Water Hammer. Tackling Transient Events at San Jose Water Company. Jake Walsh, P.E. Andy Yang, P.E. October 21, 2014

Transcription

1 Water Hammer Tackling Transient Events at San Jose Water Company Jake Walsh, P.E. Andy Yang, P.E. October 21, 2014

2 Introduction [map of SJWC] Map data 2014 Google

3 Introduction What is Water Hammer? Water hammer events (transient events) are disturbances in water flow from one steady-state condition to another. (adapted from AWWA Manual M32; Mays, Water Resources Engineering 2005 Edition) What are Typical Causes of Water Hammer? Pump operations Valve operations Main breaks Rapid demand changes (hydrant flow)

4 Wave Propagation Animations Pump Start Up OFF ON Hi Pressure Scale Pump Shut Off Low OFF ON

5 Hydraulic Transient Concerns at SJWC Hydraulic transient related concerns at SJWC: Infrastructure damage Property damage Regulatory compliance Public safety (pipe ruptures) Public health (negative pressures) Complaints

6 Transient Analysis Goals and Approach SJWC Goals Verify existence and extent of problem Determine mitigation measures SJWC Approach Obtain necessary knowledge and analysis tools Conduct field tests Analyze data Select surge protection devices

7 Transient Analysis Vickery Pump Station Background History of problems and mitigation efforts New booster pumps installed with pump control valves Surge tanks installed

8 Transient Analysis Vickery Pump Station Field Testing Select strategic locations to install pressure loggers Pump discharge High pressure regions Low pressure regions Dead end mains Coordinate with Operations department Pump operations

9 Transient Analysis Vickery Pump Station Transient Analysis Vickery Pump Station Logger 1 Pump Discharge Logger 3 High Pressure Hydrant Logger 2 Low Pressure Service

10 Transient Analysis Vickery Pump Station psi Pump Start Up Pump Control Valve Setting psi

11 Transient Analysis Vickery Pump Station psi Pump Shut Off Pump Control Valve Setting 12 psi 11 psi 10 s 1

12 Transient Analysis Vickery Pump Station Pump Start Up and Shut Down Pump Discharge psi 186 psi 132 psi 11 psi

13 Transient Analysis Vickery Pump Station Pump Start Up With Surge Tank - Pump Discharge 186 psi psi psi

14 Transient Analysis Vickery Pump Station Pump Shut Off With Surge Tank - Pump Discharge 132 psi 88 psi 11 psi 1

15 Transient Analysis Vickery Pump Station Pump Start Up and Shut Down Low Pressure Service 125 psi psi 73 psi psi -20

16 Transient Analysis Vickery Pump Station Pump Start Up With Surge Tank Low Pressure Service 125 psi psi psi

17 Transient Analysis Vickery Pump Station Pump Shut Off With Surge Tank - Low Pressure Service 73 psi psi psi

18 Transient Analysis Vickery Pump Station Pump Start Up and Shut Down High Pressure Hydrant 197 psi Static Pressure ~ 171 psi Run Pressure ~ 173 psi psi 120

19 Transient Analysis Vickery Pump Station Pump Start Up With Surge Tank High Pressure Hydrant 197 psi psi Record Start Trigger ~ 178 psi Record Stop Trigger ~ 173 psi Static Pressure 171 psi

20 Transient Analysis Vickery Pump Station Upper Record Start Trigger ~ 178 psi Pump Shut Off With Surge Tank High Pressure Hydrant Static Pressure 171 psi Lower Record Start Trigger ~ 161 psi With surge tank online, transient waves remained within recording triggers psi 120

21 Transient Analysis Pavilion Pump Station Background History of problems Mitigation efforts

22 Transient Analysis Pavilion Pump Station Field Testing Strategic locations to install pressure loggers Coordination with Operations department Surge Modeling Calibration of existing system Future system (with surge protection device)

23 Transient Analysis Vickery Pavilion Pump Station Transmission Main Split Logger Pump Discharge Reservoir

24 Transient Analysis Vickery Pavilion Pump Station psi psi Pump Start Up - Pump Discharge Reflection wave from transmission main split Reflection wave from reservoir psi

25 Transient Analysis Vickery Pavilion Pump Station psi 186 psi Pump Shut Off - Pump Discharge 200 psi 196 psi 186 psi psi 64 psi Reflection wave from reservoir Reflection wave from transmission main split

26 Transient Analysis Pavilion Pump Station Initial Surge Tank Sizing: T c = 2L a T c = 2 4, 080 ft 1, 800 ft/s = 4. 5 s Surge Tank Volume = T c Q Surge Tank Volume = 4. 5 s 8. 7 gal/s = 40 gal

27 Transient Analysis Vickery Pavilion Pump Station psi 200 psi Pump Start Up - 50% Water / 50% Air gal 80 gal gal gal psi

28 Transient Analysis Vickery Pavilion Pump Station psi 200 psi Pump Start Up - 35% Water / 65% Air gal 80 gal 160 gal 265 gal psi

29 Transient Analysis Vickery Pavilion Pump Station Pump Trip - 2 Pumps 50% Water / 50% Air psi 40 gal 80 gal 160 gal 265 gal psi

30 Transient Analysis Vickery Pavilion Pump Station Pump Trip - 2 Pumps 35% Water / 65% Air psi gal 160 gal gal psi

31 Conclusion Hydraulic transients are regularly occurring in water distribution systems Transient waves can be far more extreme than anticipated Transient waves propagate further than expected Certain surge protection devices can be very effective, others not as effective Surge protection devices can help mitigate potential public safety and public health concerns Surge modeling is highly recommended for sizing surge protection devices More transient analysis needs to be performed

32 Contact Information Jake Walsh, P.E. Engineering Unit Manager Andy Yang, P.E. Associate Engineer