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City of Black Hawk Water Hammer September 2002
Arber
Water Hammer
Travis Meyer, P.E.Richard P. Arber Associates
City of Black Hawk Water Hammer September 2002
Arber INTRODUCTION
• Background• Water Hammer Modeling• System Improvements• Results• Conclusions
City of Black Hawk Water Hammer September 2002
ArberCity of Black HawkDistribution System
1
2
3
4
5
Pressure Reducing StationPump Station
Dory HillTank
MesaTank
City of Black Hawk Water Hammer September 2002
Arber Distribution System ProfileGradeHydraulic Grade Pressure Reducing Station
Dory Hill Tank (8375 ft)
Mesa Tank
(8775 ft)
1
2
3 140psi
120/40
160/70
34
5
140/90
140/65
70
Pump Station
Pump Suction Line
City of Black Hawk Water Hammer September 2002
Arber Problem
City of Black Hawk Water Hammer September 2002
Arber Water Hammer - Causes
• Sudden Velocity Change– fire hydrant– fire sprinkler system– pumps
• Vapor Cavity Formation– pressure down surge at a low
pressure dead end
• Equipment Malfunction– fire hydrants, valves, PRVs
City of Black Hawk Water Hammer September 2002
ArberSURGE 5 MODEL
SUDDEN VALVE CLOSURE
50
100
150
200
250
300
-5 0 5 10 15 20 25 30 35 40 45 50 55 60
Time (seconds) - Valve closure initiated at Time 0
Pre
ss
ure
(p
si)
1" Pressure Relief Valve
2" Pressure Relief Valve
3" Pressure Relief Valve
No Pressure Relief
2,000 GPM TO 0 GPM IN 3 SECONDS
City of Black Hawk Water Hammer September 2002
ArberSURGE 5 MODEL
SUDDEN VALVE OPENING
-50
0
50
100
150
200
-5 0 5 10 15 20 25 30 35 40 45 50 55 60
Time (seconds) - Demand change initiated at Time 0
Pre
ss
ure
(p
si)
Main St & Mill St
Lodge Garage
Dory Hill PRV Station
Pump Station
Vapor Cavity Formation
Vapor Cavity Collapse
Model Not Valid Beyond This Line
0 GPM TO 2,000 GPM IN 3 SECONDS
City of Black Hawk Water Hammer September 2002
ArberSURGE 5 MODEL
SUDDEN VALVE OPENING
-50
0
50
100
150
200
-5 0 5 10 15 20 25 30 35 40 45 50 55 60
Time (seconds) - Demand change initiated at Time 0
Pre
ssu
re (
psi
)
Lodge Garage
Main St & Mill St
Dory Hill PRV Station
0 GPM TO 2,000 GPM IN 3 SECONDS
PUMP SUCTION ISOLATED
City of Black Hawk Water Hammer September 2002
ArberWater Hammer Modeling
Conclusions
• Sudden Large Demand Changes Can Initiate a Water Hammer Event
• Vapor Cavity Formation and Collapse Can Occur in the Pump Suction Line
• Unable to Model PRV Behavior During Water Hammer– Cause of Extended Hammers?
City of Black Hawk Water Hammer September 2002
Arber Water Hammer - Solutions
• Sudden Velocity Changes– Pressure Relief Valves– Surge Tanks– Surge Anticipation Valves– Standpipe
• Vapor Cavity Formation– Eliminate Low Pressure Dead
Ends– Connect System High Points to
Open Tanks
City of Black Hawk Water Hammer September 2002
ArberRecommended Improvements
• Reconfigure Pump Suction to Eliminate Possibility of Vapor Cavity Formation and Collapse
• Install Pressure Relief Valves in Pressure Zones 3 and 4
• Reconfigure Existing, Unused 12” Pipe as a Standpipe
• Optimize PRV Settings• Lower System Pressures• Require Surge Tanks for New
Construction with Fire Service
City of Black Hawk Water Hammer September 2002
Arber System Improvements
1
2
3
4
5
6
Pressure Reducing Stationwith Pressure Relief ValvePump Station
Standpipe
City of Black Hawk Water Hammer September 2002
Arber System ImprovementsGradeHydraulic Grade Pressure Reducing Station
Dory Hill Tank (8375 ft)
Mesa Tank
(8775 ft)
1
2
3
120/40
160/70
34
5
140/90
140/65
70
Pump Station
Pump Suction Line
City of Black Hawk Water Hammer September 2002
Arber Initial Implementationof Improvements
• Isolated Pump Suction Line• Installed Temporary
Pressure Relief Valves• Put Locks on Fire Hydrants• Lowered System Pressures
Where Possible (Zone 4)
City of Black Hawk Water Hammer September 2002
Arber Initial Implementation
City of Black Hawk Water Hammer September 2002
Arber Initial Implementation
City of Black Hawk Water Hammer September 2002
Arber Water Hammer Test
• Fire Dept Indicated That One Fire Hydrant Always Seemed to Cause Water Hammer
• Initiated a Water Hammer Event on Purpose
• Monitored System Pressures and PRV Behavior During Water Hammer
City of Black Hawk Water Hammer September 2002
Arber Water Hammer Test
City of Black Hawk Water Hammer September 2002
Arber Water Hammer TestConclusions
• Damaged Stem Extension on Fire Hydrant– City Subsequently Inspected
All Fire Hydrants for Damage
• Pressure Regulating Valves– Appeared to Operate Smoothly
During Water Hammer
City of Black Hawk Water Hammer September 2002
Arber Final Implementationof Improvements
• Pump Suction Line Reconfigured
• Standpipe On-Line• Two New PRV Stations with
Pressure Relief Valves On-Line
• System Pressures Lowered to Final Levels
City of Black Hawk Water Hammer September 2002
Arber Another Water Hammer
City of Black Hawk Water Hammer September 2002
Arber Probable Cause
• Contractor Started Work Approximately Same Time as Water Hammer– May Have Filled Water Truck
from Fire Hydrant
• Pressure Regulating Valve– Corrosion Buildup on Stem
Guide Caused Valve to Stick and Operate Unevenly
City of Black Hawk Water Hammer September 2002
Arber Another Water Hammer
City of Black Hawk Water Hammer September 2002
Arber Final Adjustments - PRV Stations
Pressure Zone
PrimarySupply100 psi
SecondarySupply95 psi
EmergencySupply90 psi
Pressure Zone
100 psi 100 psi
100 psi
City of Black Hawk Water Hammer September 2002
Arber Success!!??
City of Black Hawk Water Hammer September 2002
Arber Conclusions
• To Avoid Water Hammer– Eliminate Potential for Vapor
Cavity Formation (Low Pressure Dead-End Lines)
– Maintain Fire Hydrants, System Valves, Fire Protection Systems, Pressure Regulating Valves for Proper Operation
– Try Alternate PRV Strategy for Multiple PRV Pressure Zones
City of Black Hawk Water Hammer September 2002
Arber Conclusions
• To Protect System and Customers– Install Pressure Relief Valves– Install Standpipes– Require Surge Tanks on Fire
Service Taps– Lower System Pressure
City of Black Hawk Water Hammer September 2002
Arber Proud Papa
Jeffrey - Born 9/10/02
