L1B - Fundamental concept of building fire.pdf - FACULTY OF...

This preview shows page 1 - 16 out of 65 pages.

FACULTY OF SCIENCE AND TECHNOLOGYSBS5313FIRE SERVICESFUNDAMENTAL CONCEPT OF BUILDING FIREC.W.Fok
BASIC CONCEPT IN FIREUnderstanding the fire phenomena is a first step in developing tools for Fire Protection.Fire may occur in :Open air- natural fireA compartment/enclosure- compartment fire2
Fire triangle and fire tetrahedron4 September 2019
Stages in a Compartment/Enclosure Fire
3
4
Terms and definitionsSmouldering ( smoldering悶燃)FlashoverBackdraftFire loadFire load densityT-square FireFuel controlled fireVentilation control fireSprinkler control fire
TERMS AND DEFINITIONSSmouldering ( smoldering悶燃)A burning process without flame due to limited supply of oxygen. Surface oxidation which provides the heat necessary to cause further degradation of the neighbouring layer of combustible materials. 5
TERMS AND DEFINITIONSFlashoverA stage in the development of an enclosure fire at which fire spreads rapidly to give large merged flames throughout the space. This is due to the whole content in the space reaching the ignition temperature.
TERMS AND DEFINITIONSFlashover
TERMS AND DEFINITIONSBackdraftThe accumulation of fuel rich gases and their sudden exposure to air causing a dramatic extension of flames through the compartment/enclosure.6
TERMS AND DEFINITIONSComparison between Flashover and Backdraft
TERMS AND DEFINITIONS - BACKDRAFTSmoke under door - smoke being drawn in along with the air under doors, windows, etc.
Terms and DefinitionFire load Fire load(FL) is a measure of the heat potential due to combustible items in the building and is expressed in J.FL = ∑ Mi CiWhere Mi = mass of fuel i, Ci = calorific value of the icombustible itemFire load densityFire load density(FLD) is the fire load per unit area (J/m2). Normalized by floor area A to give :FLD = FL/A (J/m2)As specified in FSD CoP, when Fire Load Density is larger than 1135MJ/m2, smoke extraction system and staircase pressurization in most cases will be required.
Terms and Definition Calorific values of common materials
Terms and Definition – Fire load and fire load densityExample :A store room of area 100 m2storing 2000 Kg newspaper (calorific value of 18.6 MJ/Kg) and 500 Kg wooden boards (calorific value of 14 MJ/Kg). What is the (i) Total fire load of the store room(ii) Fire load density of the store roomSolution :(i) Total Fire load = ∑Mi Ci= 2000 x 18.6 + 500 x 14= 37200 + 7000= 44200 MJ(ii) Fire load density = 44200/100 MJ/m2= 442 MJ/m2

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture