Coarse Size Reduction of Raw Materials

Coarse size reduction of raw materials (module 03 of the cement training series, 43 pages) is the training module of the crushing department: the comminution of the blasted quarry rock into the size that the raw mill can consume: the module takes the learner stone by stone through the theory of breakage, the machines of the plant (the jaw crushers, the gyratory, the hammers, the impactors, the rolls), the reduction ratios, the screening and the circuits of the crusher: it is the foundational training of every crushing engineer, quarry foreman and mill operator: the surfaces of the industry start here.

The Complete Cement Technical Package (931 files: books, courses, Excel tools, $249.99 one-time, instant download after the PayPal payment) delivers this module in its series: after the raw materials and the mix calculation, before the drying and the raw grinding: the crushing chain of the formation: this guide presents the content of the module: the breakage theory, the machines, the circuits and the maintenance of the coarse reduction stage.

1. Why Size Reduction Is a Department of Its Own

The raw materials leave the quarry as the blasted rock whose size spans from the dust to the boulders of a cubic meter: the cement mill can eat grains of a few millimeters: the journey between the two is the province of the coarse and the fine size reduction: and the plant spends a meaningful share of its energy and its wear there: the crushing stage consumes about 2–8 kWh per tone of the rock and absorbs the first heavy wear costs of the process: the module devotes its pages to the understanding of this stage because the quality of the crushing is judged by the downstream parts: the undersized feed of the raw mill, the constant throughput of the plant and the cost of the spare parts.

In the formation series the module sits in its right place: after the raw materials module (what the rock is) and after the mix calculation (what chemistry the plant needs), the module teaches the first transformation of the geometry: the commounters: the trainee who masters the crushing understands the whole material flow of the plant from the face to the silo.

2. The Theory of Size Reduction in the Module

The module does not ignore the theory, because the machines of the plant are the descendants of the theory: the pages open with the fundamentals:

• The mechanism of breakage: the compression, the impact, the attrition and the shear: the four ways the machines of the plant break the rock, and the machines that use each: the compression (the jaws, the cones), the impact (the hammers, the rotors), the attrition (the rolls and the mill liners).
• The reductions ratio: the ratio of the feed size to the product size: the classic numbers of the module: the coarse crusher 4:1 to 8:1, the secondary 10:1 or more: the module derives how the ratio is measured (the 80% passing size, the F80 and the P80 of the daily talk): the numbers the plants quote every morning.
• The distribution of the product: the curves of the product size: the module shows the typical grading of the crusher downstream and the meaning of the curve: the module does not let the trainee believe that a crusher produces a single size: it produces a distribution, and the distribution must fit the downstream.
• The energy laws: the Rittinger and the Kick in the background of the module (with the Bond work index developed in the companion module of the package, the 06 Bond grinding work index module): the coarse side of the same physics: the energy increases as the size gets smaller: the module explains why the crushing is done in the coarse stages and never in the mill when avoidable.

The theory of the module is served in the language of the plant: the equations are few and the results are anchored in the practice: the trainee passes from the physics to the concrete without the vertigo of the academic.

3. The Machines of the Coarse Stage: The Jaw Crushers

The module proceeds machine by machine, and the first of the coarse stage is the jaw:

• The construction: the fixed jaw and the swing jaw, the frames, the toggle plates, the pitman, the flywheels: the throat of the crusher, the max feed size, the discharge opening.
• The working: the movable jaw presses the rock against the fixed jaw, breaks the blocks, the discharge falls when the jaw regresses: the periodic cycle of the breakage and the throughput it permits.
• The setting and the adjustment: the CSS (the closed side setting) of the jaw: the adjustment screw and the hydraulic: the module trains: the finer setting, the higher the ratio, the lower the throughput and the more the flakes.
• The applications: the jaw as the primary of the small and medium plants: the 60–100 cm feed, the capacities in the hundreds of tons per hour: the plants’ first choice where the rock is hard.
• The wear and the maintenance: the jaw plates in the manganese steel, the life and the turnaround: the frequency of the measurement of the wear: the module’s maintenance page: the wear of the liners is the cost of the primary.

The jaw is the mutton of the coarse stage: the module devotes it the pages proportional to its presence: every trainee of the quarry line knows the jaw before the end of the module.

4. The gyratory and the Cone Crushers

Where the production demands the primary and the second stage of the high tonnage, the module presents the gyratory family:

The primary gyratory: the bowl and the mantle, the eccentric bushing, the continuous compression around the circle: the gyratory crushes around the clock in the big plants: the capacity of the tale of the cactus: the first stage of the million-ton plants: the module: the headquarters of the class exchange and the mantle adjustment: the open side setting: the gyratory outlives the jaw when the tonnage is huge.

