Crushing in Cement Plants: Complete Guide

Crushing is the first size reduction step of the cement plant: the rock of the quarry is reduced from the meter to the millimeter before the grinding takes over: the crusher does the coarse work: the jaw, the cone, the impact, the hammer: the selection, the calculation and the operation of the machine: the crushing section is the front door of the entire production line: if the crusher fails, the quarry stops, the raw mill starves and the kiln stands: the practical knowledge of the crushing is therefore the first knowledge of the cement engineer.

The Complete Cement Technical Package (931 files including the books, the courses, the Excel tools and the presentations: $249.99 one-time: instant download via the PayPal payment) includes this crushing guide with its tables, its calculation sheets and the crusher selection examples: the one-time price: the instant delivery: the lifetime library: this article walks the file from the quarry gate to the crusher discharge: the engineer follows with the document in hand and learns the logic that sizes and runs the machines.

This page is organized the way the crushing file itself is organized: the theory, the machines, the selection criteria, the calculations, the operation, the problems and the safety: the reader who finishes the page has the complete frame of the crushing department: the numbering follows the file paragraph by paragraph, so the reader can open the document and follow parallel to this article.

1. The Purpose of the Crushing in the Cement Process: Why We Crush

The size reduction has one purpose: to present the material to the grinding stage at the size that the mill wants: the raw mill babble:

• The quarry feed: the blasting and the ripping deliver the material up to 1 to 1.5 meters in size: the motor can eat the biggest rock;
• The mill feed: the raw mill is happy with the feed of 25 to 60 mm: something the ball mill and the vertical mill accept: the smaller the feed, the more efficient the grinding;
• The crushing purpose: to reduce the 1000 mm rock to the 30 to 60 mm feed with the minimum energy and cost: the crusher transforms the quarry block into the mill feed;
• The relation to the energy: the crushing is cheap energy when compared to the grinding: the Bond law: the energy rises as the size falls: crushing to the small feed buys the cheap grinding later: the optimization of the crushing pays the plant’s electricity bill;

THE COMMINUTION LAW: the stage of the crushing is the cheapest of the size reduction: the operation reduces the size proportion compared with the grinding: the first law of the process design: the crushers of the pre-stages and the mills of the finish: the boundary lies where the energy of the crushing equals the energy of the grinding: the file details the choice of this boundary.

2. The Crushing Stage Selection: One, Two, Three Stages

Not every plant needs three crushers: the choice depends on the quarry rock and the feed of the mill:

• The single stage: the mobile crushers and the small plants: one impactor or the hammer crusher receives the rock of 1 m and delivers the 25 mm: simple and compact: the rock must be soft to medium: the limestone of the big percolation:
• The two stages: the classic: the primary jaw or gyratory reduces to the 100-250 mm: the secondary cone or hammer reduces to the 25-60 mm: the intermediate screening between the stages;
• The three stages: the hard rock and the high capacity: the primary, the secondary and the tertiary crusher plus the screens: the sand plants of the aggregates also have the quaternary: the cement plants normally stop at the secondary;
• The raw material process: the clay needs no crushing (the wet questions); the limestone the two stages: the additive the single: the flowsheet of each raw material its own path;

THE CRUSHING TOWER of the plant is the vertical sequence of the machines: the feed hopper at the top and the belts at the bottom: the number of the stages is the economics: the more stages, the more equipment, the more screening and the more maintenance: the fewer the stages, the larger the machines, the stronger the feed of the crusher: the file presents the decision table with the capacities of each configuration.

3. The Jaw Crusher: The Primary Muscle

The jaw crusher is the primary machine of the classic plant: the vice jaw that squeezes the rock between the fixed plate and the swinging plate: the principles:

• The mechanism: the eccentric shaft swings the movable jaw; the rock is squeezed across the variable opening; the broken rock falls when the jaw opens; the cycle of the crushing: Rapid, about 200-300 strokes per minute for the small jaws and 60-100 for the giants;
• The setting: the closed-side setting (CSS) determines the top size of the product: the adjustments by shim or hydraulic cylinders: the CSS is the most important single number: too wide, the oversized product; too narrow, the slow feed;
• The nipping and the pitman: the angle between the jaws (the nip angle) that traps the rock: too big the rock escapes upward: the optimum around 20-23 degrees: the pitman, the connecting rod of the swing;
• The feed opening: the mouth size: the gape by the width: the rock of the feed must be the fraction of the gape: the block rules: the wedge exactly 80% of the gape;
• The capacity and the power: the jaw power is proportional to the opening and the stroke: the spec sheets the capacity curves at the CSS: the kW per ton of the jaw is about 0.2 to 0.5, and the jaw is by far the lightest user of the specific energy;

