Life Safety and Fire Fighting Systems – The weakest link

Unlike different cables, fire resistant cables have to work even when directly uncovered to the fire to maintain essential Life Safety and Fire Fighting gear working: Fire alarms, Emergency Lighting, Emergency Communication, Fire Sprinkler pumps, Fireman’s Lift sub-main, Smoke extraction fans, Smoke dampers, Stair pressurization followers, Emergency Generator circuits and so on.
In order to categorise electric cables as fireplace resistant they’re required to bear testing and certification. Perhaps the first common hearth tests on cables had been IEC 331: 1970 and later BS6387:1983 which adopted a gas ribbon burner test to provide a flame by which cables had been placed.
Since the revision of BS6387 in 1994 there have been eleven enhancements, revisions or new check standards introduced by British Standards for use and software of Fire Resistant cables but none of those appear to deal with the core concern that fireside resistant cables the place examined to frequent British and IEC flame check requirements aren’t required to perform to the same fireplace performance time-temperature profiles as every other structure, system or component in a building. Specifically, where hearth resistant structures, systems, partitions, fire doors, hearth penetrations hearth limitations, floors, partitions and so on. are required to be fire rated by constructing regulations, they’re tested to the Standard Time Temperature protocol of BS476 elements 20 to 23 (also often recognized as ISO834-1, ASNZS1530pt4, EN1363-1 and in America and Canada ASTM E119-75).
These checks are carried out in large furnaces to copy real submit flashover fire environments. Interestingly, Fire Resistant cable test requirements like BS 6387CWZ, SS299, IEC 60331 BS8343-1 and a pair of, BS8491 solely require cables to be exposed to a flame in air and to decrease last take a look at temperatures (than required by BS476 pts 20 to 23). Given Fire Resistant cables are likely to be exposed in the same hearth, and are needed to make sure all Life Safety and Fire Fighting techniques stay operational, this reality is perhaps surprising.
Contrastingly in Germany, Belgium, Australia, New Zealand, USA and Canada Fire Resistant cable techniques are required to be examined to the identical hearth Time Temperature protocol as all different constructing elements and this is the Standard Time Temperature protocol to BS476pts 20-23, IS0 834-1, EN1363-1 or ASTM E119-75 in USA.
The committees developing the standard drew on the steerage given from the International Fire Prevention Congress held in London in July 1903 and the measurements of furnace temperatures made in lots of hearth exams carried out within the UK, Germany and the United States. The tests had been described in a collection of “Red Books” issued by the British Fire Prevention Committee after 1903 in addition to those from the German Royal Technical Research Laboratory. The finalization of the ASTM standard was heavily influenced by Professor I.H. Woolson, a Consulting Engineer of the USA National Board of Fire Underwriters and Chairman of the NFPA committee in Fire Resistive Construction who had carried out many exams at Columbia University and Underwriters Laboratories in Chicago. The small time temperature differences between the International ISO 834-1 test as we all know it right now and the America ASTM E119 / NFPA 251 checks doubtless stemmed from this time.
Image courtesy of MICC Ltd.
The curve as we see it right now (see graph above) has turn out to be the usual scale for measurement of fireplace take a look at severity and has proved related for many above floor cellulosic buildings. When parts, buildings, components or methods are tested, the furnace temperatures are managed to adapt to the curve with a set allowable variance and consideration for initial ambient temperatures. The requirements require components to be examined in full scale and underneath circumstances of support and loading as outlined so as to represent as precisely as potential its functions in service.
This Standard Time Temperature testing protocol (see graph right) is adopted by almost all nations all over the world for fire testing and certification of just about all building structures, parts, methods and elements with the attention-grabbing exception of fireside resistant cables (exception in USA, Canada, Australia, Germany, Belgium and New Zealand the place hearth resistant cable methods are required to be tested and permitted to the Standard Time Temperature protocol, identical to all different building constructions, elements and components).
