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Protecting force mains with valves

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Considers hydraulic problems (from surge), air-related problems (both vacuum and air-release), and mechanical problems (from slam) that can be addressed with valves. A technical presentation, but light on math and heavy on metaphorical examples that make the hard-to-see inner workings of a fluid system easy to visualize and understand.

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Protecting force mains with valves

  1. 1. HOW TO USE VALVES TO PROTECT FORCE MAINS Brian Gongol DJ Gongol & Associates, Inc. January 28, 2015 Nebraska Snowball Conference
  2. 2. Let's start with a beer keg
  3. 3. If you pump a few times, you add pressure
  4. 4. Pumping too much creates foamy beer
  5. 5. Beer is relatively incompressible
  6. 6. Releasing a little volume eases lots of pressure
  7. 7. Water in a pressurized system: Same behavior
  8. 8. Not zero like a solid (steel or concrete)
  9. 9. But close
  10. 10. Squirt guns and belly flops prove it
  11. 11. Water is not like air in a storm door cushion
  12. 12. But also unlike pushing on a pool cue
  13. 13. Energy is transmitted quickly but not instantly
  14. 14. Energy is conducted as a wave
  15. 15. Surge is like a train starting or stopping
  16. 16. Energy transmits through couplers
  17. 17. Slam is the train sliding back downhill
  18. 18. Blood pressure is a surge event
  19. 19. Everyone with a dishwasher knows surge
  20. 20. Driving while hauling tank of liquid
  21. 21. Don't jam on gas or brake
  22. 22. Operate smoothly
  23. 23. Sudden starts/stops could drop a transmission
  24. 24. Momentum/inertia matters
  25. 25. Centrifugal pump from stop to 100%
  26. 26. Like hitting gas pedal to floor
  27. 27. Shock demand is hard on transmission
  28. 28. Rotative speed isn't 100% instantaneously
  29. 29. Pipe friction
  30. 30. Fire hose/garden hose/flexible hose
  31. 31. PVC pipe
  32. 32. Ductile iron, copper, and other metal pipe
  33. 33. More friction means more surge dissipation
  34. 34. But also more headloss and energy use
  35. 35. High efficiency trade-off with surge potential
  36. 36. Magic number: 10 critical periods
  37. 37. Cross-cancellation of wave action
  38. 38. Surge moves at the speed of sound in water...
  39. 39. ...modified by pipe characteristics
  40. 40. Published tables of surge wave speed ("a")
  41. 41. "a" for plastic pipe is 900 fps (615 mph)
  42. 42. "a" for ductile iron is 5,000 fps (3400 mph)
  43. 43. Plastic expands and absorbs the wave energy
  44. 44. Metal disspates less wave energy
  45. 45. Surge mitigation techniques
  46. 46. VFDs might help But what part of the scale is actually effective on surge?
  47. 47. Depends upon static head
  48. 48. Soft starters might help  But what about pump shutdown?
  49. 49. What about power failure?
  50. 50. Automatic pressure-control valves
  51. 51. Air is also a problem
  52. 52. Air release upon pipeline fill
  53. 53. Dynamic operation to release air
  54. 54. Vacuum-breaking upon pressure drop
  55. 55. Air in solution in water: About 2%
  56. 56. Air valves
  57. 57. Air restricts pipe diameter
  58. 58. Can be significant
  59. 59. Air pockets will build
  60. 60. Imagine trapping a tough balloon in the pipe
  61. 61. Lots of compression possible...
  62. 62. ...but dangerous high pressure results
  63. 63. Weight of a column of water  4" diameter, 500' long  43.55 cubic feet  325.75 gallons
  64. 64. At 8.3 lbs per gallon: 2700 lbs. (a Honda Civic)
  65. 65. You have to break that vacuum
  66. 66. Pipe is not like a drinking straw  Something has to give eventually
  67. 67. How it's harmful
  68. 68. Long-term wear on pipes
  69. 69. Main breaks
  70. 70. Valve failures
  71. 71. Backspinning pumps
  72. 72. Pipe swings inside plant
  73. 73. Leaks
  74. 74. Contamination by negative-pressure events
  75. 75. We've covered hydraulic problems (air/water)
  76. 76. Upsurge and downsurge are hydraulic
  77. 77. Slam is mechanical
  78. 78. Slam comes from column reversal
  79. 79. Slam and surge are independent
  80. 80. Check valves are used for protection
  81. 81. Prevent simple column reversal
  82. 82. Ball check valves
  83. 83. Weighted-flapper check valves
  84. 84. Cushioned check valves
  85. 85. Non-slam check valves
  86. 86. Close fast enough to prevent slam
  87. 87. Don't close too fast for pumps and systems
  88. 88. Quick self-closure isn't actual slam
  89. 89. Slam is involuntary seating of the valve
  90. 90. Some valves can control both surge and slam  Checktronic  Overcoming high head after bringing pump up to speed
  91. 91. Illustrations
  92. 92. Tank to closed valve
  93. 93. Pump to closed valve
  94. 94. Demo: Surge valve
  95. 95. Demo: Sewage air-release valve
  96. 96. Demo: Water air-release valve
  97. 97. Demo: Wide-body air-release valve
  98. 98. To recap  Pipes, valves, and equipment are endangered by three problems:  Hydraulic upsurge and downsurge  Hydraulic consequences of air  Mechanical slam  These problems can be resolved through multiple means  Automatic valves are often the best choice
  99. 99. You don't have to figure it out alone  Free surge analysis available  Call: 515-223-4144  Email: info@djgongol.com
  100. 100. Questions?  Thank you for coming!
  101. 101. Thank you for your attention!  Contact us anytime with questions  Brian Gongol  DJ Gongol & Associates  515-223-4144  info@djgongol.com
  102. 102. References  Catalog photos of valves are courtesy GA Industries  All other photos are original work by Brian Gongol. All rights reserved.

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