The jaw is ROBUST and the cheap: it eats the 1 meter rock and the surprises: the jib. The iron and the alloy with the grinding media it spits them out: the hydraulic adjustment of today and the automatic liner change: the maintenance: the jaw plates reversed when the wear arrives: the classic: the crushed rock from the jaws, the cleanest of the plant.

4. The Gyratory and the Cone Crushers: The Continuous Court

Where the jaw interrupts its cycle, the gyratory/cone families work continuously: the conical mantle inside the concave bowl: the rock is squeezed between the rotating mantles:

• The gyratory primary: the giant of the quarry: the 1.5 m rock to the 250 mm: the 10,000 ton/h beasts of the mines: the cement plants rarely use the full giants but the medium gyratory primary appears in the large new dry process plants where the throughput is the peak;
• The cone secondary/tertiary: the cone crusher of the limestone: the feed from the jaw, the product of the 20-60 mm: the synchronized squeeze and the choke feed: the crusher does the work of the cone crushing the secondary stage;
• The nip and the shape: the cone product is the cubic part: the elongated flat particles are the weak side: the cone design (the eccentric, the setting, the chamber profile) shapes the gradation;
• The hydraulic system: the CSS adjusted by the hydraulics under load: the iron protection that allows the tramp metal to pass: the automatic reset, the modern head of the cone;
• The liners: the concave and the mantle: the two wear pyramids: the half the liner life and the settings drift: the CMS (the chamber measurement) today: the wear measurement without stopping: the liner profile is the crushing profile;

The cone is the machine of the consistent shape and the cubic product: the modern cone with the chamber monitoring holds the product gradation within the narrow band: the limestone of the cement raw mix edges in the cones: the plant that needs the fine secondary product and the stable gradation takes the cone of the package.

5. The Impact Crushers: The Hammer and the Blow Bar

The impact crusher is the specialty of the cement plants: the rock is smashed against the blow bars and the impact walls by the kinetic energy of the rotor:

• The hammer crusher (vertical/horizontal): the rotor with the hammers strikes the rock and it rebounds on the impact plates: the single stage hammer crusher accepts the 1 m rock and gives the 60-90 mm in one machine: the darling of the soft and medium limestone plants;
• The blow bars and the aprons: the wear parts are the blow bars; the aprons set the product size: the adjustment of the clearance between the aprons affects the product: the classic hammer operations, the crusher of the cement: the input of the clay lumps;
• The reversible impact crusher: the rotor can both rotate: the wear on the two sides of the bars, double the life between the changes: the sturdy of the cement plants for the limestone;
• The selective crushing: the impeller fracture the softer minerals and leaves the hard ones whole: the crushing of the clay and the limestone mixtures, the removal of the hard flint at the feed;
• The grinding stages: some hammer crushers also fulfill the “crusher + dry” role in the newer plants: the crushing with the hot gas drying in the same machine: the flow of the plant simplifies but the complexity of the gas circuit is the price;

The impact crusher is THE workhorse of the cement’s pre-crushing: the highest reduction ratios (1 to 1 vs the jaw 4-5); the cubic product comes out; the abrasive hard rock is their enemy: the blow bar life on the flint can be days: the choice between the impact and the cone is the abrasiveness of the rock: the file includes the abrasive test: the flint test of the raw material: the decision goes by the numbers, not by the tradition.

