Fire Commander Fire Extinguishing Water Calculation

I. Fire water consumption calculation: Q=Aq

Note: A is the burning area of ​​the fire, q---the intensity of the fire extinguishing water supply, generally 0.15 L / (S · m 2 ) , the high-rise building is 0.2 L / (S · m 2 ) , the underground confined space and the cotton fiber products are taken 0.3 L / (S · m 2 )

Example: A fire occurred in a residential building of 100 square meters . Try to calculate the amount of fire water used.

Solution: The fire extinguishing water supply intensity of residential buildings takes 0.15 L / (S · m 2 ) ,

The fire water quantity of the fire site Q , according to the formula Q=Aq=100 m 2 *0.15 L/(S · m 2 )=15L/S

Second, the water pressure loss calculation: hd = SQ2

Note: HD --- Pressure loss per 20 m of hose, each hose impedance is S ---, --- the water with a flow Q, Φ 65mm impedance factor S = 0.035, Φ 80mm impedance factor S = 0.015

Example: One hand lifts the pump to absorb water from the natural water source, and uses 10 Φ 65mm plastic hoses to supply water for 1 Φ 19mm water gun. The water column of the water gun is required to be not less than 15m . Calculate the pressure loss of the water supply mains.

Solution: It is known that the impedance coefficient of the Φ 65mm rubber hose is 0.035 .

When the Φ 19mm water gun is filled with a water column of 15m , the flow rate at the nozzle of the water gun is 6.5L /s .

The pressure loss of the hose is Hd=nSQ2=10 × 0.035 × 6.52=14.8 ( 104Pa )

Third, the fire truck water supply calculation:

( 1 ) Known water guns and hose lines for the export pressure of fire engines: Hb=hq+hd+h1-2

Note: Hb --- Fire pump outlet pressure, hq --- pressure at the nozzle

HD --- water mains with a pressure loss, h1-2 --- elevation difference

Example: a fire engine from a natural water source, water absorption, using 10 enrich the water column in the water Φ 65mm plastic strip is a water gun Φ 19mm, outdoor fire fighting, gun requires not less than 15m, flat water to the fire. Try to calculate the pump outlet pressure.

Solution: If the water source is flat to the fire, H1-2=0.

When the water pressure of the Φ 19mm water gun is 15m and the pressure and flow at the nozzle of the water gun are 27 × 104Pa and 6.5L /s respectively, the pressure loss of each hose is 1.48 × 104Pa . The pressure loss of the 10 hoses is: Hd =10 × 1.48=14.8 ( 104Pa ) or the impedance coefficient of the hose in Φ 65mm is 0.035 .

When the Φ 19mm water gun is filled with a water column of 15m , the flow rate at the nozzle of the water gun is 6.5L /s .

Then Hd=nSQ2=10 × 0.035 × 6.52=14.8 ( 104Pa )

The pressure loss calculated by the above two methods was 14.8 × 104Pa .

Fire truck water pump outlet pressure: Hb=hq+hd+H1-2=27+14.8+0=41.8 ( 104Pa )

( 2 ) Calculation of maximum water supply distance for fire engines: Sn= ( r Hb-hq-H1-2 ) /hd

Note: Sn --- the maximum water supply distance of the fire truck (how many lengths of the hose), r --- the coefficient of use of the pump lift pump, generally take 0.6 ~ 0.8 , Hb --- fire pump pump head (outlet pressure), --- gun nozzle pressure at HQ, H1-2 is --- elevation difference, the pressure loss of each hose. HD ---

Example: CG36/40 fire truck, pump head is 120 × 104Pa , with Φ 90mm rubber hose in single trunk water supply, the supply of 2 Φ 19mm water gun is 15m , and the water source is flat to the fire site. Calculate the maximum water supply distance for the fire truck relay.

Solution: When the Φ 19mm water gun is filled with a water column of 15m , the outlet pressure is 10 × 104Pa , and the flow rate of each water gun is 6.5L /s . The flow rate of the two water guns is 13L /s .

When the flow rate of the hose in the Φ 90mm adhesive is 13L /s , the pressure loss of each hose is 1.35 × 104Pa (also calculated by the hose pressure loss formula hd = SQ2 ).   If the water source reaches the fire site with a flat potential , the elevation H1-2=0 . The maximum relay water supply distance for CG36/40 fire engines is:

Sn = ( r Hb-hq-H1-2 ) /hd = ( 120-10-0 ) /1.35 = 81.48 (Articles) 81 items are actually used .

The water supply distance is 81X20=1620 meters .

Answer: The maximum water supply distance for the fire truck relay is 81 hose lengths, 1620 meters .

( 3 ) Calculation of maximum water supply height for fire engines: H1-2=Hb-hq-hd

Note: H1-2---The height of water supply for fire engines, Hb---The pump lift for fire engines,

Hq --- nozzle pressure at the water gun, hd--- pressure loss in the hose system

Example: A fire broke out in a high-rise building. The fire truck was parked at a fire hydrant 20 meters away from the building . The fire truck was a CG36/40 type fire truck with a pump head of 120 × 104Pa . The hose was supplied with a Φ 90mm rubber hose in a single trunk line. , The supply of 2 Φ 19mm water guns is 15m . Calculate the maximum water supply for the fire truck.

