Pumps and types of pumps in detail

1. PUMPS PUMPS PUMPS PUMPS PUMPS PUMPS PUMPS PUMPS
CHAPTER  CHAPTER  CHAPTER  CHAPTER  CHAPTER  CHAPTER  CHAPTER  CHAPTER ––––– –––111111 1111 1111 11
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2. INTRODUCTION INTRODUCTION INTRODUCTION INTRODUCTION INTRODUCTION INTRODUCTION INTRODUCTION INTRODUCTION
DESIGNING OF ANY FLUID FLOWING SYSTEM REQUIRES;
1. Design of system through which fluid will flow
2. Calculation of losses that will occur when the fluid flows
3. Selection of suitable device which will deliver enough energy
to the fluid to overcome these losses
Devices: Deliver Energy To Liquids/Gases: Pumps/Compressors Pumps/Compressors
TYPES OF PUMPS TYPES OF PUMPS
POSITIVE DISPLACEMENT PUMPS POSITIVE DISPLACEMENT PUMPS
DYNAMIC PUMPS DYNAMIC PUMPS
ROTARY PUMPS ROTARY PUMPS RECIPROCATING PUMPS RECIPROCATING PUMPS
CENTRIFUGAL CENTRIFUGAL
PUMPS PUMPS
Devices: Extracts Energy From Fluids: TurbinesTurbines

3. POSITIVE DISPLACEMENT PUMPS, (PDP’S) POSITIVE DISPLACEMENT PUMPS, (PDP’S) POSITIVE DISPLACEMENT PUMPS, (PDP’S) POSITIVE DISPLACEMENT PUMPS, (PDP’S) POSITIVE DISPLACEMENT PUMPS, (PDP’S) POSITIVE DISPLACEMENT PUMPS, (PDP’S) POSITIVE DISPLACEMENT PUMPS, (PDP’S) POSITIVE DISPLACEMENT PUMPS, (PDP’S)
WORKING PRINCIPLE AND FEATURES; WORKING PRINCIPLE AND FEATURES;
1. Fixed volume cavity opens
2. Fluid trapped in the cavity through an inlet
3. Cavity closes, fluid squeezed through an outlet
4. A direct force is applied to the confined liquid
5. Flow rate is related to the speed of the moving parts of the pump
6. The fluid flow rates are controlled by the drive speed of the pump
7.
In each cycle the fluid pumped equals the volume of the cavity
7.
In each cycle the fluid pumped equals the volume of the cavity
8. Pulsating or Periodic flow
9. Allows transport of highly viscous fluids
10.Performance almost independent of fluid viscosity
11.Develop immense pressures if outlet is shut for any reaso n, 
HENCE
1. Sturdy construction is required
2. Pressure-relief valves are required (avoid damage from 
complete shutoff conditions)

4. PDP’S, contd. PDP’S, contd. PDP’S, contd. PDP’S, contd. PDP’S, contd. PDP’S, contd. PDP’S, contd. PDP’S, contd.
RECIPROCATING TYPE PDPS
Diaphragm pumps
Piston OR Plunger pumps
Double acting Simplex pump
Single acting piston pump
Double diaphragm pump
Single diaphragm pump
Double acting Simplex pump
Double diaphragm pump
Double acting Duplex pump

5. ROTARY TYPE PDPS ROTARY TYPE PDPS ROTARY TYPE PDPS ROTARY TYPE PDPS ROTARY TYPE PDPS ROTARY TYPE PDPS ROTARY TYPE PDPS ROTARY TYPE PDPS
SINGLE ROTOR
MULTIPLE ROTORS
Flexible tube or lining
Gear Pump
Sliding vane pump
2 Lobe Pump
AND MANY MORE AND MANY MORE AND MANY MORE AND MANY MORE AND MANY MORE AND MANY MORE AND MANY MORE AND MANY MORE
3 Lobe Pump
Screw pump
Radial Pump

6. DYNAMIC PUMPS DYNAMIC PUMPS DYNAMIC PUMPS DYNAMIC PUMPS DYNAMIC PUMPS DYNAMIC PUMPS DYNAMIC PUMPS DYNAMIC PUMPS
WORKING PRINCIPLE AND FEATURES WORKING PRINCIPLE AND FEATURES 1. Add somehow momentum to the fluid
(through vanes, impellers or some special design
2. Do not have a fixed closed volume
3. Fluid with high momentum passes through open passages and
converts its high velocity into pressure
TYPES OF DYNAMIC PUMPS TYPES OF DYNAMIC PUMPS
ROTARY PUMPS ROTARY PUMPS
SPECIAL PUMPS SPECIAL PUMPS
Centrifugal Pumps Centrifugal Pumps
Axial Flow Pumps Axial Flow Pumps
Mixed Flow Pumps Mixed Flow Pumps
Jet pump or ejector
Electromagnetic pumps for liquid metals
Fluid=actuated: gas=lift or hydraulic=ram

7. DYNAMIC PUMPS, contd. DYNAMIC PUMPS, contd. DYNAMIC PUMPS, contd. DYNAMIC PUMPS, contd. DYNAMIC PUMPS, contd. DYNAMIC PUMPS, contd. DYNAMIC PUMPS, contd. DYNAMIC PUMPS, contd.
Jet pump or ejector
Centrifugal Pumps Centrifugal Pumps Axial Flow Pumps Axial Flow Pumps
hydraulic=ram
1 vane Pump 1 vane Pump
Axial Flow Pumps Axial Flow Pumps Mixed Flow Pumps Mixed Flow Pumps
Diffuser Pump Diffuser Pump

