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Tom JenkinsJenTech Inc.
6789 N. Elm Tree RoadMilwaukee, WI 53217
Energy Saving Measures - 2
J enTec h Inc .
2
• Blower Types and Characteristics
• Energy Impact of Blower Controls
• Evaluating the Savings of DO Control
• Influence of Advanced Control Strategies
Understanding Blower Systems, Dissolved Oxygen, and Aeration
Process Controls and How they Affect Energy Costs
3
Aeration Energy Concerns
Aeration is the Largest Energy Use for most WWTPs
4
Aeration Process Concerns
• Aeration Supplies O2 to Bacteria• Bacteria Metabolizes Wastes• Several Technologies Used
• Mechanical Surface Aerators• Mechanical Brush Aerators• Diffused Aeration
• Diffused Aeration is Most Common• Diffused Aeration is Most Efficient• If Plant Has Mechanical Aeration Consider
Replacement with Diffused Aeration
5
Aeration System Efficiency
• Controlled Primarily by System Design
• Aerator Efficiency– SOTE for Diffused Aeration, %– SOTR for Mechanical Aeration, lb O2/hp-hr
Aerator Type
Low SRT AE at 2 mg/L DO
High SRT AE At 2 mg/L DO
High Speed
Low Speed
Turbine 0.6-0.9 0.9-1.4 (0.4-0.6) (0.6-0.8)
Coarse Bubble
0.5 – 1.2 (0.3-0.7)
0.6–1.6 (0.4-0.9)
Fine Pore 1.2-1.6 (0.7–1.0)
3.3-4.4 (2–2.6)
1.5–2.2 (0.9–1.3) 0.7–1.4 (0.4-0.8)
2.5–3.5 (1.5–2.1) 1.2-2.5 (0.7–1.5)
SAE lbO2/hp-h (kgO2/kW-h)
2.0-3.0 (1.2-1.8)
6.0–8.0 (3.6–4.8)
1.0-2.5 (0.6 –1.5)
Data: Doctor M. Stenstrom, UCLA
6
It’s all about the bubbles!
Diffusers release air at the bottom of the aeration tank to create the bubbles!
7
Blowers Supply Air to the Diffusers
• Positive Displacement (PD) Blowers
• Multi-Stage Centrifugal Blowers
• Single Stage Centrifugal Blowers
• Turbo Blowers
Blower Types and Characteristics
8
• Blower Power is a Function of Flow Rate and Pressure
• Pressure Difference from Inlet to Discharge Determines Power
• Minimize Inlet Filter Losses and Discharge Pressure to Minimize Power for Given Flow Rate
bhpICFM
eb 64.85Pin
0.717Pdis
0.283 Pin =
Blower Types and Characteristics
9
100 20 30 40 50 60 70 80 90 100 110% M A S S F L O W R A T E
60
50
70
80
90
100
110
120
% G
AU
GE
PR
ES
SU
RE
100 20 30 40 50 60 70 80 90 100 110% M A S S F L O W R A T E
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% G
AU
GE
PR
ES
SU
RE
S T A T IC P R E S S UR E
F R IC T IO N L O S S E SS Y S T E M C UR VE W IT H
PD BLOWER
C E N T R IF UG A L B L O W E RC H A R A C T E R IS T IC C UR VE
The Aeration and Piping System Determines Bower Discharge Pressure
Required
10
Positive Displacement (PD) Blowers
• Constant Flow at Constant Speed• Pressure Varies with System Requirements• Use VFDs (Variable Frequency Drives) to
Modulate Air Flow• Turndown is Limited by Blower and Motor
Temperature
Courtesy Dresser Roots
11
Positive Displacement (PD) Blowers
12
212
412
612
812
1012
1212
1000 2000 3000 4000 5000
BLOWER SPEED (RPM)
ICF
M Performance
Design
12172227323742475257
1000 2000 3000 4000 5000
BLOWER SPEED (RPM)
BH
P @
Co
nst
atn
t P
ress
ure
Performance
Design
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Multistage Centrifugal Blowers
• Multistage Centrifugal• Variable Flow at Defined Pressures and Inlet
Conditions• Usually Controlled by Inlet Throttling to Modulate
