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1
Training Session on Energy Training Session on Energy EquipmentEquipment
Pumps & Pumping Pumps & Pumping SystemsSystems
Presentation from the
“Energy Efficiency Guide for Industry in Asia”
www.energyefficiencyasia.org
©© UNEP 2006 UNEP 2006
El ect ri cal E
quipment /
Pum
ps
2
©© UNEP 2006 UNEP 2006
Training Agenda: PumpsTraining Agenda: Pumps
Introduction
Type of pumps
Assessment of pumps
Energy efficiency opportunities
El ect ri cal E
quipment /
Pum
ps
3
©© UNEP 2006 UNEP 2006
IntroductionIntroduction
• 20% of world’s 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 SystemsEl ect ri cal E
quipment /
Pum
ps
4
©© UNEP 2006 UNEP 2006
IntroductionIntroduction
Objective of pumping system
What are Pumping SystemsEl ect ri cal E
quipment /
Pum
ps
(US DOE, 2001)
• Transfer liquid from source to destination
• Circulate liquid around a system
5
©© UNEP 2006 UNEP 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 SystemsEl ect ri cal E
quipment /
Pum
ps
6
©© UNEP 2006 UNEP 2006
IntroductionIntroduction
• Head• Resistance of the system
• Two types: static and friction
• Static head• Difference in height between
source and destination
• Independent of flow
Pumping System CharacteristicsEl ect ri cal E
quipment /
Pum
ps
destination
source
Static
head
Statichead
Flow
7
©© UNEP 2006 UNEP 2006
IntroductionIntroduction
• Static head consists of• Static suction head (hS): lifting liquid relative to
pump center line
• Static discharge head (hD) vertical distance between centerline and liquid surface in destination tank
• Static head at certain pressure
Pumping System CharacteristicsEl ect ri cal E
quipment /
Pum
ps
Head (in feet) = Pressure (psi) X 2.31 Specific gravity
8
©© UNEP 2006 UNEP 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 system only has friction head(no static head)
Pumping System CharacteristicsEl ect ri cal E
quipment /
Pum
ps
Frictionhead
Flow
9
©© UNEP 2006 UNEP 2006
IntroductionIntroduction
In most cases:
Total head = Static head + friction head
Pumping System CharacteristicsEl ect ri cal E
quipment /
Pum
ps
Systemhead
Flow
Static head
Frictionhead
Systemcurve
System head
Flow
Static head
Friction head
Systemcurve
10
©© UNEP 2006 UNEP 2006
IntroductionIntroduction
Pump performance curve
• Relationship between head and flow• Flow increase
• System resistance increases
• Head increases
• Flow decreases to zero
• Zero flow rate: risk of pump burnout
Pumping System CharacteristicsEl ect ri cal E
quipment /
Pum
ps
Head
Flow
Performance curve for centrifugal pump
11
©© UNEP 2006 UNEP 2006
IntroductionIntroduction
Pump operating point
Pumping System CharacteristicsEl ect ri cal E
quipment /
Pum
ps
• Duty point: rate of flow at certain head
• Pump operating point: intersection of pump curve and system curve
Flow
Head
Static head
Pump performance curve
System curve
Pump operating point
12
©© UNEP 2006 UNEP 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 suction exceeds liquid vapor pressure
• NPSH Required: pump suction needed to avoid cavitation
Pumping System CharacteristicsEl ect ri cal E
quipment /
Pum
ps
13
©© UNEP 2006 UNEP 2006
Training Agenda: PumpsTraining Agenda: Pumps
Introduction
Type of pumps
Assessment of pumps
Energy efficiency opportunities
El ect ri cal E
quipment /
Pum
ps
14
©© UNEP 2006 UNEP 2006
Type of PumpsType of Pumps
Classified by operating principle
Pump ClassificationEl ect ri cal E
quipment /
Pum
ps
DynamicPositive
Displacement
Centrifugal Special effect Rotary Reciprocating
Internal gear
External gear
LobeSlide vane
Others (e.g. Impulse, Buoyancy)
Pumps
DynamicPositive
Displacement
Centrifugal Special effect Rotary Reciprocating
Internal gear
External gear
LobeSlide vane
Others (e.g. Impulse, Buoyancy)
Pumps
15
©© UNEP 2006 UNEP 2006
Type of PumpsType of Pumps
Positive Displacement PumpsEl ect ri cal E
quipment /
Pum
ps
• 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
16
©© UNEP 2006 UNEP 2006
Type of PumpsType of Pumps
Positive Displacement PumpsEl ect ri cal E
quipment /
Pum
ps
• Reciprocating pump• Displacement by reciprocation of piston
plunger
• 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
17
©© UNEP 2006 UNEP 2006
Type of PumpsType of Pumps
Dynamic pumpsEl ect ri cal E
quipment /
Pum
ps
• Mode of operation• Rotating impeller converts kinetic energy
into pressure or velocity to pump the fluid
• Two types• Centrifugal pumps: pumping water in
industry – 75% of pumps installed
• Special effect pumps: specialized conditions
18
©© UNEP 2006 UNEP 2006
Type of PumpsType of Pumps
Centrifugal PumpsEl ect ri cal E
quipment /
Pum
ps
How do they work?
