Post on 13-May-2017
05/03/23 1
“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