Flow• Using VFDs to Modulate Air Flow Will Improve
Efficiency and Turndown (with appropriate curves)
Courtesy Continental Blowers LLC
13
Multistage Centrifugal Blowers
100 20 30 40 50 60 70 80 90 100 110% M ASS F L O W R AT E
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50
70
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100
110
120
% G
AU
GE
PR
ES
SU
RE
100 20 30 40 50 60 70 80 90 100 110% M ASS F L O W R AT E
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50
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100
110
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% G
AU
GE
PR
ES
SU
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100 20 30 40 50 60 70 80 90 100 110% M ASS F L O W R AT E
% P
OW
ER
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50
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100
110
40
AVER AGE T EM P
SYST EM C U R VE
N O C O N T R OLH IG H T EM P 100 F
N O C O N T R OLH IG H T EM P 100 F
N O C O N T R OL
AVER AGE T EM PIN L ET T H R O T T L ED
AVER AGE T EM P 61 FIN L ET T H R O T T L ED
N O C O N T R OLAVERAGE TEMP 61 F
AVER AGE T EM PR E D U C ED SP EED 57.3 H z
AVER AGE T EM PR E D U C ED SP EED 57.3 H z
14
Single Stage Centrifugal Blowers
• Variable Flow, Variable Pressure, High Efficiency• Inlet Guide Vanes and/or Variable Discharge
Diffusers to Modulate Flow and Improve Turndown - Dual Vane Control Optimizes Efficiency
• Can Use Variable Speed (Typically Medium Voltage)
Courtesy Dresser Roots
15
Single Stage Centrifugal Blowers
100 20 30 40 50 60 70 80 90 100 110% M ASS F L O W R AT E
60
50
70
80
90
100
110
120
% G
AU
GE
PR
ES
SU
RE
100 20 30 40 50 60 70 80 90 100 110% M ASS F L O W R AT E
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50
70
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100
110
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% G
AU
GE
PR
ES
SU
RE
100 20 30 40 50 60 70 80 90 100 110% M ASS F L O W R AT E
% P
OW
ER
60
50
70
80
90
100
110
40
ST AT IC PR ESSU R E
F R IC T ION L OSSES
M AX IGV O PEN IN G
M AX IGV O PEN IN G
R E D U C ED IG V OPEN IN G
R E D U C ED IG V OPEN IN G
Inlet Guide Vane (IGV) Control
16
Single Stage Centrifugal Blowers
Variable Diffuser Vane (VDV) Control
100 20 30 40 50 60 70 80 90 100 110% M ASS F L O W R AT E
60
50
70
80
90
100
110
120
% G
AU
GE
PR
ES
SU
RE
100 20 30 40 50 60 70 80 90 100 110% M ASS F L O W R AT E
60
50
70
80
90
100
110
120
% G
AU
GE
PR
ES
SU
RE
100 20 30 40 50 60 70 80 90 100 110% M ASS F L O W R AT E
% P
OW
ER
60
50
70
80
90
100
110
40
ST AT IC PR ESSU R E
F R IC T ION L OSSES
M AX D D V OPEN IN GM IN D D V OPE N IN G
M IN D D V OPE N IN G
M AX D D V OPEN IN G
17
Mechanical Equipment Efficiency
% Rated Capacity
25% 50% 75% 100%
100%
75%
50%
25%
0%
% R
ate
d P
ow
er
Inlet Thro ttling
Inlet G u ide Vanes Variable Speed
18
Turbo Blowers
• Variable Flow at Defined Pressures – Characteristic Curve Similar to Multistage
• Controlled by Built-In Special VFDs to Modulate Flow
• New Technology - Designed for High Efficiency
Courtesy HSI, Inc.
19
Turbo Blower Variations
• Bearing Types– Magnetic– Air Bearings
• Combined Control: Variable Speed with Variable Diffuser Vanes
• Most Manufacturers Limited to 300 hp (for now)
20
Turbo Blowers
Courtesy HSI, Inc.