6. The Rolls and the Sizers: The Sizing Machines

The less famous family of the crushing: the rolls and the sizers:

• The double roll crusher: two counter-rotating roll shells crush between them: the setting decides the product: the soft materials and the clays: the toothed rolls for the coal: the rolls of the mines, the care in the cement
• The sizers: the low-speed high-torque teeth parallel the rock against the bar: the high capacity and the low height: the top-size control by the tooth geometry: the mobile crushers of the quarries like the sizers for the tight space:
• Polycom and high pressure grinding rolls (HPGR): the HPGR whether it belongs to the crushing or the grinding: the high-pressure milling of the clinker and the raw: the inter-particle crushing: the feed to the ball mill much cheaper: the kWh savings the big story of the modern plants: the associated dimensioning Excel of the package;

The tradition of the cement, the roll crushers were for the earliest stages; today the HPGR is the rising star of the pre-grinding: the 20-40% reduction of the power of the ball mill: the crushing and grinding boundaries move: the modern packaged plant includes the HPGR hypercube in the flowsheet: the file explains the machine and the boundaries of the two stages.

7. The Feed and the Hopper: The Beginning of the Crushing Plant

No crusher works without the raw feed control: the first elements of the line:

• The feed hopper: the dump the dimension of the tractor: the 100-300 ton hopper: the v notch for the block rock: the truck cleansing into the hopper: the level of the hopper keeps the flow of the crusher full while the dumper cycles:
• The apron feeder: under the hopper: the heavy feeder of the tracks and the pans: moves the 1 m rock at the steady rate: the variable speed drive tailors the feed to the crusher load: the chain of the apron feeder the first controlled element of the line;
• The grizzly / the scalping screen: the bars often of the trapezoid: passes the fines, feeds the oversize to the crusher: the removal of the DC fines (the clay) protects the jaw from the diamonds; the primary bypass:
• The metal detection and the removal: the magnet over the belt, the metal detector, the magnetic drum: the rock drilling steel: the protection of the crusher, the most expensive insurance of the plant;
• The belt conveyor: the valker of the crushed rock: the transferring the rock from the crushers: the conveyor belts, the idlers, the drives: the line of the whole crushing circuit;

The plant before the crusher is the “feed section”: the smooth feed is the majority in the practice: the choke feeding (the crushing always full) is the ast trick of the good operation: the crushing cavity maintained full gives the stone-on-stone action: the finished: the same feed: the steady flow: the continuous crusher of the continuous plant.

8. The Calculation of the Crusher: The Numbers of the Selection

The selection of the crushing equipment is the calculation: the flow of the numbers:

• The capacity requirement: the plant’s tph: the crusher capacity = the feed X the positive factor: the theoretical capacity at the setting and the material: the typical design factor 1.2 to 1.3;
• The feed top size: the F80 / F100: the mouth of the crusher: the 80% of the feed passing: the capacity sensitivity to the feed: the finer the feed, the higher the capacity:
• The reduction ratio: the ratio between the feed and the product: the jaw at 4-6, the impact up to 15-20: the total plant ratio = the ratio of the stages multiplied;
• The product specification: the top size to the mill: the P80 target: the gradation band (the boulder 20 roughness) required by the grinding stage:
• The abrasiveness and the crushability: the abrasion test: the standard test of the crushing, the Los Angeles: the clay content: the selection of the family (impact vs cone);
• The power and the belt: the P80, the F80 into the equations: the basic: whiteness P = the Bond W * the tonnage: the kW & then the selection of the motor and the drive:

THE SELECTION WORKSHEET in the Excel of the package: the input: the tonnage, the F80, the P80, the material factors: the output: the reduction ratio, the kWh/t, the theoretical capacity: the engineer then selects the crusher from the catalog curves of the file and draws the flowsheet symbols: the practical day of the engineering office: the same notebook the selection from the pit sand to the lifting.

9. The Operation of the Crushing Plant: The Daily Rules

The daily of the crushing: OPERATION of each machine: the steps:

• The start sequence: the belts downstream first, the crushers after, the feeder last: the empty line starts the machines: the interlock logic of the line: the finished: clean and empty before the start:
• The choke feeding: the crusher full of material feeding the cavity fully: the cone especially: the choke improves the attrition: the breaking capacity: never starve the cone: the bulk of the throughput:
• The setting watch: the CSS and the product size: the measurement of the hourly product: the adjustments when the product drifts: the lining delivers the setting:
• The tramp iron: the off scene: every iron that enters the crusher is a price: the magnets, the crossing, the operator with the window, the load sharing with the shielded chute: the classic: iron-checked before the crusher:
• The housekeeping: the spillage under the conveyors, the level, the dust scrubbers: the clogged chute stops theline in 15 minutes: the cleanliness is the smooth line:
• The shift records: the hour-time, the feed rates, the power draw, the setting, the tomography: the visual inspection: the bearing temperatures: the record is the diagnosis of the coming failure:

The crushing plant operation wears many caps: the operator is the feed controller, the quality controller and the first maintenance man: the file lays the checklists of the shift start, the hourly patrol and the shift handover: the discipline of the checklists builds the healthy career.

10. The Common Problems of Crushing: The Troubleshooting

Even the good plant gets the troubles: the manual maps the diagnostics:

• The material hardening / the blockage: the sticky clays and the mud block the jaw: the low the feed, the spray water, the preselection screens: the breaking of the block:
• The oversize product: the settings unsupervised: the liner loosening: the checks of the CSS and the counter: the bad Eve on the gauge: the daily product sieve analysis:
• The power low / low wonder: the motor not pulling the nominal: the choke missing, the setting too wide: the feed lean: the power is the meter of your crusher:
• The vibration then the damage: the imbalance of the rotor, the bar loose: the man: the broken blow bar?? The precarious dust: the stats: the vibration analysis when the OCR smile trouble:
• The belting of the crusher: the slippage of the belts on the jaw/fla: the tension: the pulleys: the v-belts: the adjustment <... the sequence:
• The surge deck void: the lumps and the belt: the chute down and the belt tear: the relief and the allowance of the winter: the pile: the breaker of the lumps on the chute:

THE TROUBLESHOOTING FLOW of the package: the symptom, the possible cause, the check procedure, the solution: for each trouble: the sheet at the end: the plant marks its own history of the combat: the wood: the collection improves the lives of the crushing: the experience the master the manual: and the file: the sum of the decades of the crushing: the diagnosis papers fill the days of the puzzling.

11. The Environmental & the Safety of the Crushing

The crushing is the noisiest and the dustiest section of the plant:

• The dust: the dust collection: the bag filters on the crusher discharge and the transfer points: the water spray at the tips, the chute seals, the purge chutes: the collection hoods at the jaw and the transfer: mill:
• The noise: the crusher and the screens: the 90 dB + in the plant: the hearing protection: the abs the bars: the quietened the building: the noise level (85 dB) enforces by the authorities the vibration of the machine and the nearby the village:
• The confined space: the crusher cavity, the shaft, the pockets: the feeding truck: the lock-out: the caves of the crusher: the safety rules of the manual: the permit of the entry and the watching:
• The stockpiles: the hazards, the towers of the aggregates: the sharp edges: the soft sand traps: the cones of the stockpile discipline of the shelves;
• The blocked cavity rescue: the specific procedures: nobody enters the cavity while the crusher is free: the manpower of the raised with the pins: the slow: this top of the file:

THE CRUSHING SKELETON of the safety: the area is the section with the highest lost-time incidents: the clients: the file takes gifts not seriously: the section includes the permit forms, the risk analysis for the task in the tunnel (church card) and the personal protection matrix: the union nuclear same hours as the production: they drop the forever: the day of the plant takes them forever.

12. The Design of the Complete Crushing Circuit: The Complete Session

The large session of the workbook: the complete design of the plant crushing from the scratch:

• The given data: the quarry of the limestone: 400 tph of the feed, the F100 900 mm, the clay contents 5%, the abrasives to the test, the target: P80 of 50 mm with the stockpile:
• The stages: essential: the primary jaw (F100=900, setting 200 mm), the secondary impact (feed 200, P80=50): the screen between the check the closed circuit: the alternative: the single hammer crusher for where the limits…
• The numbers: the jaw capacity at the 250 mm set: 400 tph: the impact succeeded; the hammer capacity check: the two parallel lines or one line: the AFC feed with the STD the power: the belt to the stockpile:
• The selection: the family from the mental: the jaw for the primary (the oversize and the iron), the impact for the secondary (the cubicity), the metro, etc.:
• The drawings: the flowsheet: the hood of the jaw: the control: the values: the discharge: the hooks of the chamber: the final flush: the LPF the 2nd sieve of the analysis:

THE ANSWERS AND THE COMPLETED LOADING appear in the appendix of the file: the engineer checks his own flow: the session shows the practical workflow too: the numbers of the vendor curves, the margins of the flows: the plants the 931-file includes the similar white: the reader is ready for crush selection in any committee: the skill: the numbers, the charts, the installation: from the “stone” to the design: this is the file the engineer keeps in the binder on his desk.

