Slurry Handbook

GUIDELINES FOR SLURRY PUMPING

 Slurry
A mixture of solids and liquid,
generally water. The particles
may not be abrasive although
this is common.
Table of Contents

Introduction................................................................ 4
» Slurry Pumps................................................................. 5
» Applications.................................................................. 5
» Slurry Pump Types........................................................ 6

Flygt Slurry Pumps................................................ 8

» Drive Unit....................................................................... 9
» Hydraulic Design........................................................ 13

Slurry Properties...................................................15
» Slurry Parameters....................................................... 16
» Slurry Characteristics................................................. 18
» Liquid Definitions....................................................... 20

Slurry Pump Systems....................................... 21

» Pump Performance..................................................... 21
» Calculating.................................................................. 22
» System Design............................................................ 23
» Sizing the Pump.......................................................... 25
» Other Considerations ............................................... 26

Application guide............................................... 30
» Types of Installation................................................... 30
» Application Areas....................................................... 31

Appendix................................................................... 36
» Step by Step Calculation........................................... 36
» Index............................................................................ 45
» Designations and Formulas...................................... 46
» Slurry Questionnaire.................................................. 47
 Introduction
• Where are slurry pumps used?
• Can submersible slurry pumps replace other types
of pumps?
• Which parts are of special importance in a
submersible slurry pump?
• How can slurries be classified?
• Which parameters of the slurry and pipe system are
required to be able to dimension a pump correctly?

The purpose of this book is, in a simple way, to

describe slurry pumps, slurry pumping and the various
parameters required when selecting submersible
slurry pumps using Xylect.

To provide a deeper understanding of the

calculations, a manual calculation example is given in
the appendix of the book.

If you are not sure about the type of slurry, the choice
of pump, the design of the pipe system, etc., you can
always contact your Xylem support for advice.

4
Slurry Pumps
Slurry pumps are a heavy and robust version of
centrifugal pumps, capable of handling tough and
abrasive duties.
Slurry pumps should also be considered a generic
term, to distinguish them from other centrifugal pumps
mainly intended for clear liquids.

Applications
Slurry pumps are used to move mixtures of liquid and
solids in many industries with a broad spectrum of
applications, for example mine drainage, dredging of
settling lagoons and pumping of drilling mud.

The purpose can be:

• To pump a medium where abrasive particles are
present
• To transport as much solids as possible, hydraulically
• To pump the end product in a process

Flygt submersible pumps are used in many different

industrial segments like:
• Iron and steel
• Power generation
• Pulp and paper
• Oil and gas
• Waste water treatment
• Mining
• Mineral processing
• Construction

Chapter 5 — Application guides — gives a brief overview

of some common industries and applications for slurry
pumps.

5
 Slurry Pump Types
Three main types of pumps are used for slurry
pumping:
• Horizontal slurry pumps
• Vertical slurry pumps
• Submersible slurry pumps

Horizontal Slurry Pumps

These types of pumps are often called dry mounted as
the hydraulic end and the drive unit are located outside
the sump. It is the main group of slurry pumps and
they are available for a wide range of head and flow
conditions and material options.

These types of pumps

normally use standardized Outlet
electrical motors and
seals.
In plants where there
is a risk of flooding,
there can be reasons for
replacing a horizontal
pump by a dry-mounted, Inlet
submersible, slurry pump.

Vertical Slurry Pumps

This type of pump can be subdivided into two main
groups:
• Tank pumps
• Cantilever/sump pumps Inlet

Tank pumps are considered as dry installed pumps.

The sump is incorporated in the pump. Open sump
and vertical inlet prevent air blocking and give smooth
operation. There are no submerged bearings or shaft
seals, but quite a long shaft overhang from lower
bearing to the impeller. Outlet

6
Cantilever/sump pumps are considered as semi-
dry installed, as the hydraulic end is lowered into the Outlet
slurry, but the drive unit and support structure are
dry installed. Similarly to tank pumps there are no
submerged bearings or shaft seals, but a long shaft
overhang.
Depending on size the pump is either mounted with
a base plate over the sump or hung from the roof.
Cantilever-pumps have a number of disadvantages
which make them suitable for replacement with
submersible pumps:
• Long distance between motor and volute makes the
pump bulky to handle.
• Limited access to the sump. Problems with sediment
build-up when used in sumps deeper than 2 m.
• Not water-proof. Flooding will damage the motor. Inlet
• High noise level.

Why Submersible?
Some slurry pump users may have limited knowledge
of submersible slurry pumps. It is therefore important
to advance arguments for the submersible concept.
Submersible pumps offer a number of benefits
over dry and especially semi-dry mounted pumps
(cantilever):
• Operating directly in the slurry, the submersible
slurry pump requires no support structure. It
therefore occupies less space.
• The motor and volute are one integrated unit,
compact and easy to install.
• Operation underwater means low noise levels or
even silent operation.
• Motor cooled by surrounding liquid allows for up to
30 starts/hour, resulting in smaller and more efficient All the information that follows
in this book, such as technical
sumps.
descriptions, calculation
• Flexible installation with several installation modes, examples, etc., is applicable to
all of which are either portable or semi-permanent. submersible slurry pumps.
• Possibility to practice Clean sump technology (see
page 28).
7
 Flygt Slurry Pumps
The main difference between slurry and waste water
pumps is in the parts that are in direct contact with
the slurry and thus subject to wear by the slurry’s solid
particles.

Important factors for slurry pumps such as cooling,

seals and especially the hydraulic design, are
described in this chapter.