21
Blower Flow Control
• Select Blowers for Efficiency Across Operating Range
• Evaluate at Realistic Operating Conditions• Look at Control Options• Look at New Speed for PDs (VFD or Sheaves)• Look at New Impellers for Centrifugals
• Select Blowers for Turndown• 2:1 turndown available for most blowers• Provide At Least 5:1 Turndown Compared to Design
Flow• Use 4 blowers @ 33% of Design Flow OR 2 blowers
@ 25% plus 2 @ 50% of Design Flow
22
• Controlling Flow to Match Demand Reduces Power
• Flow Control Technique Influences Efficiency• Throttling is LEAST Efficient (NEVER with PD)• Guide Vanes Next in Efficiency
• Inlet Guide Vanes (IGV)• Variable Diffuser Vane (VDV)• Dual Vanes
• Variable Speed MOST Efficient
• Variable Frequency Drive - VFD• Also Referred to as Inverter• Also Referred to Adjustable Speed Drive (ASD)
• Most Blowers Can Provide 40% to 60% Turndown
Blower Flow Control
23
Centrifugal Blowers: • VFD Will Typically Save 15% to 20% vs. Throttling
• VFD Will Typically Save 5% to 10% vs. Guide Vanes
• Blowers with Flat Curves not Suitable for VFD Control
• 1.5 psi rise to surge• Steadily Increasing Pressure vs. Flow
PD Blowers:• Flow and Savings Proportional to Speed
• Minimum Speed Usually 50% of Nominal Speed
Blower Flow Control
24
• Converts 60 Hz AC Input to Output at Required Hz• Typically 3-Phase• 480 VAC• 4160 VAC In Larger hp• Output Voltage Cannot Exceed Input Voltage
• Rating Actually by Current, not hp• Must Confirm Motor FLA (Full Load Amps)
Variable Frequency Drives
25
• Load Type• Variable Torque
• Centrifugal Pumps and Blowers• Constant Torque
• PD Pumps and Blowers• Bypass Contactors
• Use Only When Required• Newer Drives More Reliable
• Motor dV/dt and Insulation Damage• Limit Cable Length VFD to Motor (Typically Req’d Cable < 100 ft.)• Depends on Manufacturer and Motor Power• Reflective Wave Traps
• Motor Bearing Damage (Fluting)• Uncommon• Good Grounding and Close Coupling will Usually Prevent It• Insulated Bearings and Shaft Grounding Brushes Available
VFD Application Considerations
26
VFD Application Considerations
An Example of Motor Bearing Fluting – The VFD was too far from the motor
27
• VFDs Can Create Harmonics in Power Supply
• “Clean Power” is ONLY Referring to Line Side• NO Impact on Motor• IEEE-519 Intended to Protect Other Utility Customers• PCC (Point of Common Coupling) is Utility/Plant Transformer• Should Perform Harmonics Study to Verify Need
• Clean Power Techniques• Line Reactors• Active Filters• 12 and 18-Pulse VFDs• All Reduce Efficiency• All Increase Equipment Cost
VFD Harmonics(Beware of Snake Oil)
28
• VFD Power Factor Typically > 95%• Motor and VFD Efficiency Vary with Load
• Must Look at System Efficiency
VFD and Motor Efficiency
29
• Dissolved Oxygen (DO) Control is The Way to Determine the Process Air Demand the Blowers Must Satisfy
• DO Control Will Typically Save 25% to 40% Compared to Manual Blower Control
Aeration & DO Control
30
DO Control System Objectives:
1. Satisfy the Oxygen Demand of the Treatment Process
