# Water Supply Analysis

1.16 The circular clapper on the water side of a dry pipe sprinkler valve has a diameter of 4 inches (10 cm). What force will be acting on this clapper due to a water pressure of 72 psi (5 bar)?

1.17 The circular clapper on the air side of a dry pipe sprinkler valve has a diameter of 10 inches (25 cm). What force will be acting on this clapper due to an air pressure of 40 psi (3 bar)?

1.18 If 4-inch (100 mm) Schedule 40 sprinkler piping has an actual inside diameter of 4.026 inches (102.3 mm). how many gallons (liters) of water could be contained in 135 feet (40 meters) of this pipe? How much would the water in this pipe weigh?

1.19 If 1-inch (25 mm) Schedule 40 sprinkler piping has an actual inside diameter of 1.049 inches (26.6 mm), how many gallons (liters) of water will 800 feet (240 meters) of this pipe hold? How much would the water in this pipe weigh?

1.20 It is commonly desired to keep water velocities in automatic sprinkler systems below 20 feet per second (fps) (6 m/s). How many gallons per minute (liters per minute) would be represented by a water velocity of 20 fps (6 m/s) in 1-inch (25 mm) pipe with an actual inside diameter of 1.049 inches (26.6 mm)?

Selected answers found on page 347.

Chapter 1 • Fire Protection Hydraulics and Water Supply Analysis 13

Chapter Two Exercises 2.1 If an elevated tank containing water is 85 feet (26 m) high, wha: :::·2ss _ ·=

will exist at the base of the tank if the tank is fu ll? 2.2 If a spherical water storage tank has a diameter of 50 feet (1 5 rr,1. ::- :

the top of the tank is 106 feet (32 m) above the ground, w hat pressw ·= exists at ground level when the tank is full?

2.3 If a tank of identical height as the tank in Exercise 2.1 is constructed with twice the volume, how does this affect the pressure ava ilable at the base of the tank?

2.4 If a tank of identical height as the tank in Exercise 2.2 is constructed with a diameter of 75 feet (23 m), how does this affect the pressure at ground level?

2.5 If a high-rise building is 108 feet (33 m) tall, how much pressure must be available at ground level to overcome elevation and deliver the 100 psi (6.9 bar) standpipe water pressure requirement at the roof ?

2 .6 If the standpipe in Exercise 2.5 is attached to a city water main and filled with water, what pressure will exist at the roof level if the pressure at ground level is 127 psi (9 bar)?

2.7 A 500,000 barrel crude oil storage tank is 46 feet (14 m) high. If the tank is full and the oil has a specific gravity of 0.89, what pressure will exist at the base of the tank?

2.8 A tank containing 200,000 gallons (750 m3) of regular gasoline is 32 feet (10 ml high. If the tank is full, what pressure in psi (bar) will exist at the base of the tank?

2.9 In the hydraulic system shown in Figure 2.15, what force (F 2

) must be applied to attain a state of equilibrium if the circular surface upon which F, acts has a diameter of 6 inches (15 cm), t he circular surface acted upon by F

2 has a diameter of 18 inches (46 cm), and F, is 85 pounds (39 kg)?

Figure 2.15 Illustration for Exercise 2.9.

2.10 In a dry-pipe sprinkler valve, the air seat typically has a surface area on

which the air pressure acts six t imes as large as the water seat upon which the water pressure acts. If the water pressure is 105 psi (7.2 bar). what air pressure is required to attain a state of equilibrium?

2.11 In a multiple-story building, a water column has formed on the top side of a dry-pipe sprinkler valve having a 6:1 air seat to water seat ratio. If the column of water is 42 feet (12.8 ml high, and the city water pressure is 60 psi (4.1 bar). will the dry valve be able to open when the air pressure is evacuated from the system?

Chapter 2 • Fire Protection r. . .:-=- =~ =..- : .= .. -;– .: – – – :. – –

2.12 In Figure 2.16, the w eighr of 1:he upper piston (W) is 85 pounds (39 kg) and has a surface area of 113 in” 1729 cm1 ) . The w e ight (W

2 ) of the lower

piston is 14 pounds (6 kg) and has a surface area of 12.6 in2 (81 cm2 ). If the liquid in the hydraulic system is an oil with a specific gravity of 0.90, what force (F) will be required to atta in a state of equilibrium?

Figure 2.16 Illustration for Exercise 2.12.

F

12 inches (30 cm)

_______ __!

2.13 If the industrial fire pump (Figure 2.17) is developing 270 feet (82 m) of head at the discharge port of the pump (Point A), what pressures in psi (bar) will be indicated by the gauges at Points B. C, and D?

Figure 2.17 Illustration for Exercise 2.13 and 2.20.

105 feet (32 m)

L __

B

55 feet (17 m)

l __ D

c . ✓

2.14 If a system contains an oil with a specific gravity of 0.87, what height in inches (cm) on a piezometer tube would indicate a pressure of 1.0 psi (0.07

bar)?

34 Chapter 2 • Fire Protection Hydraulics and Water Supply Analysis

d= 10 inches – {25.4cm) 25 feet

(7.6 m)

8 feet {2.4 m)

__ L

2.15 In Figure 2.18, the liquid contained in the system is water. What is t he pressure reading on Gauge Pin psi (bar) if W

1 is 1,500 pounds (680 kg)

and F1 is 1,000 pounds (450 kg)? What force (F 2) would be required to achieve equilibrium? Assume both cylinders have circular cross sect ions.

2.16 A cargo ship has a volume of 480,000 ft3 (13,590 m 3) . The sh:o 2Icne weighs 800,000 pounds (360,000 kg). What weight of cargo car : rie s” ·o carry and still remain afloat? Assume the ship is to be used in ccsc- water (w = 64 lb./ft3 and 1.026 g/cm3).

2.17 A barge with a rectangu lar cross section of 40 feet (12 m) w ide by – : feet (3 ml high is used on the Mississippi River for transporting oil. If :he: barge is 60 feet (18 m) long, how much does it w eigh when empty if 7 feet (2 m) of the barge extends above the water surface? How much of the barge would extend above the water surface if half full of oil (Sg = 0.9)?

2.18 If a man is placed into a completely full container of water and his body causes 24.9 ga llons (94 liters) of water to run over the top, how much does the man weigh?

2.19 If a solid sphere of some material has a diameter of 15 in. (38 cm) and weighs 2 lb. (0.9 kg), what is the specific weight of the material and what percent of the sphere’s volume extends above the surface if placed in a vat of water?

2.20 In Figure 2.17, if Point C is at ground level. calculate the total potential energy in feet (meters) of water existing at all fou r gauge locations.

Selected answers found on page 347.

Figure 2.18 Illus:·,;: : – for Exercise 2.15.

Chapter 2 • Fire Protection Hydraulics a-c • ·. :::=· :; _:: . 2.-; .-: ~ 35