8. COMPARISON OF PDPS AND DYNAMIC PUMPS COMPARISON OF PDPS AND DYNAMIC PUMPS COMPARISON OF PDPS AND DYNAMIC PUMPS COMPARISON OF PDPS AND DYNAMIC PUMPS COMPARISON OF PDPS AND DYNAMIC PUMPS COMPARISON OF PDPS AND DYNAMIC PUMPS COMPARISON OF PDPS AND DYNAMIC PUMPS COMPARISON OF PDPS AND DYNAMIC PUMPS
CRITERIA PDPS DYNAMIC PUMPS
Flow rate Low, typically 100 gpm As high as 300,000 gpm Pressure As high as 300 atm Moderate, few atm Priming Very rarely Always
Flow Type Pulsating Steady
Constant flow rate for virtually
Constant
RPM
Constant flow rate for virtually
any pressure
OR
Flow rate cannot be changed
without changing RPM
Hence used for metering
Head varies with
flow rate
OR
Flow rate changes with
head for same RPM
Viscosity Virtually no effect Strong effects

9. CENTRIFUGAL PUMPS CENTRIFUGAL PUMPS CENTRIFUGAL PUMPS CENTRIFUGAL PUMPS CENTRIFUGAL PUMPS CENTRIFUGAL PUMPS CENTRIFUGAL PUMPS CENTRIFUGAL PUMPS
Centrifugal Pumps: Construction Details and Working
1. A very simple machine
2. Two main parts
1. A rotary element, IMPELLER
2. A stationary element, VOLUTE
3. Filled with fluid & impeller rotated
4.
Fluid rotates & leaves with high velocity
nYYQM;SA;FELof nYYQM;SA;FELoy
Impeller
o
1
Impeller
o
5
4.
Fluid rotates & leaves with high velocity
5. Outward flow reduces pressure at inlet,
(EYE OF THE IMPELLER), more fluid
comes in.
6. Outward fluid enters an increasing area
region. Velocity converts to pressure
FImpeller Impart Energy/Velocity By Rotating Fluid
FVolute Converts Velocity To Pressure
Impeller
o
1
nGgNYYNSoy nGgNYYNSom nGgNYYNSoh
Impeller
o
5
nGgNYYNSor

10. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd.
Centrifugal Pumps: Working Principal 1. Swinging pale generates centrifugal force →holds water in pale
2. Make a bore in hole→water is thrown out
3. Distance the water stream travels tangent to the circle = f(V
r)
4. Volume flow from hole = f(V
r)
5.
In centrifugal pumps, flow rate & pressure =
f
(V
r) (tip velocity)
5.
In centrifugal pumps, flow rate & pressure =
f
(V
r) (tip velocity)
A freely falling body achieves a velocity V = (2gh)
1/2
A body will move a distance h = V
2
/2g, having an initial velocity V
OR
Find diameter that will generate ‘V’ to get required ‘h’ for given ‘N ’

11. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd.
Q. FOR AN 1800 RPM PUMP FIND THE DIAMETER
OF IMPELLER TO GENERATE A HEAD OF 200 FT.
Find first initial velocity V = (2gh)
1/2
= 113 ft/sec
Convert RPM to linear distance per rotation
1800 RPM = 30 RPS →V/RPS = 113/30 = 3.77 ft/rotation
3.77 = circumference of impeller
→
diameter = 1.2 ft = 14.4 inches
3.77 = circumference of impeller
→
diameter = 1.2 ft = 14.4 inches
CONCLUSION CONCLUSION
FLOW THROUGH A CENTRIFUGAL PUMP FOLLOWS THE
SAME RULES OF FREELY FALLING BODIES
DO WE GET
THE SAME DIAMETER OR HEAD OR FLOW RATE
AS PREDICTED BY THESE IDEAL RULES

12. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd.
BASIC PERFORMANCE PARAMETERS BASIC PERFORMANCE PARAMETERS
The Energy Equation for This Case
2 2
1 2
1 1 1 2 2 2
2 2
shaft vis
V V
Q W W m h gz m h gz
   
− − = − + + + + +
       
&& && &
Assumptions:
• No heat generation
• No viscous work.
• Mass in = mass out
2 2
2 1
2 2 1 1
2 2
shaft
V V
W m h gz h gz
 
   
= + + − + +
 
       
 
&&

13. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd.
What would be the difference in ‘z’, can we assume z
2
=z
1
≈0
Hence
2 2
2 1
2 1
2 2
shaft
V V
W m h h
 
   
= + − +
 
       
 
&&
2 2
2 2 1 1
2 1
2 2
shaft
p V p V
W m u u
ρ ρ
 
   
= + + − + +
 
       
 
&&
2 1
2 2
shaft
W m u u
ρ ρ
= + + − + +
 
       
 
Thermodynamically, u = u(T)
only and T
in
≈T
out
2 2
2 2 1 1
2 2
shaft
p V p V
W m ρ ρ 
   
= + − +
 
       
 
&&
2 2
2 2 1 12 2
shaft
p V p V
W Q
ρ
ρ ρ
 
   
= + − +
 
       
 
&

14. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd.
2 2
2 1
2 1
2 2
w shaft
V V
P gHQ W Q p p
ρ ρ
ρ
 
   
= = = + − +
 
       
 
&
( )
2 2
2 1
2 1
1
2 2
w
PV V
H p p
gQ g
ρ ρ
ρ ρ
 
 
= = − + −
 
   
 