Flygt 5150-series submersible

pump equipped with agitator

Motor Cooling jacket

Inspection chamber
Seal

Impeller

Strainer

Stand
Agitator

8
Drive Unit
Motor
Important factors for slurry pump motors:
• Effective cooling
• Insulation

Effective Cooling
Water cooling is superior to air cooling and gives
the submerged motor a high power density and Standard motor
Standard design
motor design
comparatively low temperature. Standard motor design
In the Flygt motor the rotor diameter is bigger and
the stator thinner than in standard motors. This directs
more of the losses (heat release) to the stator and to
the surrounding, cooling liquid. The short heat transfer
distance makes the cooling effective and keeps the
working temperature low.
The pump can be cooled in three ways depending
on the slurry temperature and other circumstances:
• Pumps that work fully submerged in slurry, cooled
by the ambient liquid. The slurry temperature may
not exceed 40°C.
• Pumps that work at times with the motor partially
Flygt motor design
or totally un-submerged, can be equipped with a
cooling jacket for internal cooling, where a cooling Flygt motor
Flygt motor designdesign
medium (glycol mixture) circulates (5100/5150).
• Pumps that often work in a low level, in hot slurry
or are dry installed can be cooled using an external
supply of cooling liquid, connected to the cooling
jacket.

The ways in which the various cooling methods are

used is described on page 27.

Pump with internal cooling

system

9
 Insulation
Class H insulation (180°C) is applied to the stator
winding by a trickle impregnation system. The Flygt
pump has a motor limit to Class B (140°), which
reduces thermal stress resulting in extended lifetime.
Trickle impregnation gives a winding fill much
greater than typical dip and bake systems. This gives
much higher protection against short circuits in the
winding.

Shaft and Bearings

Important factors for shafts and bearings:
• Shaft design and dimensioning
• Bearing type and protection

Shaft Design and Dimensioning

The shaft and bearings are of sturdy design. The
distance between the lower bearing and the impeller
is minimal, eliminating shaft deflections. This provides
long seal and bearing life, low vibration and silent
operation.

Bearing Type and Protection

All slurry pumps have two row angular contact ball
bearings as the main bearing, because they give a
high load capability in the radial as well as the axial
direction.
The bearings are well protected with a lifetime
lubrication of high performance grease.

Pump shaft and bearings

10
Seals
Important factors for submersible pump seals:
• Low leakage or even zero leakage!
• Wear resistance

Leakage and Wear Resistance

In conjunction with leakage rate, the most important
feature for seals in slurry applications is the ability to
resist wear from abrasive particles.
The seals for the slurry pumps are designed to cope
with highly abrasive pump media. Only the seal rings
are exposed to the media. Other parts of the seal, such
as springs and torque locks are protected from wear,
clogging and corrosion inside the seal housing.
In addition, an isolation zone takes the pressure of
the mechanical seal.
The pre-mounted Plug-in™ seal unit (5100/5150) is
fast and easy to handle. The seal faces are closed and
cannot be contaminated or damaged during service.
The seal rings are always properly aligned to eliminate
run-out.
Active Seal™ offers increased sealing reliability and
zero leakage into the motor, thus a reduced risk for
bearing and stator failure.
Active Seal™ features a rotating inner seal ring with
laser cut pumping grooves that acts like a micro-pump,
continuously preventing liquid from entering the
motor.

It all adds up to:

• Reduced downtime Plug-in™ seal (5100/5150)
• Fewer required service inspections
• Fewer unscheduled maintenance checks
• Lower your operation costs

11
 Protection Systems
Important factors for submersible pump protection:
• The possibility of detecting a leaking seal before any
damage occurs
• Spin-out™ seal protection
• Overheating protection

Possibility of Detecting a Leaking Seal

5500: In the area that contains cooling oil above the
seal, there is a sensor that emits a warning if water
enters. In addition, the oil is discoloured by water
leakage and this can be seen through an inspection
screw on the side of the pump.

Stator housing leakage: A float switch shuts the pump

down if water is detected.

5100/5150: The inspection chamber between the seal

unit and the bearings has a built-in sensor for early
detection of fluid leakage. The space can be inspected
and emptied via a screw, which is easily accessible from
the outside.

Spin-out™ Seal Protection

A patented outer seal design that protects the seal by Inspection chamber,
expelling abrasive particles. 5100/5150

Overheat Protection
Thermal sensors are embedded in the stator windings
to prevent overheating.

Spin-out™ seal protection

12
Hydraulic Design
Important factors for submersible pump hydraulic parts:
• Efficiency
• Wear
• Agitator

Efficiency
Pumping slurry can cause a severe reduction in the
hydraulic efficiency of a pump. The Flygt impeller
is designed to minimize this drop. Higher pumping
efficiencies also correlate with lower wear rates.

Wear
Experience shows that the design of the impeller and
volute is as important as the choice of material, in order
to minimize the wear rate.

The shape of the impeller used in slurry handling

is important in ensuring high wear resistance and
hydraulic efficiency. When pumping slurries the
medium moves faster than the solids. The result is
very high wear rate. The Flygt impeller has a more
back swept design than conventional impellers, which
ensures a more homogenous flow between the vanes.
This minimizes the separation of solids from the carrier
liquid, leads to high hydraulic efficiency resulting in Slurry pump impeller
extremely low wear rates.

Standard hydraulic design makes slurry move at Flygt hydraulic design reduces slurry velocity
high velocity

13
 Because of the tangential outflow of particles from the
impeller, suspended particles hit the volute wall at an
almost parallel angle, thus decreasing line wear. The
larger volute size also means a lower internal velocity,
which further reduces the amount of wear.