13. The Excel Tools of the Crushing: The Fast Numbers

Behind the page, the calculators of the package:

• The crusher capacity calculator: the input the family (jaw/cone/impact), the setting, the liner condition, the material: the output the theoretical capacity curve, the tph at the desired setting: the immediate for the feed/planning:
• The reduction ratio of the flow: the multi-stage line, the F100/P100 with the denominators: the products quantity per stage:
• The power estimator: the Bond-based number with the connection to the crushing family factors: the kWh/t vs the kW: the installed recalculation of the crushers:
• The sieve log template: the product sieve analysis form, the graph, the убыток P: the daily quality of the crushing checked in the excel: the asset:
• The comparison sheet: the two flows considering CAPEX OPEX: the stages, the screening, the dust, the maintenance and the spare parts: the decision table of the management:

The calculators serve the estimators and the designers: the values for the tender, the check of the tender, the capacity upgrades: the tools are the quick part of the file: the engineer types the setting and the answer is the screen: the tools comply with the methods of the book and the practice of the industry: they are the motive of the “second man” of the office.

14. Frequently Asked Questions on the Crushing

Which crusher is the best for the limestone of the cement plant?

For the standard: the line: the two-stage jaw: b low moral parameter: the hammer impact for the soft stones and the cost: the cone for the cubic product of the hard rock: the decision is the test bench: the abrasiveness of the rock: the answer to the file is the data: the limestone that wants the jaw and the impact crusher is the overwhelming the majority of the cement plants: the hammer crusher when the dry and squishy; the jaw + impact when the quartz in the limestone.

What the difference between the crushing and the grinding?

The crushing to about 100 mm and more (coarse), the grinding below it: the same Bond law extended: the crushing is the coarse work (the jaw etc.): the grinding is the fine work (the mills): the distinction practical: the energy and economics: they are the stages of the same law of the energy and the decreasing sizes: the plant keeps both inside the fenced circle of the comminution.

Why the crushing ahead of the mill saves the energy of the plant?

The Bond law: the W of the size reduction rises as the 80% goes finer: the crushing at the coarse end is cheap kWh/t; the mill then works with the smaller stones and the cheaper kWh/t in the total: the total grind from the 900 to 50 mm also saves the mill time: the 20 to 30 mm feed vs the 100: the throughput of the mill leaps: the crushing the front of the energy chain: every mm of the crushing saves the cents of the grinding.

The crushing the same for the cement and the other industries?

The machines the same: the classifiers, the sizers: the principle universal: the cement, the aggregates, the mines: the site-specific: the cement targets the raw meal chemistry and the continuous: the aggregates the grading gradations: the mines the metal: the cement presses the soft constructions of the limestone: the practice within the same bread: the engineer changes the material but not the rules.

Do I need the Excel tools even if my plant already has the crushers?

The designers need them for the upgrades; the operators mostly for the log analysis and the estimates: the upgrade of the plant: the crusher capacity check: the limitation of the product; the new setting: the tools calculate the plan otherwise the notion: the daily use pays the years of the convenience: the tight margins need the quick numbers: the tools save the hours of the engineering per week: the package (and this file) the decisions with the numbers: the one-time $249.99 can be recovered by the first correct setting for the plant.

15. Conclusion: The Crushing, the First Victory of the Size Reduction

The crushing: the open of the cement plant unit: the muscles, the numbers and the schedules: the crude rock from the quarry enters the plant and the last of the entire line is attached to the quality of this first step: the crushing stage is the anchor forest: the jaw, the gyratory, the impact: the selection of the machine family, the running of the line and the diagnosis of the troubles: the complete practice in this article: the complete lessons inside the file of the 931 set.

The Complete Cement Technical Package (931 files: $249.99 once: the PayPal: the instant download) brings all these manuals, the Excel tools and the visits: the crusher selection workbook, the capacity calculators and the whole library of the cement equipment: the crushing engineer, the plant designer or the young career: the package delivers the knowledge of the cement the 931-fold: the crushing guide the door: the sweep of the industry opens at the click: the cement knowledge, the professional library: yours, with the PayPal button.

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.