Foam Design Wakelin

NFPA 409: 2001Standard on Aircraft Hangars

A comparison of Foam SystemsJuly 11, 2002

Alison Wakelin

Presentation Contents

Structure of NFPA 409Classification of HangarsGroup I & II Construction RequirementsGroup I Hangar Protection Systems New Design OptionsGroup II Hangar Protection SystemsGroup III & IV Requirements

NFPA 409 Structure

Chapter 4 – Hangar ClassificationChapter 5 – Group I & II Building RequirementsChapter 6 – Group I Protection (major revisions 2001)Chapter 7 – Group II Protection

NFPA 409 Structure

Chapter 8 – Group III RequirementsChapter 9 – Group IV RequirementsChapter 10 – Periodic Inspection & Testing

NFPA 409 Chapter 4

Aircraft Hangar Groups

Hangar Classifications

Group I, either:Door height or aircraft with tail height > 28’ (8.5 m); orSingle fire area > 40,000 ft2 (3,716 m2)

Group II:Door height < 28’ (8.5 m); ANDFire area limits for construction types meeting Table 4.1.2.

Hangar Classifications

Group III:Door height < 28’ (8.5 m); ANDFire area limits for construction types meeting Table 4.1.3.

Group IV:Membrane covered, rigid, steel frame.

NFPA 409 – Chapter 5

Construction of Group I and Group II Aircraft Hangars

Group I & II Construction Highlights

Group I – Type I or II constructionGroup II – Type I through V construction depending on hangar areaInternal Separations:

Between aircraft hangar bays 3-hour Between hangar bay and service area 1-hourService areas between hangar bays –1 wall 3-hours and 1 wall 1-hour

Group I & II Internal Fire Separations

1-hour1-hour 1-hour 1-hour

3-hour3-hour

3-hour

1-hour

Hangar 1 Hangar 2 Hangar 3 Hangar 4

Office and Shop Area Office and Shop Area

Offi

ce a

nd S

hop

Area


Main steel columns in the hangar shall have 2-hour fire resistance rating or column sprinkler protectionTrench drains

required to restrict spread of fuel and reduce fire and explosion hazardsystem designed and constructed to prevent build up of flammable liquids over the drain inlet with all fire protection systems dischargingWhere do they discharge to?


Landing Gear Pits, Ducts, and TunnelsVentilation system utilizing flammable vapor detectionElectrical equipment suitable for hazardous locationsPressure venting or explosion protection

Ceiling Draft Curtains divide sprinkler systems into areas not greater than 700 m2


Protection of Group I Aircraft Hangars

Existing Group I Protection Systems

NFPA 409 - 1995 editionFor Group I hangars a single option for the suppression system:

Overhead foam water deluge system (primary foam supply), with aSupplementary system to protect shadow areas under large wing areas (secondary foam supply)

New Group I Protection Options

Two new design options in 2001 editionExchange the roles of the fire protection systemsLow level system becomes the primary system supplying foam to the hangar floorOverhead sprinkler becomes the secondary system to prevent structural collapse of the building, wet adjacent aircraft, etc

New Group I Protection Options

NFPA 409 - 2001 editionFor Group I hangars two additional options were added:

Overhead Closed head wet pipe overhead sprinkler system, with aLow level foam system to provide complete coverage of floor area with foam using either:

• Low-level low expansion foam system, or• Low-level high expansion foam system

Option 1 Features

An overhead foam water deluge sprinkler system

Coverage area using 100-ft radius ruleSupplementary foam system for under the shadow areas of large wing aircraft

Monitor nozzles

Typical System Plan

Option 2 Features

Low-level AFFF deluge system covering entire floor area to within 1.5m of the hangar walls Trench or monitor nozzlesAn overhead closed head wet pipe sprinkler system using quick response sprinklers

Design area 15,000 ft2

Grate Nozzle Installation

Low-level AFFF Discharge

Option 3 Features

Low-level hi-ex foam deluge system covering entire floor area to within 1.5m of the hangar wallsCeiling or wall mounted hi-ex foam generators are used to provide foam

Outside air requiredAn overhead closed head wet pipe sprinkler system using quick response sprinklers

Design area 15,000 ft2

Sidewall Hi-ex Foam Generator

Start of Hi-ex Discharge

Hi-ex Foam 1-m Depth

Which Option?

Best option depends very much on combination of factors:

Site conditions such as water supply;Type of aircraft;The area of the hangar bay;Is the building new or existing;Costs;Maintenance.


Protection of Group II Aircraft Hangars

Group II Protection Options

There are 4 design options:The 3 options for Group I hangars

Design area closed head sprinkler system reduced to 5,000 ft2

A closed-head foam-water sprinkler system

Design area is the entire hangar bay


Group III Aircraft Hangars

Group III Requirements

All requirements for this group are contained in chapter 8Construction limits

Floor area limited for the construction typeFixed protection portable extinguishers

Unless hazardous operations including fuel transfer, welding, spray painting, etcHazardous operations = Group II hangar


Group IV Aircraft Hangars

Group IV Requirements

Membrane flammability limitsFire separation of office and shop areasLanding gear Pits, Ducts and TunnelsFire Protection Systems:

All hangars shall have low-level foam system, andHangars with floor area > 12,000 ft2 shall have wet pipe sprinkler system (5,000 ft2 design area)

Group I Hangar Water Supply Requirements

Sprinkler System Foam System Total [gpm, liters]

Deluge O/H, Supplementary U/W AFFF

75,000 x 0.16 x 1.2 = 14,400 gpm

90 ft by 200 ft U/W area # = 90 x 200 x 0.1 = 1,800 gpm

16,200 gpm 61, 330 l

Wet Pipe O/H, LL AFFF (grate nozzle)

15,000 x 0.17 x 1.2 = 3,060 gpm

96 nozzles @ 152 gpm = 15,000 gpm

18,060 gpm 68,370 l

Wet Pipe O/H, LL Hi-ex

15,000 x 0.17 x 1.2 = 3,060 gpm

26 generators* @ 60 psi 26 x 220 = 5,720 gpm

8,780 gpm 33,240 l

All scenarios based on 300 ft by 400 ft hangar bay # Based on single large wing aircraft eg Boeing 747-400, multiple aircraft and parking positions lead to much larger area requiring coverage * Application rate (3 cfm/ft2) x hangar area + sprinkler breakdown factor (NFPA 11A) = 3 (300 x 400) + 10 (15,000 x 0.17) = 385,500 cfm Using 15,000 cfm hi-ex generators require total of 26 generators

Any questions?

Foam Design Wakelin

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