the fundamentals of pump sizing feb 2014
TRANSCRIPT
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
1/44
Slurry handling solutionsThe fundamentals of pump sizing
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
2/44
Metso Metso
The fundamentals of pump sizing
Introduction
This presentation is aimed at providing abrief overview of pump sizing
Pumps may well be the oldest mechanicalinvention for the conversion of naturalenergy to useful work, but they are also the
most misunderstood of all machines
Mechanically very simple, pumps can alsobe very complicated hydraulically, andcertainly troublesome under the wrongconditions
2
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
3/44
Metso Metso
The fundamentals of pump sizing
Centrifugal slurry pumps
There are literally hundreds of centrifugal pumpmanufacturers, but very few who manufacture a true
slurry pump Slurry pumps represent 5% of all centrifugal pumps
installed in the process industry
Of the 5% installed, slurry pumps represent 80% ofthe total operating costs
These operating costs increase significantly when aslurry pump is sized incorrectly, or misapplied
It is therefore essential to have a clear understandingof all aspects relating to pump sizing and indeedpump design and application
3
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
4/44
Metso Metso
The fundamentals of pump sizing
Its never easy
All pump ranges have limited hydraulic coverage (capacity and head).Coverage across various ranges is generally good but not infinite
Slurry pump sizing is often very much an art form, there are guidelinesbut no fixed or firm rules especially when extremes are encountered
Common sense must prevail to succeed. Pump sizing software is oftenavailable, but this will not help if the basic selection is wrong
Good pump sizing relies on not only a basic understanding of hydraulics,but also an understanding of site needs and applications
4
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
5/44
Metso Metso
The fundamentals of pump sizing
The right pump for the job
Every manufacturer has various pump ranges designed for a wide varietyof slurry applications, from dirty water to mill discharge
Numerous adjectives are used to describe a particular range including;- Solution- Mining
- Heavy Duty- Extra Heavy Duty- Severe Duty
Materials of construction may vary, there may be extra material at known
points of wear, but most manufacturers refer to the impeller aspect ratio the ratio of impeller diameter to impeller eye diameter (pump inlet)
Good practice requires a high aspect ratio for the most abrasive duties
5
Increasingimpeller
diameter
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
6/44
Metso Metso
The fundamentals of pump sizing
Materials of construction
Material selection plays a big part in pump sizing, get it wrong and thepump will fail much sooner then expected
Elastomers are superior for abrasion but are more likely to fail due topoor adjustment, vacuum, temperature, additives or oversized solids
Metal can withstand a lot more abuse and as such it is often a bestcompromise except where corrosion also exists
While manufacturers make selection at or close to BEP, as processeschange, so does the duty point relative to BEP
A pump that is too large can wear out just as quickly as a pump that istoo small
Efficiency reflects turbulence which in turn reflects rate of wear. Goodefficiency with smooth hydraulic flow and the minimum of recirculationwill always provide good service
6
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
7/44
Metso Metso
Pumps are simple machines, buttheir sizing for and application in a
system (their working environment)can be complicated, and indeedvery difficult with slurries
Often considered only one up fromvalves, the smallest of pumps canshut down a complete plant
The fundamentals of pump sizing
Simple machines
7
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
8/44
Metso Metso
To every action there is always opposed an equal reaction
In our world, whatever we do when designing and or specifying plant,there will always be a consequence
Pump sizing is therefore often a compromise, to accommodate avariety of parameters set by others
Careful thought beforehand is a must, the more information madeavailable when sizing a pump, the greater the chances of success
The fundamentals of pump sizing
Isaac Newton discovered that
8
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
9/44
Metso Metso
Details of the application willalways help with pump sizing
In short, what is the pumpexpected to do?
- Feed spray bars
- Dewater a pit- Feed a cyclone- Transfer slurry- Feed a press
The fundamentals of pump sizing
What is the application?
9
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
10/44
Metso Metso
The fundamentals of pump sizing
Where from, where to and everything in between?
