Impactors are a type of size reduction equipment that utilize impaction, which is a collision-wrought force, as opposed to sheer pressure to break apart or deform various materials. Impaction is defined as a force that is transmitted through the striking of one body against another, or a collision, in which crushing occurs as the result of the pressure created by the two opposing forces.
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Often used as a secondary method of pulverizing rather than a primary method, impactors are also often referred to as impact crushers. Able to be used on a wide range of materials, impactors are typically used to crush soft, non-abrasive materials such as phosphate, gypsum, coal, soft metallic cores and seeds, but they can also be used to crush hard, abrasive materials such as basalt, gravel, concrete and asphalt. However, they are best suited for materials of medium-hardness. As a result, there are numerous industries that utilize impactors, including road and bridge construction, for the impaction of building materials; mining, in the impacting of mined and quarried materials; industrial manufacturing, to impact various materials for use in further processing applications; and water conservancy, for the impaction of aggregates required for various applications.
There are two main types of impactors: a horizontal shaft impactor (HSI) and a vertical shaft impactor (VSI). A HSI crusher consists of impeller bars, curtain liners and adjustable liner plates. The impaction process begins when the material reaches the breaker-plate, where hammers are fixed to the outer edge of a spinning rotor. Despite the different types, all impactors share the design feature of a solid metal cage, which functions to contain the materials and has openings on the bottom, end or side in order to let the pulverized material exit once it has attained the desire size. HSI crushers cannot be used for hard, abrasive materials and are best suited for soft materials such as weathered shales, dolomite aluminum and clay. A VSI crusher is very similar in construction to a HSI crusher, but also features a high speed rotor and a crushing chamber that is designed to throw the materials against, thus impacting them using velocity rather than solely using surface force. As a result, VSI crushers are more high-powered and higher-efficiency than HSI crushers and are consequently better suited for harder materials such as magnesium sand, metallurgical slag, quartz minerals, limestone and bauxite.
