Chapter 03


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Chapter 03

  1. 1. Water Supplies for Fire Protection Systems Chapter 3
  2. 2. Learning Objectives <ul><li>Define the terms pressure, flow, and duration as they relate to the movement of water </li></ul><ul><li>Identify and describe the components of a water supply and distribution network </li></ul><ul><li>Discuss the difference between a municipal/public water system and private water system </li></ul>
  3. 3. Learning Objectives (continued) <ul><li>Describe how gravity, pumped, and combined supply systems operate </li></ul><ul><li>Define friction loss and discuss how it affects water flow </li></ul><ul><li>Define static pressure and residual pressure </li></ul><ul><li>List and discuss the characteristics of the two types of NFPA-approved stationary fire pumps </li></ul><ul><li>Define churn, rated performance, and peak performance </li></ul>
  4. 4. Introduction <ul><li>Some areas have access to ground and surface water sources </li></ul><ul><ul><li>Other areas have only one source of water available </li></ul></ul><ul><li>Demand for water changes by day, week, month and year </li></ul><ul><ul><li>Engineers determine community’s demands </li></ul></ul><ul><li>Water-based fire protection depends on water pressure, flow, and duration </li></ul><ul><ul><li>Must be adequate to support proposed design </li></ul></ul>
  5. 5. Water Supply Systems <ul><li>Most water supply systems divided into source/supply network and distribution network </li></ul><ul><li>Components of the source/supply network: </li></ul><ul><ul><li>Water source, water intake, pumping </li></ul></ul><ul><ul><li>Treatment, purification system, transmission mains </li></ul></ul>
  6. 6. Water Supply Systems (continued) <ul><li>Components of the distribution network: </li></ul><ul><ul><li>Water storage facilities, distribution pumps, water distribution mains </li></ul></ul><ul><li>Municipal public water systems responsible for water system supply </li></ul>
  7. 7. Source/Supply Network <ul><li>Gravity system: water at a higher elevation than the location it serves </li></ul><ul><ul><li>Eliminates the need for pumping equipment </li></ul></ul><ul><li>Pumped system: lower elevation than the location it serves </li></ul><ul><ul><li>Water from a well, or from a surface source </li></ul></ul><ul><li>Combined system: pumps fill water towers </li></ul><ul><ul><li>Feed water distribution system by gravity </li></ul></ul><ul><li>Majority of systems treat and purify the water </li></ul>
  8. 8. Figure 3-1 Gravity-fed water distribution system
  9. 9. Figure 3-2 Direct pump water distribution system
  10. 10. Figure 3-3 Combination gravity-pumped water distribution system
  11. 11. Distribution Network <ul><li>Water purveyor treats water to make it potable </li></ul><ul><li>Treated water flows into distribution system water main piping network </li></ul><ul><ul><li>Transmission mains, distribution mains, service laterals/lines </li></ul></ul><ul><li>Transmission mains: very large piping that transport the bulk of the water </li></ul><ul><li>Distribution mains transport water from transmission mains to smaller areas </li></ul>
  12. 12. Distribution Network (continued) <ul><li>Service laterals/lines take water from distribution mains to individual properties </li></ul><ul><ul><li>Supply fire hydrants and water storage facilities </li></ul></ul><ul><li>Water flows from different directions connected in loops and grids </li></ul><ul><ul><li>Minimizes service interruption and improves reliability </li></ul></ul><ul><li>Fire lines or fire mains describe service laterals/lines that feed fire protection systems </li></ul><ul><ul><li>In many jurisdictions, no other lines can connect </li></ul></ul>
  13. 13. Figure 3-4 Schematic of grid or looped piping
