Pumping Downhill Can Be A
Good Solution
Hydraulic Transient Analysis Case Study
City Of Indianapolis, IN
Unique Challenges To
Pumping Downhill
March 20, 2012
Randy Vanderwerf, P.E., Clark Dietz, Inc.
Omkar Ghavi, E.I., Clark Dietz, Inc.
Belmont North Service Area
Belmont North
Interceptor (BNI)
BNI System
• Separate Sanitary Sewer System
Sewers 27 inch to 54 inch
• Limited Interceptor Capacity
• Wet Weather Sanitary Sewer Overflows
• Separate Relief Interceptor
• Eliminate Wet Weather Capacity Limit
20-year Build-out of Service Area
BNRI Advanced Facility Plan
50 ft Drop
~ 25 ft
~ 40 ft
BNRI Advanced Facility Plan
• Population Projection
• Rainfall Pattern
Flow Reduction
• Constructability
• Environmental Impacts
Alternative Routes
• Construction Costs
• Present Worth
Project Costs
Value Engineering
BNRI Advanced Facility Plan
780
760
740
720
700
680
Peak Hour … 38 MGD
Daily Average … 7 MGD
Daily Minimum … 3 MGD
Pumps
3 Operating
1 Standby
Belmont North Lift Station Flows
Belmont
North Lift
Station
BNRI Force Main Profile
50 ft Drop
Standpipe
Force Main
Static HGL
745.00
Steady State HGL at 38 MGD
735.00
Air
Pockets
Belmont
North Lift
Station
Standpipe
BNRI Force Main
Force Main Present Worth Analysis
42” Force Main
Pump Cost
Electrical
Cost
Ferric Chloride
Cost
BNRI Advanced Facility Plan
• Project Cost: $222 Million
• Lift Station & Force Main
Savings
$ 49 Million
Belmont
North Lift
Station
Standpipe
42”
42”
42”
42”
Criteria
• TDH > 50 ft
• Flow > 500 GPM
• Pipe > 1,000 ft
• High Points
• Profile: ‘Knees’
BNRI Conditions
• TDH ~ 116 ft
• Flow = 26,200 GPM
• Force Main ~ 28,350 ft
• Valleys and Peaks
• Knee at ~ 15,000 ft
Surge Analysis: Criteria
✓ ✓ ✓ ✓ ✓
Investigate
Hydraulic
Transients
• Valve Movement : Opening / Closing
• Starting or Stopping Pump(s) with
Other Pump(s) Operating
• Change in Flow Demand
• Frequent Variation in Water Level
• Pump Trip due to Power Failure
Typical Causes
Impacts of Transients
• High Pressure
Failure Pumps, Valves
Pipe Rupture
Disintegration of Pipe Lining
Pipe Leaks
• Low Pressure
Cavitation and Column Separation
Collapsing of Pipe
Intrusion of Contaminants
Vapor Cavities: Very High Pressures
Surge Analysis: Importance
• Select & Design Pipe to Withstand
Pressures
• Select Appropriate Check Valves
• Surge Control Devices
Alleviate Adverse Transient Effects
Proper Selection and Location
Start-up / Shutdown Procedures
Surge Control Devices
Active Devices
Modify Conditions by
Providing Liquid or Air to Piping System
Surge Tank
Passive Devices
Limit Extent of High or
Low Pressure
Air Release Valves
Surge Control Devices
Surge Tanks
• Normally Located at Lift Station
Protection against Pump Power Loss
• Pressurized Vessels (Air + Water)
• Supply Liquid to Pipeline
Must Not Empty / Allow Air to Enter
• Initial Air Quantity: Large
Limit Rate of Pressure Drop
Surge Model Layout
Surge Analysis Model
Peak Flow at 38 MGD • Steady State
• Pump Trip: 100% to 0% in 4 seconds
• Monitor Pressures for 320 seconds
Belmont
North Lift
Station
760
780
800
820
840
740
720
700
Standpipe
1600
1400
1200
1000
800
Surge Analysis at 38 MGD
Pressure Envelope
Force Main
Steady State HGL at 38 MGD
HGL after 16 seconds
Very High
Positive Head Several
Times Steady
State
Pressure
Negative Head
Elevation
Steady State Force Main
Steady State HGL at 38 MGD No Surge
Protection
• Max. Pressure 183 psi
• Min. Pressure -14.4 psi
• Conditions Full Vacuum
• Location Everywhere
• Duration 320 sec
Important ARV Features
• Avoid Rapid Air Expulsion
Secondary Surges
Two / Three Stages: Restrict Air Release
Proprietary Designs:
Surge Check Valves
Bias Mechanisms
Throttling Devices
• Sealing Pressure < Static Head
Valve Doesn’t Seal: Discharge Sewage
ARV Selection
Air Valve Considerations
• Non-slam Feature
• Sealing Pressure
• Materials
• Cost
Belmont
North Lift
Station
Standpipe
Force Main
Steady State HGL at 38 MGD
Air Valve
Static HGL
ARV Sealing Pressure Criteria
Force Main
Steady State HGL at 38 MGD
Air Valve
Static HGL
Belmont
North Lift
Station
Standpipe
Valve Sealing Head
Surge Analysis Model: Modifications
700
720
740
760
780
800
820
840
Surge Analysis at 38 MGD
Pressure Envelope
Force Main
Steady State HGL at 38 MGD HGL after 16 seconds
1600
1400
1200
1000
800
Surge Conditions with
No Protection
Air Valves
• Max. Pressure 55 psi
• Min. Pressure -14.4 psi
• Conditions Partial Vacuum
• Location Several
• Duration 320 sec
Surge Tanks: Sewage Applications
Hydro-pneumatic Tank
• Air Compressor: Control Gas Volume
Bladder Tank
• Pre-charged Pressurized Bladder
Hybrid Tank
• Air Vent: Utilize Atmospheric Air
Surge Tanks: Sewage Applications
Hybrid Tank
Courtesy: Charlatte America
Cost
O&M
Issues
Effectiveness
Sewage Surge Tanks Evaluation
Hydro-
Pneumatic
Bladder Hybrid
✓ ✓ ✗
✓ ✓ ✓
820
840
800
780
760
740
720
700
Surge Analysis at 38 MGD
Pressure Envelope
Force Main
Steady State HGL at 38 MGD HGL after 16 seconds
Air Valves &
Hybrid Tank
• Max. Pressure 52 psi
• Min. Pressure -12 psi
• Conditions Partial Vacuum
• Location One
• Duration <0.1sec
PCCP
Force Main
Installation: Standpipe
Installation: Lift Station
Acknowledgements
• Citizens Water, City of Indianapolis
• Dr. Don Wood, KYPipe
• Gwen Phalempin, Charlatte Of America
• Frank Smith, Pipe Tech, Inc.
• Naftali Zloczower, A.R.I. Valves
• Garren Amdur, Vent-O-Mat Valves
• Larry Beynart, Pulsco