The cone crushers: the secondary and the tertiary: the finer and the higher ratio: the hydraulic setting, the tramp iron pass, the chokes: the module explains the selection: the cones are the men of the middle: the sizes of the 5–50 mm product: the feed of the raw mill too coarse and the cones deliver it.

The module compares the two on the spread table: the shape of the product (the cubical of the cone, the slab of the compression), the energy, the wear, the moisture tolerance: the designer of the circuit chooses with the numbers of the table: the module’s comparison trains the selector.

5. The hammer and the impact crushers: the stone cold of the plants

The third family of the module is the specialist of the cement: the hammer and the impact crushers:

• The hammer crusher: the rotor and the hammers (the bars), the grates and the breaker plates: the breakage by the impact and the attrition: the limestone: the ratio up to the huge (1:50 in the single stage) and the product the direct feed of the raw mill: the module: the typical choice of the cement plants for the limestone of the moderate hardness: the calcium: the limestone.
• The impact crushers: the rotor and the breaker plates: the free flight of the rock: the ratio is large and the product cubical: the feed of the damp materials, and the calcaire: the application.
• The aprons and the setting: the adjustable breaker plates of the hammer mills: the plain gap: the size: the module: the aprons and the rejection: the prevention of the tramp: the foreign bodies: the grate: the opening: the module’s the practice and the ear standard of the plant.
• The wear of the hammers: the interchangeable, the reversible hammer heads, the hard facing: the life in the hours or the tones: the module: the relative the hammer cost: the module’s maintenance page compares all the machines: the hourly cost of the wear.

The hammer crusher is the perfect machin of the cement’s raw: single stage from the boulder to the mill feed, and the module devotes its longest chapter: the train the selected as the soul of the crushing department.

6. The Roll crushers and the others

The module gives the collectors the remaining machines:

• The roll crushers: the two or gears: the compression of the particles between the cylinders: the medium hardness, the sticky materials: the dusty uses of the limestone: the module- the roll: the machine of the feed.
• The sledges and the pick types: the early crushers of the small plants: the historyca in, the module remembers their place: the slow speed, the high torque: the blockages.
• The sizers: the double: the fines, the grit: the modern: the module: the civil.

The selection table of the module closes: the type, the feed, the product, the curve, the energy, the wear cost: the operative calls the annex in the morning: the seven machines of the course in the one sheet: the training.

7. The crushing plant and the circuits: the module’s central practice

The machine is half the story: the circuit is the other half, and the module leads the trainee through the practical arrangement:

• Single and two-stage circuits: when the jaw’s ratio suffices and when the hammer replaces the second stage: the module: the design of the tonnage and the product.
• The open vs closed circuit: the open (all the product moves on) vs the closed (the oversized returns to the crusher): the module: the closed circuit multiplies the efficiency: the cost of the recirculation: the ratings.
• The by-pass and the pile structure: the surge pile after the crusher: the buffer between the crushing and the raw mill: the stacking and the reclaiming part of the department: the fraction.
• The dust collection and the noise: the filters of the crusher buildings, the belt stations, the silo: the module: the environmental chapter: the extract, the bag house, the enclosure: the operator: the helmet.

The circuit chapter is the most practical of the module: the diagram on the board, the control the trainee designed: the module’s the exercise: draw the circuit of your plane: the plants’ courses apply the exercise to their own departments: the module’ answer already adapted.

8. The feeding and the drives

The module is complete to the feeding: the crushers are fed, the consistency and the distribution are the quality of the crushing:

• The feeders: the apron feeder (the heavy rocks), the vibratory feeders (the control the flow), the belt feeders: the feeding of the primary must be regular: the module: the jam of the crusher, the hunger of the crusher: the two enemies of the throughput.
• The drives: the motors of the coupling, the flywheels: the constant energy: the DOL and the SF drives: the soft starts on the grid: the module: the current reading and the load: the monitoring of the operator.
• The metal detector and the sorting: the mine of the metal: the tramp the digger teeth and the tools: the detector and the magnet: the module: the protection of the crusher: the cost of the millions.

The feeding train: the least glamorous pages of the module and the most critical of its practice: the plants diagnose most of the crusher stoppages in the feeding side: the module gives the habit of the checking: the apron, the plate, the magnet: the first fifteen minutes of the shift.

