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UNEP 2006UNEP 2006
Training Agenda: PumpsTraining Agenda: Pumps
Introduction
Type of pumps
Assessment of pumps
Energy efficiency opportunities
E l e
c t r i c al E
q ui pm en
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P um
p s
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UNEP 2006UNEP 2006
IntroductionIntroduction
20% of worlds electrical energy
demand 25-50% of energy usage in some
industries
Used for Domestic, commercial, industrial and
agricultural services
Municipal water and wastewater services
What are Pumping SystemsE l e
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UNEP 2006UNEP 2006
IntroductionIntroduction
Objective of pumping system
What are Pumping SystemsE l e
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(US DOE, 2001)
Transfer liquidfrom source todestination
Circulate liquidaround a system
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UNEP 2006UNEP 2006
IntroductionIntroduction
Main pump components
Pumps Prime movers: electric motors, diesel engines,
air system
Piping to carry fluid
Valves to control flow in system Other fittings, control, instrumentation
End-use equipment
Heat exchangers, tanks, hydraulic machines
What are Pumping SystemsE l e
c t r i c al E
q ui pm en
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UNEP 2006UNEP 2006
IntroductionIntroduction
Head Resistance of the system
Two types: static and friction
Static head
Difference in height betweensource and destination
Independent of flow
Pumping System CharacteristicsE l e
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q ui pm en
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destination
source
Stati
chead
Statichead
Flow
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UNEP 2006UNEP 2006
IntroductionIntroduction
Static head consists of
Static suction head (hS): lifting liquid relative topump center line
Static discharge head (hD) vertical distancebetween centerline and liquid surface indestination tank
Static head at certain pressure
Pumping System CharacteristicsE l e
c t r i c al E
q ui pm en
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p s
Head (in feet) = Pressure (psi) X 2.31Specific gravity
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UNEP 2006UNEP 2006
IntroductionIntroduction
Friction head
Resistance to flow in pipe and fittings Depends on size, pipes, pipe fittings, flow
rate, nature of liquid
Proportional to square of flow rate
Closed loop systemonly has friction head(no static head)
Pumping System CharacteristicsE l e
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Frictionhead
Flow
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UNEP 2006UNEP 2006
IntroductionIntroduction
In most cases:
Total head = Static head + friction head
Pumping System CharacteristicsE l e
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q ui p
m en
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Systemhead
Flow
Static head
Frictionhead
Systemcurve
Systemhead
Flow
Static head
Frictionhead
Systemcurve
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UNEP 2006UNEP 2006
IntroductionIntroduction
Pump performance curve
Relationship betweenhead and flow Flow increase
System resistance increases
Head increases Flow decreases to zero
Zero flow rate : risk of pump burnout
Pumping System CharacteristicsE l e
c t r i c al E
q ui p
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Head
Flow
Performance curve for centrifugal pump
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UNEP 2006UNEP 2006
IntroductionIntroduction
Pump operating point
Pumping System CharacteristicsE l e
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Duty point: rate of flow at certainhead
Pump operatingpoint:intersection of pump curve andsystem curve
Flow
Head
Statichead
Pump performancecurve
System
curve
Pumpoperatingpoint
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UNEP 2006UNEP 2006
IntroductionIntroduction
Pump suction performance (NPSH) Cavitation or vaporization: bubbles inside pump
If vapor bubbles collapse Erosion of vane surfaces Increased noise and vibration
Choking of impeller passages Net Positive Suction Head
NPSH Available: how much pump suctionexceeds liquid vapor pressure
NPSH Required: pump suction needed to avoidcavitation
Pumping System CharacteristicsE l e
c t r i c al E
q ui p
m en
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UNEP 2006UNEP 2006
Training Agenda: PumpsTraining Agenda: Pumps
Introduction
Type of pumps
Assessment of pumps
Energy efficiency opportunities
E l e
c t r i c al E
q ui p
m en
t /
P um
p s
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UNEP 2006UNEP 2006
Type of PumpsType of Pumps
Classified by operating principle
Pump ClassificationE l e
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DynamicPositive
Displacement
Centrifugal Special effect Rotary Reciprocating