(Sahdev M)
• Liquid forced into impeller
• Vanes pass kinetic energy to liquid: liquid rotates and leaves impeller
• Volute casing converts kinetic energy into pressure energy
19
©© UNEP 2006 UNEP 2006
Type of PumpsType of Pumps
Centrifugal PumpsEl ect ri cal E
quipment /
Pum
ps
Rotating and stationary components
(Sahdev)
20
©© UNEP 2006 UNEP 2006
Type of PumpsType of Pumps
Centrifugal PumpsEl ect ri cal E
quipment /
Pum
ps
Impeller Sahdev)
• Main rotating part that provides centrifugal acceleration to the fluid
• Number of impellers = number of pump stages
• Impeller classification: direction of flow, suction type and shape/mechanical construction
Shaft• Transfers torque from motor to impeller during pump
start up and operation
21
©© UNEP 2006 UNEP 2006
Type of PumpsType of Pumps
Centrifugal PumpsEl ect ri cal E
quipment /
Pum
ps
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
22
©© UNEP 2006 UNEP 2006
Training Agenda: PumpsTraining Agenda: Pumps
Introduction
Type of pumps
Assessment of pumps
Energy efficiency opportunities
El ect ri cal E
quipment /
Pum
ps
23
Assessment of pumpsAssessment of pumps
• Pump shaft power (Ps) is actual horsepower delivered to the pump shaft
• Pump output/Hydraulic/Water horsepower (Hp) is the liquid horsepower delivered by the pump
How to Calculate Pump PerformanceEl ect ri cal E
quipment /
Pum
ps
Hydraulic power (Hp):Hp = Q (m3/s) x Total head, hd - hs (m) x ρ (kg/m3) x g (m/s2) / 1000
Pump shaft power (Ps):Ps = Hydraulic power Hp / pump efficiency ηPump
Pump Efficiency (ηPump): ηPump = Hydraulic Power / Pump Shaft Power
©© UNEP 2006 UNEP 2006
hd - discharge head hs – suction head, ρ - density of the fluid g – acceleration due to gravity
24
©© UNEP 2006 UNEP 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 pressure gauges & measuring instruments
• Calibration not always carried out
• Correction factors used
Difficulties in Pump AssessmentEl ect ri cal E
quipment /
Pum
ps
25
©© UNEP 2006 UNEP 2006
Training Agenda: PumpsTraining Agenda: Pumps
Introduction
Type of pumps
Assessment of pumps
Energy efficiency opportunities
El ect ri cal E
quipment /
Pum
ps
26
©© UNEP 2006 UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
1. Selecting the right pump
2. Controlling the flow rate by speed variation
3. Pumps in parallel to meet varying demand
4. Eliminating flow control valve
5. Eliminating by-pass control
6. Start/stop control of pump
7. Impeller trimming
Electri cal E
quipment /
Pum
ps
27
©© UNEP 2006 UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
1. Selecting the Right PumpEl ect ri cal E
quipment /
Pum
ps
Pump performance curve for centrifugal pump
BEE India, 2004
28
©© UNEP 2006 UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
1. Selecting the Right PumpEl ect ri cal E
quipment /
Pum
ps
• 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
29
©© UNEP 2006 UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
2. Controlling Flow: speed variation
El ect ri cal E
quipment /
Pum
ps
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. ½) = large power reduction (e.g. 1/8)
30
©© UNEP 2006 UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
El ect ri cal E
quipment /
Pum
ps
Variable Speed Drives (VSD)
• Speed adjustment over continuous range
• 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: speed variation
31
©© UNEP 2006 UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
El ect ri cal E
quipment /
Pum
ps
Benefits of VSDs
• Energy savings (not just reduced flow!)