Where P
w
= water power
2 2
gQ g
ρ ρ
 
 
Generally V
1
and V
2
are of same order of magnitude
If the inlet and outlet diameters are same
( )
2 1
1
w
P
H p p
gQ g
ρ ρ
 
= ≅ −
 

15. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd.
The power required to drive the pump; bhp
The power required to turn the pump shaft at certain RPM
torque required to turn shaft
bhp T T
ω
= =
The actual power required to drive the pump depends upon efficiency
w
P
gQH
bhp T
ρ
η
ω
= =
bhp T
ω
Efficiency has three components;
Mechanical
1. Losses in bearings
2. Packing glands etc
Hydraulic
• Shock
• friction,
• re=circulation
Volumetric
• casing leakages
v
L
Q
Q Q
η
=
+
1
f
m
P
bhp
η
= −
1
f
v
s
h h
η
= −
v h m
η η η η
=

16. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd.
Torque estimation ⇒1D flow assumption 1=D angular momentum balance gives
(
)
2 2 1 1
t t
T Q rV rV
ρ
= −
V
t1
and V
t2
absolute circumferential
or tangential velocity components
(
)
(
)
2 2 1 1 2 2 1 1
w t t t t
P T Q rV rV Q uV uV
ω ωρ ρ
= = − = −
Torque, Power and Ideal Head depends on,
Impeller tip velocities ‘u’ & abs. tangential velocities V
t
Independent of fluid axial velocityif any
(
)
( )
2 2 1 1
2 2 1 1
1
t t w
t t
Q uV uV P
H uV uV
gQ gQ g
ρ
ρ ρ
−
= = = −
Euler turbo=
machinery
equations;
DO DO
DETAILS DETAILS
IN TUTORIAL IN TUTORIAL

17. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd.
Doing some trigonometric and algebraic manipulation
( ) ( ) ( )
2 2 2 2 2 2
2 1 2 1 2 1
1
2
H V V u u w w
g
 
= − + − + −
 
2 2 2
2 2
p w r
z const
g g g
ω
ρ
+ + − =
BERNOULLI EQUATION IN ROTATING COORDINATES
Applicable to 1, 2 and 3D Ideal Incompressible Fluids
One Can Also Relate the Pump Power With Fluid Radial Velocity
(
)
2 2 2 1 1 1
cot cot
w n n
P Q uV uV
ρ α α
= −
2 1
2 2 1 1
2 2
n n
Q Q
V and V
rb rb
π π
= =
With known b
1
, b
2
, r
1
, r
2
, β
1
, β
2
and ωone can find centrifugal pump’s
ideal power and ideal head as a function of Discharge ‘Q’
DO DO
EX. 11.1 EX. 11.1
IN TUTORIAL IN TUTORIAL

18. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd. CENTRIFUGAL PUMPS, contd.
EFFECT OF BLADE ANGLES β
1
, β
2
ON PUMP PERFORMANCE
( )
2 2 1 1
1
w
t t
P
H uV uV
gQ g
ρ
= = −
Angular momentum out
Angular momentum in
>>
2
2 2
2
n
Q
V
rb
π
=
momentum out
momentum in
2 2 2 2
cot
t n
V u V
β
= −
Doing all this leads to
2
2 2 2
2 2
cot
2
u u
H Q
g rbg
β
π
≈ −
if β< 90, backward curve blades, stable op
if β= 90, straight radial blades, stable op
If β> 90, forward curve blades, unstable op

19. CENTRIFUGAL PUMPS, CHARACTERISTICS CENTRIFUGAL PUMPS, CHARACTERISTICS CENTRIFUGAL PUMPS, CHARACTERISTICS CENTRIFUGAL PUMPS, CHARACTERISTICS CENTRIFUGAL PUMPS, CHARACTERISTICS CENTRIFUGAL PUMPS, CHARACTERISTICS CENTRIFUGAL PUMPS, CHARACTERISTICS CENTRIFUGAL PUMPS, CHARACTERISTICS
1. Whatever discussed earlier is qualitative due to assumptions.
2. Actual performance of centrifugal pump →
3. The presentation of performance data is exactly s ame for
4. The graphical representation of pumps performance data obtained
experimentally is called “PUMP CHARACTERSTICS” OR “PUMP
extensive testing
1.   Centrifugal pumps2.   Axial flow pumps
3.   Mixed flow pumps4.   Compressors
experimentally is called “PUMP CHARACTERSTICS” OR “PUMP CHARACTERSTIC CURVES”
1. This representation is almost always for constant shaft speed ‘N’
2. Q(gpm) discharge is the independent variable
3. H(head developed), P(power),
ηηηη
(efficiency) and NPSH(net
positive suction head) are the dependent variables
4. Q(ft
3/
m
3
/min), discharge is the independent variable
5. H(head developed), P(power),
ηηηη
(efficiency) are the dependent
variables
(LIQUIDS)
(LIQUIDS)
(GASES)
(GASES)

20. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd.
Typical
Characteristic Curves
of Centrifugal Pumps

21. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. General Features of Characteristic Curves of Centrifugal Pump s
1. ‘H’ is almost constant at low flow rates
2. Maximum ‘H’(shut off head) is at zero flow rate
3. Head drops to zero at Q
max
4. ‘Q’ is not greater than Q
max
→‘N’ and/or impeller size is changed
5. Efficiency is always zero at Q = 0 and Q = Q
max
6.
η
is not an independent parameter
→
w
P
gHQ
ρ
η
= =
6.
η
is not an independent parameter
→
7.η= η
max
at roughly Q=0.6Q
max
to 0.93Q
max
8.η= η
max
is called the BEST EFFICIENCY POINT (BEP)
9. All the parameters corresponding to η
max
are called the design
points, Q
*
, H
*
, P
*
10.Pumps design should be such that the efficiency curve should be
as flat as possible around η
max
11.‘P’ rises almost linearly with flow rate
w
P
gHQ
P P
ρ
η
= =

22. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd.
Typical Characteristic Curves of Commercial Centrifugal Pump s
1. Having same casing size but different impeller diameters
2. Rotating at different rpm
3. For power requirement and efficiency one needs to interpolate
(a ) basic casing with three basic casing with three basic casing with three basic casing with three
impeller sizes impeller sizes impeller sizes impeller sizes
(b) 20 percent larger casing with three 20 percent larger casing with three 20 percent larger casing with three 20 percent larger casing with three
larger impellers at slower speed larger impellers at slower speed larger impellers at slower speed larger impellers at slower speed

23. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd.
Calculate the ideal Head to be developed by the pump
shown in last figure
( ) ( )
2 2
2 2
2
2
1170 2 /60 / 36.75/2 12
( )1093
32.2 /
o
rad s ft r
H idealft
g ft s
π ω
× ×
= ==
Actual Head = 670 ft or 61% of H
o
(ideal) at Q=0
Differences are due to
1. Impeller recirculations, important at low flow rates
2. Frictional losses
3. Shock losses due to mismatch of blade angle and flow
inlet important at high flow rates

24. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd.
IMPORTANT POINTS TO REMEMBER
1. EFFECT OF DENSITY
1. Pump head reported in ‘ft’ or ‘m’ of that fluid  →ρimportant
2. These characteristic curves, valid only for the liqu id reported
3. Same pump used to pump a different liquid  →H and η
would be almost same. OR. A centrifugal pump will alwa ys 
develop the same head in feet of that liquid regardless  of the  develop the same head in feet of that liquid regardless  of the  fluid density
4. However P will change. Brake HP will vary directly  with the 
liquid density
2. EFFECT OF VISCOSITY
1. Viscous liquids tend to decrease the pump Head, Di scharge 
and efficiency →tends to steepen the H-Q curve with  η↓
2. Viscous liquids tend to increase the pump BHP

25. CentiPoise
cP)
centiStokes
(cSt)
Saybolt Second
Universal (SSU) Typical liquid
Specific 
Gravity
1 1 31 Water 1
3.2 4 40 Milk -
12.6 15.7 80 No. 4 fuel oil 0.82 - 0.95
16.5 20.6 100 Cream -
34.6 43.2 200 Vegetable oil 0.91 - 0.95
88 110 500 SAE 10 oil 0.88 - 0.94
176 220 1000 Tomato Juice -
352 440 2000 SAE 30 oil 0.88 - 0.94
820 650 5000 Glycerine  1.26
1561 1735 8000 SAE 50 oil 0.88 - 0.94
1760 2200 10,000 Honey -
5000 6250 28,000 Mayonnaise -
15,200 19,000 86,000 Sour cream -
17,640 19,600 90,000 SAE 70 oil 0.88 - 0.94

26. Viscosity Scales
CentiPoises (cp) = CentiStokes (cSt) / SG (Specific Gravity)
SSU = Centistokes (cSt) ×4.55
Degree Engler ×7.45 = Centistokes (cSt)
Seconds Redwood  ×0.2469 = Centistokes (cSt)

27. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd. CENTRIFUGAL PUMPS, CHARACTERISTICS, contd.
    ≥ 300    
w
or     > 2000 SSU
PDP’s are preferred
    
≤≤≤≤10    
w
or     < 50 SSU
Centrifugal pumps are preferred

28. SUCTION HEAD AND SUCTION LIFT SUCTION HEAD AND SUCTION LIFT SUCTION HEAD AND SUCTION LIFT SUCTION HEAD AND SUCTION LIFT SUCTION HEAD AND SUCTION LIFT SUCTION HEAD AND SUCTION LIFT SUCTION HEAD AND SUCTION LIFT SUCTION HEAD AND SUCTION LIFT
• A centrifugal pump cannot pull or suck liquids
• Suction in centrifugal pump →creation of partial vacuum at pump’s
inlet as compared to the pressure at the other end of liquid
• Hence, pressure difference in liquid →drives liquid through pump
• How one can increase this pressure difference
–
Increasing the pressure at the other end
–
Increasing the pressure at the other end
• Equal to 1 atm for reservoirs open to atmosphere
• > or < 1 atm for closed vessels
–Decreasing the pressure at the pump inlet
• Must be > liquid vapor pressure →
• By increasing the capacity →
temperature very important
Bernoulli's equation

29. SUCTION HEAD AND SUCTION LIFT SUCTION HEAD AND SUCTION LIFT SUCTION HEAD AND SUCTION LIFT SUCTION HEAD AND SUCTION LIFT SUCTION HEAD AND SUCTION LIFT SUCTION HEAD AND SUCTION LIFT SUCTION HEAD AND SUCTION LIFT SUCTION HEAD AND SUCTION LIFT
MAXIMUM SUCTION DEPENDS UPON
• Pressure applied at liquid surface at liquid source, hence
–Maximum suction decreases as this pressure decreases
• Vapor pressure of liquid at pumping temperature
–Maximum suction decreases as vapor pressure increases
• Capacity at which the pump is operating
CASE OF OPEN RESERVOIRS CASE OF OPEN RESERVOIRS
• Maximum suction varies inversely with altitude
CAsYNof
CASE OF HOT LIQUIDS
• Maximum suction varies inversely with temp.
CAsYNoy
CASE OF INCREASING CAPACITY
• Maximum suction varies inversely with capacity
CAsYNom

