Bucket Elevator Excel Sheet & Calculations

The bucket elevator is the vertical backbone of the cement plant: the raw meal climbs to the preheater, the clinker climbs to the silo, the cement climbs to the packer, and in every one of those climbs the bucket elevator carries the tonnes on a chain of buckets that never stop: the engineer who designs, checks or modifies a bucket elevator faces one central question: how many tonnes per hour will this chain of buckets carry, and what motor will it take to lift them? The answer is not guessed: it is computed from the capacity formula, the chain speed, the bucket pitch and the bulk density of the material, and then the power is computed from the lift, the tonnage and the efficiency of the drive.

The Complete Cement Technical Package (931 files including the Excel tools, the books, the courses and the presentations: $249.99 one-time: instant download via the PayPal payment) includes the bucket elevator Excel sheet: the engineer opens the file, enters the material, the capacity and the lift, and reads the bucket size, the chain speed, the chain size, the motor power and the running cost of the elevator: this article walks the workbook: its sections, its method, the numbers of a worked example and the engineering judgment that the selection demands: the reader finishes with the confidence to open the file and to deliver a bucket elevator that the plant can operate.

Why such a simple machine carries such weight: the bucket elevator is the shortest path between two points in the vertical plane, and for the granular and pulverized materials of the cement plant it is often the only practical one: the conveyor belt gives up at the angle of repose, the screw conveyor loses its grip on the vertical, the pneumatic lift spends the compressed air: the bucket elevator takes the material straight up, bucket after bucket, chain link after chain link, at a speed that the plant can count on: the design of the elevator is the arithmetic of the bucket: the bucket holds a volume, the chain presents the buckets at a rate, and the product of the volume and the rate is the tonnage: this page follows the order of the workbook, so the reader can work through the article with the spreadsheet open: the inputs first, the capacity second, the chain third, the power fourth, the worked example and the conclusions last.

1. What the Bucket Elevator Excel Sheet Does

The bucket elevator Excel sheet of the package is a selection and verification workbook, not a brochure: the engineer enters the operating data of his elevator and the sheet returns the engineering numbers that the purchase order and the motor schedule demand: the sheet is organized in linked sections, each one a worksheet with its own purpose, and the results of one section feed the next: the whole workbook reads as one continuous calculation, from the tonnes per hour at the inlet to the kilowatts on the motor nameplate.

• The input sheet: the material (name, bulk density, moisture, abrasiveness), the required capacity in tonnes per hour, the lift in meters, the operating hours per day, the ambient conditions: the engineer enters these once and the rest of the workbook follows;
• The capacity sheet: the bucket size, the bucket pitch, the chain speed and the fill factor: the sheet computes the theoretical capacity and compares it with the required capacity, flagging the combinations that fall short;
• The chain sheet: the chain size, the breaking load, the computed working tension and the safety factor: the sheet checks the chain against the load of the loaded buckets and the weight of the chain itself;
• The power sheet: the lifting power, the take-up power, the friction and the drive efficiency: the sheet computes the required motor power and the recommended motor frame;
• The summary sheet: the complete bill of the elevator: the bucket, the chain, the motor, the reducer, the head shaft, the running cost per hour and the annual power cost;

The workbook is a template of honest engineering: the shaded cells are the inputs, the white cells are the calculations, and every calculated cell carries the formula so the engineer can trace the number to its origin: no black boxes, no hidden assumptions, no marketing factors: the sheet does for the bucket elevator what the balance sheet does for the plant: it puts every number in its line.

2. The Capacity Equation: The Formula of the Bucket Elevator

The capacity of a bucket elevator is the product of the material carried by each bucket and the rate at which the buckets pass the discharge point: the classic metric formula of the industry writes the capacity as:

Q = 3.6 x v x (i / a) x rho x psi

Where Q is the capacity in tonnes per hour, v is the chain speed in meters per second, i is the volume of one bucket in liters, a is the bucket pitch in meters, rho is the bulk density of the material in tonnes per cubic meter, and psi is the fill factor, the fraction of the bucket volume that is actually filled with material: the factor 3.6 converts the liters per second to tonnes per hour.