The adjustable impeller (5100/5150)/suction cover

(5500) makes it possible to compensate for wear and
thus prevent deteriorations in efficiency. Standard impeller slams solids
into the volute.

Agitator
The pump can be equipped with an agitator. The unique
design of Flygt agitators create a strong vertical thrust,
which forces settled solids into suspension. This makes
the particles easier to transport and ensures a cleaner
sump at the end of the pumping cycle.

The use of the agitator is also described on page 28.

Flygt impeller keeps solids
moving with the flow.

Agitator

14
Slurry Properties
Pumping slurry, i.e. a liquid containing solid particles,
raises different requirements for a pump compared to
pumping just water.

A number of characteristics of the slurry and of the

system must be known to be able to select a slurry
pump correctly.

When selecting a slurry pump, it is necessary to know

certain parameters. These are covered in this chapter.

”Slurry Questionnaire”, on page 47 shows the

parameters that should be included when making
calculations for a slurry pump. The accuracy of the
results will be better if more exact and a larger
number of these values are available. In cases when
assumptions must be made, it is important that the
customer is informed of them.

It is always possible to send samples for full rheology

tests to the Xylem laboratory in Sweden.

15
 Slurry Parameters
The following parameters must be determined when
calculating a slurry pump application.

Particle Size and Distribution

Particle size d50 (d85) is a measure of the percentage of
particles in the slurry with a certain size or smaller.
3
The value is determined by sifting the solids through
screens with varying mesh and then weighing each
fraction. A sieve curve can then be drawn and the
percentage of particles of different sizes read.

Ex: d85= 3 mm means that 85% of the particles have a

diameter of 3 mm or less. 85%

Mass Fraction of Small Particles Sieve curve

The fraction of particles smaller than 75 µm.

It is important to determine the percentage of small

particles in the slurry. Particles smaller than 75 µm
can to some extent facilitate the transport of larger
particles. However, if the percentage of particles
smaller than 75 µm exceeds 50%, the character of the
slurry changes towards non-settling.
» Non-settling slurry,
see page 18
Concentration of Solids
The concentration of particles in the slurry can be
measured as a volume percentage, Cv, and a weight
percentage, Cm.

Solids
Cm =
Concentration
of solids
by weight
Cv =
Concentration
of solids
by volume

16
Density/Specific Gravity
Solids
The density of the solids is stated as the Specific
Gravity. This value, SGs, is determined by dividing the
density of the solid by the density of the liquid.

Water
The density of water is 1000 kg/m³ . The SG of
water is 1.0 at 20°C. The value varies somewhat with
temperature.

Slurry
The specific gravity of the slurry can be determined
using a nomograph (see page 39) or calculated (see
page 38). Two of the values of SGs, Cv, and Cm, must be
known.

SGsl is calculated based on the values above.

Particle Shape
The shape of the particles is very significant for the
behaviour of the slurry when pumping and for the wear
on the pump and the pipe system.

The form factor denotes the deviation of the slurry

particles from a perfect sphere.
Sand

Mica

17
 Slurry Characteristics
Slurries can be divided into settling and non-settling
types, depending on the parameters mentioned on

NON-SETTLING SLURRY
previous pages.

Non-settling Slurry
A slurry in which the solids do not settle to the bottom,
but remain in suspension for a long time. A non-settling
slurry acts in a homogeneous, viscous manner, but the
Homogeneous mixture
characteristics are non-Newtonian (see page 20).

Particle size: less than 60-100 µm.

A non-settling slurry can be defined as a homo-

geneous mixture.

Homogeneous Mixture
A mixture of solids and liquid in which the solids are
uniformly distributed.
Pseudo-homgeneous
mixture
Settling Slurry
This type of slurry settles fast during the time relevant
to the process, but can be kept in suspension by
turbulence. Particle size: greater than 100 µm.
SETTLING SLURRY

A settling slurry can be defined as a pseudo-

homogeneous or heterogeneous mixture and can be
completely or partly stratified.
Heterogeneous mixture,
Pseudo-homogeneous Mixture partly stratified
A mixture in which all the particles are in suspension
but where the concentration is greater towards the
bottom.

Heterogeneous Mixture
A mixture of solids and liquid in which the solids
are not uniformly distributed and tend to be more
concentrated in the bottom of the pipe or containment
vessel (compare to settling slurry).
Heterogeneous mixture,
fully stratified

18
The diagram shows how different types of slurry behave,
depending on particle size, and transport speed.

Stratified
Heterogeneous
Pseudo-homgeneous

Particle
transport
speed

Particle size

A high transport When the particle size is At low transport speeds

speed and/or small larger and the transport and/or large particles,
particles means speed is lower, the the slurry tends to
that all the particles particles tend to become collect/glide. A slurry
are in suspension. more concentrated consisting of large
The slurry behaves towards the bottom particles can also move
pseudo-homogeneously. of the tube or are in like a sliding bed.
mechanical contact with
it. The slurry behaves
heterogeneously.

19
 Liquid Definitions
Except for density (see page 17) the characteristics of a
liquid are decided by its viscosity.
Newtonian

Liquids deform continuously as long as a force is

Shear stress
applied to them. They are said to flow. When a flow
takes place in a liquid, it is opposed by internal
friction arising from the cohesion of the molecules. Non-
This internal friction is the property of a liquid called Newtonian

viscosity.

