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OBJECTIVES Define: Velocity Discharge Nozzle pressure Nozzle reaction
OBJECTIVES Find Velocity when head is known Velocity when NP is known GPM using the discharge formula Nozzle reaction for smoothbores Nozzle reaction for fog nozzles
Velocity Defined The velocity flow of water is the speed which it passes a certain point in a certain direction. The velocity flow of a stream from a discharge opening is dependent on the NP or Head pressure causing the flow.
Velocity and NP Tests have revealed that the practical working limits for velocity for fire streams are within 60 to 120 feet per second. These limiting velocities are produced by nozzle pressures of 25 to 100psi. IFSTA Pumping Apparatus Driver Operator Handbook. First edition Page 136
Velocity Formulas The fire service uses two velocity formulas: When a nozzle or orifice is used. V = 12.14 NP When head pressure is used. V = 8 H
Velocity (continued Find velocity in feet per second (fps) when head is known. V = 8 H V = 8 H Where H = 85 feet Then V = 8 85 = (8) (9.22) = 73.76 fps
Velocity (continued Find Velocity in feet per second (fps) when NP is known. V = 12.14 NP V = 12.14 NP Where P = 45 psi Then V = 12.14 45 = (12.14) (6.70) = 81.44 fps
Velocity Drill #1 Find the velocity flow fps.
Velocity in FPS without NP Velocity in feet per second formula. V = 8 H V=8 Height = 125 V=8 125 V=(8)(11.18) V=89.44 fps
Velocity Drill #2 Find the velocity flow (feet per second). 2 tip at 80psi NP
Velocity in FPS with NP Velocity in feet per second formula with NP V = 12.14 NP V=12.14 NP=80 V= (12.14)( 80) V=(12.14)(8.94) V=108.53fps
Velocity Activities Practical Activity Sheet 7-1 Figure the velocity for problems 4 and 5 (U.S.) that means not metric. Not the discharge- the velocity. Practical Activity Sheet 6-2 Figure the velocity for problems 1 and 2 (U.S.) that means not metric. Not the discharge- the velocity.
Velocity (Cont ) Why is Velocity important? For every action there is an equal and opposite reaction. Velocity will create force which leads to nozzle reaction.
Determining Flow From a Solid Stream Nozzle Solid stream Stream from a fixed orifice. Opening is no more than 1/2 the diameter of the hose on hand lines. The velocity of the stream (nozzle pressure) and the size of the discharge opening determine the flow (gallons per minute). Nozzle pressure is generally 45psi for handlines and 80psi for masterstreams.
The Discharge Formula GPM = 29.72D 2 NP Where: GPM = Discharge in gallons per minute 29.72 = A constant D = diameter of orifice in inches NP = Nozzle pressure in pounds per square inch IFSTA Pumping Apparatus Driver Operator Handbook. First edition Page 127
Developing the GPM Formula The discharge formula is related to: Area of the opening Velocity of flow Cubic inches in a gallon Discharge = AV Where A = area of the opening A =.7854D 2 V= velocity of flow V= 12.14 P
Developing the GPM Formula (continued) Discharge = AV 231 231= cubic inches in one gallon Where A =.7854D 2 V= 12.14 P x 720 Then Discharge = (.7854D 2 )(12.14 P x720) 231 = 29.72D 2 P 720= inches per minute.
Using the GPM Formula Using the formula for an 1 1/8 tip @ 45 psi NP GPM = 29.72 D2 x NP GPM = 29.72 (1.125 x 1.125) x 6.70 = 29.72 x 1.26 x 6.70 = 250.72 gpm On the fireground we use 250 gpm.
Nozzle Reaction
Nozzle Reaction Nozzle Reaction: Counter-force directed against the firefighter holding the nozzle, or a device holding the nozzle, by the velocity of water being discharged. Newton s Third Law of Motion: For every action there is an equal and opposite reaction...
Nozzle Reaction (continued) Two formulas: NR = 1.57D 2 x NP (for smoothbores) NR =.0505 X GPM x NP (for fogs)
NR for a smooth bore Find for NR = NR = 1.57D 2 x NP NR = 1.57(1.25 x 1.25) x 45 1.57 x 1.56 x 45 = 110.21 pounds
Nozzle Reaction for a 75 psi Fog Nozzle Find for NR =.0505 X GPM x NP 75 psi fog Liveline 150 gpm NR =.0505 X 150 x NP NR =.0505 X 150 X 8.66 NR = 65.59 pounds
Nozzle Reaction for a 100psi Fog Nozzle Find for NR =.0505 X GPM x NP 100 psi fog Liveline 150 gpm NR =.0505 X 150 x NP NR =.0505 X 150 X 10 NR = 75.75 pounds Or...
Nozzle Reaction for a 100psi Fog Nozzle Find for NR = 1/2 GPM 100 psi fog Liveline 150 gpm NR = 1/2 x 150 (GPM) NR = 75 Pounds
Summary Name these formulas!! GPM = 29.72 D 2 x NP NR = 1.57D 2 x NP V = 8 H NR = 1/2 GPM V = 12.14 NP.0505 X GPM x NP
Question # 1 50 feet 50 feet Find the velocity flow fps.
Question # 2 1 1/8 tip @ 45 psi NP Find the velocity flow fps.
Question # 3 1 3/4 tip @ 80 psi NP Find the Discharge.
Question # 4 1 3/4 tip @ 80 psi NP Find the Nozzle Reaction.
Question # 5 100 psi NP Fog flowing 800 gpm Find the Nozzle Reaction.
Question # 1 V = 8 H 50 feet V = (8)(7.07) V = 56.56
Question # 2 1 1/8 tip @ 45 psi NP V = 12.14 NP V = 12.14 NP Where P = 45 psi Then V = 12.14 45 = (12.14) (6.7) = 81.33 fps
Question # 3 1 3/4 tip @ 80 psi NP GPM = 29.72D 2 NP =29.72 x 3.06 x 8.94 = 813.03 gallons
Question # 4 1 3/4 tip @ 80 psi NP NR = 1.57D 2 x NP =1.57 x 3.06 x 80 = 384.33 pounds
Question # 5 100 psi NP Fog flowing 800 gpm NR =.0505 x GPM x NP =.0505 x 800 x 10 = 404 pounds NR = 1/2 GPM
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