• The chain speed v: the speed at which the chain and its buckets travel: typical speeds for the cement plant range from 0.5 m/s for the delicate large buckets to 1.5 m/s for the small fast buckets of the raw meal: the speed decides the fill, the discharge and the wear;
• The ratio i/a: the bucket volume per meter of chain: a large bucket on a long pitch gives a high volume per meter, a small bucket on a short pitch gives the finer stream: the ratio is the heart of the sizing;
• The bulk density rho: the density of the loose material in the bucket: the clinker at about 1.3 to 1.5 t/m3, the raw meal at about 1.1 to 1.3 t/m3, the cement at about 1.1 to 1.4 t/m3: the same bucket carries different tonnes of different materials;
• The fill factor psi: the practical filling of the bucket: 0.6 to 0.75 for the coarse lumpy materials, 0.8 to 0.9 for the fine free-flowing meal: the fill factor is the honesty of the calculation: the bucket never carries its full geometric volume;

The formula is one line, but the judgment is in the factors: the sheet carries the recommended fill factors and the typical speeds in the lookup tables, so the engineer enters the material and reads the factors instead of inventing them: the capacity that the formula returns is the design capacity, and the required capacity must sit comfortably below it, with the margin that the plant’s peaks demand.

3. The Worked Example: The Elevator of the Clinker Silo

The workbook carries a worked example, and this article follows it: the case is the clinker elevator of a mid-size dry process plant, lifting the clinker from the kiln cooler discharge to the clinker silo: the numbers of the example are the numbers of a real design, rounded for the lesson.

• The material: the clinker at 1.40 t/m3 bulk density, cooled, free of the long lumps, abrasive;
• The required capacity: 220 t/h continuous, with a design margin to 260 t/h for the kiln peaks and the cooler surges;
• The lift: 42 meters from the inlet at the cooler discharge to the head at the silo top;
• The hours: 24 hours per day, 330 days per year, about 7,920 hours per year of operation;
• The constraints: the space at the silo foot is limited, the clinker is abrasive, the downtime of a chain failure is a full kiln stoppage;

The example runs through the sheets in the order of the workbook: the capacity first, the chain second, the power third, and each result feeds the next: the reader can follow the numbers with the spreadsheet open, changing the inputs and watching the design respond: the worked example is the fastest way to learn the tool, because the engineer sees the calculation think.

4. The Inputs: The Data the Engineer Enters First

The input sheet of the workbook is the first stop, and the quality of every downstream number depends on the quality of the inputs: the sheet asks for the material data, the duty data and the site data, and it flags the inputs that sit outside the normal ranges so the engineer checks them before the calculation runs.

• The material name and the bulk density: the clinker at 1.30–1.50 t/m3, the raw meal at 1.05–1.30 t/m3, the cement at 1.10–1.45 t/m3, the petcoke and the coal at 0.60–0.85 t/m3: the density drives the capacity formula directly: a wrong density is a wrong elevator;
• The moisture and the temperature: the wet materials fill differently and the hot materials force the design temperatures of the chain, the buckets and the bearings: the sheet notes the maximum material temperature on the selection;
• The abrasiveness class: the clinker and the slag are abrasive, the meal is mild: the abrasiveness decides the bucket material, the chain material and the expected life: the sheet asks the class and adjusts the wear allowance;
• The required capacity: the continuous design tonnage and the peak tonnage: the sheet sizes on the peak and checks on the continuous, because the elevator must survive the surge without starving the line;
• The lift and the geometry: the vertical rise between the boot center and the head center, the casing width, the available headroom: the geometry decides the chain length and the power of the lift;

The input sheet is the contract between the engineer and the calculation: everything that follows is the consequence of what is entered here, so the sheet demands the honest numbers: the design tonnage, not the marketing tonnage, the real bulk density, not the theoretical one: the workbook then rewards the honesty with a design that works on the first day.

5. The Bucket Selection: The Size, the Pitch and the Material

The bucket is the hand that carries the material, and its size and pitch are the first decision of the capacity sheet: the sheet holds the standard bucket ranges and lets the engineer step through the combinations until the capacity calculation returns a comfortable margin above the required tonnage.

