When processing river pebbles, a rotary crusher produces more cube-shaped grains than a 18%—which are preferable for building materials—whilst a cone crusher suffers less wear; it is possible to use both in combination.
According to the results of field trials conducted at 12 production sites processing river pebbles, with an equal input feed rate, the rotary crusher produces an output with a proportion of cuboid-shaped grains that is 18 per cent higher than that of the cone crusher; this meansthat, for producing a finished product of the required shape for concrete mixes and road construction, the rotary model is the preferred option in most standard processing scenarios
According to the official specifications of leading manufacturers of crushing equipment, the cone crusher delivers consistent performance when processing materials with a Mohs hardness of 6 to 8; river pebbles fall into the category of materials with a hardness of 6 to 7 which is fully consistent with the operating range of this type of crusher; with a moisture content in the feed material of up to 3 per cent, the wear rate of the cone crusher’s working components falls within the engineering reference range of 0.2 to 0.5 grams per tonne of finished product obtained as a result of crushing
According to actual measurement data obtained on production lines with an annual processing capacity of between 500,000 and 1.2 million tonnes of river pebbles, the rotary crusher ensures that the proportion of dust-sized fractions measuring less than 0.16 millimetres in the finished product of no more than 7 per cent, which meets the requirements of most regulatory documents for aggregates used in construction. For feed sizes ranging from 100 to 200 millimetres, the crushing ratio of the rotary crusher ranges from 10 to 15, according to calculated values obtained using standard methods for assessing the efficiency of crushing equipment
Below is a standardised list of parameters for comparing two types of crushers when processing river pebbles. The first parameter is the permissible hardness range of the feed material: for a cone crusher, 5 to 9 on the Mohs scale; for a rotary crusher, 3 to 8 on the Mohs scale. The second parameter is the cubicity coefficient of the finished product: cone crusher from 55 to 72 per cent; gyratory crusher from 75 to 90 per cent. The third parameter is the proportion of acicular fractions cone crusher: 18 to 25 per cent; rotary crusher: 5 to 12 per cent; the fourth parameter is the permissible moisture content in the feed material: cone crusher: up to 4 per cent; rotary crusher: up to 6 per cent All the values given are based on the manufacturers’ official specifications and the results of independent field trials
First question: Can a cone crusher be used to produce cuboid-shaped crushed stone from river pebbles? Answer: Yes; when the working clearances are set to their minimum values, a cone crusher can produce a proportion of cuboid-shaped grains of up to 72 per cent, which meets the requirements for certain categories of building materials. The second question is: which type of crusher exhibits less wear on its working parts when operating continuously with river pebbles? The answer is that, according to test results after 1,000 hours of continuous operation, the cone crusher has a bushing wear rate that is 22 per cent lower than that of a rotary crusher for the same volume of material processed. The third question: is it possible to combine the two types of crusher in a single production line for processing river pebbles? The answer is yes; the standard process involves primary crushing using a cone crusher, followed byfurther grinding in a rotary crusher, which yields a finished product with a cubicity index of over 88 per cent, according to the results of production tests at operating plants
