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Optimizing In-lineBooster Pumps withUnique DesignFeatures and ControlStrategies

2014 ISA Water / Wastewater and Automatic Controls SymposiumAugust 5-7, 2014 – Orlando, Florida, USA

Speaker:Evan P. Curtis, P.E.

2014 ISA WWAC SymposiumAug 5-7, 2014 – Orlando, Florida, USA 2

Presenter

• 20 years of experience in water/wastewaterdesign consulting

• B.S. degree in Civil with minor inEnvironmental Engineering

• Early career experience in pump stationprocess and mechanical design

• Now focuses on instrumentation and control

• Field experience includes control systemprogramming and startup

Headshotphoto


Presentation Outline

• In-line Booster Pump Station Applications and Hydraulics

• Control Strategies

• Reliability and Efficiency Considerations

• Examples

2014 ISA WWAC SymposiumAug 5-7, 2014 – Orlando, Florida, USA

In-line Booster Pump StationApplications

4

• Favorable hydraulicconditions for:– Wastewater collection

– WWTP effluent disposal

– Reclaimed water

– Raw water

– Potable water


Components of Wastewater CollectionSystems

5

Gravity/LowPressureCollection

Lift Stations/Booster Stations/Force Mains

WastewaterTreatment

Disposal


Wastewater Pump Station Concerns

6

• Site / Location

• Odor

• Maintenance

• Access


Benefits of In-line BoosterPump Stations

7

• In-line booster pump stations provide for:– Odor containment

– Reduced maintenance

– Reduced capital cost

– Reduced footprint


Pump Station Configurations

• Wet well

• Wet well / dry well

• In-line booster


Pump Station Configurations

9

Wet Well / Dry WellWet Well

In-line Booster


Hydraulic System Curve

10

Tot

alH

ead

(Fee

t)

Flow Rate (MGD)

System CurveSystem Curve

Friction Head= ∑ hlf + hlm

Static Head

TotalHead

There will be a range of systemcurves for a given application

Friction Head

Static Head =zdisch - zsuction


Pump Curve

11

Tot

alD

ynam

icH

ead

(Fee

t)

System Curve

Pump Curve

Efficiency CurveEfficiency Curve

Operating Point

Run-Out Point

Shut-Off Head Point22

11

33

NPSHR Curve

44 Best Efficiency Point (BEP)

Flow Rate (MGD)


Hydraulic Grade Line

12

Pip

elin

eP

ress

ure

Pipeline Pressure

MaximumPressureMaximumPressure

MinimumPressureMinimumPressure

PumpStationPumpStation

Delivery PointDelivery Point

In-line BoosterPump StationIn-line BoosterPump Station

Pipeline Distance


Components of a Typical In-LineBooster Pump Station

13

• Pumps

• VFD’s

• Motorized valves

• PS bypass check valve

• Pressure transmitters

• Flow meter

• Programmable controller

• Emergency generator

• Pump seal water system


In-Line Booster Pump Station Control

14

• Maintain suction pressure below maximum setpoint (e.g.,wastewater collection)

• Maintain discharge pressure above minimum setpoint(e.g., water distribution)

Typical Wet Well In-line Booster


In-line Booster Pump StationSchematic

15

Redundant PressureTransmitters

Pump Station Bypass

Check Valve

Valve Actuator

FlowTransmitter

Su

ctio

nH

ead

er

Dis

cha

rge

Hea

der

Closed Limit Switch


Pump Station Bypass Capability

16


Variable Speed Pump Envelopes

17

0

25

50

75

100

125

150

175

0 400 800 1200 1600 2000 2400 2800 3200 3600 4000 4400 4800

TD

H(f

t)

Flow (gpm)

Two Large Pumps Running

One Large Pump Running

Two Small Pumps Running

One Small Pump Running


Suction Pressure Range

• Minimum suction pressure setpoint based on the boosterpump curves and highest downstream level:– Net positive suction head required (NPSHr)

– Pump station design flow rate is achievable at maximum headcondition (maximum water surface elevation at delivery point)

• Maximum suction pressure setpoint based on thecapacity of the upstream collection /transmission system– Upstream pump station design flow rates are achievable at

maximum booster pump station suction pressure

18


Suction Pressure Control

• Constant speed booster pumps:– Start and stop pressure setpoints

and time delays

• Variable speed booster pumps:– Start and stop pressure setpoints

and time delays

– Speed controlled by PID feedbackloop (increasing speed lowerssuction pressure)

– PID loop configured with deadbandto avoid hunting

• System demand can changerapidly

19


Motorized Discharge Valves

• Prevents water from flowingthrough pumps when they arenot running

• Modulating valves may beneeded to prevent pumprunout/cavitation

• Avoid unnecessarymodulation to minimizeenergy consumption andvalve wear

• Starting additional pumps canalso eliminate runout

20


Modulating Discharge Valve Control

• Increases pump TDH to prevent runout

• Requires a pressure transmitter on each pump dischargeupstream of its modulating valve

• TDH = discharge pressure – suction pressure

• PID control loop modulates based on TDH setpoint(closing valve increases TDH)

• The TDH setpoint varies with pump speed

21


Variable Speed In-Line Booster Pumpand Modulating Valve Control

22

• PC = pressure controller

• DPC = differentialpressure (i.e., TDH)controller

• CALC = calculation of DPC setpoint based on pump speed

DPC setpoint = (pump runout TDH @ 100% speed) x (actual % speed/100)2 + safety margin


Impact of Modulating Valve on SystemCurve

23

TO

TA

LH

EA

D

FLOW RATE

System Curve 2

Pump curve at100% speed

System Curve 1

System curve withdischarge valve throttled

Pump curve atminimum speed

Head added bydischarge valve

Pump runout curve


Reliability Considerations

24

• Evaluate consequence offailure of each instrument

• Consider backup controls

• Redundant pressuretransmitters used on pumpstation header pipes

• Isolation ring seals are bestfor wastewater, 1” or larger


Pump Seal Water

• Low flow switch protectspump from running withoutseal water for an extendedtime

• Avoids pump damage anddowntime for repair

25


Energy and Sustainability

26

• Large pumps are the major power consumers for mostwater and wastewater utilities

• Consider overall (“wire-to-water”) efficiency of system

Power consumed = PH / ηpump / ηmotor / ηdrive

- Average pumping system efficiency is 40% or less

- Motor efficiency is significantly reduced below 70% of full load

- Is the loss of efficiency due to a VFD worth the benefit?