It is essential to understand that utility requirements from BS, IEC, ASNZS, DIN, UL and so forth. the place hearth resistive cables are specified to be used, are only ‘minimum’ requirements. We know right now that fires aren’t all the identical and research by Universities, Institutions and Authorities around the globe have recognized that Underground and a few Industrial environments can exhibit very completely different hearth profiles to those in above ground cellulosic buildings. Specifically in confined เกจ์อาร์กอนsumo like Road and Rail Tunnels, Underground Shopping centers, Car Parks fire temperatures can exhibit a really quick rise time and might attain temperatures nicely above those in above floor buildings and in far less time. In USA today electrical wiring systems are required by NFPA 502 (Road Tunnels, Bridges and different Limited Access Highways) to face up to fireplace temperatures up to 1,350 Degrees C for 60 minutes and UK British Standard BS8519:2010 clearly identifies underground public areas similar to automobile parks as “Areas of Special Risk” the place more stringent check protocols for essential electric cable circuits could have to be considered by designers.
Standard Time Temperature curves (Europe and America) plotted towards widespread BS and IEC cable tests.
Of course all underground environments whether road, rail and pedestrian tunnels, or underground public environments like purchasing precincts, automobile parks etc. could exhibit different hearth profiles to those in above floor buildings as a end result of In these environments the heat generated by any hearth cannot escape as easily as it might in above floor buildings thus relying more on warmth and smoke extraction tools.
For Metros Road and Rail Tunnels, Hospitals, Health care services, Underground public environments like buying precincts, Very High Rise, Theaters, Public Halls, Government buildings, Airports and so forth. this is significantly essential. Evacuation of these public environments is usually gradual even during emergencies, and it is our accountability to ensure everyone is given the very best likelihood of safe egress throughout fire emergencies.
It is also understood right now that copper Fire Resistant cables where installed in galvanized steel conduit can fail prematurely throughout fire emergency due to a reaction between the copper conductors and zinc galvanizing contained in the metallic conduit. In 2012 United Laboratories (UL®) in America eliminated all certification for Fire Resistive cables the place put in in galvanized metal conduit for that reason:
UL® Quote: “A concern was delivered to our attention related to the efficiency of these products in the presence of zinc. We validated this discovering. As a results of this, we modified our Guide Information to indicate that all conduit and conduit fittings that are available in contact with fireplace resistive cables should have an inside coating freed from zinc”.
Time temperature profile of tunnel fires using cars, HGV trailers with different cargo and rail carriages. Graph extract: Haukur Ingason and Anders Lonnermark of the Swedish National Testing and Research Institute who introduced the paper on the First International Symposium in Prague 2004: Safe and Reliable Tunnels.
It would appear that some Standards authorities all over the world might must evaluate the present test methodology currently adopted for fireplace resistive cable testing and perhaps align the efficiency of Life Safety and Fire Fighting wiring methods with that of all the other fire resistant buildings, parts and methods in order that Architects, constructing designers and engineers know that once they need a hearth score that the important wiring system will be equally rated.
For many energy, management, communication and information circuits there may be one technology obtainable which may meet and surpass all current fire exams and applications. It is an answer which is frequently used in demanding public buildings and has been employed reliably for over 80 years. MICC cable technology can present a total and complete answer to all the problems related to the fire security risks of contemporary flexible organic polymer cables.
The metallic jacket, magnesium oxide insulation and conductors of MICC cables make certain the cable is effectively hearth proof. Bare MICC cables have no natural content so simply can not propagate flame or generate any smoke. The zero fuel-load of those MICC cables ensures no warmth is added to the hearth and no oxygen is consumed. Being inorganic these MICC cables can’t generate any halogen or toxic gasses in any respect including Carbon Monoxide. MICC cable designs can meet all of the current and constructing hearth resistance efficiency requirements in all international locations and are seeing a major enhance in use globally.
Many engineers have beforehand considered MICC cable technology to be “old school’ but with the new analysis in fireplace performance MICC cable system are actually confirmed to have far superior fire performances than any of the newer extra modern flexible hearth resistant cables.
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