Page 125 - Water Engineering Hydraulics, Distribution and Treatment

2
From Table 4.13, column Type I-A, for 70,960 ft ,
Fire flow = 3000 gpm and duration = 3h.
2
From Table 4.13, column Type I-B, for 70,960 ft ,
Fire flow = 7,250 gpm and duration = 4h.
Combined fire flow for the two buildings connected together
= 0.3095 × 3,000 + 0.6905 × 7,250 = 5,934 gpm
Select duration = 4h.
Solution 2 (SI System):
2
a. Area occupied by the four-story building = 4 (510) = 2,040 m = 21,960 ft 2 4.4 Variations or Patterns of Water Demand 103
From Table 4.13, column Type V-B,
3
Fire flow = 4,000 gpm = 15.14 m /min and duration = 4h.
2
b. Area occupied by the five-story building = 5 (910) = 4,550 m = 49,000 ft 2
From Table 4.13, column Type I-A,
3
Fire flow = 2,500 gpm = 9.46 m /min and duration = 2h.
2
2
c. Total area of two buildings = 2,040 + 4,550 = 6,590 m = 70,960 ft .
Fractional area of the four-story building = 2,040/6,590 = 0.3095.
Fractional area of the five-story building = 4,550/6,590 = 0.6905.
2
From Table 4.13, column Type I-A, for 70,960 ft ,
Fire flow = 3,000 gpm and duration = 3h.
2
From Table 4.13, column Type I-B, for 70,960 ft ,
Fire flow = 7,250 gpm and duration = 4h.
Combined fire flow for the two buildings connected together
3
0.3095 × 3,000 + 0.6905 × 7,250 = 5,934 gpm = 22.46 m /min.
Select duration = 4h.

EXAMPLE 4.5 DETERMINATION OF FIRE FLOW BASED ON COMMUNITY POPULATION
Estimate the fire flow requirement of a community with a population of 121,000.

Solution 1 (US Customary System):

0.5
0.5
Q fire = 1,020(P ) [1 − 0.01(P ) ]
k
k
0.5
0.5
= 1,020(121) [1 − 0.01(121) ]
= 9,986 gpm.
Solution 2 (SI System):
0.5
Q fire = 3,860.7(P ) [1 − 0.01(P )0.5]
k
k
0.5
0.5
= 3,860.7(121) [1 − 0.01(121) ]
3
= 37,796.25 L∕min(or37.796 m ∕min).