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VSI Applications

Jun 26, 2013 - 6 years ago

By Supply Post

All impact type crushing machines use speed to crush. While there are many factors that affect the crushing efficiency of impact crushers, the most important of this is the material velocity. This determines the amount of crushing that is done and the overall grading of the crusher discharge. Generally, the faster the material is accelerated, the greater the amount of crushing that is achieved. For this reason, it is essential that the impact crusher used have a wide operating speed range to accommodate a broad spectrum of material types and feed gradings. Vertical shaft impact crushers have the broadest operating range, as per the Rotor Velocity Scale below.

Shaping Range – 100 to 175 feet per second (30 mps to 53 mps). At this speed tumbling, rubbing and mild impacts shape the stone. Soft materials can often be reduced at these lower speeds, which produce superior aggregate shape in all particles fed to the crusher. Very hard rocks may only be mildly cubed at these speeds.

General Crushing Speed – 175 to 250 feet per second (53 mps to 75 mps). This is the crushing range for producing typical aggregate products for construction materials. Severe impact, high attrition and compression of the rock stream cause particle failure. This results in a significant production of smaller particles when compared to those being fed to the crusher. Usually it is best to experiment with speed within this range because the fracture characteristics of rocks vary widely. To get good crushing with a balance of recycle load and controlled production of fines, it is only necessary to achieve the threshold speed of fracture and additional speed consumes extra power raising energy cost and often generating undesirable size distribution in the crusher discharge.

Fine Grinding and Pulverizing – 250 to 325 feet per second (75 mps to 100 mps). Speeds above 250 feet per second are reserved for applications when pulverizing and grinding of the material is desired. At these higher speeds, it is possible to produce manufactured sand and many industrial mineral products requiring fine sizes, in many cases smaller than 1 millimeter. The applications require care, technical knowledge of processing and experience in good processing circuit design. This way the highest production of the needed fine product can be achieved without excess energy consumption and with acceptable overall operating cost.

There are several success stories across Western Canada using the REMco VSI crusher for specific results. From iron stone removal in concrete rock, elimination of F&E’s, making asphalt rock from “reject” material to concrete sand production, we have applications that you can see in operation. Copyright REMco Rock Engineered Machinery Company 2013.

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