HKIE CPD Training Course (II) 23, 25 June and 7, 9 …fe.hkie.org.hk/FireDigest/Document/Images/20110622144214839/... · HKIE CPD Training Course (II) 23, 25 June and 7, 9 July 2009

HKIE CPD Training Course (II)

23, 25 June and 7, 9 July 2009Organization by

The Hong Kong Institution of Engineers – Fire Division

Co-organized by the Association of Registered Fire Service

Installation contractors of Hong Kong Ltd (FSICA)

Gas and Foam SuppressionSystems

The Hong Kong Institution of Engineers – Fire DivisionHKIE CPD Training Course

Peter Bressington Arup Fire – 9 July 2009

Gas Suppression Systems

Halon - Ozone depleting gas- No longer manufactured- Total ban 2003

Inert gases -Inergen- Argon- Nitrogen- Argonite

Chemical or halocarbon gas - CEA 410

- FM 200- FE13- NAF S III

Carbon Dioxide - CO2




Choice of system

discharge damage to equipmenthazard to occupantsfire fighting effectivenesseffect on other building systemsinstallation space requirementsongoing system maintenanceenvironmental acceptabilitycostdesign standards BS ISO 14520,NFPA2001

Gas Suppression SystemsElectrical/Electronic hazardsTelecommunications facilitiesFlammable & combustible liquids & gasesHigh valve assets (Bank Vaults, Art Storage etc)Acceptable to the relevant AuthorityTotal FloodingAutomatic in operationFitting with a means of system isolationFitted with audible & visual alarmsComplete with warning signsFitted with a means of ventilation after dischargeEffectively earthed.


Use and features


Reduces oxygen contents in enclosure to a level where combustion cannot be sustained or ignition prevention (Nitrogen rich)Large quantity of gas required 50% by volume Venting requiredHigh enclosure build specificationEnvironmentally friendly


Inert Gas


extinguish fire by reducing the oxygen contentinitial over-pressurisation of 500 pascalsclassified as 'clean agents' on the EPA SNAP listgood extinguishant as a total flooding agentstorage containers can be housed remote from the risk area


Inert Gas


Removes heat to the point that the combustion reaction is not sustainableLower design concentrations required 18% - FE13 to 8.6% FM200Venting required High build specGlobal warming potential


Halocarbons



Halocarbonsextinguish fire mainly by removing heat from the firegas is stored and initially discharged as a liquidliquid changes to a gas expansion occurs – room ventingusually 10 minute period for extinguishmentgreenhouse gases and each produce toxic by-productslarge space requirement for cylindershigh build specification for the enclosure required


Reduces oxygen content from 21% to 14% and maintains these level.By Air ExchangeExperimental Suppression SystemNo Regulatory Guidelines


Oxygen Reduction



Design check list• Agreed with the Client/Architect/FSD/Building Department • The use of a Gaseous Fire Extinguishing System for the Risk• The Type of Extinguishant (i.e. Inert or Halocarbon)• Design Standard Method of Application• Method of Activation Method of Detection• Method of Manual Release Type of Visual Alarm• Type of Audible Alarms• Control Panel Location Personnel Safety Means of Exit from Enclosure• 2. Agreed with the Client/Project Manager• Selection of Specialist by Name -or-• Selection of Specialist by Pre-tender -or-• Selection of Specialist by Competitive Quotation• 3. Agreed with the Architect• Location of Cylinders Enclosure • Pressure Rating where applicable• Location of Discharge Nozzles where applicable• Type/Style of Detector to be used where applicable



Design check listAgreed with Structural Engineer• Enclosure Strength• Enclosure IntegrityAgreed with other Disciplines• Principles of Routing & Space Allocation • Shut Down of Air Conditioning Systems• Ambient Temperature Range• Electrical Interfaces• Shut Down of Electrical Systems• Post Discharge Extraction System• Enclosure Venting ArrangementsAgreed with FS Contractor• Discharge Nozzle Characteristics• Clearances between Equipment and Unenclosed & Uninsulated

Live Electrical Components• Pipe Support & Restraint Method• System Flow Calculations• System Design & Performance • Validation Enclosure Integrity Test Method

Foam Suppression Systems

“…an aggregate of air-filled bubbles formedfrom aqueous solutions which is lower indensity than flammable liquids. It is usedprincipally to form a cohesive floating blanketon flammable and combustible liquids, andprevents or extinguishes fire by excluding airand cooling the fuel. It also prevents re-ignitionby suppressing formation of flammable vapors.It has the property of adhering to surfaces,which provides a degree of exposureprotection from adjacent fires” (NFPA 11)


What is foam?