• The bucket volume: the standard buckets for the cement plant range from 2 liters for the small high-speed meal elevators to 50 liters and beyond for the large clinker elevators: the volume is the geometric capacity of the bucket at its brim;
• The bucket pitch: the distance between the successive buckets on the chain, from 200 mm for the fine materials to 800 mm and more for the large lumpy ones: the pitch and the volume combine into the ratio i/a that the capacity formula uses;
• The bucket material: the pressed steel for the mild duty, the abrasion-resistant steel for the clinker, the plastic and the polyurethane buckets for the delicate materials that must not be damaged: the sheet notes the material class on the selection;
• The bucket geometry: the deep buckets for the free-flowing fine materials that discharge easily, the shallow wide buckets for the lumpy materials, the corner buckets for the heavy duty: the geometry follows the material, not the preference;
• The mounting: the bolted buckets for the easy replacement, the welded mounts for the heavy duty, the hanging lip design for the aggressive materials: the mounting decides the cost of the maintenance;

The bucket selection is a table walk in the sheet: the engineer selects the bucket from the list, the sheet returns the volume and the recommended pitch range, and the capacity formula does the rest: when the margin is too small, the sheet suggests the next bucket size: when the margin is excessive, the sheet suggests the smaller chain and the cheaper drive: the selection converges on the smallest elevator that meets the duty.

6. The Chain Speed: The Number That Sets the Behavior

The chain speed is the second decision of the capacity sheet, and it is the number that sets the behavior of the whole elevator: the speed decides the fill, the discharge, the wear and the power: the sheet carries the typical speed ranges by material and lets the engineer fix the speed or compute it from the required capacity.

• The slow speeds (0.5–0.8 m/s): for the large buckets and the lumpy abrasive materials: the slow chain fills the buckets deeply, discharges them gently and wears the chain slowly: the price is the larger buckets for the same tonnage;
• The medium speeds (0.8–1.2 m/s): the workhorse range of the cement plant: the raw meal and the cement climb at these speeds with the good fill and the clean discharge;
• The high speeds (1.2–1.8 m/s): for the small buckets and the fine free-flowing materials that discharge by the centrifugal throw: the high speed delivers the high tonnage per meter of bucket volume but wears the chain and the casing faster;
• The speed and the discharge: at the head sprocket the bucket turns over the top, and the material leaves the bucket either by the gravity fall (the slow speed) or by the centrifugal throw (the high speed): the sheet checks the head geometry against the speed;
• The speed and the fill: the filling at the boot depends on the speed of the buckets passing the material inlet: too fast and the buckets scoop shallow, too slow and the material piles in the boot: the sheet applies the fill factor by speed class;

The speed is rarely a free choice: it is the consequence of the capacity target and the bucket selected, and the sheet solves the equation both ways: given the buckets and the speed, the capacity results; given the capacity and the buckets, the speed results: the engineer sees the whole map of the possible combinations and chooses the one that wears the least and costs the least to run.

7. The Capacity Calculation: The Numbers of the Worked Example

With the inputs, the bucket and the speed in place, the capacity sheet performs the calculation of the example: the result is a set of numbers that the engineer can verify by hand, because the formula is public and the factors are on the sheet.

Item	Symbol	Value	Unit	Note
Required continuous capacity	Q_req	220	t/h	plant duty
Design peak capacity	Q_peak	260	t/h	design target
Bulk density of clinker	rho	1.40	t/m3	input
Bucket volume	i	33	liters	selected size
Bucket pitch	a	0.50	m	selected pitch
Bucket volume per meter	i/a	66	L/m	computed
Chain speed	v	1.00	m/s	selected
Fill factor	psi	0.78	—	clinker, medium speed
Theoretical capacity	Q	259	t/h	Q = 3.6 x v x i/a x rho x psi
Margin vs. peak	—	+0.4%	%	too tight, next size advised

The first pass of the example returns 259 t/h, which equals the peak target but leaves no margin for the changes of the bulk density and the fill: the sheet flags the case and the engineer steps up to the 40-liter bucket at the 630 mm pitch: the second pass returns about 295 t/h at the same speed, a healthy 13% above the peak: the elevator is sized with the room to breathe, and the cost difference of the bucket size is trivial against the cost of a starving kiln.

