Technology

Technologies for primary crushing of hard clays

30/06/2021

The choice of an effective grinding process is very important for obtaining products with high technical and aesthetic qualities. Based on experience acquired in more than 100 years of operation in the heavy clay industry, Bongioanni Macchine has developed three types of machine suitable for primary crushing of particularly hard clays with various levels of moisture content.

These are the primary crusher type 612FR, the clay crusher type RR1200 and the clay disintegrator type 13LD, rugged solutions built with high abrasion resistant materials that guarantee consistent long-term quality. The machine dimensions were carefully designed so as to obtain an output particle size that would ensure smooth machine operation during subsequent processing. The primary crusher and the clay crusher can be installed immediately downstream of the box feeder or can be supplied with material discharged from wheel loaders. The output particle size will be suitable for directly feeding a clay disintegrator or a wet pan mill.

The clay disintegrator 13LD is designed to chop up clay and crush any stones still present inside the raw material at the pre-processing stage to a size that will be suitable for feeding a roughing roller mill. It features a smooth roller with a large diameter which rotates at slow speed opposite a smaller diameter roller equipped with interchangeable blades, which instead rotates at high speed. The combined action of the rotating movement towards the centre of the two rollers, and in particular the high speed of the bladed roller, allows the clay to be crushed and the stones to be split into smaller pieces. The safety and smooth operation of the entire process is ensured by safety breaking pins capable of absorbing any accidental overloads between the rollers. Clay is fed from the top by means of a belt conveyor, while a feeding hopper carries it towards the central portion of the rollers.

The RR1200 clay crusher is designed to crush and crumble hard clays that may have stone intrusions originating from the quarry, thereby facilitating and optimising the subsequent raw material processing treatments. Using a belt transmission system, two motors drive the coaxial gearboxes mounted on the two shafts which rotate at the same speed. The shafts are fitted with star-shaped discs made of anti-wear steel and further hardened by means of a welding process, which serve to crush and crumble the raw material at the preparation stage.

The pulleys on each gearbox are fitted with a mechanical breaking pin and both shafts are equipped with rotation speed control. If the maximum permissible effort is exceeded, the mechanical breaking pin breaks and the rotational speed control sends a signal to cut power to the motors and to stop feeding clay to the machine.

The clay is fed from the top by means of a belt conveyor and passes through a hopper to ensure correct feeding towards the central portion of the machine, where scrapers are present to ensure proper cleaning of rollers. On request, a third independently controlled shaft equipped with feeding reels can be mounted.

The 612FR primary crusher is designed to crush and crumble clods of hard clay coming from the quarry to a particle size that will guarantee good operation of the subsequent machines. The primary crusher consists of two strong steel sides containing the housings for the bearings that support two rollers placed at a fixed centre-to-centre distance and which rotate at the same speed. These rollers consist of a shaft on which steel crushing stars with anti-wear coated tips are mounted. The rollers are actuated by epicyclical reduction gears driven by a system of motors, pulleys and V-belts. A rugged electrowelded sheet steel hopper conveys the clay to the crushing discs and at the same time supports a set of scrapers for roller cleaning. The side walls of the hopper are protected by an anti-wear plate and all the bearings are lubricated with grease.

612FR primary crusher – Technical data

Roller dimensions  (Ø x width) 600 x 1200 mm
No. of crushing points per star 5
No. of crushing stars 10 -  9
Roller speed 14 - 17 rpm
Roller power (standard) 30  o 37 kW
Max. output 200 - 300 ton / h 
Weight 7600 kg
Required performance level ( PLr ) “c”
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