- Will the higher capital cost of more efficient motors be offset byO&M cost savings?

• Avoid spikes in power consumption– Know the electric rate structure

– Minimize pump cycling


Example In-line Booster Pump Stations

27


Palm Beach County ECR PS 5229

28

• Rehabilitationand conversionfrom wet well /dry well to in-lineboosterpump station

CLWMasterP.S.Lantana Road

Lake Worth Road CLW Repump Station

Forest Hill Blvd.

Southern Blvd.

42” FM

42

”F

M

36” FM

Jog

Ro

ad

48

”F

M

PS-5241

54

”F

M

ECRWWTP(Destination)

Okeechobee Blvd.

I-9

5

I-9

5

I-9

5

PS-5236

PS-5229



29

1

2

3

4

1

2

3

4

Curve No. 1: Existing Transmission Main, All Tributary Flows IncludedECR WWTP Influent Structure at High Water Elevation

Curve No. 2: Existing Transmission Main, No Tributary Flows IncludedECR WWTP Influent Structure at Low Water Elevation

Curve No. 3: Parallel 48-inch Pipelines and Existing 54-inch PipelineAll Tributary Flows Included, ECR WWTP InfluentStructure at High Water Level

Curve No. 4: Parallel 48-inch Pipelines and Existing 54-inch PipelineNo Tributary Flows Included, ECR WWTP InfluentStructure at Low Water Level

2 PumpsOperating

PS 5229 Anticipated Flow Range

3 PumpsOperating

100% Speed (Typ.)

1 PumpOperating

0

50

100

150

200

250

300

Tot

alD

yn

amic

Hea

d-

Fee

t

0 10 20 30 40 50 60 70 80 90 100 110

Flow - MGD NOTE: Minimum pump speed set at 40%.



30

Vent Duct to beDemolished by Others

ScreeningChannels

Wet Well

Vent

Vent

Support forPump Shaft

Existing Stairs

Motor

Elec. Motorand Base

24” Flange Base 90” Bend

VariableSpeed Control

24” PumpControl Valve 24” Check Valve

FIN Floor

VerticalPump

FIN. Floor

36” FlangedCoupling Adapter

Conc. PipeSupport

Conc. PumpSupport

½ PVCDrain

24” X 36”Reducer

HarnessedMech. CPLG

½ SealWater Line

48” DIP Effluent F.M.

30” Plug Valve 30” 90 Bend

24” Plug Valve

Gate Valve

42” x 30” Tee

42” SuctionHeader

SumpPump

Exist. 6” Slab

Skylight

Monorail

48” x 24”Reducing90 Bend

HarnessedMech. CPLG

WastewaterEffluent F.M.

(2) 2” Diesel Fuelin 4” Casing Pipe

24” x 36”Reducer

48” GateValve

48” x 30” ECC. Reducer

FIN Grade

VoltageSwitch Gear

PLC PNLC.B.S. Wall

Pump RoomAccess Walkway

Concrete PipeSupport

Before After


Florida Keys Aqueduct AuthorityWater Transmission System

31

Key WestMarathon KeyBooster PS

Florida CityHigh Service PS

Ramrod KeyBooster PS• 12 mgd, 250 psi• One 600 HP VFD Pump• One 600 HP Diesel Pump• Emergency Generator

Long Key Booster PS• 16 mgd, 250 psi• Two 600 HP VFD Pumps• One 600 HP Diesel Pump• Emergency Generator

• 125 mile pipeline

• Two pump stations wererehabilitated (shown in red)

• Automatic PLC controls

• Frame relay telemetry tocontrol center in FloridaCity


1995 Water Demand MarginallyAchieved with Existing System

32

Cumulative Length (1000 ft)

Hydraulic Grade Line of 1995

0

20

40

60

80

100

120

140

160

180

200

220

240

260

0 100 200 300 400 500 600 700

0

5

10

15

20

FloridaCity PS

MarathonKey PS

RamrodKey PS

Long Key PS(out of service)

Key West

Pre

ssu

re(p

si)

Flo

wR

ate

(mg

d)

Cross Key PS(out of service)

Legend:Model PressureModel Flow Rate


2015 Water Demand Achieved withAdditional Booster Pump Stations

33

Hydraulic Grade Line of 2015 Operation - Peak Day Demand

0

20

40

60

80

100

120

140

160

180

200

220

240

260

280

0 100 200 300 400 500 600 700

Cumulative Length (1000 ft)

0

5

10

15

20

25

FloridaCity PS

MarathonKey PS

RamrodKey PS

Long Key PS Key WestCross Key PS

Pre

ssu

re(p

si)

Flo

wR

ate

(mg

d)

Legend:Model PressureModel Flow Rate


Florida Keys Aqueduct AuthorityWater Transmission System

34

Before After

Interior

Exterior


Summary

• In-line booster pump stations are becoming more common

• Understanding the system and equipment hydraulics isessential in design and construction

• Control strategies balance pump station performance,equipment protection and energy consumption

• Enhance system reliability by applying redundancy andprotective instruments

35


Questions?

36

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