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Smooth Bore Nozzles vs. Combination Nozzles How is a fire stream best formed?

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Presentation on theme: "Smooth Bore Nozzles vs. Combination Nozzles How is a fire stream best formed?"— Presentation transcript:

1 Smooth Bore Nozzles vs. Combination Nozzles How is a fire stream best formed?

2 Smooth Bore Nozzles Advantages:  Simple in design  Inexpensive Disadvantages:  Has only one correct operating pressure to develop optimum velocity and reach  Tip size must be changed to change flow  Must have variety of tips for different flows  No fog capabilities  Not effective for mechanical ventilation Advantages:  Simple in design  Inexpensive Disadvantages:  Has only one correct operating pressure to develop optimum velocity and reach  Tip size must be changed to change flow  Must have variety of tips for different flows  No fog capabilities  Not effective for mechanical ventilation

3 Unequal Velocity of Smooth Bore  Greater velocity at center of stream  Lower velocity at outside of stream  Caused by side wall turbulence  Causes outside of stream to “peel” away  Less reach than straight stream from combination nozzle Side Wall Friction Center "core" at higher velocity than outer circle of stream. Stream expansion begins upon exiting tip

4 Equal Velocity of Combination Nozzle  Equal velocity across stream  Partial vacuum within the pattern focuses stream a short distance from the nozzle  Re-converged stream has a uniform cross-sectional velocity  Tighter stream with more reach than smooth bore Partial Vacuum Water exits nozzle at EQUAL velocity and pressure Focused Point

5 Equal Velocity of Combination Nozzle Partial Vacuum Water exits nozzle at EQUAL velocity and pressure Focused Point

6 At Equal Flows... Which stream has more reach?

7 At Equal Flows... Combination Nozzle Reaches Farther Than Smooth Bore Nozzle

8 Straight Stream From Combination Nozzle...  Because of higher nozzle pressure & velocity than smooth bore, combination nozzle stream hits harder  Not hollow as seen by Pitot gauge pressure reading at focal point

9 Impact Force of Stream F = M V Force = Mass times Velocity Force = Mass times Velocityor WV WV g M = Mass of water /unit of time V = Velocity of water /unit of time W = Weight of water /unit of time W = Weight of water /unit of time g = Gravitational constant 32.2 ft/sec 2 F = M V Force = Mass times Velocity Force = Mass times Velocityor WV WV g M = Mass of water /unit of time V = Velocity of water /unit of time W = Weight of water /unit of time W = Weight of water /unit of time g = Gravitational constant 32.2 ft/sec 2 F =

10 Impact Force of 150 GPM Stream... WV WV 32.2 ft./sec ft./sec. 2 W = 150 GPM x 8.34 lb./gal = 1251 lb./min. W = 1251 lb./min. divided by 60 sec./min. W = lb./sec. V = 150 GPM 7/8” Smooth 44 psi = 80 ft./sec. (54.5 MPH) Combination 75 psi = ft./sec. (72.9 MPH) Combination 100 psi = 121 ft./sec. (82.5 MPH) WV WV 32.2 ft./sec ft./sec. 2 W = 150 GPM x 8.34 lb./gal = 1251 lb./min. W = 1251 lb./min. divided by 60 sec./min. W = lb./sec. V = 150 GPM 7/8” Smooth 44 psi = 80 ft./sec. (54.5 MPH) Combination 75 psi = ft./sec. (72.9 MPH) Combination 100 psi = 121 ft./sec. (82.5 MPH) F =

11 Comparison of 150 GPM Nozzle TypeNozzle PressureVelocity  7/8” Smooth Bore 44 psi54.5 mph  Combination Nozzle 75 psi72.9 mph  Combination Nozzle100 psi82.5 mph Nozzle TypeNozzle PressureVelocity  7/8” Smooth Bore 44 psi54.5 mph  Combination Nozzle 75 psi72.9 mph  Combination Nozzle100 psi82.5 mph

12 7/8” Smooth 44 psi lb./sec. x 80 ft./sec lb./sec. x 80 ft./sec ft./sec ft./sec. 2 Combination 75 psi lb./sec. x ft./sec lb./sec. x ft./sec ft./sec ft./sec. 2 Combination 100 psi lb./sec. x 121 ft./sec lb./sec. x 121 ft./sec ft./sec ft./sec. 2 7/8” Smooth 44 psi lb./sec. x 80 ft./sec lb./sec. x 80 ft./sec ft./sec ft./sec. 2 Combination 75 psi lb./sec. x ft./sec lb./sec. x ft./sec ft./sec ft./sec. 2 Combination 100 psi lb./sec. x 121 ft./sec lb./sec. x 121 ft./sec ft./sec ft./sec. 2 F = = 51.8 lb. Force F = = 69.2 lb. Force F = = 78.3 lb. Force Comparison of Impact 150 GPM

13 Comparison of Nozzle Reaction 150 GPM Nozzle Nozzle Pressure Reaction Force  7/8” Smooth 44 psi52.8 lb. force  Combination 75 psi67.5 lb. force  Combination 100 psi79.2 lb. force Nozzle Nozzle Pressure Reaction Force  7/8” Smooth 44 psi52.8 lb. force  Combination 75 psi67.5 lb. force  Combination 100 psi79.2 lb. force

14 Impact Force & Velocity...  Combination nozzle has higher velocity  Smooth Bore has lower velocity  Higher velocity with same flow equals more force  Therefore, harder hitting stream is typically realized from combination nozzle at higher pressure  Combination nozzle has higher velocity  Smooth Bore has lower velocity  Higher velocity with same flow equals more force  Therefore, harder hitting stream is typically realized from combination nozzle at higher pressure

15 Stream Impact Testing...  Flow of 160 GPM (typical of smooth bore & combination nozzles)  Differing distances and target sizes used  Flows & Pressures closely monitored for valid test results  Results: Harder hitting, farther reaching stream from combination nozzles because of higher stream velocity


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