73584148 Fire Fighting

Fire Fighting Design Case study

Prof. Dr Ali Hammoud

OUTLINE

• Chapter 1: Definitions

• Chapter 2: Fire Fighting Equipments

• Chapter 3: Project Description

• Chapter 4: Hand Calculations

• Chapter 5: Elite Software Calculations

• Chapter 6: WaterCAD Software Calculations

• Chapter 7: Fire Pump Selection

Introduction

Fire protection has three major goals:

• Life safety (minimum standard in fire and building codes)

• Property protection (typically an insurance requirement, or a regulatory requirement where the protection of building components is necessary to enable life safety)

• Continuity of operations (typically an insurance requirement or an item of self-motivation for building owners - not a regulatory issue). Interruption of operations due to fire damage can be very costly.

Chapter 1

Definitions

Fire:

• Fire is the visible heat and light energy

released during a chemical reaction

• Fires start when a flammable and/or a

combustible material with an adequate

supply of oxygen or another oxidizer is

subjected to enough heat and is able to

sustain a chain reaction.

Fire Triangle

Fire is a chemical reaction

involving rapid oxidation of a

fuel. Three things must be

present at the same time in

order to produce fire:

• Fuel

• Oxygen

• Heat

Chemical, exothermic

reaction

Fire Tetrahedron

• chain reaction must

take place

The Critical Stages of Fire

• The incipient period

• The growth period

• The fully developed

stage “ Burning”

• The decay period

Incipient Period

• The incipient period is the pre-fire period before the flames develop. The typical accidental fire begins as a slow growth, smoldering process, which may last from a few minutes to several hours.

• During this period heat generation increases, producing light to moderate volumes of smoke. The characteristic smell of smoke is usually the first indication that an incipient fire is underway.

Growth Period

• The growth period commences with ignition and

ends with 'flashover', which is best thought of as the

transition between the second and third stages.

• In the growth period, most fires spread slowly at first

on combustible surfaces, then more rapidly as the

fire grows, providing radiant feedback from flames

and hot gases to other fuel items.

Fully developed (Burning)

• In fully developed period all combustible

materials will become involved, and flames

will emerge through the upper parts of any

opening (door, window, etc.)

Decay

• The fire is dying out because either the fuel

is burning out or there is insufficient air

supply

• The temperature of the enclosure drops

gradually

Fire Classes

• Class A - Ordinary Combustible

• Class B - Flammable Liquids

• Class C - Electrical Hazards

• Class D - Combustible Metals

• Class K - Cooking Oil or Fat

Class A - Ordinary Combustible

Materials: Ordinary Combustiles

• Wood

• Paper

• Rubber

• Plastic

Extinguishing methods:

• Cooling with water

Class B - Flammable Liquids

Materials:

• Flammable or combustible

fuels

• Liquids

• Gases


• Removing fuel

• Reducing temperature

Class C - Electrical Hazards

Materials:

• Energized electrical

equipment


• Non conducting extinguishing

agent (halon, dry chemicals,

carbon dioxide)

Class D - Combustible Metals

Materials:

• Magnesium

• Titanium

• Zirconium

• Lithium

• Calcium

• Zinc


• Dry powders

Class F - Cooking Oil or Fat

Materials:

• Cooking oils

• Hotter than other typical

combustible liquids.


• Wet chemical extinguisher.

Hazard Classes of Occupancies

The Classes of Occupancies are:

1) Light Hazard.

2) Ordinary Hazard.– Ordinary Group 1 Hazard

– Ordinary Group 2 Hazard

3) Extra Hazard.– Extra Group 1 Hazard

– Extra Group 2 Hazard

Light Hazard

• Combustibility of the contents is low

• Quantity of the combustible is low

• Low rates of heat release

Example:

• Residential

• Hospitals

• Schools

Ordinary Group 1 Hazard

• Combustibility of contents is moderate

• Moderate rates of heat release are expected

Example:

• Bakeries

• Laundries

Ordinary Group 2 Hazard

• Combustibility of contents is moderate to high

• Moderate to high rates of heat release are expected

Example:

• Parking

• Post offices

• Libraries

Extra Group 1 Hazard

• Quantity and combustibility of contents is

very high

Examples:

• Die casting,

• Metal extruding

Extra Group 2 Hazard

• Moderate amounts of flammable or

combustible liquids

Examples:

