’s available to the operator. How much reduction each crushing stage is capable of infliction of rocks (reduction ratio) is driven by the angles between the 2 surfaces on each side and holding the rocks-to-be-crushed as the move towards and away from each other. Typical hard-rock crushers like jaw, gyratory and cones break rock by nipping the ore between a fixed/stationary and a moveable wear-resistant surface/liner. Since each size reduction stages of crushing is limited to around 6-to-1 (average), you need to blast as fine as possible to minimize the number of stages in crushing and crushers needed to reduce the run-of-mine’s hard-rock most economically as you can. Conveyors and transfer chutes are limited in size and I say AMEN! to that as if you are left to the mining engineers, they’d blast and send 60″ rock to the SAG mill □ ![]() ![]() Less abrasive and softer rocks or stones are crushed by impact and shear but also compressive mechanisms produced by Rock Crushers.Īfter the mine has blasted the ore, the first reason why we crush rock is really to be able to transport it onto the next same. In principle, compression crushing is used on hard and abrasive rocks by placing them between a high wear-resistant plate/surface. Depending of the type of rock ( geometallurgy) to be crushed, there are 2 largely different techniques at your disposition for crushing rocks. In mineral processing or metallurgy, the first stage of comminution is crushing.
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