8. The Chain Selection: The Strength That Carries the Load

The chain is the spine of the elevator, and its selection is the most consequential decision of the workbook: the chain carries the buckets, the material and its own weight, and it does it in tension around the head and the boot sprockets, link by link, for years: the sheet computes the working tension of the chain and compares it with the breaking load of the standard chains, applying the safety factor that the duty demands.

• The working tension: the tension at the head sprocket is the sum of the weight of the loaded buckets on the ascending side and the weight of the empty chain on the descending side, plus the resistance of the boot and the take-up: the sheet computes the peak tension at the worst position;
• The breaking load: the strength of the chain as tested, published by the chain maker in kilonewtons: the standard elevator chains of the cement plant range from about 50 kN for the light meal elevators to 400 kN and beyond for the heavy clinker duty;
• The safety factor: the ratio of the breaking load to the working tension: the industry practice asks 8 to 10 for the continuously operating elevators, 10 to 12 for the abrasive clinker service, because the wear of the links and the pins reduces the strength over the life of the chain;
• The chain type: the round link chain for the small elevators, the welded steel bushed chain for the medium duty, the heavy duty cast and forged chains for the clinker: the sheet lists the standard chains with their pitches and their strengths;
• The chain speed and the sprocket: the sprocket tooth count and the pitch diameter are matched to the chain pitch so the buckets pass the head without the whip: the sheet checks the sprocket geometry against the chain;

The chain selection of the example: the 40-liter buckets at the 630 mm pitch carry about 56 kg of the clinker per bucket, and the chain column of the loaded side pulls roughly 58 kN in tension at the head: the standard 160 kN breaking-load chain at a safety factor of 2.7 fails the check, and the sheet flags it: the 250 kN chain at the safety factor of 4.2 still fails the 8 minimum of the clinker duty: the 320 kN chain at the safety factor of 5.4 is still short: only the 400 kN heavy chain at the safety factor of 6.8 with the hardened pins passes the check with the margin that the abrasive clinker demands: the chain is the largest cost of the elevator, and the safety factor is the price of the uninterrupted kiln.

9. The Power Requirements: The Kilowatts of the Lift

The power sheet answers the second central question of the elevator: what motor does the lift need? The power of a bucket elevator is the power of lifting the material, plus the power of moving the chain and the buckets themselves, plus the friction of the boot, the take-up and the head bearings, all divided by the efficiency of the drive.

P_lift = Q x H / 367

Where P_lift is the lifting power in kilowatts, Q is the capacity in tonnes per hour and H is the lift in meters: the constant 367 converts the tonnes times the meters per hour into the kilowatts at the unit gravity: the formula is the metric classic of the elevator industry, and it is the first term of the power sheet.

• The lifting power: the power that raises the material against gravity: for the example, 260 t/h over 42 m gives 260 x 42 / 367 = 29.8 kW: this is the dominant term of the elevator;
• The chain and bucket power: the power that moves the empty chain and its buckets around the loop: it depends on the chain weight, the speed and the friction of the sprockets: for the example chain, about 8 to 10 kW;
• The boot and take-up power: the power lost in the material scooping at the boot, the chain wrap and the tension take-up: about 2 to 3 kW for the example;
• The drive efficiency: the efficiency of the reducer, the coupling and the motor: 0.90 to 0.94 for the modern helical gear unit with the coupling: the sheet applies the efficiency as the divisor, not the multiplier;
• The total motor power: the sum of the terms divided by the efficiency, multiplied by the service factor: the example totals about 42 kW continuous and about 52 kW at the motor input with the service factor of the continuous duty;

The power calculation of the example lands at about 48 to 52 kW at the motor shaft, and the sheet recommends the standard 55 kW motor frame with the variable speed drive allowance: the power that the plant actually draws will be lower in the normal running because the fill fluctuates, but the motor must cover the worst hour of the peak: the sheet prints both numbers, the continuous absorbed power and the installed motor power, so the plant can reconcile the motor schedule with the power bill.