• Asphalt saturating

• Flammable liquids spraying

• Flow coating

Chapter 2

Fire Fighting Equipments

Fire Control Systems1. Active Control

– Sprinklers

– Fire Extinguishers

– Sensors

2. Passive Control

– Furniture

– Carpets

– Walls

– Floors

Active Protection

Manual or automatic suppression of fire that would:

1. Control and extinguish fires

2. Protect people and surrounding structures from the effects of fire

Passive Protection

Materials by nature of design, or physical arrangement would:

1. Resist damage due to heat and flame

2. Resist or prevent the spread of heat, smoke and flame.

3. Facilitate the safe evacuation of people

4. Aid fire-suppression operations

Manual Fire Suppression

• Fire hose reels

• Standpipe system

• Portable extinguishers

Hose Reel

• Nominal diameter : 2.5 in

• Temperature range: -20 to

50°C

• Hose Length: not less than

32 m.

• FHC Spacing between two

adjacent: 20 m

• Minimum allowable hose

diameter is 1 in at the flow

rate of 33 gpm.

Portable Extinguishers

• Portable fire extinguishers are

intended as a first line of defense

to cope with fires of limited size

• Use CO2 extinguisher in rooms

containing electrical equipments

• Use dry chemical fire extinguisher

for remaining areas

• Fire extinguishers used shall not

exceed 12 kg

Stand Pipe System

• A standpipe is a type of rigid water piping

which is built into multi-story buildings in a

vertical position, to which fire hoses can be

connected, allowing manual application of

water to the fire. Within buildings standpipes

thus serve the same purpose as fire

hydrants.

Dry standpipe system • A "dry" standpipe is a pipe

extending into a building that

can be used by the fire

department to supply fire

fighting water to the interior of

the structure.

• The pipe is fixed, located near a

road or driveway so that a fire

engine can supply water to the

system.

Wet standpipe system

• A "wet" standpipe, on the

other hand, is filled with

water and is pressurized at

all times.

• wet standpipes may be used

by building occupants.

• they come with hoses so

that building occupants may

fight fires quickly.

System Component Definitions

• Branch Lines: The pipes in which the sprinklers are

placed, either directly or through risers.

• Cross Mains: The pipes supplying the branch lines,

either directly or through risers.

• Feed Mains: The pipes supplying cross mains,

either directly or through risers.

• Risers: The vertical supply pipes in a sprinkler

system.

System Component Definitions

Sprinkler Systems

• There are 3 systems:

1. Tree System

2. Grid System

3. Looped System

Tree System

• It is a system of dead-end

branch lines that is centrally

fed by a cross main. The

cross main is the pipe that

supplies water to the branch

lines, Long branch lines

should, if possible, be fed so

that the cross main is

equidistant from the ends of

the branch lines.

Grid System

• A grid is a system of branch

lines interconnected by

cross main on both ends of

the branch lines. A grid can

be used only for wet pipe

systems to provide a

hydraulic advantage for

systems with numerous

branch lines by providing

water flow to sprinklers from

more than one direction.

Looped System

• A looped system connects

cross mains at two or more

locations. This arrangement

can provide a hydraulic

advantage over the

traditional tree system by

providing water flow to

sprinklers from more than

one direction. It is used for

wet & dry systems.

Type of Sprinklers Head

• Pendent Sprinkler: A sprinkler designed to

be installed in such a way that the water

stream is directed downward against the

deflector.

• Upright Sprinkler: A sprinkler designed to be

installed in such a way that the water spray

is directed upwards against the deflector.

Type of Sprinklers Head

Detectors

• The first step in fire fighting

is the detection of the fire

• Fires are detected either by

persons or by electrical

detectors

• Electrical detectors can be

– Heat detectors

– Smoke detectors

– Flame detectors

Detectors

• According to NFPA standards

detectors shall be located at a

distance of 7 m from each other

• We can know the number of detectors

we need per floor by dividing the area

to be protected by the area protected

by each detector

• Smoke detectors are installed in

offices and parking garages

• heat detectors are installed in pantries

Alarm bell

• After detecting the fire ,alarm bells ring to

warn occupants and personnel.

• Alarm bells are directly connected to the

detectors and rings automatically ,and they

can be manually operated.

Chapter 3

Project Description

Project Description

• The project consists of designing a fire

fighting system for “ABRAJ ACHRAFIEH” in

BEIRUT. The building consists of 3

residential buildings (Block A, B and C):

each containing four basements, a ground

floor, a mezzanine floor, a +6.55 floor, a

technical floor, 21 floors, and a roof.

Project Description

• Concerning the type of hazards, we have:

- Light hazard occupancy for apartments.

- Ordinary hazard occupancy, group 1 for parking Lots.

