pump selection made easy? - the water environment ... pump selection is easy! static head friction...
TRANSCRIPT
Pump Selection Made Easy?
Not So Much When Pumps Operate in Parallel
One Pump Selection is easy!
Stat
ic H
ead
Fric
tion
and
Form
Los
ses
Fric
tion
and
Form
Los
ses
Tota
l Dyn
amic
Hea
d
System Curve ∩ Pump Curve = Operating Point
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Pump Curve
Operating Point
System Curve
Pumps in Parallel – More Complicated
Suction
Discharge
Objectives
• Parallel Pumping vs. Series Pumping
• System Curves
• Pump Curves
• Pump Performance
• Pump Performance in Parallel
• How to get the most efficient Performance in Parallel
Parallel Pumping vs Series Pumping
• Parallel Pumping ▪ Pump Discharge is additive
• Series Pumping▪ Pump Head is additive
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2-Pumps in Series
2-Pumps in Parallel
1-Pump
System Curves
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System
Fric
tion,
Fo
rm
Loss
es
• Static Head = Discharge Level –Suction Level
• Friction Losses▪ Hazen-Williams▪ Darcy-Weisbach
• Form Losses▪ Equivalent Lengths▪ K times Velocity Head
• Velocity Head▪ 𝑣𝑣2
2𝑔𝑔Stat
ic
Head
Developing Families of System Curves
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Static Head Variation
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Pipe Roughness Variation
System Curve Family
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Put them all together:
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Top and Bottom define system range:
Pump Curves
Discharge Head Curve
EfficiencyCurves
Power Curves
NPSH Required Curve
Allowable Operating
Range
BEP
Pump Curves
Discharge Head Curve
Efficiency Curve
NPSH Required Curve
Power Curve
MCSFAllowable Operating
Range
Allowable Operating
Range
BEP
Preferred Operating
Range
Preferred Operating
Range
Family of System Curves
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High Static Head
High FrictionLow H-W “C”
Avg. Static Head
Low FrictionHigh H-W “C”
Low Static Head
Avg. FrictionAvg. H-W “C”
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One Pump
System Curve
Pump Curve
Pump Efficiency73%
18.4 MGD @ 320 FT TDH
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Two Pumps
System Curve
73%
18.4 MGD @ 320 FT TDH
33.6 MGD @ 390 FT TDH
78.3%
15.2 MGD
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Three Pumps
System Curve
73%
18.4 MGD @ 320 FT TDH
33.6 MGD @ 390 FT TDH
78.3%
15.2 MGD
45.0 MGD @ 453 FT TDH
11.4 MGD
81.7%
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Four Pumps
System Curve
73%
18.4 MGD @ 320 FT TDH
33.6 MGD @ 390 FT TDH
78.3%
15.2 MGD
45.0 MGD @ 453 FT TDH
11.4 MGD
81.7%
52.0 MGD @ 506 FT TDH
82.3%
7.0 MGD
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Five Pumps
System Curve
73%
18.4 MGD @ 320 FT TDH
33.6 MGD @ 390 FT TDH
78.3%
15.2 MGD
45.0 MGD @ 453 FT TDH
11.4 MGD
81.7%
52.0 MGD @ 506 FT TDH
82.3%
7.0 MGD
5.0 MGD
57.0 MGD @ 537 FT TDH
80.3%
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One Pump
System Curve
Pump Curve
Pump Efficiency73%
18.4 MGD @ 320 FT TDH
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Each Individual Pump – Two in Parallel
Individual Pump Curve
Individual Pump Efficiency
78.3%
16.8 MGD @ 390 FT TDH
33.6 MGD @ 390 FT TDH
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Each Individual Pump – Three in Parallel81.7%
Individual Pump Curve
Individual Pump Efficiency
15.0 MGD @ 453 FT TDH
45.0 MGD @ 453 FT TDH
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Each Individual Pump – Four Pumps in Parallel82.3%
Individual Pump Curve
Individual Pump Efficiency
13.0 MGD @ 506 FT TDH
52.0 MGD @ 506 FT TDH
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Each Individual Pump – Five Pumps in Parallel80.3%
Individual Pump Curve
Individual Pump Efficiency
11.4 MGD @ 537 FT TDH
57.0 MGD @ 537 FT TDH
Flat vs Steep Pump Curves
Steep Pump Curve
Flat Pump Curve
Compare Parallel OperationFlat Pump Curves Steep Pump Curves
Define System Curves and Operating Range
Max
Pum
ping
Min
Pum
ping Normal
Range
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Compare Pump Curves
2-pump Operating Point
2-pump BEP
2-pump Efficiency
1-pump exceeds min rate
5-pump exceeds max rate
Design Point Selection
Choose # of pumps
Set Design Flow
Calc. System Head
Select Pumps
Compare Selections
3
12 MGD
403 FT12 MGD @ 403 FT
Design Pt. @ BEP?
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New Pump Selection – Best Efficiency Point
BEP: 83.6%
11.8 MGD @ 451 FT TDH
1378 HP
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New Pump Selection
37 MGD @ 406 FT TDH
83.4%
1-Pump <minimum
5-Pumps >Maximum
Summary
• Parallel Pumping vs. Series Pumping
• System Curves
• Pump Curves
• Pump Performance
• Pump Performance in Parallel
• Design for most common operating range = Most efficient pumping system