Yield stress
The viscosity of liquids decreases rapidly with
increasing temperature. Shear rate

Newtonian Liquids
Newtonian liquids give a shearing stress that is linear
and proportional to the velocity gradient, or the
shearing rate. Water and most liquids are Newtonian.

Non-Newtonian Liquids
Some liquids, such as water based slurries with fine
particles, do not obey the simple relationship between
shearing stress and shearing rate (compare non-
settling slurry, page 18). They are referred to as non-
Newtonian liquids.

Some non-Newtonian liquids have a unique property

of not flowing until a certain minimum shear stress is
applied. This minimum shear stress is known as the
yield stress.

20
Slurry Pump Systems
Pump Performance
The performance of a centrifugal pump pumping
slurry differs from the performance with clean water
depending on the amount of solid particles in the
slurry.

This difference depends on the characteristics of the

slurry (particle size, density, and shape, as described in
the previous chapter).

The factors that are affected are the power (P), head
(H), and efficiency (η). The differences between slurry
and water are shown schematically in the curves
below.

Slurry
Power (P) Water

Head (H)

Efficiency (η)

21
 Calculating
To be able to dimension a pump that will function
correctly with a certain type of slurry in a particular pipe
system, data about the slurry is needed (chapter 3) as
well as information about the head, required flow, and
the design of the pipe system in question.

A correctly dimensioned slurry pump must be capable

of overcoming the losses caused by friction in the » The “slurry question-
pipes and valves. It is also important that the flow naire” on page 47
velocity does not fall below the critical velocity (see is a checklist which
page 24) otherwise sedimentation will result. shows the para-
meters that should
It is important that all the parameters for the slurry and be included when
pipe system, are specified as accurately as possible. making calculations
In cases when assumptions must be made in the for a slurry pump
calculations, it is important that the customer is made selection.
aware of them.

22
System Design
Static Head
Static head is the vertical height difference from the
surface of the slurry source to the discharge point.

Friction Losses
When the liquid starts to flow through the discharge
line and valves, friction will arise. When pumping slurry, » For manual calcu-
lation of the friction
friction losses caused by pipe roughness, bends and
losses for slurry,
valves, are different compared to the corresponding
see page 41.
losses when pumping water. The calculation is done
based on the parameters collected.

Total Discharge Head

This value is used for pump calculations and comprises
the static head plus friction losses caused by pipes and
valves, converted to metres of water.

Friction loss converted

to meters

Total discharge head

Static head

23
 Critical Velocity
In general, the flow velocity in the pipes must be kept
above a certain minimum value.

If the flow velocity is too high, friction losses will

increase. This may also increase the wear in the pipe
system. Flow velocities that are too low will result in
sedimentation in the pipes and, thus, increased losses.

This is illustrated in the diagram below, in which the

critical velocity (Vc) indicates the optimum velocity
where losses are kept to a minimum.

When making calculations for a slurry pump for a

certain flow, the desired flow velocity (V) must be
compared to the critical velocity (Vc) for the slurry and
the pipe system in question. As the figure below shows,
the ideal velocity (marked green) is immediately above
the critical velocity but with a margin for the extreme
cases that can arise.

To determine the critical velocity, the pipe diameter

and the particle size (d85) must be known. The value »   d85, see page 16
is then corrected with a factor, which depends on the
specific gravity of the solids.

Slurry
Friction losses

Water

Vc V

24
Sizing the Pump
After the calculation on page 26 and further on, Xylect
will match a clean water duty point to a slurry pump.
www.xylect.com

(H)

Critical velocity Slurry

Water

System curve
with correlation
for settling
slurry effects

Duty point,
slurry

(Q)

The diagram above shows, schematically:

— the pump curve for water
— the reduced curve for slurry
— the duty point for slurry, i.e. the point at which the
pump system curve and the performance curve
intersect.
— the system curve

25
 Other Considerations
Besides the actual calculation work, a number of
practical viewpoints should be taken into consideration 10 −
when designing systems and selecting pumps.

Vapour pressure, m
8 −

NPSH 6 −

Whenever centrifugal pumps are used, it is important 4 −

that the pump’s inlet pressure exceeds the vapour
2 −
pressure of the liquid inside the pump. The necessary
inlet pressure that is stated for the pump, NPSHreq* | | |
20 40 60 80 100
| |

must be less than the available value in the pump Temperature, °C

system, NPSHa*.
Vapour pressure for water at
The available value depends on the ambient air different temperatures

pressure (height above sea level), the vapour pressure

ft m NPHS
of the liquid, the density of the slurry, and the level in 12
35
the sump. 10
28
Head of water

Example: Pumping a water-based slurry at a height 21

6

of 1000 m above sea level. Liquid temperature 40°C, 14 4

liquid level 2 metres above the pump inlet. 7 2

0
0 1000 2000 3000 m

Formula: 0 2000 4000 6000 8000 10000 ft

Height above sea level
NPSHa= air pressure − vapour pressure + level in sump
Air pressure in head of water at
NPSHa = 9.2 − 0.4 + 2 = 10.8 different heights.

Submergence
depth

2m

The value of NPSHa

must exceed the
value specified for
the pump, NPSHreq

* NPSHreq = NPSH required, NPSHa = NPSH available

26
Cavitation
If NPSHa is lower than NPSHreq vapour bubbles will
occur in the impeller. When the bubbles reach the area
where the pressure is higher, they burst and can cause
damage to the impeller and volute.

Besides damage to the pump, cavitation can result in

lower efficiency, vibration, and noise.

pH and Chlorides
To prevent damage caused by low pH values, the
pumps are painted with epoxy paint (pH-limit 5.5). For
high chloride content, zinc anodes are used in addition
to the epoxy paint.