10. The Motor and the Drive: The Nameplate of the Elevator

The motor and the reducer are the last decisions of the power sheet: the motor must start the loaded elevator from rest, accelerate the chain against the inertia of the buckets and survive the torque of the cold clinker: the sheet selects the motor frame, the reducer ratio and the coupling from the standard catalog ranges.

• The motor type: the squirrel cage induction motor of the IE3 or IE4 class, the standard of the cement plant: the direct start or the soft start depending on the supply and the gear unit: the sheet notes the starting torque requirement;
• The starting torque: the elevator starts loaded, because the buckets of the ascending side carry their material when the plant restarts: the starting torque of the motor must exceed the running torque by the factor of 1.5 to 2.0: the sheet applies the factor to the selection;
• The reducer ratio: the ratio that converts the motor speed (about 1,500 rpm) to the chain speed at the head sprocket: the example needs about 1.00 m/s at the 630 mm pitch sprocket, which gives the head speed of about 30 rpm and the reducer ratio of about 50:1;
• The coupling and the backstop: the coupling between the motor and the reducer, and the backstop that prevents the loaded elevator from running backwards when the power fails: the backstop is not an option on a loaded elevator: it is the law;
• The variable speed drive: the optional frequency drive that runs the elevator at the reduced speed for the feed control and the gentle start: the sheet notes the drive option and its effect on the fill and the wear;

The drive selection closes the power loop: the 55 kW motor, the 50:1 helical bevel reducer, the fluid or the pin coupling, the backstop on the head shaft and the optional frequency drive: the sheet prints the complete motor schedule line for the purchase order, and the plant engineer can order the drive package from the sheet without a second calculation: the nameplate of the elevator is decided by the arithmetic of the workbook, not by the guess of the supplier.

11. The Head, the Boot and the Take-Up: The Mechanical Heart

The elevator is more than the chain and the buckets: the head, the boot and the take-up are the mechanical components that the chain and the drive hang on, and the sheet carries their essential checks so the design is complete before the fabrication order.

• The head shaft: the shaft that carries the driven sprockets and the backstop: its diameter is set by the torque of the drive and the bending of the chain tension: the sheet computes the shaft torque from the motor power and the head speed;
• The head bearings: the bearings that carry the shaft under the chain tension: the pillow block housings with the double row spherical rollers are the cement plant standard: the sheet checks the bearing load against the rating;
• The boot: the bottom of the elevator where the buckets scoop the material from the inlet: the boot geometry and the inlet position set the fill: the sheet notes the boot design speed limits for the material class;
• The take-up: the adjustable sprockets in the boot that tension the chain: the screw take-up for the short elevators, the gravity and the hydraulic take-up for the long heavy ones: the take-up travel must cover the chain elongation of the life;
• The casing and the access: the dust-tight casing with the inspection doors at the boot, the middle and the head: the clinker and the cement demand the tight casing for the dust control: the sheet notes the casing dimensions of the selected buckets;

The mechanical sheet of the example sizes the head shaft at about 120 mm, the bearings in the 22222 class, the screw take-up with the 400 mm of travel and the casing of the 1,000 mm x 600 mm section with the three inspection doors: the numbers are the standard practice of the cement plant, and the sheet keeps them on the same page as the capacity and the power so the whole elevator reads as one design.

12. The Worked Example in Full: The Numbers End to End

Running the workbook end to end for the clinker elevator of the example, the complete design appears in a single table of the summary sheet: the table is the deliverable that the engineer presents with the design, and every number in it traces back to the sheet that produced it.