• Improved process control
• Improved system reliability
• Reduced capital and maintenance costs
• Soft starter capability
2. Controlling Flow: speed variation
32
©© UNEP 2006 UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
3. Parallel Pumps for Varying DemandEl ect ri cal E
quipment /
Pum
ps
• Multiple pumps: some turned off during low demand
• Used when static head is >50% of total head
• System curvedoes not change
• Flow rate lowerthan sum ofindividual flow rates
(BPMA)
33
©© UNEP 2006 UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
4. Eliminating Flow Control ValveEl ect ri cal E
quipment /
Pum
ps
• Closing/opening discharge valve (“throttling”) to reduce flow
• Head increases: does not reduce power use
• Vibration and corrosion: high maintenance costs and reduced pump lifetime
(BPMA)
34
©© UNEP 2006 UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
5. Eliminating By-pass ControlEl ect ri cal E
quipment /
Pum
ps
• Pump discharge divided into two flows
• One pipeline delivers fluid to destination
• Second pipeline returns fluid to the source
• Energy wastage because part of fluid pumped around for no reason
35
©© UNEP 2006 UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
6. Start / Stop Control of PumpEl ect ri cal E
quipment /
Pum
ps
• 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 maximum demand (pumping at non-peak hours)
36
©© UNEP 2006 UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
7. Impeller TrimmingEl ect ri cal E
quipment /
Pum
ps
• 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 more expensive and not always possible
37
©© UNEP 2006 UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
7. Impeller TrimmingEl ect ri cal E
quipment /
Pum
ps
Impeller trimming and centrifugal pump performance
(BEE India, 2004)
38
©© UNEP 2006 UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
Comparing Energy Efficiency Options
El ect ri cal E
quipment /
Pum
ps
Parameter Change control valve
Trim impeller VFD
Impeller diameter
430 mm 375 mm 430 mm
Pump head 71.7 m 42 m 34.5 m
Pump efficiency 75.1% 72.1% 77%
Rate of flow 80 m3/hr 80 m3/hr 80 m3/hr
Power consumed
23.1 kW 14 kW 11.6 kW
39
Training Session on Energy Training Session on Energy EquipmentEquipment
Pumps & Pumping Pumps & Pumping SystemsSystems
THANK YOUTHANK YOU
FOR YOUR ATTENTIONFOR YOUR ATTENTION
©© UNEP 2006 UNEP 2006
El ect ri cal E
quipment /
Pum
ps
40
© UNEP 2006© UNEP 2006
Disclaimer and ReferencesDisclaimer and References
El ect ri cal E
quipment /
Pum
ps
• This PowerPoint training session was prepared as part of the project “Greenhouse Gas Emission Reduction from Industry in Asia and the Pacific” (GERIAP). While reasonable efforts have been made to ensure that the contents of this publication are factually correct and properly referenced, UNEP does not accept responsibility for the accuracy or completeness of the contents, and shall not be liable for any loss or damage that may be occasioned directly or indirectly through the use of, or reliance on, the contents of this publication. © UNEP, 2006.
• The GERIAP project was funded by the Swedish International Development Cooperation Agency (Sida)
• Full references are included in the textbook chapter that is available on www.energyefficiencyasia.org