Cooling
Submerged slurry pumps of standard type can
normally be cooled by the surrounding slurry if the
slurry temperature is max. 40°C.

There are however occasions when special measures to » See also:

cool the pump are required: Effective cooling,
page 9
1. If the liquid surface level is below the stator, Clean sump
permanently or for periods longer than 10 minutes. technology,
2. If the pump is dry installed. page 28
3. If the temperature of the medium being pumped
exceeds 40°C.

In these cases cooling can be arranged using a cooling

jacket. Pumps of the type 5100/5150 can in cases 1 and
2 above be cooled by an internal cooling system and in
case 3 by an external supply of coolant.

Pumps of type 5500 should in cases 1 — 3 be cooled

using an external coolant supply.

27
 Wear
Wear inside a slurry pump varies significantly
depending on the velocity, concentration and impact
angle of the particles. The wear is typically most severe
on the impeller followed by the pump housing and
discharge connection.
Wear rate and service intervals depend on the
type of application. Ensuring the customer is aware
that Flygt service and spare parts are available, is an
important part of the sales process.

Over-estimation of System Losses

Over-estimation of the losses can lead to over-
dimensioning of the pump. This in turn can cause
problems such as:
• Too large flow Pump with agitator
• Higher power consumption
• Overloading the motor
• Cavitation

Clean Sump Technology

This concept means effective slurry handling without
sediment build up. The slurry is kept in suspension
by the use of an agitator or mixer. Combined with the
pump cooling system and an effective sump design
this ensures the sump can be emptied efficiently. Pump with side-mounted mixer

Agitator
When pumping coarse slurries, an agitator mounted on
the pump shaft resuspends settled particles and makes
them possible to transport.

Mixer
For large sumps with very coarse and heavy particles,
where the agitator is not enough, a standalone or
a side-mounted mixer can be mounted to prevent
sediment build-up.
Flygt submersible mixers have
the power to keep sumps clean

28
Cooling System
An internal/external cooling system means that the
pump can continue pumping down to low slurry levels.
See also Cooling on page 27.

Sump Design
A bigger so called launder sump has a sedimentation
area for solids before the overflow into the smaller part
where the pump is installed. The sedimentation area Pump with internal cooling
permits an excavator to enter in order to remove the system
sediment.

Screen Sedimentation area

Smaller sumps with sloping walls create turbulence and

high velocity in the sump, preventing the slurry from
settling. Settling solids slide down into the zone directly
under the pump inlet.

Coarse screen

29
 Application Guide
Flygt slurry pumps can be used in many different
industries and applications. The purpose of this
chapter is to give a brief overview of some common
industries and applications for slurry pumps.

Types of Installation
Flygt submersible slurry pumps can be installed in
many ways as mentioned earlier. However there are
some general rules regarding installation that should
be considered irrespective of application.

Dry Installation
The slurry pump must always be installed with a
cooling system. For the 5500 series, water for the
cooling jacket must be supplied externally. And further
the holes for the pressure isolation zone must be
plugged or external seal flushing added.

Consider the design of the sump in order to feed the

pump with the slurry. An agitator and side
mounted mixer cannot be used in this installation
method.

Submerged Installation
If possible the sump should be equipped with sloping
walls to allow the sediment to slide down to the area
directly under the pump inlet. Use an agitator when
there is a high solids content and when the density of
the particles is high. A standalone or a side-mounted
mixer is an excellent option to resuspend the solids,
when the sump is large or lacks sloping walls.

The mixer can also help the agitator when pumping

very high density particles.

30
Raft Installation
A raft installation is an option to be considered when
pumping sediments from dams or lagoons. An agitator
is recommended as well as one or more mixers.

The mixer can either be mounted on the pump or

directly on the raft.

Application Areas
Iron & Steel
Pumps for Mill Scale Transportation
Water from the cooling process is collected in sumps.
This water has a high content of mill scale, which
is normally very abrasive. These particles are often
separated and the water reused in the cooling process.

Pumps for Cooling Water

Cooling water may have a high content of abrasive
particles from earlier use.

31
 Removal of Sediments from Tailing Dams
Dust and solids from the process plant is often
collected in settling dams. This is suitable for raft
installations using an agitator and side mounted mixer.

Pumps for Cooling Oil in Machining Processes

Cooling oil containing metallic waste from grinding or
similar machining processes.

32
Coal-fired Power Plants
Pumping Bottom Ash Slurry
Pumping bottom ash and water to settling lagoons.

Run-off Water
Run-off water from the coal storage, coal cleaning and
coal conveyor areas must be collected and pumped to
further treatment.

Pulp & Paper

Collecting Tanks and Overflow Sumps
Black liquor from recovery boilers containing sand, fly
ash, boiler grit, pine knots, etc.

Oil & Gas

Pumping Drilling Mud
Return mud with a high content of abrasive materials. A
pump is normally used for transporting the mud from a
supply ship to a mud recycling plant. Normally drilling
mud should be considered to be homogeneous slurry.

33
 Waste Water Treatment Plant
Grit Chamber/Sand Trap
Pumps installed after primary screening for pumping
the sediment solids for disposal.

Mining Operations
Sump Pumping of Thicker Slurries

Cleaning Pump Basin from Settled Solids

Suitable for raft installation with agitator and side
mounted mixer.

Mineral Processing
Sump Pumping at the Lowest Level in the
Processing Plant
Watch out for larger heavier objects and particles that
may end up on the sump floor.

If possible, mount an inlet screen cover on top of the

sump or a screen basket.