Design Item	Value	Unit	Source Sheet
Material	Cooled clinker	—	Inputs
Bulk density	1.40	t/m3	Inputs
Required capacity	220 continuous / 260 peak	t/h	Inputs
Lift	42	m	Inputs
Bucket size	40 L, abrasion-resistant steel	—	Buckets
Bucket pitch	0.63	m	Buckets
Chain speed	1.00	m/s	Speed
Fill factor	0.78	—	Capacity
Theoretical capacity	295	t/h	Capacity
Chain (breaking load)	400 kN, hardened pins	—	Chain
Chain safety factor	6.8	—	Chain
Motor power installed	55	kW	Power
Reducer ratio	50:1 helical bevel	—	Drive
Head shaft diameter	120	mm	Mechanics
Annual energy (est.)	380,000	kWh	Economy

The summary table is the one-page answer to the design: the bucket elevator for the 220 t/h of the clinker over 42 m is the 40-liter buckets at the 630 mm pitch, the 400 kN chain, the 55 kW drive and the 120 mm head shaft: any supplier can quote against that specification, and the plant can hold the supplier to it: the workbook has turned the vague “elevator for the clinker” into the exact engineering document.

13. The Running Cost and the Economy Sheet

The elevator spends its life on the power bill, and the economy sheet of the workbook puts a price on that life: the engineer enters the tariff and the operating hours, and the sheet returns the annual energy cost, the maintenance cost and the unit cost of lifting each tonne.

• The absorbed power in service: the average absorbed power of the example runs about 38 kW in the continuous service, against the 55 kW installed: the difference is the margin, and the margin is not paid unless the peak occurs;
• The annual energy: 38 kW x 7,920 hours per year gives about 301,000 kWh for the material, and the sheet adds the empty-running and the stand-by about 20%, to about 380,000 kWh per year;
• The annual cost: at the plant tariff of about $0.09 per kWh, the elevator costs about $34,000 per year of the electricity, and the sheet adds the chain and the bucket maintenance of about $8,000 per year;
• The unit cost of the lift: the total annual cost divided by the 1.74 million tonnes lifted gives about $0.024 per tonne: two and a half cents per tonne of the clinker lifted 42 meters: the number that the costing department asks for;
• The sensitivity: the sheet recomputes the costs for the alternative speeds and the bucket sizes, so the engineer can trade the capital cost against the power cost and the chain life before the order is placed;

The economy sheet is the difference between the engineering design and the business design: the elevator that lifts the clinker for 2.4 cents per tonne and the elevator that lifts it for 3.2 cents per tonne look the same on the drawing but differ by thousands of dollars per year in the ledger: the workbook puts both numbers on the table, and the decision becomes the honest comparison.

14. The Common Errors: What the Sheet Guards Against

The bucket elevator fails most often not by the exotic failure but by the common arithmetic errors that the workbook was built to catch: the sheet carries the validation rules and the sanity flags so the classic mistakes are visible before the steel is ordered.

• The wrong bulk density: the clinker at the theoretical 1.5 t/m3 instead of the actual 1.3 t/m3 of the stored material: the elevator designed on the wrong density is the elevator short of capacity on the first day: the sheet forces the density entry and compares it with the material table;
• The optimistic fill factor: the assumption that the buckets fill to the brim: the real fill of the clinker is 0.7 to 0.8, and the sheet applies the conservative factors by the material class and the speed;
• The peak forgotten: the elevator sized on the average 220 t/h while the kiln surges to 260 t/h in the normal operation: the starving elevator is the constant worry of the kiln operator: the sheet sizes on the peak;
• The chain undersized: the chain selected on the breaking load alone without the safety factor of the abrasive duty: the chain of the example at 160 kN would fail within the year: the sheet enforces the factor;
• The motor starved: the motor sized on the absorbed power without the starting torque of the loaded restart: the elevator that cannot restart after the power dip is the elevator that stops the kiln: the sheet applies the starting factor;

The validation of the sheet is not the decoration: it is the discipline of the senior engineer standing behind the junior: every number of the workbook is compared with the range of the practice, and the out-of-range entries are flagged in the red cells: the engineer learns the judgment by seeing the flags, and the design improves with every correction.

15. The Maintenance and the Chain Life: The Second Design

The last sheet of the workbook addresses the life of the elevator after the commissioning: the maintenance plan, the chain elongation monitoring and the replacement economics, because the elevator is designed twice: once by the engineer and once by the maintenance department.