30. NET POSITIVE SUCTION HEAD NET POSITIVE SUCTION HEAD NET POSITIVE SUCTION HEAD NET POSITIVE SUCTION HEAD NET POSITIVE SUCTION HEAD NET POSITIVE SUCTION HEAD NET POSITIVE SUCTION HEAD NET POSITIVE SUCTION HEAD
•Problem of Cavitation
–The lowest pressure occurs at the pump’s inlet
–Pressure at pump inlet < liquid vapor pressure →cavitation occurs
–What are the effects of cavitation
• Lot of noise and vibrations are generated
• Sharp decrease in pump’s ‘H’ and ‘Q’
• Pitting of impeller occurs due to bubble collapse
•
May occur before actual boiling in case of dissolved gases /
•
May occur before actual boiling in case of dissolved gases / low boiling mixtures of hydrocarbons
• Hence ‘P’ at pump’s inlet should greater than the P
vp
• This extra pressure above P
vp
available at pump’s inlet is called
Net Positive Suction Head ‘NPSH’
•Mathematically →→→→
2
1
2
vp
i
P
V P
NPSH
g g
ρ ρ
= + −

31. NET POSITIVE SUCTION HEAD, contd. NET POSITIVE SUCTION HEAD, contd. NET POSITIVE SUCTION HEAD, contd. NET POSITIVE SUCTION HEAD, contd. NET POSITIVE SUCTION HEAD, contd. NET POSITIVE SUCTION HEAD, contd. NET POSITIVE SUCTION HEAD, contd. NET POSITIVE SUCTION HEAD, contd.
•NPSH calculated from this equation is the
specified by manufacturer →→→→
• The NPSH actually available at the pump’s inlet is called
••‘AVAILABLE NPSH’ must be ‘AVAILABLE NPSH’ must be ≥≥≥≥≥ ≥≥≥‘REQUIRED NPSH’ ‘REQUIRED NPSH’
• Rule of thumb for design
ft of liquid
“PUMP’S CHARACTERISTIC” “PUMP’S CHARACTERISTIC”
“SYSTEM’S CHARACTERISTIC” “SYSTEM’S CHARACTERISTIC”
‘REQUIRED NPSH
’
‘AVAILABLE NPSH’
→→→→
‘AVAILABLE NPSH’ ‘AVAILABLE NPSH’
≥≥≥≥≥ ≥≥≥
(2+‘REQUIRED NPSH’ (2+‘REQUIRED NPSH’
)
HOW TO CALCULATE AVAILABLE NPSH
Write Energy Equation between the free surface of fluid reservoir
and pump inlet
Thus Z
i
can be important parameter in designers hand to ensure that
cavitation does not occur for a given P
surface
and temperature
ft of liquid
surface vp
available i fi
P P
NPSH Z h
g g
ρ ρ
= − − −
‘AVAILABLE NPSH’ ‘AVAILABLE NPSH’
≥≥≥≥≥ ≥≥≥
(2+‘REQUIRED NPSH’ (2+‘REQUIRED NPSH’
)

32. NET POSITIVE SUCTION HEAD, contd. NET POSITIVE SUCTION HEAD, contd. NET POSITIVE SUCTION HEAD, contd. NET POSITIVE SUCTION HEAD, contd. NET POSITIVE SUCTION HEAD, contd. NET POSITIVE SUCTION HEAD, contd. NET POSITIVE SUCTION HEAD, contd. NET POSITIVE SUCTION HEAD, contd.
EFFECT OF VARYING HEIGHT
Given, P
surface, P
vpand h
fi, Z
ican 
be varied to avoid cavitation
The 32=in pump of Fig. 11.7 a is to pump 24,000 gpm of water at 1170 rpm from a
reservoir whose surface is at 14.7 psia. If head lo ss from reservoir to pump inlet is 6
ft, where should the pump inlet be placed to avoid cavitation for water at ( a) 60°F,
p
vp
0.26 psia, SG 1.0 and (
b
) 200
°
F,
p
vp
11.52 psia, SG 0.9635?
surface vp
i fi
P P
NPSHA Z h NPSHR
g g
ρ ρ
= − − − ≥
An Example
p
vp
0.26 psia, SG 1.0 and (
b
) 200
°
F,
p
vp
11.52 psia, SG 0.9635?
Pump must be placed at least 12.7 ft belowthe reservoir surface to
avoid cavitation.
38.4
i
Z
≤−
Pump must now be placed at least 38.4 ft belowthe reservoir surface,
to avoid cavitation
62.4
g
ρ
=
(
)
( )
1
14.7 0.26
406
62.4 144
surface vp
i fii
P P
NPSHR Z h Z
g g
ρ ρ
−
−
= ≤ − − − = − − 62.4 .9653 60.1
g
ρ
= × =
12.7
i
Z≤−

