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A glimpse about centrifugal pumps
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© Metso Minerals, Inc. 20031
We move solids with centrifugal slurry pumps
© Metso Minerals, Inc. 20032
Dale Carter
• British Coal- 1970 to 1988- Mechanical apprentice- Engineer - Workshop Engineering Supervisor
• Joy Process Equipment- Denver / Denver Sala- Svedala- Metso UK- 1988 to date- Service engineer- Commissioning Engineer- Product Support Engineer- UK Pump Sales Manager- Global Service Manager
- Hobbies include Golf and Flying
Service Supply And Support Training Options
Metso Slurry Pumps Service Supply And Support Options For Vedanta
November 2006
Dale Carter
© Metso Minerals, Inc. 20034
Maintaining
Equipment
Through
Service
Options
Metso
© Metso Minerals, Inc. 20035
We move solids – with centrifugal slurry pumps
© Metso Minerals, Inc. 20036
Presentation Overview
Pump Components and Basic Designs Costs of Slurry Pumps Impeller Types and Variations Performance Curves & Best Efficiency Total Dynamic Head Calculations Material Selection
© Metso Minerals, Inc. 20037
Basic DefinitionsSlurry ~ mixture of water and solids (and possibly air)
Slurry Pump ~ a robust centrifugal pump, handling tough abrasive duties
© Metso Minerals, Inc. 20038
Slurry Pumps Distribution vs. Cost
• Slurry pumps represent only 5% of all centrifugal pumps installed in industry
• Slurry pumps represent 80% of the operating cost of all centrifugal pumps!
© Metso Minerals, Inc. 20039
Slurry Pumps Operation Cost
Wear PartsWear Parts
Electrical EnergyElectrical EnergySeal WaterSeal WaterMaintenanceMaintenance
Goal = Total Lowest Cost
© Metso Minerals, Inc. 200310
Slurry Pump Basic Components
1. Impeller
2. Casing
3. Sealing arrangement
4. Bearing assembly
5. Drive
© Metso Minerals, Inc. 200311
Horizontal Basic Design
1. Impeller
2. Casing
3. Seal arrangement
4. Bearing assembly
5. Drive
© Metso Minerals, Inc. 200312
Shaft Seals
Mechanical Seal (spring loaded flat faces) Dynamic Seal
(Expeller)
Soft Packing Seal (soft packed gland)
© Metso Minerals, Inc. 200313
Vertical Sump Basic Design
1. Impeller
2. Casing
3. Seal arrangement
4. Bearing assembly
5. Drive
© Metso Minerals, Inc. 200314
Vertical Tank Basic Design
1. Impeller
2. Casing
3. Seal arrangement
4. Bearing assembly
5. Drive
© Metso Minerals, Inc. 200315
Slurry Pump Impeller
Impeller transfer kinetic energy to slurry mass and accelerates it.
© Metso Minerals, Inc. 200316
Slurry Pump Casing
Casing creates a desirable flow pattern. Converts kinetic energy into pressure energy.
© Metso Minerals, Inc. 200317
Semi-Open Impeller
Less prone to clogging than closed impeller
Slightly lower efficiency than closed impellers
© Metso Minerals, Inc. 200318
Closed Impeller
More efficient than open impellers
More prone to clogging
Clogging is more critical with smaller impellers
© Metso Minerals, Inc. 200319
Closed Impeller~ High Efficiency, Low Wear
© Metso Minerals, Inc. 200320
Induced Flow Impeller
Prevents clogging of fibrous, stringy or sticky particles
Gentle solids handling
Lower efficiency than closed or semi-open impeller
© Metso Minerals, Inc. 200321
© Metso Minerals, Inc. 200322
Number of Vanes
More vanes gives higher efficiency…but the maximum number of vanes in practice is five.
© Metso Minerals, Inc. 200323
Impeller Width
The larger the impeller WIDTH, the greater the FLOW produced at a given speed
© Metso Minerals, Inc. 200324
Impeller Diameter
The larger the impeller DIAMETER, the greater the HEAD produced at a given speed
© Metso Minerals, Inc. 200325
Pressure and Head
© Metso Minerals, Inc. 200326
© Metso Minerals, Inc. 200327
Head
Flow
© Metso Minerals, Inc. 200328
Aim ~ Operate Near B.E.P.
© Metso Minerals, Inc. 200329
Radial Forces and B.E.P.
© Metso Minerals, Inc. 200330
Total Dynamic Head (TDH)
TDH = H2 - H1 + friction losses
© Metso Minerals, Inc. 200331
Friction Head Calculation
Straight Pipes
• Diameter
• Length
• Material (roughness)
• Flow Rate
Fittings
• Elbows
• Long / Short Bends
• Valves
• Tees
Need to consider the following:
© Metso Minerals, Inc. 200332
© Metso Minerals, Inc. 200333
The System Curve
© Metso Minerals, Inc. 200334
© Metso Minerals, Inc. 200335
Impeller Wear Rate
i.e. Half the speed = 5.7 times longer life !
Conclusion:
Reduce head by selecting a larger pipe diameter.
This will increase wear life and also save on electrical requirements.
Wear rate Speed Ratio2.5
© Metso Minerals, Inc. 200336
Slurry Effects on Friction Head
Head Correction for slurry must be made before plotting on performance curve
Hea
d Lo
ss
Velocity Flow
© Metso Minerals, Inc. 200337
Slurry Correction Factors
• The correction for head and efficiency for slurries is quite involved.
• Based on Particle size distribution,
Particle specific gravity and % solids
• Today, calculated with computer software
© Metso Minerals, Inc. 200338
© Metso Minerals, Inc. 200339
© Metso Minerals, Inc. 200340
© Metso Minerals, Inc. 200341
Critical Flow Velocity
• The solids in a slurry must be kept in suspension to avoid settling in the pipe
• If the flow velocity is sufficiently high, turbulence will keep solids in suspension
• Particle size ~ critical velocity increases
• Specific gravity ~ critical velocity increases
© Metso Minerals, Inc. 200342
What happens when the Total Dynamic Head (TDH) is OVER ESTIMATED?
© Metso Minerals, Inc. 200343
© Metso Minerals, Inc. 200344
Multiple Pump Installations
© Metso Minerals, Inc. 200345
Net Positive Suction Head (NPSH)
NPSH = ATM Pressure + Static Head
- System Losses - Vapor Pressure
© Metso Minerals, Inc. 200346
Cavitation
• If NPSHA (Available) < NPSHR (Required)
• Pressure in pump inlet drops to liquid vapour pressure.
• Vapour bubbles form and travel to areas
of higher pressure (eye of the impeller)
• These bubbles or “cavities” violently collapse
© Metso Minerals, Inc. 200347
Rubber-lined Wet End Metal Wet End
Wear Parts ~ Rubber vs. Metal
© Metso Minerals, Inc. 200348
Wear Part Material Selection
© Metso Minerals, Inc. 200349
Vertical Tank Pump
• Tank, Pump and
Motor in one unit
• “Self- Priming”
• Seal-less design
= Easy maintenance
© Metso Minerals, Inc. 200350
Thank you for attending!
Slurry Pumps Division