9. The wear and the maintenance of the coarse stage

The economics of the crushing department rest on the wear, and the module devotes its whole chapter:

• The wear parts inventory: the jaw plates, the cones and the mantles, the hammers, the aprons, the breaker bars, the liners: the life tables of the module: the wear is defined as the money: the cost per tone of each machine at the module’s numbers.
• The wear mechanisms: the abrasion of the quartz, the impact cracking the wear: the hardness of the rock dictates the rate: the module: the wear of the hammer mills with the abrasive limestone is the life of the thousand: the choice of the materials: the alloy steels, the chromium, the carbide implants.
• The change outs: the turnaround of the plates, the rebuilding and the hard facing: the module: the planning: the shift gears the hammer set to the breakage: the spares in the store: the module: the cycle of the maintenance plans of the resident.

The wear: the module makes the trainer unafraid of the dressing floor: the mechanical eyes of the simple: the measurement of the growth, the checking of the gap, the schedule of the change: the maintenance culture of the package: it starts in this module of the coarse.

10. The safety of the crushing department

No training of the plant is complete without the safety pages, and the module of the coarse reduction keeps the tradition: the crusher is the machine of the heavy hazard: the module:

• the isolation and the lockout of the crushers during the maintenance: the never-under-the-jaw rule: the training: the man alone: forbidden;
• the ignition and the flyrock of the blasting: the helmets, the glasses: later the crushing of the rock: the ears: the module: the protecting;
• the belt: the nip points, the entries, the pinch rollers: the guards of the module: the reject of the metal: never the hand;
• the house: the spills, the blocked chutes: the dislodging: the rod and the pole: never the rags: the module: the safe access: the stairs, the railings;

these pages are the module’s most serious: the training of the safe habits at the foot of the quarry: the vegetation of the cement plants.

The module dedicates its last safety pages to the specific case of the isolation during the maintenance: one operator in the chamber of the crusher, the machine locked and tagged by the two keys, the guard of the opening: the module teaches the procedure of the locked access and the check of the head before the start: the incidents of the industry are the memory of every janitor of the plants: the module wrote the memory into the discipline: the safety chapter of the module 03 is the safety of the whole material handling family, and the plants run it every day of the operation.

11. The module in the formation of the series

The formation of the series places the module between the mix: as the numbers: after the raw material and the mix, the crushing (with the two modules of the drying and the Bond grinding) opens the equipment family of the processing: the trainee’s progression: the material → the number → the size: the module gives the lecture with the structure of the user’s guide of the ten facts: the objectives, the slides, the quiz: the evaluation: the 10-15 minute quiz of the module on the machines, the ratios and the circuits: the answer key: the whole.

11. The Size Reduction Calculations: The Sizing Pages of the Module

The module closes its technical body with the sizing pages: the arithmetic that the designer and the purchaser of the plant use, and that the operating plant uses to check its own machines:

• The F80 and the P80: the 80% passing size of the feed and of the product: the two numbers that define the reduction ratio of every machine in the standard language: the module trains the sieve analysis of the sampler: the sizes, the screens, and the reading of the curve.
• The reduction ratio of the circuit: the total ratio feed to product, and the check that each machine stays inside its championed range (4-8 for the primary, 8-15 for the secondary): the module: a machine asked beyond its ratio is a machine of the stoppages.
• The capacity of the crusher: the empirical relations of the throughput: the open side setting, the closed side setting, the feed grading, the density of the material: the module: the capacity check of the design against the demand of the plant.
• The aperture of the grizzly and the screens: the separation sizes: the module: the first screen at the second stage: the chaff: the separation of the undersize: the load of the crushers that the screening removes.
• The Bond work index of the coarse stages: the bridge to the fine module: the module uses the WI of the companion (the module 06 of the package, the grinding work index according to Bond) and shows the calculation of the stage power: the few equations of the coarse sizing full.

These calculations turn the module from the descriptive to the engineering: the trainee ends with the ability to write the size-reduction block of the plant’s equipment sheet: the same block that the engineering offices of the plant verify on the commissioning: the module gives the numbers: the plants check the numbers: the respect grows.

12. The Inspection Rounds: The Practical Habit of the Module

The last practice the module installs is the daily inspection of the crushing department, because the failures of the crushers announce themselves long before the breakdown:

• The morning round: the oil levels and temperatures of the bearings and the gearboxes, the vibration of the crushers and the screens, the belt alignment, the spillage under the chutes, the magnets and the detector test: the fifteen minutes that save the day;
• The weekly round: the wear measurements (the jaw profile, the hammer length, the mantle shoulder), the screen cloth condition, the dust collector differences, the tightening of the fasteners;
• The monthly round: the current peaks of the drive, the calibration of the metal detector, the housekeeping scores, the stored spare parts inventory;
• The recording: the logbook of the machine: the module: every stoppage is a sentence in the history of the machine: the history is the diagnosis: the trends of the wear, the repeats of the problems;

The checklist habit is the quiet half of the module’s maintenance chapter: the wear table tells what to change, and the checklist tells when the change is due: the combination turns the crushing department from the reactive into the planned: the module’s measured contribution to the plant’s availability.