2. Achieve Process Requirements at the Lowest Possible Cost – i.e. Lowest Energy use
Aeration & DO Control
31
Aeration & DO Control
• Process Considerations ALWAYS Outweigh Energy Considerations
• DO (Dissolved Oxygen) concentration is an indirect indicator of proper air flow to the process
• “Normal” DO concentration means the process is not oxygen limited
• If you have very low or zero DO you cannot have adequate process performance in an aerobic system
• You can have high DO and not have adequate process performance
32
• Choose Correct DO Concentration– Use minimum DO that gives required process
performance– Most operators set DO concentration too high
• Conventional Wisdom: 2.0 ppm for BOD removal – can be as low as 1.0 ppm
• Conventional Wisdom: 3.0 ppm for Nitrification – can be as low as 1.0 ppm
• If BNR use as low DO concentration as possible to avoid “oxygen poisoning” in recycle flow
Aeration & DO Control
33
In Most Municipal Facilities Diurnal Load Varies 2:1
12:00 AM04:00 AM
08:00 AM12:00 PM
04:00 PM08:00 PM
12:00 AM
Time of Day
0
20
40
60
80
100
120
140
Flo
w, %
AD
F
Typical Diurnal Flow Variation
Aeration & DO Control
34
In Most Municipal Facilities Diurnal Load Varies 2:1
Hours/Day Duty Cycle Weighting
Factor (% of Time)
Flow Factor (% ADF)
Totalization Factor (%Time x %ADF)
5 20.8% 70.0% 14.58%
3 12.5% 90.0% 11.25%
2 8.3% 100.0% 8.33%
8 33.3% 107.5% 35.83%
6 25.0% 120.0% 30.00%
24 100.0% 100.00%
Aeration & DO Control
35
• With Manual Control Air Flow is Set to Handle Peak Load
• Power is Wasted by Excess Aeration During Most Of the Day
Aeration & DO Control
36
The Relationship of DO and Air Flow Is Complex and Non-Linear, Making DO Control Difficult
0.00
1.00
2.00
3.00
4.00
5.00
6.00
20.0 40.0 60.0 80.0 100.0 120.0
Oxygen Transfer Rate (OTR), kg/hr
DO
, ppm
Oxygen Transfer Rate Variation with Air Flow
SCFM/diffuser1.0 2.0 3.0 4.0 5.0
Response to 20% Organic Load Increase
1) Initial operation at 50 kg/hr OTR, 2 SCFM per diffuser, 3.0 ppm DO
1
2
3
2) 20% load increase to 60 kg/hr OTR, 2 SCFM per diffuser, DO drops to 1.3 ppm3) Operation at 60 kg/hr OTR, air flow increases to 2.5 SCFM per diffuser, restore 3.0 ppm DO
OTE & DO Control
Example: Response of DO to 20% Load Increase with System Set to Maintain 3.0 ppm DO
37
• Low DO can cause undesirable organisms to develop
• High DO can cause poor settling, undesirable organisms to develop
• Excess DO does not usually result in more biological activity
• Bugs don’t work twice as hard at 4.0 ppm DO than they do at 2.0 ppm DO
• High DO just wastes power
Aeration & DO Control
38
Aeration Energy Cost
Excess DO means significantly more aeration power.
Blower Power Ratio (Compared to 2.0 ppm DO)
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
4.50
0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00
Nom
inal
Pow
er M
ulti
plie
r
Actual DO Concentration, ppm
Blower Power Ratio (Compared to 2.0 ppm DO)
Based on 500' ASL, 55 °F, 9.9 ppm Csat
actual
actual
CC
C
Q
Q
*
20
*20
0.2
0.2
39
Aeration Energy Savings
Excess DO means significantly more aeration power.