33. NET POSITIVE SUCTION HEAD, contd. NET POSITIVE SUCTION HEAD, contd. NET POSITIVE SUCTION HEAD, contd. NET POSITIVE SUCTION HEAD, contd. NET POSITIVE SUCTION HEAD, contd. NET POSITIVE SUCTION HEAD, contd. NET POSITIVE SUCTION HEAD, contd. NET POSITIVE SUCTION HEAD, contd.
TYPICAL EXAMPLE
A pump installed at an altitude of 2500 ft and has a suction lift of 13 ft
while pumping 50 degree water. What is NPSHA?Ignore friction
Actual NPSHA = 17.59 –2 = 15.59 ft
31 13 0 .41 17.59
surface vp
available i fi
P P
NPSH Z h ft
g g
ρ ρ
= − − − = − − − =
TYPICAL EXAMPLE
We have a pump that requires 8 ft of NPSH at I20 gpm. If the pump is
installed at an altitude of 5000 ft and is pumping cold water at 60
o
F,
what is the maximum suction lift it can attain? Ignore friction
2 8 2 28.2 0 .59 17.59
surface vp
i fi i
P P
NPSHA NPSHR Z h Z ft
g g
ρ ρ
= + = + = − − − = − − − =

34. DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE--------11111111
THREE PERFORMANCE PARAMETERS
1. Head ‘H’ (or pressure difference ∆ P=recall that ∆P= ρgH)
2. Volume Flow Rate ‘Q’
3. Power ‘P’
TWO "GEOMETRIC" PARAMETERS:
1.
D diameter
EVERY PUMP HAS EVERY PUMP HAS
1.
D diameter
2. n (or ω) rotational speed
THREE FLUID FLOW PARAMETERS:
1. ρ density
2. X viscosity
3. ε roughness
Above parameters involve only three dimensions, M=L=T

35. DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE--------22222222
Buckingham π Theorem suggests
7 =3 = 4 π’sto represent the physical phenomena in a pump.
Any pump’s performance parameters are
1. Head H (or gH ) →
2. Power P →
(
)
1
, , , , ,
gH f Q D n
u 3 8
=
(
)
2
, , , , ,
P f Q D n
u 3 8
=
Hence The Two πGroups Are
WHERE
Dε
     
= relative roughness
(
)
2
nD D
nD
ρ ρ
3 3
 
 
=
 
 
 
 
= Re. Number
3
Q
Q
C
nD
 
=
 
 
= Capacity Coefficient
3 5
P
P
C
n D
ρ
 
=
 
 
= Power Coefficient
2
1 2 2 3
, ,
gH Q nD
g n D nD D
ρ ε
3
 
=
   
2
2 3 5 3
, ,
P Q nD
g
n D nD D
ρ ε
u 3
 
=
   
2 2
H
gH
C
n D
 
=
 
 
= Head Coefficient

36. DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE--------33333333
Reynolds number inside a centrifugal pump
1.≈0.80 to 1.5x10
7
)
2. Flow always turbulent
3. Effect of Re, almost constant
4. May take it out of the functions g
1
and g
2
5. Same is true for ε/ D
Hence, we may write:
(
)
H H Q
C C C
=
(
)
P P Q
C C C
=
For geometrically similar pumps, For geometrically similar pumps,
Head and Power coefficients should be (almost)
unique functions of the capacity coefficients.
In real life, however:
=manufacturers use the same case for different rotors
(violating geometrical similarity)
=larger pumps have smaller ratios of roughness and clearances
=the fluid viscosity is the same, while Re changes with diameters.

37. DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE--------44444444
C
H
, C
P
and C
Q 
combined to give a coefficient having practical meaning
( )
H Q
Q
P
C C
C
C
η η
= =
Similarly one can also define the C
NPSH
the NPSH coefficient as
(
)
g NPSH
⋅
= =
(
)
2 2
NPSH NPSH Q
g NPSH
C C C
n D⋅
= =

38. DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE--------55555555
Representing the pump performance data in dimensionless form
Pump data
•Choose two geometrically
similar pumps
•32 in impeller in pump (a) & 38
in in pump (b)
•
Pump (b) casing 20% > pump
Results in graphical form Results in graphical form Results in graphical form Results in graphical form
•
Pump (b) casing 20% > pump
(a) casing.
•Hence same diameter to casing
ratios
DISCRIPENCIES
•A few % in ηand C
H
•pumps not truly dynamically similar
•Larger pump has smaller roughness ratio
•Larger pump has larger Re. number

39. DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE DIMENSIONLESS PUMP PERFORMANCE--------66666666
The BEP lies at η=0.88, corresponding to,
C
Q*
≈0.115 C
P*
≈0.65 C
H*
≈5.0 C
NPSH*
≈0.37
A unique set of values
• Valid for all pumps of this geometrically similar family
• Used to estimate the performance of this family pumps at BEP
Comparison of Values
D, ftn, r/s
Discharge
nD
3
, ft
3
/s
Head
n
2
D
2
/g, ft
Power
n
3
D
5
/550, hp
Fig. 11.7a32/121170/60 370 84 3527
Fig. 11.7b38/12 710/60 376 44 1861
Ratio = = 1.02 0.52 0.53

40. SIMILARITY RULES/AFFINITY LAWS SIMILARITY RULES/AFFINITY LAWS SIMILARITY RULES/AFFINITY LAWS SIMILARITY RULES/AFFINITY LAWS SIMILARITY RULES/AFFINITY LAWS SIMILARITY RULES/AFFINITY LAWS SIMILARITY RULES/AFFINITY LAWS SIMILARITY RULES/AFFINITY LAWS--------11111111
If two pumps are geometrically similar, then
1. Ratio of the corresponding coefficients =1
2. This leads to estimation of performance of one based on the
performance of the other
MATHEMATICALLY THIS CONCEPT LEADS TO
2
3
Q
C
n D
2
2 2
gH
C
n D
2
3 5
P
C
n D
ρ
2
1
3
2 2
1
3
1 1
1
Q
Q
C
n D
Q C
nD= =
3
2 2 2
1 1 1
Q n D
Q n D
 