When recommending our slurry pumps for low pH,

for high chloride content (i.e. sea water), and when
the slurry contains copper sulphate (used in flotation
processes), consider recommendations on page 27 or
contact your Flygt support.

If the slurry is frothy, the volume capacity of the pump

must at least be doubled.

Specify if possible our clean sump design (to minimize

sedimentation).

Recovering Material from the Plant Emergency Dam

Suitable for a raft installation with an agitator and side
mounted mixer.

34
Quarries
(crushed stone, sand and gravel)
Dredging (lower capacity)
Suitable for a raft installation with an agitator and side
mounted mixer.

Quarry Sumps
Suitable for raft or permanent installation for pumping
solids containing ground water or flood drainage, or
for transfer of slurries comprising sand and gravel
products.

Sump Pumping in a Concrete Recycling Plant

Suitable for pumping slurries of sand and cementious
solids for recycling of returned concrete.

Used in combination with a submersible mixer.

35
 Appendix
Step by Step
Calculation
See page 37 for values used in the example.

1. Determine SG/density of the liquid. If the density

is unknown, it can be determined by using the »   Pages 38, 39
formula or nomograph.

2. Calculate the critical velocity using the table and

curve. Choose a pipe diameter so that the pipe »   Page 40
velocity is higher than the critical velocity. If the
velocity is too low, losses, wear and also the risk of
blockage increase.

3. Calculate the total discharge head, which is the

sum of the static discharge head, the losses in the »   Page 41
pipe system, and the pipe discharge pressure (if
required).

The losses in the pipe system consist of friction

losses and losses caused by fittings like pipe
bends and valves etc. The friction losses can be
established using the graph. If the concentration
is more than 15% by volume, the value should
be adjusted using the correction factor graph.
For slurry pumping, pipe bends with a large
radius and valves with free through flow should
be selected. In this way, losses in fittings can be
neglected when estimating the total losses.

4. The required duty point has now been established.

If the solid concentration exceeds 15% by volume, »   Page 42
the discharge head of the pump must be reduced.
By dividing the duty head with the reduction
factor, the equivalent clean-water pump head is
obtained.

36
5. The pump can now be selected based on the flow
and head values above. »   Page 43

The type of installation conditions in question

should also be considered. Overall operating
expenses, including wear, maintenance and
energy consumption are equally important points
to be considered.

6. Corresponding
versus slurry.
power consumption, clean-water
»   Page 44

The power curves for the pumps are based on

clean water and these must then be multiplied
by the specific gravity of the slurry to obtain the
corresponding value for slurry pumping. Normally
variations in the slurry can be expected and the
motor should therefore be relatively large. Xylem
recommends a motor with a 20% excess power
margin for slurry applications.

EXAMPLE
Calculate the size of a pump in a coal mine, pumping coal slurry from the mine.

Data from customer:

Voltage 380 V, 50 Hz
Water temp max 40°
Concentration of solids by volume Cv = 30%
Density of solids: 1800 kg/m³ SGs = 1.8
Requested flow Q = 50 l/s
Static head Hs = 22 m
Pipe diameter 150 mm
Pipe length L = 50 m
Size of solids d85 = 1

These values are used in the example on the following pages.

37
 1. Specific Gravity (SG) of Slurry
Determine the specific gravity of the slurry. Use the formula below or the nomograph
on the next page.

Specific gravity is the density of a particular material normalised by the density of

water.

Example: Density of coal is normally 1800 kg/m³.

SG of coal is then 1.8.

SGsl = 1 + Cv(SGs − 1)

or
SGs
SGsl =
SGs − Cm(SGs − 1)

SGsl = Specific gravity of the slurry

SGs = Specific gravity of the solids
Cv = Concentration of solids by volume
Cm = Concentration of solids by weight

SGsl C
= v
SGs Cm

EXAMPLE
Calculate the specific gravity (SG) of the slurry

SGsl = 1 + Cv(SGs − 1) = 1 + 0.3(1.8 − 1) = 1.24

You can also use the nomograph 1a on the next page.

38
Nomograph showing the relationship of concentration
to specific gravity in aqueous slurries.

90 1.1
90 1.1
2
1.1
5
80
1.2
80
70 1.2
1.3
Cv SGs
70 60 1.4

1.5 1.3
50 1.6
60 1.7
40 1.8
1.
2 9 1.4
30
50 Cm 2.5 SGsl
20 3
1.5
10 54
40 6

1.6

30
1.7

1.8
20

If two out of four values are known, 1.9

draw a line between them and the
10 other two values are given. 2

Graph 1a

39
 2. Critical Velocity
Calculate the critical velocity using the table and curve below. Choose a pipe
diameter so that the pipe velocity is higher than the critical velocity. If the velocity is
too low, the losses, wear and also the risk of blockage will increase.
Critical velocity (Vcr ) m/s (for d85 and SGs=3)

Pipe size Particle size @ d85

Mesh 65  48 32 24 16 9 <4
mm inch mm 0.2 0.3 0.5 0.7 1.0 2.0 >5
25 1 1.3 1.4 1.4 1.4 1.4 1.4 1.4
50 2 1.3 1.7 1.8 1.8 1.8 1.8 1.8
Critical velocity

75 3 1.6 1.8 1.9 1.9 1.9 1.9 1.9

100 4 1.7 1.9 2.0 2.1 2.1 2.1 2.1
150 6 1.7 2.0 2.1 2.4 2.4 2.4 2.4
200 8 1.8 2.0 2.3 2.5 2.5 2.5 2.5
300 12 1.8 2.1 2.4 2.7 2.8 3.0 3.0
400 16 1.8 2.1 2.5 2.8 2.9 3.1 3.6
Table 2a