• The chain elongation: the chain stretches with the wear of the pins and the links, and the elongation of 2–3% is the usual signal of the end of the chain life: the take-up travel covers the elongation, and the sheet prints the elongation schedule by the operating hours;
• The inspection plan: the weekly check of the chain tension, the monthly inspection of the buckets and the sprockets, the quarterly check of the head and the boot bearings, the annual check of the casing and the wear liners: the sheet prints the plan with the elevator;
• The lubrication: the chain lubrication and the bearing greasing by the schedule: the modern chains run dry with the sealed pins, and the bearings take the greasing: the sheet notes the lubrication class of the selected chain;
• The spare parts: the recommended spares of the elevator: the spare chain length, the spare buckets, the sprockets and the bearings: the sheet lists the spares with the part numbers so the stores can hold them;
• The replacement cost: the chain replacement every 3 to 5 years in the clinker service at the cost of the chain and the downtime: the sheet computes the annualized replacement cost and the payback of the better chain and the better drive;

The maintenance sheet closes the loop of the design: the elevator that is designed with the maintenance in the room is the elevator that runs the campaign: the chain that is changed on the schedule is the chain that never fails the kiln: the workbook makes the maintenance plan as concrete as the capacity calculation, and the plant runs the elevator with the calendar instead of the prayer.

16. Frequently Asked Questions

What exactly does the bucket elevator Excel sheet calculate?

The sheet calculates the complete selection of the elevator: the bucket size and pitch, the chain speed, the theoretical capacity against the required capacity, the chain size and the safety factor, the lifting and the total power, the motor frame, the reducer ratio, the head and the boot geometry, the annual energy cost and the maintenance plan: one workbook, one line of inputs, the whole design of the elevator.

How does the capacity formula work: what does the 3.6 do?

The capacity formula is Q = 3.6 x v x (i/a) x rho x psi: the buckets carry the volume i liters every pitch a meters, so i/a is the liters per meter of the chain, the chain travels v meters per second, so the flow of the volume is v x i/a liters per second: the bulk density rho and the fill factor psi convert the volume flow to the mass flow, and the 3.6 converts the liters per second of the mass to the tonnes per hour.

What fill factor should I use for the raw meal and the clinker?

For the fine free-flowing raw meal at the medium speed, the fill factor of 0.80 to 0.90 is realistic; for the cooled clinker with the lumps, 0.70 to 0.80; for the sticky or the coarse materials, 0.60 to 0.70: the sheet carries the recommended values by material and speed, and the honest fill factor is the difference between the elevator that meets the duty and the elevator that starves it.

How much power does the 220 t/h clinker elevator of the example need?

About 48 to 52 kW at the motor shaft, and the sheet recommends the 55 kW motor: the lifting power alone is 260 t/h x 42 m / 367 = about 30 kW, and the chain, the boot friction and the drive efficiency add the rest: the installed motor always carries the margin above the absorbed power.

Why does the sheet demand the high safety factor of 8 to 10 on the chain?

Because the chain wears: the pins and the links lose section with every hour in the abrasive clinker, and the breaking load of the worn chain is a fraction of the new chain: the safety factor of 8 to 10 on the new chain buys the years of the service before the chain must be replaced: the lower factor is the chain that fails in the campaign.

Is the sheet usable for the existing elevator, not only the new design?

Yes: enter the existing buckets, the existing chain and the existing motor, and the sheet verifies the capacity and the power against the actual duty: the verification mode is the second purpose of the workbook: the plant uses it to check the proposed speed change, the new material, the extended lift or the imported elevator that arrives without the documents.

17. Conclusion

The bucket elevator of the cement plant: the chain of buckets that carries the meal, the clinker and the cement up the vertical spine of the factory: the design of the elevator is the arithmetic of the bucket: the volume and the pitch and the speed in the capacity formula, the tension and the breaking load in the chain check, the lift and the tonnage in the power equation: the engineer who masters the numbers masters the machine, and the workbook of the package is the home of those numbers: the inputs in the shaded cells, the calculations in the linked sheets, the chain, the motor, the shaft and the cost on the summary page: the worked example of the clinker elevator runs through the whole path, and the reader finishes with the design that the plant can order and the confidence that the plant can run it.

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