Blower Power Ratio (Compared to 2.0 ppm DO)
-20%
-10%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00
Nom
inal
Pow
er S
avin
gs
Actual DO Concentration, ppm
Blower Power Savings (Compared to 2.0 ppm DO)
Based on 500' ASL, 55 °F, 9.9 ppm Csat
actual
actual
Q
QQSavings 0.2
40
Additional System Control Considerations:• In Many Cases Mixing Limits Dictate Minimum
Air Flow, Not DO– Most Plants Operate at 1/3 of Design Capacity– For Fine Pore System Convention is 0.12 CFM/sq. ft.– 0.08 CFM/sq. ft. Has Been Adequate in Field Testing– Consider Taking Some Basins Out of Service To
Eliminate Mixing Constraints
• If Blowers Are at Minimum Flow– Consider Adding Smaller Blowers or Changing
Impellers (Centrifugal)– Consider VFD or Sheave Change (Positive
Displacement)
Aeration & DO Control
41
Additional System Control Considerations:• Increased MCRT (Mean Cell Retention Time)
results in Increased OTE (Process Permitting)
• Denitrification Can Recover 25% of O2 Used for Nitrification
• Proper Diffuser Maintenance Is Necessary to Keep OTE Near Design Values
Aeration & DO Control
42
Aeration Process Control: A System Approach is Required
Energy Efficiency Optimization Includes• Equipment and Controls• Aeration Basins• Blowers
43
• Basin Air Flow Control
• Pressure Control
• Most-Open-Valve Control
Additional Aeration Control Techniques
44
Basin Flow Control
• DO Concentration is Controlled by Controlling Air Flow
• Total System Air Flow is Controlled by the Blowers
• Flow Control Valves at Each Aeration Basin are Used to Balance Air Between Basins– Air flow distribution not inherently uniform– Influent flow distribution not inherently uniform– RAS flow distribution not inherently uniform– All vary with diurnal and seasonal loading
• Flow Control Valves at Each Drop Leg are Used to Balance Air Within a Basin
45
Basin Flow Control
• For Many Facilities Manual Control of Basin Air Flow Balancing is Adequate (Typically Blowers < 200 hp)
• DO Concentration will Typically Differ by 0.5 ppm to 1.5 ppm Between Basins
• Automatically Controlling Basin Air Flow Balance to Eliminate the Difference Will Typically Add 5% to the Savings – Example: 25% Savings will Increase to 30% Savings
• If the Additional Savings Will Pay for the Extra Valves and Flow Meters, then Automatic Flow Control for Each Basin is Justified
46
Basin Flow Control
• In Very Large Facilities Automatic Control of Each Drop Leg MAY be Justified (Typically Blowers > 500 hp)
• Drop Leg Control Allows Tapered DO Setpoints– Typical 1.0 ppm @ Influent to 2.0 ppm @ Effluent End
of Basin– If BNR Process Effluent DO Setpoint May Be Lower
• Savings Should be Estimated to Justify the Extra Hardware Expense
DISTANCE TO REACTOR INLET
OX
YG
EN
DE
MA
ND
47
Pressure Control
• Pressure Control is NOT Required for Blower Control
• Pressure Control is a Device Used to Minimize Interaction Between Parallel Basins
• Pressure Control is Used Indirectly for Matching Total Blower Air Flow to Basin Air Flow Demand
• Pressure Control is a Historical Artifact Necessitated by Independent PID Loop Control Algorithms
48
Pressure Control
• In an Old House What Happens When Someone Flushes a Toilet When You’re Taking a Shower?
• Manipulating Parallel Air Flow Control Valves has the Same Effect!
49
Pressure Control
Typical DO Control System with Pressure Control
50
Pressure Control
The Blower Curve is the Blower Capability in Terms of Pressure as a Function of Air Flow
51
Pressure Control
The System Curve is the System Back Pressure as a Function of Air Flow
52
Pressure Control
When the Two Curves Are Combined the Intersection Defines the Actual Operating Point
53
Pressure Control
• If Constant Pressure Is Maintained Changes in One Valve Won’t Affect Other Basin’s Air Flows
• If Pressure Setpoint is Too High Power Is Wasted
Typical Centrifugal Blower & System Curves
5.0
Flow, SCFM
Pre
ssur
e, p
sig
0 500 1000 1500 2000 2500 3000 3500 4000 4500
7.0
9.0
6.0
8.0
10.0
Pressure Setpoint
Wasted Power
54
Direct Flow Control
Some Systems Eliminate Pressure Control and Use Direct Flow Control for Basins and Blowers
55
Most-Open-Valve Control
• Most-Open-Valve (MOV) Control is NOT Necessary for DO Control or Blower Control
• MOV is a Technique for Minimizing System Pressure by Keeping at Least One Basin Valve at Max Position at All Times.