As the SGs is below 3 correction 7,000 −

of the value must be done
Specific gravity

6,000 −
according to the graph (2b).
5,000 −
4,000 −
3,000 −

1.8 2,000 −
| | | | | | | | | | | |
0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6
Factor
Graph 2b

EXAMPLE
Check that the velocity in the pipe is above the critical velocity.
Pipe diameter: 150 mm
Size of solids: d85 = 1
Vcr =2.4 m/s (table 2a)

Correction factor
Density of solids: 1800 kg m³ = SGs = 1.8 => factor 0.7 (graph 2b)

Critical velocity using correction factor 0.7

Vcr = 2.4 × 0.7 = 1.7 m/s
Q 50 × 10−3
Actual velocity V = = =2.8 m/s
A* 3.14 × 0.075²
2.8 m/s > 1.7 m/s Well above! *A is the pipe area

40
3. Total Discharge Head
Determine the total 2" 3" 4" 6"
(50mm) (75mm) (100mm) (150mm)
discharge head, by 100
80

Friction losses (meters/100 m of hose)

adding the friction losses 60
40
8" (200mm)

to the static head. 20

10" (250mm)

10
8
6 6
4 m/s
4
The graph (3a) shows the
2
frictional losses for clean
0.1
water and the value must 0.8 2 m/s
0.6
be multiplied with a 0.4

correction factor 0.2

for slurry (graph 3b). 0.1

1 2 3 4 5 7 10 20 30 40 50 70 100 200 300
Flow (l/s)
50

Graph 3a

40 −
Solids by volume, C

30 −

20 −

10 −

| | | | | | | | |
1.0 1.1 1.2 1.3 1.4 1.5 1,6 1.7 1.8
Correction factor

Graph 3b

EXAMPLE
Friction losses
For steel pipe with a diameter 150 mm and flow rate, Q=50 l/s, the top
graph (3a) gives friction losses for clean water:
6 m/100m = 0.06 m/mpipe

For pipe length 50 m: 50 × 0.06 = 3m

Correction factor
Correction factor for slurry Cv 30% = 1.5 (graph 3b)

Head
Hfrsl  = 3 × 1.5 = 4.5 m ;
Htotsl = Hfrsl + Hs = 4.5 + 22 = 26.5 m

41
 4. Clean-water Pump Head
Since the performance curves are for clean water the graph below (4a) must
be used to determine the reduction factor HR for calculation of the equivalent
clean water head, Hcw

300 200 150 100 72 52 36 25 18 14 10 7 5

0

Solids SG = 1.5
0.04

1.75

0.1 2.0

2.5
Factor K

3.0

3.5

0.2 4.0

5.0

Diagram for 8.0

reduction factor
HR

0.6 0.8 0.9 .2 .4 .6 .8 1 2 4 6 d85

Graph 4a

EXAMPLE
Reduction factor HR
With d85 = 1 and SGs = 1.8 the graph gives K = 0.04 (4a)
Cv 30
HR = 1 — K × = 1 — 0.04 × = 0.94
20 20
Htotsl 26.5
Hcw = = = 28.2 m
HR 0.94
Choose a pump with a clean water curve for duty point:
Hcw=28.2 m (Hsl=26.5) and Q=50 l/s.

42
5. Select Pump
The pump is selected based on the flow and head values. The type of installation
conditions in question should also be considered. Overall operating expenses,
including wear, maintenance and energy consumption are equally important points
to be considered.

28.2m

45.85
l/s

EXAMPLE
Select pump
Choose 5150.300, curve 53-432. It gives close to 50 l/s
at the requested head.

43
 6. Corresponding Power Consumption,
Clean-water vs Slurry
The power curves for the pumps are based on clean water and these must then be
multiplied by the specific gravity of the slurry to obtain the corresponding value for
slurry pumping.

Shaft
power
P2 21.9 Model
Rating [kW]
300
30–45

kW Rated current [A]

Weight [kg]
32–82
585
Max. height [mm] 1410
Max. width [mm] 875
Discharge Ø [in] 6"
Strainer hole [mm] 36
Warm liquid, 70°C Yes
Agitator Yes
Ex version 310

EXAMPLE
Check motor power
Check that the pump motor has a power margin to handle the higher density.

The imag above shows that the maximum permitted shaft power for the chosen
motor is between 30 and 45 kW and the performance curve shows that we need
21.9 kW shaft power for clean water at the requested duty point. Calculate the
shaft power for the corresponding slurry duty point.

SGsl × Pincw = Pinsl

1.24 × 21.9 = 27.2 kW

The value is well below the maximum permitted input power at the requested
duty point. Now check that the value is below the power limit for the input power
(30 kW) whole curve in case there are variations in the pumped head.

Pshaft max = 25 kW for the chosen curve. Pinmaxsl = 25 x 1.24 = 31 kW

The power margin is not sufficient choose a bigger motor.

Selected pump: HS 5150.300, curve 53-432 with 45 kW motor.

