What Is An Impact Crusher?

1.Introduction

An impact stone crusher refers to a type of crusher that uses impact force to crush materials. Impact crusher is one important stone crusher machine in mining industry. When aggregate industry (Cement, Ready-Mix Concrete, Asphalt, Crushed Stone, Sand & Gravel) wants to process rock, sand, and gravel to sale, one such way to process these materials is sending gravel, rock, and sand through an Impact Crusher. It employ sharp blows applied at high speed to free-falling rocks where crushing is by impact rather than compression.

2. Working Principles

2.1. Mechanism of Impact Crushing

The performance of an impact crusher is determined by the rotor size, feed capacity, product size, and rotor speed. The rotor is the main work component of the impact crusher and it has many rotors. The name suggests that the crushing mode of the impact crusher is the impact breaking mode , which are crushing by breaking and impact, and can predict the general name of the crusher being an impact crusher. The impact breaker is used in the impact crushing mode, the hammer is fixed to the rotor and all the walls are parallel to the hinged shaft with the bore shaft, so when crushing the material, the bumper strap is connected with the hammer and the gear moves in the same direction as the hammer. The material in both the rotation and the revolution is crushed from a concentrated point. It could minimize the proportion of the sand fraction from the crusher.

2.2. Types of Impact Crushers

Impact crushers may be found in two designs horizontal shaft impact crushers HSI and vertical shaft impact crushers VSI. Both work on the same principle to crush the rocks into refined products. However, they all have varying features, functionality levels as well as their optimal applications also differ. Nevertheless, you can find each one in both a stationary or mobile design. The type of demands you have at your project determines what type that you just choose.

Horizontal Shaft Impact crusher consist of a hopper, two or three cavity, a rotor, and hammers (blow bars). Essentially, large products are fed into the hopper where they come into contact with hammers on a spinning rotor which crushes the material into smaller pieces. As the larger material gets impacted by the hammers it comes into contact with each apron rebounding it back to the rotating hammers for another round of impacting until it is discharged out of the impact crusher.

3. Design Features

3.1. Rotor Design

The rotor of an impact crusher is a large flywheel that holds blow bars in place and increases the machine's power and stability. The rotor's design can vary depending on the type of impact crusher, which is classified as either horizontal shaft impact (HSI) or vertical shaft impact (VSI). The speed of the rotor varies between 500 and 3,000 rpm. Due to the high rate of wear on these machines (wear can be taken up by moving the hammers on the pins) they are limited in use to relatively non-abrasive materials. They have extensive use in limestone quarrying and in the crushing of coal.

3.2. Impact Plates and Liners

Impact crusher impact plates and liners, also known as wear liners, are consumables that are frequently worn down and need to be replaced during the crushing process. These parts protect the impact crusher housing from abrasion and are typically made from wear-resistant steel. The rate at which they wear down depends on the hardness, abrasion, and fines content of the material being crushed. For example, materials like sandstone, which contain high amounts of silica, can wear out liners more quickly.

4. Applications in the Mining Industry

4.1. Primary and Secondary Crushing Operations

Primary crushers are used to reduce large rocks to smaller rocks, while secondary crushers are used to reduce smaller rocks to sand and gravel. Take impact crusher PF1315, the max feedings size is 500mm. If the rock material is less than 500mm, impact crusher could be used as primary crusher to crush it into smaller piece. If the raw material is large size with high hardness, it will have to use jaw crusher or gyratory crusher to break firstly, then to secondary crushing stage.

4.2. Advantages and Limitations

Impact crushers have several advantages and disadvantages, including:
The impact crusher is good safety performance and high reduction ratio to crush soft rocks. It is ideal for crushing softer, non-abrasive materials like limestone, coal, and gypsum. It can also produce cubical and evenly-shaped particles. Modern wear-resistant materials have made impact crushers more popular. The finished product is of cube shape and the tension force and crack is avoided.

However, impact crusher is high wear and requires blow bars to be replaced on a regular basis. This can lead to high maintenance costs. Due to the impact crushing method, impact crusher produces more dust, so other equipment such as pulse dust collector is a need to protect environment.