Fire Protection

Hydraulic Calculations(Wet and Dry Systems)BSSI 1001

John Willden, P.Eng.

Hydraulic Equations

where: Q = USGPM AOP = Area of Sprinkler operations

1500 – 3000 ft2 for light hazard

Density = USGPM/ft2 or water/square foot

Q AOP Density for first sprinkler flow

Hydraulic Equations

where: Q = USGPM K=sprinkler factor p=pressure in psig

Q K p

2Q

p for first sprinkler pressureK

Hydraulic Equations

where: Pf = pressure drop per foot (psig/ft)

Q = USGPM pipe flow

F = friction factor from table

PF = total pressure loss

1.85

fP FQ LPP fF

Hydraulic Example

Ordinary Hazard group 1 we get 0.15 USGPM/ft2

If each sprinkler is covering 130 ft2 we have:

Q =Q = Q = Q =

P =P = P = P = P = Q =

10 ft 10 ft 10 ft 10 ft

1 in1 in1¼ in1½ in

P = Q =

16 ft

Hydraulic Example

Q = Area x Density = 130 ft2 x 0.15 USGPM = 19.5 USGPM

Q =Q = Q = Q =

P =P = P = P = P = Q =

10 ft 10 ft 10 ft 10 ft

1 in1 in1¼ in1½ in

P = Q =

16 ft

p = (Q/K)2

= (19.5/5.65)2

= 11.91 psig

Hydraulic Example

Q = 19.5Q = Q = Q =

P =P = P = P = P = Q =

10 ft 10 ft 10 ft 10 ft

1 in1 in1¼ in1½ in

P = Q =

16 ft

pf = FC120 x Q1.85

= 5.10 x 10-4 x 19.51.85

= 0.124 psig/ft

Hydraulic Example

Q = 19.5Q = Q = Q =

P =11.91P = P = P = P = Q =

10 ft 10 ft 10 ft 10 ft

1 in1 in1¼ in1½ in

P = Q =

16 ft

Pf = pf x L

= 0.124 x 10 ft

= 1.24 psig

Hydraulic Example

Q1 = 19.5Q2 = Q3 =

Q4 =

P1 =11.91P2 =

P3 = P4 = P5 = Q5 =

10 ft 10 ft 10 ft 10 ft

1 in1 in1¼ in1½ in

P = Q =

16 ft

P2 = Pf + P1

= 1.24 + 11.91

= 13.15 psig

Hydraulic Example

Q1 = 19.5Q2 = Q3 =

Q4 =

P1 =11.91P2 =

P3 = P4 = P5 = Q5 =

10 ft 10 ft 10 ft 10 ft

1 in1 in1¼ in1½ in

P = Q =

16 ft

Q2 = K P2 + Q1

= 5.65 13.15 + 19.5

= 20.49 + 19.5

= 39.99 USGPM

Hydraulic Example

Q1 = 19.5Q2 = Q3 =

Q4 =

P1 =11.91P2 =13.15

P3 = P4 = P5 = Q5 =

10 ft 10 ft 10 ft 10 ft

1 in1 in1¼ in1½ in

P = Q =

16 ft

Hydraulic Example

Q1 = 19.5Q2 =39.99 Q3 =

Q4 =

P1 =11.91P2 =13.15

P3 = P4 = P5 = Q5 =

10 ft 10 ft 10 ft 10 ft

1 in1 in1¼ in1½ in

P = Q =

16 ft

Now you try the next sprinkler

wet systems are always full of water they sprinkle when a head opens

TO SPRINKLERS

CHECK VALVE

ALARM VALVE(SPRINKLER VALVE)

INDICATING VALVE

SIAMESE CONNECTION(FIRE DEPARTMENT

CONNECTION)

FROM SERVICE MAIN

Details of Wet System

© 1997, The Viking Corporation

dry systems are full of compressed air they bleed off the air and sprinkle when a head

opens

TO SPRINKLERS

FIRE DEPARTMENT CHECK VALVE

ALARM VALVE(DRY SPRINKLER VALVE)

INDICATING VALVE

SIAMESE CONNECTION(FIRE DEPARTMENT

CONNECTION)

FROM SERVICE MAIN

CHECK VALVE

Dry Pipe System

© 1997, The Viking Corporation

TO SPRINKLERS

CHECK VALVES

ALARM VALVE(PREACTION SPRINKLER VALVE)

INDICATING VALVE

SIAMESE CONNECTION(FIRE DEPARTMENT

CONNECTION)

FROM SERVICE MAIN

CHECK VALVE

preaction systems are full of compressed air until a fire is detected

then they fill with water to get ready

TO SPRINKLERS

CHECK VALVE

ALARM VALVE(PREACTION SPRINKLER VALVE)

INDICATING VALVE

SIAMESE CONNECTION(FIRE DEPARTMENT

CONNECTION)

FROM SERVICE MAIN

CHECK VALVE

deluge systems are empty and the sprinkler heads are open

they all come on at once when a fire is detected

Sprinkler Heads three major types

of sprinkler heads upright pendant sidewall

dry type

http://www.vikingcorp.com/databook/sprinklers/

Sprinkler Arrangements

Tree systems Only one path to

each sprinkler head

Grid systems At least two

paths to each sprinkler head

Loop systems There are two paths to

each sprinkler head but the system can also be used to circulate heating or cooling water

Sprinkler Arrangements – cont’d

pendant

upright

Typical Alarm Valve

Parts of Alarm Valve

Fire Protection Symbols

pendent head – hangs down

upright head – stands up

sidewall head – sticks out sideways

upright (elevation view)

pendent (elevation view)

siamese connection – fire department

check valve

Fire Protection Symbols

ALARM VALVE (wet)

ALARM VALVE (dry)

ALARM VALVE (preaction)

ALARM VALVE (deluge)

flushing connection (flanged)

flushing connection (cap)

open stem and yoke valve (OS & Y)

FC

FC