44
Index
Agitator .........................................8, 14, 28 Particle shape ......................................... 17
Particle size.............................................. 16
Bearings .................................................. 10 Protection ..........................................10, 12
Pseudohomogeneous mixture............. 18
Cantilever pumps..................................... 6
Cooling .................................. 9, 27, 29, 30 Screening curve ..................................... 16
Critical velocity .......................... 22, 24, 40 Seals .................................................... 8, 11
Settling slurry .......................................... 18
Density ........................................17, 38, 46 Shaft ......................................................... 10
Drive unit ................................................... 9 Solids ...........................................16, 17, 38
Dry slurry pumps................................. 6, 30 Specific gravity ...........................17, 38, 46
Duty point ............................................... 25 Spin-out™................................................. 12

Head ............................................23, 41, 46 Vertical slurry pumps................................ 6

Heterogeneous mixture ........................ 18 Viscosity .................................................. 20
Homogeneous mixture ......................... 18 Volume .................................................... 16
Horizontal slurry pumps........................... 6
Weight ..................................................... 16
Inspection chamber............................... 12
Insulation ................................................. 10 Xylect ....................................................... 25

Liquid....................................................... 20
Mica.......................................................... 17
Mixer ........................................... 28, 30, 31
Motor ......................................................... 9

Newtonian liquid ................................... 20

Non-Newtonian liquid ........................... 20
Non-settling slurry ................................. 18
NPSH........................................................ 26

45
 Designations and Formulas

Q =  Flow rate (l/s)

V =  Velocity (m/s)
Vcr =  Critical velocity
A =  Pipe area
L =  Pipe length (m)
Hs =  Head (m)
SGsl =  Specific gravity of slurry
SGs =  Specific gravity of solids
Cv =  Concentration by volume (%)
Cm =  Concentration by weight (%)
d85 =  Concentration by volume
η =  Efficiency

SGw = 1

Density of solids
SGs =
Density of water
Q
V =
A

SGsl =  1 + Cv(SGs − 1)
SGsl = SGs / SGs − Cm(SGs − 1)

Hcw = Ttotsl / HR
Pinsl = Pincw × SGsl

46
Slurry Questionnaire

Contact information
• Company: _____________________________________________________________
• Contact person: _______________________________________________________
• E-mail:________________________________________________________________
• Telephone no:_________________________________________________________

Application information
• Industrial segment:_____________________________________________________
• Pump application:______________________________________________________

Pump duty
• Required flow [l/s, USgpm, m3/h]:_______________________________________ *
• Required total head [m, ft]:_____________________________________________ *
(or preferable)
• Static head + Pipe configuration
    — Static head [m, ft]:_________________________________________________
    — Pipe length [m, ft]:________________________________________________
    — Inner diameter [mm, inch]:_________________________________________
    — Number of valves:________________________________________________
    — Number of bends:________________________________________________
   — Pipe material:____________________________________________________

Information about the slurry

• Particle size [d50]:_____________________________________________________ *
• Particle size [d85]:______________________________________________________

• SG of particles:_______________________________________________________ **
• SG of liquid:_________________________________________________________ **
• Concentration by weight [%]:__________________________________________ **
• Concentration by volume [%]:__________________________________________ **
• SG of slurry:_________________________________________________________ **

• Mass fraction [% of particles < 75 µm]:____________________________________

• Particle shape [round or flat]:____________________________________________

* must be filled in ** three out of five must be filled in

47
 Nomograph

Concentration versus specific gravity

90 1.1
90 1.1
2
1.1
5
80
1.2
80
70 1.2
1.3
Cv SGs
70 60 1.4

1.5 1.3
50 1.6
60 1.7
40 1.8
1.
2 9 1.4
30
50 Cm 2.5 SGsl
20 3
1.5
10 54
40 6

1.6

30
1.7

1.8
20

If two out of four values are known, 1.9

draw a line between them and the
10 other two values are given. 2

48
Critical Velocity

Velocity check

Pipe size Particle size @ d85

Mesh 65  48 32 24 16 9 <4
mm inch mm 0.2 0.3 0.5 0.7 1.0 2.0 >5
25 1 1.3 1.4 1.4 1.4 1.4 1.4 1.4
50 2 1.3 1.7 1.8 1.8 1.8 1.8 1.8
Critical velocity

75 3 1.6 1.8 1.9 1.9 1.9 1.9 1.9

100 4 1.7 1.9 2.0 2.1 2.1 2.1 2.1
150 6 1.7 2.0 2.1 2.4 2.4 2.4 2.4
200 8 1.8 2.0 2.3 2.5 2.5 2.5 2.5
300 12 1.8 2.1 2.4 2.7 2.8 3.0 3.0
400 16 1.8 2.1 2.5 2.8 2.9 3.1 3.6

Correction factor

7,000 −

6,000 −
Specific gravity

5,000 −

4,000 −

3,000 −

2,000 −

| | | | | | | | | | | |
0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6
Factor

49
 Total Discharge Head

Friction losses

2" 3" 4" 6"

(50mm) (75mm) (100mm) (150mm)
100
80
Friction losses (meters/100 m of hose)

60 8" (200mm)
40

20
10" (250mm)

10
8
6
4 m/s
4

0.1
0.8 2 m/s
0.6
0.4

Correction factor

40 −
Solids by volume, C

30 −

20 −

10 −

| | | | | | | | |
1.0 1.1 1.2 1.3 1.4 1.5 1,6 1.7 1.8
Correction factor

50
Clean-water Pump Head to Slurry Pump Head

300 200 150 100 72 52 36 25 18 14 10 7 5

0

Solids SG = 1.5

1.75

0.1
2.0

2.5
Factor K

3.0

3.5

0.2
4.0

5.0

8.0
Diagram for
reduction factor
HR

0.6 0.8 0.9 .2 .4 .6 .8 1 2 4 6 d85

51
 1801 . SLURRY HANDBOOK . 1 . OCEANIA .1 . 20200728
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