centrifugal slurry pumps

© Metso Minerals, Inc. 20031

We move solids with centrifugal slurry pumps


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


Maintaining

Equipment

Through

Service

Options

Metso


We move solids – with centrifugal slurry pumps


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


Basic DefinitionsSlurry ~ mixture of water and solids (and possibly air)

Slurry Pump ~ a robust centrifugal pump, handling tough abrasive duties


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!


Slurry Pumps Operation Cost

Wear PartsWear Parts

Electrical EnergyElectrical EnergySeal WaterSeal WaterMaintenanceMaintenance

Goal = Total Lowest Cost


Slurry Pump Basic Components

1. Impeller

2. Casing

3. Sealing arrangement

4. Bearing assembly

5. Drive


Horizontal Basic Design

1. Impeller

2. Casing

3. Seal arrangement

4. Bearing assembly

5. Drive


Shaft Seals

Mechanical Seal (spring loaded flat faces) Dynamic Seal

(Expeller)

Soft Packing Seal (soft packed gland)


Vertical Sump Basic Design

1. Impeller

2. Casing

3. Seal arrangement

4. Bearing assembly

5. Drive


Vertical Tank Basic Design

1. Impeller

2. Casing

3. Seal arrangement

4. Bearing assembly

5. Drive


Slurry Pump Impeller

Impeller transfer kinetic energy to slurry mass and accelerates it.


Slurry Pump Casing

Casing creates a desirable flow pattern. Converts kinetic energy into pressure energy.


Semi-Open Impeller

Less prone to clogging than closed impeller

Slightly lower efficiency than closed impellers


Closed Impeller

More efficient than open impellers

More prone to clogging

Clogging is more critical with smaller impellers


Closed Impeller~ High Efficiency, Low Wear


Induced Flow Impeller

Prevents clogging of fibrous, stringy or sticky particles

Gentle solids handling

Lower efficiency than closed or semi-open impeller


Number of Vanes

More vanes gives higher efficiency…but the maximum number of vanes in practice is five.


Impeller Width

The larger the impeller WIDTH, the greater the FLOW produced at a given speed


Impeller Diameter

The larger the impeller DIAMETER, the greater the HEAD produced at a given speed


Pressure and Head


Head

Flow


Aim ~ Operate Near B.E.P.


Radial Forces and B.E.P.


Total Dynamic Head (TDH)

TDH = H2 - H1 + friction losses


Friction Head Calculation

Straight Pipes

• Diameter

• Length

• Material (roughness)

• Flow Rate

Fittings

• Elbows

• Long / Short Bends

• Valves

• Tees

Need to consider the following:


The System Curve


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


Slurry Effects on Friction Head

Head Correction for slurry must be made before plotting on performance curve

Hea

d Lo

ss

Velocity Flow


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


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


What happens when the Total Dynamic Head (TDH) is OVER ESTIMATED?


Multiple Pump Installations


Net Positive Suction Head (NPSH)

NPSH = ATM Pressure + Static Head

- System Losses - Vapor Pressure


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


Rubber-lined Wet End Metal Wet End

Wear Parts ~ Rubber vs. Metal


Wear Part Material Selection


Vertical Tank Pump

• Tank, Pump and

Motor in one unit

• “Self- Priming”

• Seal-less design

= Easy maintenance


Thank you for attending!

Slurry Pumps Division

centrifugal slurry pumps

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