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Water Hammer

Water Hammer. Travis Meyer, P.E. Richard P. Arber Associates. INTRODUCTION. Background Water Hammer Modeling System Improvements Results Conclusions. City of Black Hawk Distribution System. Dory Hill Tank. 3. 4. 2. 5. 1. Pressure Reducing Station. Mesa Tank. Pump Station.

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Water Hammer

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  1. Water Hammer Travis Meyer, P.E. Richard P. Arber Associates

  2. INTRODUCTION • Background • Water Hammer Modeling • System Improvements • Results • Conclusions

  3. City of Black HawkDistribution System Dory Hill Tank 3 4 2 5 1 Pressure Reducing Station Mesa Tank Pump Station

  4. Distribution System Profile Grade Mesa Tank (8775 ft) Hydraulic Grade Pressure Reducing Station 120/40 Pump Station 1 160/70 Dory Hill Tank (8375 ft) 2 140/90 3 140/65 140 psi 3 70 4 5 Pump Suction Line

  5. Problem

  6. 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

  7. SURGE 5 MODELSUDDEN VALVE CLOSURE 2,000 GPM TO 0 GPM IN 3 SECONDS

  8. SURGE 5 MODELSUDDEN VALVE OPENING 0 GPM TO 2,000 GPM IN 3 SECONDS

  9. SURGE 5 MODELSUDDEN VALVE OPENING 0 GPM TO 2,000 GPM IN 3 SECONDS PUMP SUCTION ISOLATED

  10. Water Hammer ModelingConclusions • 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?

  11. 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

  12. Recommended 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

  13. System Improvements Standpipe 6 3 4 2 5 Pressure Reducing Station with Pressure Relief Valve 1 Pump Station

  14. System Improvements Mesa Tank (8775 ft) Grade Hydraulic Grade Pressure Reducing Station 120/40 Pump Station 1 160/70 Dory Hill Tank (8375 ft) 2 140/90 140/65 3 3 70 4 5 Pump Suction Line

  15. Initial Implementationof Improvements • Isolated Pump Suction Line • Installed Temporary Pressure Relief Valves • Put Locks on Fire Hydrants • Lowered System Pressures Where Possible (Zone 4)

  16. Initial Implementation

  17. Initial Implementation

  18. 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

  19. Water Hammer Test

  20. 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

  21. 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

  22. Another Water Hammer

  23. 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

  24. Another Water Hammer

  25. Final Adjustments - PRV Stations Secondary Supply 95 psi Primary Supply 100 psi Emergency Supply 90 psi Pressure Zone 100 psi 100 psi Pressure Zone 100 psi

  26. Success!!??

  27. 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

  28. Conclusions • To Protect System and Customers • Install Pressure Relief Valves • Install Standpipes • Require Surge Tanks on Fire Service Taps • Lower System Pressure

  29. Proud Papa Jeffrey - Born 9/10/02

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