=
   
2
1
2 2 2 2
1
2 2
1 1
1
H
H
C
n D
gH C
n D = =
2 2
2 2 2
1 1 1
H n D
H n D
   
=
       
2
1
3 5
2 2 2
1
3 5
1 1 1
1
P
P
C
n D
P C
n D
ρ ρ
= =
3 5
2 2 2 2
1 1 1 1
P n D
P n D
ρ
ρ
   
=
       
THESE ARE CALLLED SIMILARITY RULES THESE ARE CALLLED SIMILARITY RULES THESE ARE CALLLED SIMILARITY RULES THESE ARE CALLLED SIMILARITY RULES THESE ARE CALLLED SIMILARITY RULES THESE ARE CALLLED SIMILARITY RULES THESE ARE CALLLED SIMILARITY RULES THESE ARE CALLLED SIMILARITY RULES

41. SIMILARITY RULES/AFFINITY LAWS SIMILARITY RULES/AFFINITY LAWS SIMILARITY RULES/AFFINITY LAWS SIMILARITY RULES/AFFINITY LAWS SIMILARITY RULES/AFFINITY LAWS SIMILARITY RULES/AFFINITY LAWS SIMILARITY RULES/AFFINITY LAWS SIMILARITY RULES/AFFINITY LAWS--------11111111
The similarity rules are used to estimate the effect of
1. Changing the fluid
2. Changing the speed
3. Changing the size
VALID ONLY AND ONLY FOR
Geometrically similar family of any dynamic turbo machine
pump/compressor/turbine
Effect of changes in size and speed
on homologous pump performance
(a) 20 percent change
in speed at constant size
(b) 20 percent change in
size at constant speed

42. SIMILARITY RULES/AFFINITY LAWS SIMILARITY RULES/AFFINITY LAWS SIMILARITY RULES/AFFINITY LAWS SIMILARITY RULES/AFFINITY LAWS SIMILARITY RULES/AFFINITY LAWS SIMILARITY RULES/AFFINITY LAWS SIMILARITY RULES/AFFINITY LAWS SIMILARITY RULES/AFFINITY LAWS--------11111111
For Perfect Geometric Similarity η
1
= η
2,
but
Larger pumps are more efficient due to
1. Higher Reynolds Number
2. Lower roughness ratios
3. Lower clearance ratios
Empirical correlations are available To estimate efficiencies in geometrically similar family of pumps To estimate efficiencies in geometrically similar family of pumps Moody’s Correlation
Based on size changes
14
2 2
1 1
1
1
D
D
η
η
 
−
≈
 
−
 
Anderson’s Correlation
Based on flow rate changes
0.33
2 2
1 1
0.94
0.94
Q
Q
η
η
 
−
≈
 
−
 

43. Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed- -------11111111
We want to use a centrifugal pump from the family of Fig. 11.8 to
deliver 100,000 gal/min of water at 60°F with a head of 25 ft. What
should be (a) the pump size and speed and ( b) brake horsepower,
assuming operation at best efficiency?
H
*
= 25 ft = (C
H
n
2
D
2
)/g = (5
×
n
2
D
2
)/32.2
A confusing example
H
= 25 ft = (C
H
n
D
)/g = (5
×
n
D
)/32.2
Q
*
= 100000 gpm = 222.8 ft
3
/m = C
Q
n D
3
= 0.115 ×n D
3
Bhp
*
= C
p
ρn
3
D
5
= 720 hp
Solving simultaneously gives, D = 12.4 ft, n = 62 rpm

44. Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed- -------11111111
The type of applications for which centrifugal pumps are required are ;
1. High head low flow rate
2. Moderate head and moderate flow rate
3. Low head and high flow rate
Q. Would a general design of the centrifugal pump will do all the
three jobs?
Ans. No
Q. What should be the design features to accomplish the three
specified jobs?
1. Answer to this question lies in the basic concept of centrifugal
pump working principle.
2. Vanes are used to impart momentum to the fluid by applying the
centrifugal force to the fluid.
PHYSICS FOR OUR RESCUE

45. Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed- -------22222222
3. More the diameter of the vane more will be the centrifugal force
4. More will be the diameter more will be the radial component of
velocity and lesser will be the axial component
5. More will be the radial velocity more will be the head developed
6. Hence to get more head you need longer vanes and vice versa
7.
More will be the clearance between the impeller and casing
7.
More will be the clearance between the impeller and casing more will the flow rate & also more will be the axial component
8. These simple physics principles lead us to the variation in
impeller design to accomplish the three jobs mentioned

46. Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed- -------33333333
• We represent the performance of a family of geometrically simil ar
pumps by a single set of dimensionless curves
• Can we use even a smaller amount of information or even a single
number to represent the same information?
POINT TO PONDER
• We have a huge variety of pumps each with a different diameter
impeller, shape of impeller and running at certain rpm impeller, shape of impeller and running at certain rpm
• Impeller shape ultimately dictates the type of application
• RPM is not related to the pump design however it effects its
performance
• Hence the biggest problem is to avoid diameter in the pump
performance information
Again dimensional analysis comes to rescue, a combination of 
π
’s is 
also a 
π
, giving the same information in a different form

47. Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed- -------44444444
REARRANGE THE THREE COEFFICIENTS INTO A NEW
COEFFICIENT SUCH THAT DIAMETER IS ELIMINATED
( )
( )
11
2
2
3 3
4
4
/Q
s
H
Cn Q
N
CgH
= =
Rigorous form, dimensionless
/
17182
=
s s
N N
Points to remember
1. N
srefers only to BEP
2. Directly related to most efficient
pump design
3.
Low N
means low Q, High H
( )( )
( )
1
2
3
4
,
=
s
RPM GPM
N
H ft
Lazy but common form,
Not dimensionless
3.
Low N
s
means low Q, High H
4. High N
smeans High Q, Low H
5. N
sleads to specific pump
applications
6. Low N
s means high head pump
7. High N
smeans high Q pump
Similarly one can define N
ss
, based on NPSH
Experimental data suggests, pump is in
danger of cavitation
If N
ss
≥ 8100

48. Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed- -------55555555
GEOMETRICAL
VARIATION OF SPECIFIC
SPEED
Detailed shapes

49. Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed- -------55555555
Specific speed is an indicator of
Pump performance
Pump efficiency
The Q is a rough indicator of
Pump size
Pump Reynolds Number
THE PUMP CURVES

50. Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed Concept of Specific Speed- -------55555555
Note How The Head, Power and Efficiency curves change as
specific speed changes

51. Revisit of Confusing Example Revisit of Confusing Example Revisit of Confusing Example Revisit of Confusing Example Revisit of Confusing Example Revisit of Confusing Example Revisit of Confusing Example Revisit of Confusing Example--------11111111
Dimensionless performance curves for a
typical axial=flow pump. N
s
= 12.000.
Constructed from data for a 14=in pump
at 690 rpm.
C
Q*=0.55, C
H*=1.07, C
p*=0.70, η
max= 0.84.
N
s= 12000
D = 14 in, n = 690 rpm, Q* = 4400 gpm. D = 14 in, n = 690 rpm, Q* = 4400 gpm.

52. Revisit of Confusing Example Revisit of Confusing Example Revisit of Confusing Example Revisit of Confusing Example Revisit of Confusing Example Revisit of Confusing Example Revisit of Confusing Example Revisit of Confusing Example--------22222222
Can this propeller pump family provide a 25=ft head & 100,000 gpm
discharge
Since we know the Ns and Dimensionless coefficients then using
similarity rules let us calculate the Diameter and RPM
D = 48 in and n = 430 r/min, with bhp = 750: D = 48 in and n = 430 r/min, with bhp = 750:
a much more reasonable design solution

53. Pump vs System Characteristics Pump vs System Characteristics Pump vs System Characteristics Pump vs System Characteristics Pump vs System Characteristics Pump vs System Characteristics Pump vs System Characteristics Pump vs System Characteristics
• Any piping systems has the following components in its total
head which the selected pump would have to supply
1. Static head due to elevation
2. The head due to velocity head, the fictional head loss
3. Minor head losses
(
)
2 1
sys
H z z a
= − =
, min
4
128
f la ar
LQ
h
gDm
πρ
=
2 1
sys
Mathematically,
3 possibilities
( )
2
2
2 1
2
sys
V fL
H z z K a cQ
g D
 
= − + + = +
 
 
∑ ∑
(
)
2 1 , min sys f la ar
H z z h a bQ
= − + = +
, min
4
f la ar
gD
πρ
,
'
f turbulent
h Through Moody s Method
=

54. Pump vs System Characteristics, contd Pump vs System Characteristics, contd Pump vs System Characteristics, contd Pump vs System Characteristics, contd Pump vs System Characteristics, contd Pump vs System Characteristics, contd Pump vs System Characteristics, contd Pump vs System Characteristics, contd
•Graphical Representation Of The Three Curves

55. Match between pump & system Match between pump & system Match between pump & system Match between pump & system
•In industrial situation the resistance often varies for var ious 
reasons
•If the resistance factor increases, the slope of the system 
curve (Resistance vs flow) increases & intersect the 
characteristic curve at a lower flow.
•The designed operating points are chosen as close to the  •The designed operating points are chosen as close to the  highest efficiency point as possible.
•Large industrial systems requiring different flow rates  often 
change the flow rate by changing the characteristic curve wi th 
change in blade pitch or RPM

56. If K changes system curve shifts If K changes system curve shifts If K changes system curve shifts If K changes system curve shifts

57. Pump in Parallel or Series Pump in Parallel or Series Pump in Parallel or Series Pump in Parallel or Series
•To increase flow at a given head
1. Reduce system resistance factor with valve
2. Use small capacity fan/pumps in parallel.
Some loss in flow rate may occur when operating
in parallel in parallel •To increase the head at a given flow
1. Reduce system resistance by valve
2. Use two smaller head pumps/fans in series.
But some head loss may occur.

58. PUMPS IN PARALLEL PUMPS IN PARALLEL PUMPS IN PARALLEL PUMPS IN PARALLEL

59. PUMPS IN SERIES PUMPS IN SERIES PUMPS IN SERIES PUMPS IN SERIES

60. UUUUnstable operation (Hunting nstable operation (Hunting nstable operation (Hunting nstable operation (Hunting
)
If the characteristic is
such that the system
finds two flow rates for
a given head it cannot
decide where to stay. decide where to stay. The pump could
oscillate between
points. It is called
hunting.

61. Table Table Table Table Table Table Table Table--------11111111

62. Table Table Table Table Table Table Table Table--------22222222

63. Table Table Table Table Table Table Table Table--------33333333

64. Axial flow pump cross section
Radial flow pump cross section
Mixed flow pump cross section

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