  14. 14. Distribution Network (continued) <ul><li>Water in sprinkler system stagnates and must be kept separate from domestic lines </li></ul><ul><ul><li>Must provide adequate flow, pressure and duration </li></ul></ul><ul><li>Developer or property owner responsible for installation of new water and fire mains </li></ul><ul><ul><li>Water company taps into distribution line </li></ul></ul><ul><ul><li>Installs a control valve and piping to reach the property line </li></ul></ul><ul><ul><li>Water lines constructed from ductile iron polyvinylchloride and polyethylene plastics </li></ul></ul>
  15. 15. Distribution Network (continued) <ul><li>Approving authority handles all installations, tests, and certification of new water lines </li></ul><ul><ul><li>Water lines on private property the responsibility of the property owner </li></ul></ul><ul><ul><li>Water lines in public right-of-way or easement the responsibility of local jurisdiction </li></ul></ul><ul><li>Fire flow : number of gallons of water per minute needed to fight a fire </li></ul><ul><li>If amount of water inadequate, need larger lines or looping of dead-end mains </li></ul>
  16. 16. Water Distribution System Valves <ul><li>Two types of valves: </li></ul><ul><ul><li>Control the water flow </li></ul></ul><ul><ul><li>Control the direction of water flow </li></ul></ul><ul><li>Valves that control water flow – public water systems </li></ul><ul><ul><li>Gate valve </li></ul></ul><ul><ul><ul><li>Buried under the street </li></ul></ul></ul><ul><ul><ul><li>Access by removing valve box or roadway box </li></ul></ul></ul><ul><ul><ul><li>Street key, valve key, T-wrench opens the valve </li></ul></ul></ul><ul><ul><ul><li>Usually non-indicating valves </li></ul></ul></ul>
  17. 17. Figure 3-6 Valve box for a non-indicating gate valve feeding a fire hydrant from a water main
  18. 18. Water Distribution System Valves (continued) <ul><li>Valves that control water flow – private water systems: </li></ul><ul><ul><li>Usually indicating valves </li></ul></ul><ul><ul><ul><li>Most are post indicator valves (PIVs) or outside screw and yoke valves (OS&Y) </li></ul></ul></ul><ul><ul><li>PIVs can be gate- or butterfly-type valves </li></ul></ul><ul><ul><li>OS&Y valves are only gate valves </li></ul></ul>
  19. 19. Water Distribution System Valves (continued) <ul><li>Valves that control the direction of water flow </li></ul><ul><ul><li>Check valves and backflow prevention devices </li></ul></ul><ul><ul><ul><li>Prevent water from flowing in the wrong direction </li></ul></ul></ul><ul><ul><ul><li>Prevent potable and non-potable water from mixing </li></ul></ul></ul><ul><ul><li>Check valves have a clapper that swings in the direction of water flow </li></ul></ul><ul><ul><li>Two common backflow prevention devices </li></ul></ul><ul><ul><ul><li>Double check valve assembly </li></ul></ul></ul><ul><ul><ul><li>Reduced pressure principle devices </li></ul></ul></ul>
  20. 20. Water Distribution System Valves (continued) <ul><li>Valves that control the direction of water flow (continued) </li></ul><ul><ul><li>Water purveyors install double detector check valve assembly </li></ul></ul><ul><ul><li>Reduced pressure principle/zone type backflow devices </li></ul></ul><ul><ul><ul><li>Offer best protection </li></ul></ul></ul><ul><ul><ul><li>Install on any water system but are common to systems where hazard levels are higher than normal </li></ul></ul></ul>
  21. 21. Fire Hydrants <ul><li>Provide a point of connection to a water supply </li></ul><ul><ul><li>Support manual firefighting operations </li></ul></ul><ul><li>Upon arrival, firefighters connect fire hoses to outlets on the fire hydrant </li></ul><ul><li>Opening the hydrant and removing the caps requires a hydrant wrench </li></ul><ul><li>Water flows from hydrant through hoses </li></ul><ul><li>Hydrant location and number determined by local building and fire codes </li></ul>
  22. 22. Types of Hydrants <ul><li>Dry barrel and wet barrel most common types of hydrant </li></ul><ul><li>Dry barrel commonly found where temperature drops below freezing </li></ul><ul><ul><li>Water held in the ground below frost line </li></ul></ul><ul><li>Wet barrel has water up in the barrel at all times </li></ul><ul><ul><li>Entire hydrant need not be shut off </li></ul></ul><ul><li>Outlet size varies </li></ul><ul><ul><li>Steamer outlet usually four to four and a half inches </li></ul></ul>