• MOV Control for Most Systems Works by Modifying the Pressure Setpoint
56
Most-Open-Valve Control (Pressure Based System)
• If the valve that is at maximum position (the most open valve) is MORE than 75% open, the pressure setpoint will be periodically increased by 0.05 psig
• The pressure control loop forces the blower output air flow higher, which forces the basin flow control valves to move to a less open position to restore air flow to setpoint
• The back pressure increases and causes the pressure control loop to decrease blower air flow
• The logic goes through several iterations. At the new point of equilibrium the basin air flow is the same, but with valves less open
(underlined values are typical)
57
Summary:• Aeration Control is Critical to WWTP Energy
• Blower Control is Dependent on Blower Type
• Control Technique Impacts Blower Power
• Aeration Basin Control Should Include DO Control
• Aeration Basin and Blower Control Must be Integrated to Obtain Optimum Efficiency
Aeration Process Control: DO and Blowers
58
Aeration Process Control: DO and Blowers
Questions and Answers
J enTec h Inc .
59
Useful Formulae
a
ba
ab ppT
PVRHp.SCFMACFM
5284605814
a
a
p.TSCFMACFM 714
528460
100
max
Qmin
Qmax
Q%Turndown
Ignoring Relative Humidity:
For all Blowers
RH = relative humidity, decimalPVa = saturated vapor pressure of water at actual temperature, psiTa = actual air temperature, °Fpa = actual air pressure, psiapb = barometric pressure, psia
Q= air flow SCFM
$ngsAnnualSavi
$ostEquipmentCyears,ackSimplePayb
8760 )kWkW(kWh
$$ngsAnnualSavi neworiginal
ave
7460.eff
hpkW
motor
motor
746
731 PFeff.VIhp motor
motor
effmotor= motor efficiency, decimalPF = motor Power Factor, decimalI = current, AmpsV = Voltage
60
)SlipN(DispQ
FPPDispNFbhp bg
1
212 N
NQQ
2
1
212
N
NPP
3
1
212
N
Npp
For PD Blowers
Curve Adjustments For Variable Speed Centrifugal Blowers
Q = volumetric air flow rate, ICFMDisp = blower displacement, Cubic Feet per RevolutionN = blower rotational speed, rpmSlip = slip corrected for actual operating conditions, rpmbhp = blower shaft power required, horsepowerFg = gas power constant from manufacturer (typically 0.00436)ΔPb = total pressure rise across blower, psiFP = friction power corrected for actual operating conditions, horsepower
Q1 , Q2= air flow at original and new operating speed, ICFMP1 , P2=gauge pressure at original and new operating speed, psigp1 , p2= power at original and new operating speed, horsepowerN1 , N2= original and new operating speed, rpm
61
RequiredO 2_for_BOD 1.1LbO 2
LbBOD
=
RequiredO 2_for_Nitrification 4.6LbO 2
LbNH3
=
SCFM0.335 mgd
OTEppmBOD removed 1.1 ppmNH3converted 4.6 =
Useful Formulae
OTE SCFM air %O2 OTR OUR TankVolume
u
u
v P
TSG
C.
QP
2
6622
ΔP = pressure drop through valve, psiQ = air flow rate, SCFMCv = valve flow coefficient from manufacturer’s dataSG = specific gravity of gas, dimensionless (air = 1.0)Tu = upstream temperature, °RPu = upstream pressure, psia
62
Aeration ECM Evaluation Procedure
Collect Basic Process Data:Hydraulic Loading, mgdInfluent BOD, NH3, TSS, PPrimary Clarifier Effluent BOD, NH3, TSS, PFinal Effluent BOD, NH3, NO3, P
Determine Process Type:Activated Sludge
BOD OnlyNitrificationBNR (Biological Nutrient Removal/De-Nitrification)
Trickling Filter or Chemical/Physical
For Trickling Filters and All Other Special
Evaluation Req’d.