13. The Crushing in the Complete Package: The Support Materials

The coarse module is not alone in the package: the crushing department of the plant is supported by the companion files that the package delivers with the series:

• The Bond grinding work index module (06): the sister module of the fine side: together they cover the whole size-reduction span of the plant, from the boulder to the powder: the same vocabulary, the same physics: the two modules are read as one.
• The Excel tools of the package: the capacity estimators and the power calculators that follow the formulas of the module: the trainee of the module verifies the tool’s answers by hand (the discipline of the series) and then uses the tool at production speed.
• The maintenance courses: the mechanical maintenance files of the package (the kiln, the mills and the equipment department) whose principles apply to the crushers: the module gives the machine; the maintenance courses give the craftsman.
• The drying module (04): the immediate neighbor of the process: the crusher product in the wet season is the drying module’s feed: the two modules together form the complete preparation chain.

This family shows the architecture of the package: every module is an organ of a single body: the trainee never stays in one module alone, because the plant never runs one department alone: the complete formation mirrors the complete plant, and the package is the complete.

14. Frequently Asked Questions

Why so many pages for a simple rock crushing?

The answer the module gives: because the crushing stage wears more per ton than the mill, breaks more bones than the kiln, and feeds every hour into the raw chemistry: the 43 pages pay for themselves in the first released year of the operation: the trained crews see the failures early, the wear is planned, and the circuit is run at its curve: the module is the money.

What does the trainee retain from the 43 pages?

• the four mechanisms of the breakage, and the machines that use each;
• the F80/P80 and the reduction ratio of every stage;
• the strengths and the limits of the jaw, the gyratory, the hammer and the cones;
• the open and closed circuits, and the role of the surge pile;
• the wear parts and their costs per tone of the rock;
• the safety rules of the crusher floor;

these six items are the examination of the module and the vocabulary of the crushing department: the achievement of the course: the module’s pages are short, yet dense enough to build the six answers.

Do I need the module if I buy crushed lime?

Yes for the receiving plant: the incoming size control of the delivered lime (the size curve, the fines) is the quality of their mill feed: the buyer of the crushed material must hold the same knowledge of the sizes and the curves that the module teaches: and the maintenance of the receiving station (the hoppers, the grizzlies) is the same knowledge: the module is the plant’s own department, bought or not.

Which modules of the package support the crushing?

The neighboring modules: the drying (the moisture of the feed), the grinding (the Bond the modem), the maintenance courses of the package (the equipment), and the Excel tools of the size and the capacity: the packages of the module have the crushing as the family and the family is complete: no single machine of the plant stands alone; the module series never stands alone either.

How do I get the module?

The module arrives with the Complete Cement Technical Package: the 931 files: the modules, the vertical and the horizontal series, the books, the tools: the one-time 249.99 dollars: the PayPal: the instant download: the crushing and the whole profession: the lifetime.

And the final honest note of the module: the crushing department of today is no longer the dirtiest of the plant: the enclosures, the dust collection and the remote monitoring have transformed the environment of the crusher: the modern operator of the coarse stage works quieter and cleaner than his predecessor: the module shows the new face of the stage: the profession of the crushing is a profession of the future, and the module — with the wear, the circuits and the calculations of its pages — is the passport of the profession.

15. Conclusion

The coarse size reduction of the raw materials: the third module of the cement series: 43 pages on the first machinery of the plant: the jaw, the gyratory, the hammer, the cones, the rolls: the ratios and the circuits, the wear, the safety: the module of the crusher plant: the foundation of the training: the package delivers the module within the whole: the raw materials to the fine grinding, for the one-time, the life: from the boulder to the powder, the training accompanies every stage: this is the module of the boulder.

For the engineer who must present this module tomorrow: the plan of the session is already drawn: the theory of the breakage in the morning, the machines in the middle, the circuits and the calculations after, the safety and the inspection at the end: the 43 pages of the module deliver the session without the extra preparation: the quiz of the module checks the four blocks, and the trainee who passes the quiz has the vocabulary and the numbers of the crushing department: the module, the session, the competence: the three words of the training series, and the module 03 is a complete example of the three.

The coarse size reduction of the raw materials is the first process step of the cement plant: this module covers the crushers, the impactors and the hammer mills that reduce the quarry rock to the mill feed size, with the selection criteria, the capacity formulas, the wear behavior and the operating practice of the crushing installation.

This file is part of the Complete Cement Technical Package (931 files) available from cementequipment.org. Respective rights holders; library copy for the licensed single user.