• The classifications of fires that can happen in that project are:

- Class A for apartments and parking lots.

- Class B for parking garages and fuel tanks.

- Class C for electronic and generator rooms.

Design Calculations

• The Project is mainly composed of

apartments and parking lots.

• Sprinklers are added in the four basements

which contains the parking lots.

• Hose reels are placed in the stairways at

each floor

Design Calculations

• In each residential building we have two

risers:

– One wet riser feeding the hose reels

– One dry riser feeding the landing valves

via a siamese connection

Design Calculations

The design studies should be done for:

• Temperature classification (glass bulb color).

• Fire hose reels.

• Hydraulically most demanding area (HMDA)

• Fire pumps.

Chapter 4

Hand Calculations

Temperature Classification

• The maximum ceiling temperature is

supposed to be 38°C and the temperature

rating at which the sprinkler should be active

is between 57and 77°C since there is no

boiler or furnace in the designed area. The

sprinkler glass bulb should be orange or red.



Sprinkler calculations

• Automatic sprinkler systems are designed in

accordance with NFPA 13, Standard for the

installation of sprinkler Systems.

• NFPA-13 provides the minimum

requirements for the design of sprinkler

systems protecting buildings of a wide

variety of uses.

Step1- Number of sprinkler risers needed

• Based on NFPA 13-4-2.1

• Since the parking area is less than 4831m2, one

sprinkler riser is sufficient

Step 2- Area-Density Method

Step 3- Area of Coverage/sprinkler spacing

Protection Areas and Maximum Spacing (Standard

Spray Upright/Standard Spray Pendent) for Ordinary

Hazard. NFPA-13 4.4.1.1

4.61512.1130AllAll

mftm2ft2System

type

Construction

type

Maximum

spacing

(s)

Protection

area (As)

4.61512.1130AllAll

mftm2ft2System

type

Construction

type

Maximum

spacing

(s)

Protection

area (As)

Step 3- Area of Coverage/sprinkler spacing

As = S X L

Distance between branch lines L = As / S = 12.1 / 4.6

= 2.63 m

Sprinklers Distribution

• Step 1: Meshing for distribution of sprinklers


• Step 2: Determining sprinklers needed in the uncovered areas


• Step 3: Sprinklers addition

Step 4- Calculation of the total number of sprinklers

per floor

• The area of the parking is 3000 m² with a

height of 3 m

• The protection area of one sprinkler is 12.1

m²

A total number of 247 sprinklers / floor is needed

(255 by design constraints and specifications)

Sprinklers distribution

• Adjustments

• 1- Distance from walls is between 4 in

minimum and Ls/2.

• 2- Obstructions (e.g.. Ventilation duct)

• 3- Uncovered areas (shape, Building

geometry)

Sprinklers distribution

• Actual number of sprinklers per floor is 255

Step 5-Pipe sizing

• Schedule size for Ordinary Hazard Occupancies systems

Ordinary Hazard Pipe ScheduleOrdinary Hazard Pipe Schedule

(as per NFPA(as per NFPA--13.table613.table6--5.3.2(a))5.3.2(a))

Steel Copper Steel Copper

1 in. 1 in. ………………………… 2 sprinklers 1 in. 2 sprinklers 1 in. ……………………………… 2 sprinklers2 sprinklers

11¼¼ in.in.………………………… 3 sprinklers 13 sprinklers 1¼¼ in. in. ………………………… 3 sprinklers3 sprinklers

11½½ in.in.………………………… 5 sprinklers 15 sprinklers 1½½ in. in. ………………………… 5 sprinklers5 sprinklers

2 in.2 in.……………………………… 10 sprinklers 2 in. 10 sprinklers 2 in. ……………………………… 12 sprinklers 12 sprinklers

22½½ in.in.………………………… 20 sprinklers 220 sprinklers 2½½ in. in. ………………………… 25 sprinklers25 sprinklers

3 in. 3 in. ………………………………40 sprinklers 3 in. 40 sprinklers 3 in. ……………………………… 45 sprinklers45 sprinklers

33½½ in. in. …………………………65 sprinklers 365 sprinklers 3½½ in. in. ………………………… 75 sprinklers 75 sprinklers

4 in. 4 in. ………………………………100 sprinklers 4 in. 100 sprinklers 4 in. ……………………………… 115 sprinklers 115 sprinklers