Solution: When the Φ 19mm water gun is filled with a water column of 15m , the outlet pressure is 10 × 104Pa , and the flow rate of each water gun is 6.5L /s . The flow rate of the two water guns is 13L /s .

When the flow rate of the hose in the Φ 90mm adhesive is 13L /s , the pressure loss of each hose is 1.35 × 104Pa (also calculated by the hose pressure loss formula hd = SQ2 ). If the fire truck is 20 meters away from the fire , the pressure loss on the horizontal laying of the water belt is a loss of one belt, hd is 1.35 x 104Pa . The maximum height of CG36/40 fire engines is:

H1-2=Hb-hq-hd=120×104Pa-10×104Pa-1.35×104Pa

=108.65×104Pa=1.0865×106Pa=1.0865M Pa

According to pressure formula: P= ρ gh

A standard atmospheric pressure of about 1.01 × 105Pa or 10.3 m of water,

H1-2 = 1.0865 × 106Pa / 1.01 × 105Pa = height of 10.7 atmospheres, about 110 m high water column.

Answer: The maximum water supply for the fire truck is 110 meters .

(4) the estimated water height: â‘  H = 100 (Hb- Hq) ( MPa when the pressure is uniform units)

Note: H is the water supply height in m , Hb is the pressure at the pump outlet, Hq is the pressure at the water gun outlet, and 10 m is the estimated water supply height at 0.1 MPa .

Example: A fire truck with a water pump head of 120 × 104Pa is supplying water to a high-rise building. The pressure at the water gun mouth is not less than 10 × 104 Pa . Estimate the maximum water supply of the fire truck.

Solution: fire pump head Hb is 120 × 104Pa = 1.2 × 106Pa (i.e. we are talking about 12 kilograms or pressure 1.2MPa), Hq gun outlet pressure is 10 × 104Pa = 0.1 × 106Pa (i.e. we are talking about 0.1MPa Or 1 kg pressure )

H=100 (Hb-Hq) =100 (1.2MPa-0.1MPa)=10X1.1=110 meters

Answer: The maximum water supply for the fire truck is about 110 meters .

2 P= Hq +0.04* (N-2)MPa

Note: Hq is the pressure at the outlet of the water gun, N is the number of floors, and 0.04 is the coefficient.

Fourth, the fire field transport vehicle calculation

N=(t1+t2+t3)/T+I(3)

Note: N---The number of water trucks required to ensure uninterrupted water supply for 1 vehicle at the fire site , t 1--- water truck time, t 2--- transport time for water on fire, t 3- - Return time on the way to the water truck, T---1 time when pot water is used on the fire

Example: A fire site is far away from the source of water and it needs a water truck to carry water from a water source. If the tanker watering time is 2 minutes, the transfer time of the water on the fire site is 1 minute, the return time of the water tanker is 12 minutes, and the use time of 1 pot of water on the fire site is 3 minutes, so as to ensure uninterrupted water supply to the fire site. The number of water trucks needed.

Fifth, the fire pipe network water supply capacity calculation :

( 1 ) Calculation of water flow in the pipe network: Q=0.0008D 2 v

Note: Q--- The flow of water in the ring pipe network, D---the diameter of the ring pipe, and v- the flow rate of the fire water supply pipe, generally 1.5m /s to 2.5m /s , and the branch shape to take 1m /s.

( 2 ) Calculation of water flow in the pipe network: Q=0.5 D 2 V

Note: Q--- The flow of water in the ring pipe network, D---the diameter of the ring pipe, the unit is inches, the diameter mm /25 converts the inch, v---the fire water supply pipe flow rate, generally take 1.5m /s ~ 2.5m /s , branch 1m /s .

( 3 ) Pipeline water supply capacity calculation: N=Q/Q car

Note: N--- The water supply capacity of the annular pipeline is the number of available fire engines; Q--- The flow of the annular pipeline water, Q truck --- The quantity of water supplied by each fire engine

Example 1: an annular duct fire Φ 300mm, the water pressure in the pipeline is not less than 0.2MPa. If the flow of a certain type of fire engine on the fire site is 40L /s , try to calculate the number of fire engines that can be parked on the pipeline.

Solution: The ring pipe v = 1.5m/s , then the flow of the pipe is:

Q=0.0008D2v=0.0008×3002×1.5=108L/s

N=Q/Q vehicle =108/40=2.7 (vehicle) Actual use to take 2 vehicles

Answer: The number of fire engines that the pipeline can park is 2 vehicles.

Estimation method: Q=1/2vD2=1/2 × 1.5 × (300/25) 2=108 L/s

N=Q/Q car =108/40=2.7 (vehicle)     Actual use of 2 vehicles

Sixth, the fire field water supply power calculation:

( 1 ) Calculation of control area for water gun: f=Q/q

Note: f --- the control area of each water gun , Q --- the flow rate of each water gun, q --- the water supply intensity of fire extinguishing water, which is generally 0.2 L / (S · m 2 ) , and 0.2 L / for high-rise buildings. (S · m 2 ) , underground confined space and cotton fiber products take 0.3 L / (S · m 2 ) Example : A LED LANTERN

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