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“Centrifuge 101”

Bernhard BraunerJosef Göttgens

Technical Support EngineersANDRITZ

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Summary of Seminar

Covers the basics of:– Design– Operation– Maintenance

Informational session:– Ask questions at any time!!!– Presentation in booklet form.

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Agenda

Principles of Centrifugation Decanter Design Decanter Operation Decanter Maintenance Condition Monitoring

– Vibration Analysis Special Items

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Settling Tank

Centrifugation stems from concept of the settling tank...

PoolDepth

PoolDepth

PoolDepth

Settling occurs at 1 G

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Form the tank into a cylinder...

Settling Vessel

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Centrifuge

Rotate the tank...G

G Pool Depth

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Solids Movement

What about the solids?

“Beach” EffluentConveyor turns at a slightly

lower rate than bowl.Solids

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Solids Dewatering

Beach

Straight Beach

5o

Compound Beach

7o3o

SolidsLiquid

Solids have to pass through liquid in order to exit bowl!!!

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Centrifugation(IDBowl)(RPMBowl)2

70414G=where:

– IDBowl is in inches– 70414 is a conversion constant

Fast and efficient way to obtain product. Continuous feed and output. RPM has a very strong effect on total Gs:

– For 2X Gs, you need 2X the ID. RPMs would increase by only 41%.

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Decanter Components

Rotating Assembly– Bowl Shell

Heads (Solids and Effluent) Bowl (Cylindrical, Screen, and Conical Section)

– Conveyor– Gear Unit

Drive Assembly– Drive Motor– Backdrive

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Bowl Shell Components

Effluent Head Solids Head Bowl

Conical Section

Cylinders

Screen Section

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Effluent HeadFrom the inside... How is pool depth controlled???

Effluent Wiers

Deep Pond

Shallow Pond

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Screen Section / Types

Screens

TC “Dogbone”

Slot Size

Cut Plate

Slot Size

Wedge WireSlot Size

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Screen Wash / DewateringBowl Screen Section

Solids Moisture vs. Distance TraveledStartFinish

Wash nozzles may be added to rinse the solids.

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Conveyor Components

Conveyor Body (Hub)

Feed Trunnion Gear Trunnion

Blank-Off Plate

Accelerator

Conveyor Flight(s)

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Flight Wear Protection

Ceramic Tiles Tungsten Carbide Tiles

...with “Piggyback” Holder

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T/C Tiled Conveyor Flights

Conveyor Hub

Conveyor Flight

Weld

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Ceramic Tiled Flights

Conveyor HubEpoxy

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Gear Unit

Gear Unit Housing(2 Ring Gears)

1st Stage Sun(Pinion)

1st Stage Planets

1st Stage Carrier(2nd Stage Sun)

2nd StagePlanets

2nd Stage Carrier(Female Spline)

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Rotating Assembly

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Gear Flange

Gear Flange

GearTrunnion

• Gear Unit Housing is the Input

• Gear Trunnion is the Output• Pinion is Stationary

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Machine Frame and Motor

Machine Frame

Gear EndPillow Block

Feed EndPillow Block

FeedPipe

FeedPipe

Bracket

Motor

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Case & Hopper Design

Case Top

Hoppers

Solids Wash Effluent

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Backdrive

MachineGear End

BackdriveMotor

JackshaftCoupling

Jackshaft

Shear Pin

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Decanter with Backdrive

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Decanter Operation

The R/A does the actual work of separation. Four factors affect centrifuge performance:

– Bowl Speed (RPM)– Feed Rate (Qf)– Pool Depth ()– Differential ()

Each factor relates to residence time.

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Bowl Speed

Bowl speed determines centrifugal force. G RPM2 -- doubling RPM results in 4X

the G force felt by slurry. Higher Gs increase solids dryness and

effluent clarity. Too many Gs result in the inability to convey

solids.– Recognized by decreasing effluent clarity.

$ RPM 3

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Feed Rate

Feed rate affects liquid residence time. Qf Rl -- increase in feed rate decreases

liquid residence time. Increased feed rate decreases effluent clarity.