Step 5-Pipe sizing

• Calculation of pipe diameters

Step 6- Determination of the most remote area

• Sprinkler which has the longest run and the highest pressure

drop is calculated using the equivalent length technique

Step 7- Number of sprinklers in the remote area

• The maximum probable number of operating

sprinklers at the same time is

• Ns =Ad /As

• Ns=1500/ 130 = 12

Step 8- Number of sprinklers in one branch line

• Number of sprinklers on one branch line

Where

• S= spacing between sprinklers (ft)

• Ad= sprinkler operation area (ft2)

• Step 9- Determining the flowrate of the most remote sprinkler

• Step 10- Determining the residual pressure of the most remote

sprinkler2

k

qp

Step 11- Total effective length between two adjacent sprinklers

• Equivalent Length

• Pipe Length

fT LLL

Step12- Friction Loss Formula

• Pipe friction losses shall be determined on the

basis of the Hazen-Williams formula, as follows:

• Where,

• p = frictional resistance in psi per foot of pipe

• Q = flow in gpm

• C = friction loss coefficient

• d = actual internal diameter of pipe in inches

87.485.1

85.1

52.4dC

QP

Hazen- Williams C values

• Galvanized steel is used

Nodes Distribution

• The distribution is based on the longest run

Calculation sheet

• Q = area of coverage of one sprinkler x the density

= 130 ft² x 0.15 gpm/ft² = 19.5 gpm

Calculation sheet

• Using the formula Q = K.√Pt, one can find the residual pressure at the sprinkler

Pt = (Q/K)² = (19.5/5.6) ² = 12.1 psi

Calculation sheet

• From Hazen-Williams formula:

p = (4.52 x 19.5^1.85) / (120^1.85 x 1^4.87) = 0.156 psi/ft

• Then the friction loss is Pf = p x total length = 0.156 x 7.119 = 1.116psi

Calculation sheet

• Step 3 differs slightly since a branch estimation is made as follows:

K = 39.819/√17.86 = 9.5

Calculation sheet

Step 13 we compute the effect of the elevation on the pressure by with Pel =0.433xH= 17.32 psi

Calculation sheet

• Total water required including hose reels is 320 + 4(50) = 520 gpm

• Riser pipe diameter 6 in

• Pump pressure required 94 psi

Chapter 5

Elite Software Calculations

Elite Calculations

• Selection of nodes for the calculations

Elite Calculations


Elite Calculations


Elite Calculations

• Pressure and flow required as given by Elite

Elite Calculations

• This small difference is due to the fact that the software calculates the demand of each sprinkler alone, while hand calculations required that a branch approximation be made (Kbranch = 9.5).

Hand Calculations Elite Software

Flow rate = 320 gpm Flow rate = 338 gpm

Pressure = 94 psi Pressure = 97 psi

Chapter 6

WaterCAD Software Calculations

WaterCAD Calculations

• The above picture is drawn in WaterCAD


• Pressure and flow required as given by WaterCAD


• This small difference is due to the fact that the software calculates the demand of each sprinkler alone, while hand calculations required that a branch approximation be made (Kbranch = 9.5).

Hand Calculations WaterCAD Software

Flow rate = 320 gpm Flow rate = 342 gpm

Pressure = 94 psi Pressure = 96 psi

Chapter 7

Fire Pump Selection

Design Parameters

• Total flow required including hose streams

345 + 200 = 545 gpm

• Riser pipe diameter 6 in

• Pump pressure required 97 psi

• ESP software is used to select the pump

Pump Selection

The pump highlighted in yellow is chosen due to its low cost and high efficiency

Pump Selection

• The above figure states all the pump details

Schematic drawing of the Fire pumps connection

Fire Pumps

• The main fire pump is an electrical motor

driven pump having a capacity of 545 gpm.

• The second fire pump, the diesel pump is

used as a back-up pump.

• The jockey pump is used to maintain the

design system pressure and to compensate

for minor leakages.

Jockey Pump

• Every system has a normal leakage rate that

will result in a pressure drop.

• Jockey Pump will maintain the pressure in

the system

• This will prevent the main fire pump from

starting for minor leaks

Jockey Pump

• Jockey pumps should be sized according to NFPA

20

• For 1-5 % of the flow of the main fire pump

• To provide 10 psi more pressure than the main fire

pump

• So that it cannot meet the demand of the lowest flow

fire protection fitting in the system that is less than

19.5 gpm (in our calculation).

Water Supply for fire fighting

• Tank sizing must consider 150% of the fire

pump rated flow

• 2500 gallons

• Sufficient for 30 min

THANK YOU

FOR YOUR ATTENDANCE

73584148 Fire Fighting

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