Internal
gear
External
gear Lobe
Slide
vane
Others (e.g.Impulse, Buoyancy)
Pumps
DynamicPositive
Displacement
Centrifugal Special effect Rotary Reciprocating
Internal
gear
External
gear Lobe
Slide
vane
Others (e.g.Impulse, Buoyancy)
Pumps
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UNEP 2006UNEP 2006
Type of PumpsType of Pumps
Positive Displacement PumpsE l e
c t r i c al E
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For each pump revolution
Fixed amount of liquid taken from one end Positively discharged at other end
If pipe blocked
Pressure rises Can damage pump
Used for pumping fluids other than
water
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UNEP 2006UNEP 2006
Type of PumpsType of Pumps
Positive Displacement PumpsE l e
c t r i c al E
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Reciprocating pump
Displacement by reciprocation of pistonplunger
Used only for viscous fluids and oil wells
Rotary pump Displacement by rotary action of gear, cam or
vanes
Several sub-types
Used for special services in industry
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UNEP 2006UNEP 2006
Type of PumpsType of Pumps
Dynamic pumpsE l e
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Mode of operation
Rotating impeller converts kinetic energy intopressure or velocity to pump the fluid
Two types Centrifugal pumps: pumping water in
industry 75% of pumps installed
Special effect pumps: specialized conditions
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UNEP 2006UNEP 2006
Type of PumpsType of Pumps
Centrifugal PumpsE l e
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How do they work?
(Sahdev M)
Liquid forced intoimpeller
Vanes pass kineticenergy to liquid: liquidrotates and leavesimpeller
Volute casing convertskinetic energy intopressure energy
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UNEP 2006UNEP 2006
Type of PumpsType of Pumps
Centrifugal PumpsE l e
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Rotating and stationary components
(Sahdev)
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UNEP 2006UNEP 2006
Type of PumpsType of Pumps
Centrifugal PumpsE l e
c t r i c al E
q ui p
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Impeller Sahdev)
Main rotating part that provides centrifugalacceleration to the fluid
Number of impellers = number of pump stages
Impeller classification: direction of flow, suction typeand shape/mechanical construction
Shaft Transfers torque from motor to impeller during pump
start up and operation
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UNEP 2006UNEP 2006
Type of PumpsType of Pumps
Centrifugal PumpsE l e
c t r i c al E
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Casings
Volute Casing (Sahdev) Functions Enclose impeller as pressure vessel Support and bearing for shaft and impeller
Volute case
Impellers inside casings Balances hydraulic pressure on pump shaft
Circular casing Vanes surrounds impeller Used for multi-stage pumps
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UNEP 2006UNEP 2006
Training Agenda: PumpsTraining Agenda: Pumps
Introduction
Type of pumps
Assessment of pumps
Energy efficiency opportunities
E l e
c t r i c al E
q ui p
m en
t /
P um
p s
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Assessment of pumpsAssessment of pumps
Pump shaft power (Ps) is actual horsepower delivered to the pump shaft
Pump output/Hydraulic/Water horsepower (Hp) isthe liquid horsepower delivered by the pump
How to Calculate Pump PerformanceE l e
c t r i c al E
q ui p
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Hydraulic power (Hp):Hp = Q (m3/s) x Total head, hd - hs (m) x (kg/m3) x g (m/s2) / 1000
Pump shaft power (Ps):Ps = Hydraulic power Hp / pump efficiency Pump
Pump Efficiency (Pump):Pump = Hydraulic Power / Pump Shaft Power
UNEP 2006UNEP 2006hd - discharge head hs suction head, - density of the fluid g acceleration due to gravity
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UNEP 2006UNEP 2006
Assessment of pumpsAssessment of pumps
Absence of pump specification data
to assess pump performance Difficulties in flow measurement and
flows are often estimated
Improper calibration of pressuregauges & measuring instruments Calibration not always carried out
Correction factors used
Difficulties in Pump AssessmentE l e
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UNEP 2006UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
Selecting the right pump
Controlling the flow rate by speedvariation
Pumps in parallel to meet varyingdemand
Eliminating flow control valve
Eliminating by-pass control
Start/stop control of pump
Impeller trimming
E l e
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UNEP 2006UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
1. Selecting the Right PumpE l e
c t r i c al E
q ui pm
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p s