  23. 23. Figure 3-15 Typical schematic of a dry barrel hydrant
  24. 24. Types of Hydrants (continued) <ul><li>Bollards surround hydrants to protect them </li></ul><ul><li>Wall hydrant : installed on the structure </li></ul><ul><li>Flush hydrant : installed in belowground vault </li></ul><ul><li>Yard hydrant : common at industrial facilities </li></ul><ul><li>Hydrants painted a specific color </li></ul><ul><ul><li>Caps and bonnet painted a different color </li></ul></ul><ul><li>Hydrants require different inspections and tests to ensure operability </li></ul><ul><ul><li>Responsibility varies by jurisdiction </li></ul></ul>
  25. 25. Water Flow Tests of Water Supplies <ul><li>May be simple or complex </li></ul><ul><li>Water information obtained from tests is valid for design </li></ul><ul><ul><li>Most water flow test information for new structures comes from fire hydrant flow tests </li></ul></ul><ul><li>Important to perform water flow tests after system installed </li></ul><ul><li>Perform tests at frequent intervals </li></ul>
  26. 26. Water Supply Design Considerations for Water-Based Fire Protection Systems <ul><li>Adequacy of water determined by evaluating: </li></ul><ul><ul><li>Flow </li></ul></ul><ul><ul><li>Pressure </li></ul></ul><ul><ul><li>Duration of water flow test </li></ul></ul><ul><li>When water supply is inadequate, further test determine if there are impairments </li></ul><ul><ul><li>Designer has many parameters to explore </li></ul></ul>
  27. 27. Water Pressurization for Water-Based Fire Protection Systems <ul><li>Many fire protection systems take water directly from the municipal network </li></ul><ul><ul><li>Pressure determined by water purveyor </li></ul></ul><ul><li>Designer must know the static and residual pressure and flow rate at residual pressure </li></ul><ul><li>If residual pressure is inadequate: </li></ul><ul><ul><li>Installation of gravity tanks, pressure tanks, and stationary fire pumps helps to support the design </li></ul></ul>
  28. 28. Gravity and Pressure Tanks <ul><li>Gravity tank : freestanding tank elevated above a community </li></ul><ul><ul><li>Tank capacities can be small or large </li></ul></ul><ul><ul><li>Tanks must be engineered to withstand environmental conditions </li></ul></ul><ul><ul><li>Every foot of elevation exerts a pressure of 0.433 psi </li></ul></ul><ul><li>Pressure tank uses compressed air to push water out of the tank </li></ul><ul><ul><li>Tank sizes range from 2000 – 9000 gallons </li></ul></ul><ul><ul><ul><li>Air is one-third total capacity </li></ul></ul></ul>
  29. 29. Stationary Fire Pumps <ul><li>Fire pump boosts the pressure to desired level </li></ul><ul><ul><li>Delivers a certain amount of flow </li></ul></ul><ul><ul><li>Water supply must be deemed to be capable of meeting demand </li></ul></ul><ul><li>Stationary fire pump part of an assembly that includes the driver and controller </li></ul><ul><li>Three categories of stationary fire pumps: </li></ul><ul><ul><li>Fire pumps </li></ul></ul><ul><ul><li>Booster pumps </li></ul></ul><ul><ul><li>Special fire service pumps </li></ul></ul>
  30. 30. Fire Pump Impairments <ul><li>Fire pumps with an electric driver should be exercised for ten minutes per week </li></ul><ul><li>Fire pumps with diesel drivers should be exercised for 30 minutes per week </li></ul><ul><li>Pump flow-tested by owner annually </li></ul><ul><li>Insufficient water discharge could indicate an obstruction </li></ul><ul><li>Preferable to uncover a problem during testing than during a fire emergency </li></ul>
  31. 31. Summary <ul><li>Water system is divided into supply/source network and distribution network </li></ul><ul><li>Various types of valves control water flow and direction of water flow </li></ul><ul><li>Two common barrel types: dry barrel, wet barrel </li></ul><ul><li>Water flow tests extremely important when designing fire protection systems </li></ul><ul><li>Two types of fire pumps: centrifugal and positive displacement </li></ul>