Application

High-expansion foams are used when an enclosed space, such as a basement or hangarLow-expansion foams are used on burning spillsFoam is not effective on Class C electrical fires or pressurised gasesEffective at suppressing vapors & extinguishing Class B firesMany types of systems



Systems

Oscillating monitor

Foam deluge sprinkler

Conventional sprinkler



Systems

Foam Generator

Foam pourer

Grate nozzle



Foam Types

Class A and Class BProteinFluroproteinAFFFFFFPAR-AFFF



Codes



Environmental issues

biodegradation acute and chronic toxicitypersistence (especially of fluorosurfactants) bio-accumulation potential accurate information of individual ingredients – not genericaccurate percentage proportions rather than wide bands “5 - 20%”Issues of time periods quotedContainment

Buscot Lock The Thames UK

Foam Suppression Systems - A Case Study




100 acre site RAF40,000 sq m maintenance40,000 sq m support facilities48 bay fast jet maintenanceAlso 737 and VC 10


Fire suppression effectiveness (accidental fire)UncomplicatedFlexibilityMaintainabilityOperation and high resistance to spurious dischargeGood practice and industry codes and standards


Objectives


“conventional” combustible materials, andaviation fuelvery high value contentsconsequences of large fire will have high impact on operational continuity


Nature of the hazard


Close control over ignition sourcesCharacteristics of aviation fuel:NFPA classification Grade 2 – must be heated to achieve flashpoint. Can be extinguished with water only as fuel temperature lowered.For a fire to occur all of the following conditions are required:Spillage - Fuel heating – IgnitionOn-site fire service 24 hours seven days per. week


Nature of the hazard


NFPA 409NFPA 13BS 5306 Part 2Interflam paper `96 Notarianni (NIST) and Gott (US Department of the Navy)MoD Fire Safety Standards


Codes and Standards



Low expansion foam deluge through overhead/monitorsRetain present fire tender attendance procedureUse of high expansion foam generatorsSelf-contained foam trolley unitsMobile foam skid unitsFoam/water hosereelsFast response high hazard water sprinkler systemsUV/IR detectors for aviation fuel hazard

Options considered



Low expansion foam deluge through overhead/monitors:409 criteria is based upon automatic operation with a defined area of fire zone. Foam system on this project specified to be manual. Using 409 criteria this system is impractical due to massive water/foam quantities, plant and pipe sizing. Also flexibility of aircraft type and positioning works against a fixed zoned foam deluge system. To retain present fire tender attendance procedure

Options discounted



Use of high expansion foam generatorsThis is an option given in NFPA 409 as an automatic system. This system is appropriate for smaller hangars as the foam is discharged up to a height of 1m from the floor and should not cause damage if there is a spurious discharge. However, for a large hangar, as now being considered, to meet the design criteria generators would have to be suspended from the roof to give overall coverage within the specified time period in 409. Not practical due to functionality and size.

Options discounted



Fast response high hazard water sprinkler systemsDoes not rely upon manual operation. Very resistant to accidental discharge. Clean-up easier than foam. Number of sprinklers discharging water is governed by fire size. Water will cool fuel to below flashpoint, and cool planes and structure. Complies with insurance requirements, code compliant. Will not adversely effect any foam blanket.

Options implemented



UV/IR detectors for aviation fuelWhen the hangar is occupied it is likely that a fire event will be alerted via hangar personnel. However, when the hangar is unoccupied, or if no one is in the vicinity, the detectors will provide an early warning of a flaming fire. This will be approximately 30 seconds from the start of the fire.

Options implemented



Mobile foam skid unitsIt is intended that these units will be available to the on-site fire fighters as an alternative to a fire tender and to provide cover , if required, for larger plane wing areas. These units have an integral foam concentrate tank, directional monitor and connection for water from the fire system.

Options implemented



Indicative timings

UV/IR detectors – 30 seconds

On-site fire fighter attendance – 2 minutes

Sprinkler operation 7 minutes

HKIE CPD TRAINING COURSE

Question and

Answer


Documents

HKIE CPD Training Course (II) 23, 25 June and 7, 9 …fe.hkie.org.hk/FireDigest/Document/Images/20110622144214839/... · HKIE CPD Training Course (II) 23, 25 June and 7, 9 July 2009