– Over a given period, more slurry enters bowl, more solids displace liquid -- less time for lighter solids to precipitate from the liquid.

Increased feed rate increases amp draw.

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Pond Depth

Pool depth affects liquid residence time. Rl -- increase in pond depth increases

liquid residence time. Higher pool increases effluent clarity. Higher pool decreases solids dryness.

– Beach is shorter, less area to dewater the solids. Extremely sensitive:

– Adjust only after other options have been used.

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Differential Differential affects solids residence time. 1/Rs -- decrease in differential increases

solids residence time. Decrease in increases solids dryness.

– Conveyor RPM approaches that of the bowl, less net motion, solids move more slowly on beach -- more time to dewater.

Decrease in decreases effluent clarity.– More solids build up on bowl wall.

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Differential II

(RPMBowl - RPMPinion)Gear Box Ratio

Backdrives effectively cause the gear box ratio to increase, which speeds up the conveyor relative to the bowl.

Large amounts of torque must be overcome in order to turn the pinion.

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Daily Checklist

Inspect machine for oil leaks. Check for excessive vibration:

– With and without feed. Listen for excessive bearing noise. Inspect machine for any loose hardware. Verify proper lube oil flow. Verify proper oil supply pressure. Check ammeter readings.

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Daily Checklist II

Verify bearing input oil below 100o F. Verify bearing ouput oil below 155o F. Inspect condition of isolators:

– Snubbers properly set, springs in OK condition. Inspect condition of flexible connectors. Test fault light lamps. Ensure proper backdrive operation.

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Monthly Checklist Inspect hydraulic hoses for abrasion. Check that centrifuge is level:

– Adjust isolators if needed. Remove feed tube and check for clogging. Inspect machine interior for material

packing.

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Three Month Checklist

Review operation procedures.– Review / retrain personnel.

Inspect conveyor for flight / tile wear. Check gear box oil level. Check drive belt tension. Have vibration analysis performed.

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Vibration Analysis

Why?– Data transformed into easily read and

interpreted form.– Overall vibration data can be broken down into

component vibrations associated with specific machine parts.

– Using consistent methods of data collection, component vibrations can be tracked over time.

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Time Domain

Time

Amplitude

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Waveform Components

Time

Amplitude

Period (Ty) = 0.9 Seconds

Tg = 0.3 Seconds

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Frequency / CPM

f = 1 / T– Previous example (Yellow 0.9, Green 0.3):

fy = 1 / 0.9 = 1.11 Hz fg = 1 / 0.3 = 3.33 Hz

CPM = f / 60 CPMy = 1.11 / 60 = 66.6 CPM CPMg = 3.33 / 60 = 199.8 CPM

These waves and others “add together”.

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Waveform Summation

Time

Amplitude

t = xAy= .95

Ag= -0.4

Ay + Ag = .95 + (-.4) = .55

.55

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All Waveform Components

Amplitude

All waves “add” up to form SUM WAVEFORM.

It’s very messy, and it does not tell you that much!!!

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Frequency Domain

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Frequency Domain II

1.11 3.33 5.55 7.77 Frequency

Am

plitu

de

FAST FOURIER TRANSFORM

y f x t e dtj ft( ) ( )

2

• Provides a clear and easy way to interpret data.

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Decanter Vibration

GearPinion

GearEnd

PillowBlock

FeedEnd

PillowBlock

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What Can Be “Pulled Out?”

Bowl Unbalance Conveyor Unbalance Bearing Wear / Damage Gear Unit and Components Mechanical Looseness Misaligned Parts

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How is wear recognized?

Data from previous visits are compared with data just taken.

A change in the amplitude of a component’s vibration from one time to the next creates a trend.

Trending (in the wrong direction) indicates wear and potential damage which allows repair or maintenance to be scheduled, and parts to be ordered.

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What This Means… Component wear can

be identified and tracked.

Maintenance or repair can be scheduled at your convinence.

Repair costs will be reduced.

No catastophic failure!

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Special Items (Q & A)

Ask away!!!

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Thank you for your time.

Please do not hesitate to call me with any questions or problems at:

+49 175 4054649