1. pipe, straight2. valve, butterfly3. pipe, straight4. bend, 905. pipe, straight6. bend, 90
7. pipe, straight8. bend, 90
1
2
3
4 5
6
78
Total friction losses are converted into an equivalent length of straight pipe
10
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
11/44
Metso Metso
The fundamentals of pump sizing
Static head
A. Static head is always liquid level to liquid level (high points shouldalways be specified)
B. Suction static (-/+) is liquid level on suction to pump centre line
C. Discharge static (-/+) is pump centre line to liquid level at point ofdischarge
11
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
12/44
Metso Metso
The fundamentals of pump sizing
Slurry definitions
Slurry- Any mixture composed of solid
particles and a liquid
Concentration- The amount of solids present in a
slurry expressed as a percentage
Settling slurry- Solids settle rapidly and turbulent
conditions are required to prevent
settlement
Non settling slurry- Solids settle fairly slowly or not at all
12
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
13/44
Metso Metso
The fundamentals of pump sizing
Always remember
To size a pump for a given application, it is essential to be provided with(as a minimum) the required volumetric flow rate and the total differential
head (TDH) against which the pump must produce this flow
Even with a given volumetric flow rate and TDH, numerous additionaldata is needed for a trouble free installation
Additional data should relate to both the liquid handled, solids presentand the system under which the pump is expected to operate
Various flows at the same total differential head are unlikely to berealistic. Static head may be the same for different flows but frictionvaries considerably
13
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
14/44
Metso Metso
The fundamentals of pump sizing
Computer software
Computer design enables accuratetransition from theory to practice
While modern sizing proceduresfor slurry pumps are computerisedand easy to handle, it is importantthat we know the steps for sizing
slurry pumps and the relationshipbetween them
The following slides illustrate amanual procedure, which although
approximate gives reasonableaccuracy, except in extremeapplications
14
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
15/44
Metso Metso
Establish if the slurry / liquid is a:- Clear liquid
- Settling slurry- Non settling (viscous) slurry
(particle size < 50 micron)
The fundamentals of pump sizing
Step 1 - fluid type
15
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
16/44
Metso Metso
The fundamentals of pump sizing
Step 2 - duty details
Establish the duty details which will vary depending on the type of liquidaccording to step 1 (clear liquid, settling slurry or non settling slurry)
16
Common duty details are:- Flow or tonnage
- Static lift (head)- Friction losses given or frompipe system known / selected)
- Chemical properties like pH
value, content of chlorides, oil,etc
- Temperature- Other liquid / slurry details
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
17/44
Metso Metso
The fundamentals of pump sizing
Step 2 - liquid / slurry details
Clear liquid- For clear water no further fluid details are required
- For other clear liquids the liquid S.G. and the liquid dynamic viscosity (cp)are required
- If the kinematic viscosity (cSt) is given conversion factors can be applied
Slurries
- Numerous additional data is required for slurries, formulae is used to obtainmissing data as required for pump sizing
Non settling slurries- The plastic dynamic viscosity and maximum particle size is required
Settling slurries- The maximum particle size, 80% passing particle size (d80) and the
average particle size (d50) is required
17
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
18/44
Metso Metso
The fundamentals of pump sizing
Step 2 - basic slurry formula
18
Sm = Slurry S.G.
S = Solids S.G. Q = m3/h flow rate
TPH = Tonnes per hour
Cv = Concentration by volume (%)
Cw = Concentration by weight (%)
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
19/44
Metso Metso
The fundamentals of pump sizing
Step 2 - solids tonnage or slurry flow?
Percent solids by weight is the normal way of explaining a slurry- e.g. Magnetite slurry, 40% solids by weight
This is due to the practice that production in general is measured intonnes (solids) / hour
- e.g. Magnetite feed to the circuit is 300 tonnes / hour as a slurry 40% by weight
These are meaningless figures for a slurry pump salesperson as pumps
are volumetric machines and are sized on the volumetric flow By using the solid S.G. you can calculate a volumetric flow rate
- e.g. Magnetite solids S.G. of 4.6, volumetric flow is 515 m3/h
19
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
20/44
Metso Metso
Check that the actual velocity in the pipe is greater than the criticalvelocity (refer to the adapted Wilson diagram)
If a pipe diameter has not been specified, select the first pipe sizegiving a velocity above 3 m/s, checking that the actual velocity isgreater than the critical velocity
If the actual velocity is less than the critical velocity the exercise should
be repeated for a pipe of smaller diameter (one size down) to checkthat settling does not take place
Likewise if the actual velocity is greater than the critical velocity theexercise should be repeated for a pipe of larger diameter (one size up)
to minimise friction losses NOTE - Always use the minimum anticipated flow rate to calculate the
pipe velocity
The fundamentals of pump sizing
Step 3 - settling slurries only
20
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
21/44
Metso Metso
The fundamentals of pump sizing
Step 3 - minimum settling velocity, Wilson diagram
21
Chart for minimum settling velocity (adapted from Wilson, 1976)
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
22/44
Metso Metso
The fundamentals of pump sizing
Step 3 - minimum settling velocity, Wilson diagram
Example data
- Pipe diameter = 0.25 m
- Particle size = 0.5mm (worst case)
- Particle S.G. = 3.6
- Minimum velocity = 4.25 m/sec
Minimum velocity to prevent settling is identified by;
1) Drawing a line from 250 mm pipe through 0.5 mm solids to the middle scale
(minimum velocity based on solids S.G. of 2.65)2) Drawing a second line from the middle scale through the actual solids S.G.