Pump performance curve for centrifugalpump
BEE India,2004
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UNEP 2006UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
1. Selecting the Right PumpE l e
c t r i c al E
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p s
Oversized pump Requires flow control (throttle valve or by-
pass line) Provides additional head System curve shifts to left Pump efficiency is reduced
Solutions if pump already purchased VSDs or two-speed drives Lower RPM
Smaller or trimmed impeller
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Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
2. Controlling Flow: speedvariationE l e
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Explaining the effect of speed
Affinity laws: relation speed N and Flow rate Q N
Head H N2
Power P N3
Small speed reduction (e.g. ) = largepower reduction (e.g. 1/8)
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UNEP 2006UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
E l e
c t r i c al E
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en
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Variable Speed Drives (VSD)
Speed adjustment over continuousrange
Power consumption also reduced!
Two types Mechanical: hydraulic clutches, fluid couplings,
adjustable belts and pulleys Electrical: eddy current clutches, wound-rotor
motor controllers, Variable Frequency Drives(VFDs)
2. Controlling Flow: speedvariation
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UNEP 2006UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
E l e
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Benefits of VSDs
Energy savings (not just reduced flow!) Improved process control
Improved system reliability
Reduced capital and maintenancecosts
Soft starter capability
2. Controlling Flow: speedvariation
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UNEP 2006UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
3. Parallel Pumps for VaryingDemandE l e
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Multiple pumps: some turned off during lowdemand
Used when static head is >50% of total head
System curvedoes not change
Flow rate lower than sum of individualflow rates
(BPMA)
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UNEP 2006UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
4. Eliminating Flow Control ValveE l e
c t r i c al E
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p s
Closing/opening discharge valve (throttling)to reduce flow
Head increases:does not reducepower use
Vibration andcorrosion: highmaintenancecosts and reducedpump lifetime
(BPMA)
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UNEP 2006UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
5. Eliminating By-pass ControlE l e
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Pump discharge divided into two
flows One pipeline delivers fluid to destination
Second pipeline returns fluid to the source
Energy wastage because part of fluidpumped around for no reason
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UNEP 2006UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
6. Start / Stop Control of PumpE l e
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Stop the pump when not needed
Example: Filling of storage tank
Controllers in tank to start/stop
Suitable if not done too frequently
Method to lower the maximumdemand (pumping at non-peak hours)
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UNEP 2006UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
7. Impeller TrimmingE l e
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Changing diameter: change in
velocity Considerations
Cannot be used with varying flows
No trimming >25% of impeller size Impeller trimming same on all sides
Changing impeller is better option but moreexpensive and not always possible
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UNEP 2006UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
7. Impeller TrimmingE l e
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p s
Impeller trimming and centrifugal pump performance
(BEE India,2004)
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UNEP 2006UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
Comparing Energy EfficiencyOptions
E l e
c t r i c al E
q ui pm
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P um
p s
11.6 kW14 kW23.1 kWPower consumed
80 m 3/hr 80 m 3/hr 80 m 3/hr Rate of flow
77%72.1%75.1%Pump efficiency
34.5 m42 m71.7 mPump head
430 mm375 mm430 mmImpeller diameter
VFDTrim impeller Changecontrol valve
Parameter
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Training Session on EnergyTraining Session on EnergyEquipmentEquipment
Pumps & PumpingPumps & PumpingSystemsSystems
THANK YOUTHANK YOU
FOR YOUR ATTENTIONFOR YOUR ATTENTION
UNEP 2006UNEP 2006
E l e
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