Pit & Quarry, July 2018
CRUSHING HYDRAULIC BREAKING between a moving piece of steel and a stationary piece The discharge size is controlled by the setting or the space between those two pieces of steel The tighter the setting the smaller the output size and the lower the throughput capacity As a compression crusher jaw crushers generally produce the coarsest material because they break the rock by the natural inherent lines of weakness Jaw crushers are an excellent primary crusher when used to prepare rock for subsequent processing stages Cone and gyratory crushers These are also compression type machines that crush material between a moving and a stationary piece of steel The setting between the two pieces controls the output Although the chamber is round in shape the moving piece of steel is not meant to rotate Instead a wedge is driven around to create compression on one side of the chamber and discharge opening on the opposite side Cone crushers are used in secondary and tertiary roles as an alternative to impact crushers when shape is an important requirement but the proportion of fines produced needs to be minimized Impact crushers An impact crusher uses mass and velocity to break down feed material First the feed material is reduced as it enters the crusher with the rotating blow bars or hammers in the rotor The secondary breakage occurs as the material is accelerated into the stationary aprons or breaker plates Impact crushers tend to be used where shape is a critical requirement and the feed material is not very abrasive The crushing action of an impact crusher breaks a rock along natural cleavage planes giving rise to better product quality in terms of shape FINAL THOUGHTS When selecting the crusher to best suit your operation its important to understand your needs for each stage During the primary stage look to get material to a size your conveyors and other processing machines can handle Some operations need further crushing in the secondary and tertiary crushing stages These stages are used to better control and size the output Understanding how to best match the type of crusher to the right crushing stage will ensure crushing efficiency throughout your operation and overall profitability P Q Gerry Mangrich is a process engineering specialist at McLanahan Corp Engineered for Accuracy B u i l t to Endure Trusted to Last WY15 Conveyor Belt Scale WY10 Conveyor Belt Scale HY15 Conveyor Belt Scale WF10 Weigh Belt Feeder Control Gates Data Collection Custom Weighing Metering Solutions For the most demanding applications tecweigh com 8005364880 20 PIT QUARRY July 2018 pitandquarry com
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