(3.6) to the right hand scale and read of the minimum velocity (4.25 m/sec)for the given solids S.G.
22
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
23/44
Metso Metso
Similar to voltage drop in a power cable, there arefriction losses in a pipe system
The friction losses in a straight pipe vary with- Diameter- Length- Material (roughness)
- Flow rate (velocity) Friction losses can either be looked up in a table,
extracted from a diagram or calculated from formulae
Friction losses are multiplied by the total equivalentpipe length to give a friction head in metres which isadded to the static head
The fundamentals of pump sizing
Step 4 - total discharge head
23
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
24/44
Metso Metso
Additional process equipment needing pressure must also beconsidered, e.g. filter press or hydrocyclones
Pressure needs to be converted to a head in metres (dividing thepressure by the specific gravity of the fluid) and added to the static headand friction head
The fundamentals of pump sizing
Step 4 - total discharge head
24
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
25/44
Metso Metso
Example data
- Volumetric flow = 2000 l/min
- Pipe diameter = 150 mm
Friction losses identified by;
1) Drawing a line up from thevolumetric flow to the pipediameter
2) Draw a second line horizontallyacross to determine the friction
losses (2.2 m/100 m)
3) Draw a third line diagonally todetermine the flow velocity (1.9m/s)
The fundamentals of pump sizing
Step 4 - friction losses for clear water, calculation chart
25
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
26/44
Metso Metso
The fundamentals of pump sizing
Step 4 - friction losses for clear water, formula
For water and settling slurries at higher velocities, the following formulamay be used for assessing friction loss in pipe where;
- HF = Metres loss/100 metres- Q = m3/h flow rate- D = Pipe diameter in metres- C = Friction factor
Typical values for C are;- Polyurethane lined and plastic = 150- Seamless steel and spun cast iron = 140
- Spiral welded steel and cast iron = 130- Rippled bore rubber hose = 110
26
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
27/44
Metso Metso
The fundamentals of pump sizing
Step 4 - friction losses for clear water, formula
Example- Q = 120 m3/h (2000 l/min)
- D = 0.15- C = 140
If pipe length is 200m, the friction head is 4.26m which is added to thestatic head
27
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
28/44
Metso Metso
Correction factor identified by;
1) Drawing a line across from thegiven concentration by volume
(20%)
2) At point of intersection draw asecond line down to determine thefriction loss correction factor (1.15)
The fundamentals of pump sizing
Step 4 - friction losses for settling slurries
28
When calculating the pipe friction losses for a slurry it is advisable toallow for a certain increase when compared with the losses for clean
water Concentrations of up to 15% by volume behave like water
For higher concentrations friction losses should be corrected by a factor
NOTE - Calculated values must be used for rough estimates only
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
29/44
Metso Metso
The fundamentals of pump sizing
Step 4 - friction losses for non settling slurries
29
Friction loss assessments for non settling slurriesare best accomplished with the aid of computer
software There are numerous methods of making
assessments manually although these can provedifficult with all the variables
Whatever method is used full rheology of theviscous solution is necessary for any accurateassesment
Assumptions can be made but these can prove tobe very inaccurate
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
30/44
Metso Metso
The fundamentals of pump sizing
Step 4 - total equivalent length
When a system includes valvesand fittings, an allowance for
additional friction is needed The most common method is called
the equivalent pipe length
The valve or fitting is treated as a
length of straight pipe giving anequivalent resistance to flow
TEL - Total Equivalent Length- TEL = Straight pipe length + equivalent
length of all pipe fittings
30
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
31/44
Metso Metso
Select the wet end wear partsmaterial subject to the maximum
particle size
For clear liquids metal pumps arethe first choice
Check available chemicalresistance tables for the selectedwear material
The fundamentals of pump sizing
Step 5 - wear material
31
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
32/44
Metso Metso
The application will dictate if this isa horizontal pump, sump pump,
tank pump or froth pump
It can also be a pump for extreme,heavy or normal wear conditions
Some designs and ranges arealso specific and tailored for agiven industry
The fundamentals of pump sizing
Step 6 - selecting the right pump
32
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
33/44
Metso Metso
Pump performance curves are basedon clear water, corrections arerequired if other liquids or a slurry ispumped
For clear water mark the flow andtotal discharge head on the uppersection of the curve
