Life Safety and Fire Fighting Systems – The weakest link

Unlike other cables, hearth resistant cables need to work even when immediately uncovered to the fire to keep important Life Safety and Fire Fighting tools working: Fire alarms, Emergency Lighting, Emergency Communication, Fire Sprinkler pumps, Fireman’s Lift sub-main, Smoke extraction fans, Smoke dampers, Stair pressurization fans, Emergency Generator circuits and so on.
In order to categorise electric cables as hearth resistant they are required to undergo testing and certification. Perhaps the first widespread fire checks on cables were IEC 331: 1970 and later BS6387:1983 which adopted a gas ribbon burner test to supply a flame by which cables had been positioned.
Since the revision of BS6387 in 1994 there have been 11 enhancements, revisions or new take a look at standards introduced by British Standards to be used and utility of Fire Resistant cables however none of these seem to address the core problem that fireside resistant cables where tested to common British and IEC flame test requirements aren’t required to perform to the identical fire efficiency time-temperature profiles as each different structure, system or component in a constructing. Specifically, the place fireplace resistant constructions, techniques, partitions, fire doors, hearth penetrations fireplace limitations, flooring, partitions etc. are required to be fireplace rated by building rules, they’re tested to the Standard Time Temperature protocol of BS476 components 20 to 23 (also often recognized as ISO834-1, ASNZS1530pt4, EN1363-1 and in America and Canada ASTM E119-75).
These tests are performed in giant furnaces to replicate real publish flashover fire environments. Interestingly, Cheap take a look at requirements like BS 6387CWZ, SS299, IEC 60331 BS8343-1 and 2, BS8491 only require cables to be exposed to a flame in air and to decrease final check temperatures (than required by BS476 pts 20 to 23). Given Fire Resistant cables are prone to be exposed in the identical fire, and are wanted to make sure all Life Safety and Fire Fighting methods remain operational, this fact is probably stunning.
Contrastingly in Germany, Belgium, Australia, New Zealand, USA and Canada Fire Resistant cable techniques are required to be tested to the identical fireplace Time Temperature protocol as all other constructing parts and that is the Standard Time Temperature protocol to BS476pts 20-23, IS0 834-1, EN1363-1 or ASTM E119-75 in USA.
The committees creating the usual 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 fire tests carried out within the UK, Germany and the United States. The exams were described in a sequence of “Red Books” issued by the British Fire Prevention Committee after 1903 as nicely as those from the German Royal Technical Research Laboratory. The finalization of the ASTM commonplace 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 tests at Columbia University and Underwriters Laboratories in Chicago. The small time temperature differences between the International ISO 834-1 take a look at as we all know it right now and the America ASTM E119 / NFPA 251 exams likely stemmed from this time.
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The curve as we see it right now (see graph above) has turn out to be the usual scale for measurement of fire check severity and has proved related for many above ground cellulosic buildings. When elements, structures, elements or techniques are examined, the furnace temperatures are controlled to adapt to the curve with a set allowable variance and consideration for preliminary ambient temperatures. The requirements require parts to be tested in full scale and underneath situations of assist and loading as defined to have the ability to characterize as precisely as possible its functions in service.
This Standard Time Temperature testing protocol (see graph right) is adopted by nearly all nations around the world for fireplace testing and certification of nearly all constructing buildings, elements, techniques and parts with the interesting exception of fire resistant cables (exception in USA, Canada, Australia, Germany, Belgium and New Zealand the place hearth resistant cable systems are required to be tested and approved to the Standard Time Temperature protocol, similar to all different constructing structures, parts and components).
It is necessary to know that utility requirements from BS, IEC, ASNZS, DIN, UL and so forth. the place hearth resistive cables are specified for use, are only ‘minimum’ necessities. We know right now that fires aren’t all the same and analysis by Universities, Institutions and Authorities around the globe have recognized that Underground and a few Industrial environments can exhibit very completely different fire profiles to those in above ground cellulosic buildings. Specifically in confined underground public areas like Road and Rail Tunnels, Underground Shopping facilities, Car Parks fireplace temperatures can exhibit a very fast rise time and can attain temperatures properly above these in above ground buildings and in far less time. In USA today electrical wiring systems are required by NFPA 502 (Road Tunnels, Bridges and other Limited Access Highways) to withstand hearth temperatures as a lot as 1,350 Degrees C for 60 minutes and UK British Standard BS8519:2010 clearly identifies underground public areas such as car parks as “Areas of Special Risk” the place more stringent test protocols for essential electrical cable circuits may have to be thought-about by designers.
Standard Time Temperature curves (Europe and America) plotted towards common BS and IEC cable checks.
Of course all underground environments whether or not highway, rail and pedestrian tunnels, or underground public environments like purchasing precincts, car parks and so on. might exhibit different fire profiles to those in above floor buildings as a outcome of In these environments the heat generated by any fireplace can not escape as easily as it would in above ground buildings thus relying more on heat and smoke extraction tools.
For Metros Road and Rail Tunnels, Hospitals, Health care amenities, Underground public environments like buying precincts, Very High Rise, Theaters, Public Halls, Government buildings, Airports and so on. that is significantly important. Evacuation of those public environments is usually slow even during emergencies, and it is our responsibility to ensure everyone is given the easiest likelihood of secure egress throughout fireplace emergencies.
It can be understood today that copper Fire Resistant cables the place put in in galvanized metal conduit can fail prematurely during hearth emergency because of a response between the copper conductors and zinc galvanizing contained in the metallic conduit. In 2012 United Laboratories (UL®) in America removed all certification for Fire Resistive cables where installed in galvanized metal conduit because of this:
UL® Quote: “A concern was delivered to our attention related to the performance of those products within the presence of zinc. We validated this discovering. As a results of this, we changed our Guide Information to point that every one conduit and conduit fittings that are available contact with fire resistive cables ought to 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 offered 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 need to evaluation the present test methodology currently adopted for fire resistive cable testing and perhaps align the performance of Life Safety and Fire Fighting wiring techniques with that of all the opposite fireplace resistant structures, parts and methods in order that Architects, building designers and engineers know that when they need a hearth rating that the important wiring system will be equally rated.
For many power, management, communication and information circuits there is one know-how obtainable which can meet and surpass all present hearth exams and purposes. It is an answer which is regularly utilized in demanding public buildings and has been employed reliably for over 80 years. MICC cable technology can provide a total and complete reply to all the problems related to the fire safety risks of contemporary flexible natural polymer cables.
The steel jacket, magnesium oxide insulation and conductors of MICC cables make sure the cable is successfully fire proof. Bare MICC cables don’t have any natural content material so merely can not propagate flame or generate any smoke. The zero fuel-load of these 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 poisonous gasses in any respect together with Carbon Monoxide. MICC cable designs can meet the entire current and constructing fireplace resistance performance standards in all countries and are seeing a major enhance in use globally.
Many engineers have beforehand thought-about MICC cable know-how to be “old school’ but with the new analysis in hearth efficiency MICC cable system are now confirmed to have far superior hearth performances than any of the newer more fashionable flexible hearth resistant cables.
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