For Activated Sludge Evaluate Aeration System
And Blowers
Collect Power Cost Data:On Peak / Off PeakDemand, Ratchet, Power FactorCalculate Composite Power Cost
63
Aeration ECM Evaluation Procedure
Collect Aeration System Data (Mechanical Aeration):Number of Aeration BasinsBasin Type and Size L x W x D
DitchLagoonComplete Mix
Aerator Type and Performance (lb O2/hp-hr)VerticalHorizontalAspirating
Aerator ControlConstant Speed, Two Speed, Variable Speed
Determine Ave. DO and Daily Diurnal DO TrendsObtain Basin DrawingsDetermine Mixing Energy Req’dExisting Instrumentation Type and Location
DO TransmittersLevel Control Gates/Weirs
Calculate Reduced Power from DO Control
64
Aeration ECM Evaluation Procedure
Collect Aeration System Data (Diffused Aeration):Number of Aeration Basins
Number of passes per basinNumber of zones per basinNumber of Basins Operating
Type of DiffusersFine Pore, Coarse BubbleNumber, Nominal OTE
Basin TypePlug FlowComplete MixSpecial Processes (MBR, IFFAS, etc.)Submergence and Tank Depth (They’re Different)Tank Dimensions L x W
Determine Ave. DO and Daily Diurnal DO TrendsObtain Basin and Piping DrawingsExisting Instrumentation and Control Type and Location
Flow Meters, DO TransmittersFlow Control Valves (Power, Positioner Data)DCS or PLC Type and Control Strategy
Calculate Reduced Air Flow from DO ControlCalculate Reduced Pressure from MOV
65
Aeration ECM Evaluation Procedure
Collect Blower Data:Number of Blowers
InstalledOperating Summer/WinterMotor hp EachMotor Voltage
Type of BlowersPositive DisplacementMulti-Stage CentrifugalSingle Stage CentrifugalTurbo Blower
Obtain Blower Performance Curves/DataObtain Motor Data Sheets
Evaluate Multi-Stage
Evaluate PDEvaluate Single Stage
or Turbo
66
Aeration ECM Evaluation Procedure
Evaluate PD Blowers:Get Performance Curve or Data
Slip, CFR, FHPVariable Speed Performance
Determine Operating Range Each BlowerMax Flow and Pressure (hp limited)Min Flow (temperature rise limited)
Calculate System CurveDetermine kW at Typical Existing Flow and Pressure
Include Motor PerformanceDetermine kW at Typical Reduced Flow and/or Pressure
If Sheave Change Include Motor PerformanceIf VFD Include Motor and VFD Performance
Calculate Estimated Savings and Payback
67
Aeration ECM Evaluation Procedure
Evaluate Multistage Centrifugal Blowers:Get Performance CurvesDetermine Operating Range Each Blower
Max Flow and Pressure (hp or pressure limited)Min Flow (surge point)
Calculate System CurveDetermine kW at Typical Existing Flow and Pressure
Include Motor PerformanceBase on Existing Control Method
Inlet ThrottlingOn/Off OnlyVariable Speed
Decide if VFD is an OptionEquipment CostCurve Suitability
Investigate Impeller Change (Re-Rate)Determine kW at Typical Reduced Flow and Pressure
For Throttled Include Motor PerformanceFor VFD Include Motor and VFD Performance
Calculate Estimated Savings and Payback
68
Aeration ECM Evaluation Procedure
Evaluate Single Stage Centrifugal Blowers:Get Performance CurvesDetermine Operating Range Each Blower
Max Flow and Pressure (hp or pressure limited)Min Flow (surge point)
Calculate System CurveDetermine kW at Typical Existing Flow and Pressure
Include Motor PerformanceBase on Existing Control Method
Inlet ThrottlingInlet Guide VanesVariable Diffuser VanesDual Vane
Decide if VFD is an OptionEquipment Cost (Medium Voltage Typical)Curve Suitability
Investigate Impeller Change (Re-Rate) or Vane ChangesDetermine kW at Typical Reduced Flow and Pressure
Include Motor Performance And Control TypeFor VFD Include Motor and VFD Performance
Calculate Estimated Savings and Payback