From this you can estimate therequired pump speed (1880 rpm)
On the lower section of the curve
mark the flow at the running speed toestimate the power absorbed (28 kW)
The fundamentals of pump sizing
Step 7 - clear water
33
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
34/44
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
35/44
Metso Metso
Example data
- Average particle size (d50) = 0.9 mm
- Density of solids = 2.0
- Concentration by weight = 35%
HR/ER identified by;1) Drawing a line up from the average
particle size to the solids density
2) Draw a second line across to theconcentration by weight
3) Draw a third line up to determinethe HR/ER
The fundamentals of pump sizing
Step 7 - settling slurries HR/ER
35
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
36/44
Metso Metso
After establishing the HR/ER, divide thetotal discharge head by the HR factor
Mark the flow and corrected totaldischarge head point on theperformance curve, from this you canestimate the pump speed (1880rpm)
From the flow and running speedestimate the power absorbed requiredfor clear water (28kW)
Multiply the required clear water power
absorbed by the relative density to givethe required slurry power
- Relative density = Slurry density______________ Clear water density
The fundamentals of pump sizing
Step 7 - settling slurries HR/ER
36
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
37/44
Metso Metso
Pump performance is derated in accordance with the AmericanHydraulics Institute (HI) guidelines
Deration for the head, efficiency and flow are calculated from the ratedB.E.P. and not the duty point
For slurry pumps, these deration factors can be taken as being veryconservative as all development work by the HI was undertaken on
process pumps with narrow impellers Divide your duty flow and head with the correction factors and mark
them on the clear water curve to estimate the pump speed
With the corrected flow and the estimated pump speed estimate therequired clear water power
Multiply the required clear water power absorbed by the relative densityto give the required slurry power
- Relative density = Slurry density / clear water density
The fundamentals of pump sizing
Step 7 - non settling (viscous) slurries
37
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
38/44
Metso Metso
It is recommended to add a 15%safety margin to the required powerand select the next available motorsize
- Required power = 18kW- Including safety margin = 20.7kW
- Motor size = 22kW For clear water duties the safety
margin is added to the clear waterrequired power
For slurry duties the safety margin isadded to the slurry required power
The fundamentals of pump sizing
Step 8 - motor size
38
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
39/44
Metso Metso
There are two basic drive designs for slurrypumps
- Indirect drives (v-belt)- Direct drives (coupling)
Select a suitable drive to achieve therequired pump running speed
Typical maximum speed ratios for v-beltdrives is 5:1 with 1500rpm motors and 4:1with 1800rpm motors
For certain applications (varying flowconditions, long pipe lines) variable speeddrives should be used
The fundamentals of pump sizing
Step 9 - drive
39
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
40/44
Metso Metso
An international standard for slurrypumps now effectively exists
Introduced back in 2005 by the HydraulicInstitute / American National StandardsInstitute (HI/ANSI) as guidelines
Today, most manufacturers include some
if not all of the recommendations made Pump sizing recommendations in
particular have been almost universallyadopted - all aimed at providing optimum
rates of wear and longevity in service
The fundamentals of pump sizing
HI guidelines
40
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
41/44
Metso Metso
The fundamentals of pump sizing
HI guidelines for duty classification
Class 4- Extremely abrasive
Class 3- Highly abrasive
Class 2- Abrasive
Class 1- Mildly abrasive
41
Th f d l f i i
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
42/44
Metso Metso
Operating limits Casing TypeService Class
1 2 3 4
Recommendedpercent range of
BEP flow rate
Annular 20 120% 30 110% 40 100% 50 90%
Semi volute 30 130% 40 120% 50 110% 60 100%
Near volute 50 140% 60 130% 70 120% 80 110%
The fundamentals of pump sizing
HI guidelines for optimum wear relative to BEP
42
Th f d t l f i i
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
43/44
Metso Metso
The fundamentals of pump sizing
HI guidelines for maximum operating values
Adjustments are also made to inlet velocity limit for volume and size of solids
Maximum impeller speed in natural rubber = 28 m/s
Maximum impeller speed in synthetic rubbers and PU = 30 m/s Maximum speed metal impeller in rubber lined pump = 31 m/s
Service Class
1 2 3 4
Maximum head per stage:
meter 123 66 52 40
feet 400 225 160 130
Maximum impeller peripheral speed:
All metal pump
m/s 43 38 33 28
ft/min 8500 7500 6500 5500
Rubber lined pump
m/s 31 28 26 23
ft/min 6000 5500 5000 4500
43
-
8/12/2019 The Fundamentals of Pump Sizing Feb 2014
44/44
company/metso metsogroup metsoworldmetsoworld metsogroup
www.metso.com
www.metso.com/pumps