Life Safety and Fire Fighting Systems – The weakest link

Unlike different cables, hearth resistant cables should work even when immediately exposed to the fire to maintain important Life Safety and Fire Fighting equipment working: Fire alarms, Emergency Lighting, Emergency Communication, Fire Sprinkler pumps, Fireman’s Lift sub-main, Smoke extraction followers, Smoke dampers, Stair pressurization fans, Emergency Generator circuits and so on.
In order to categorise electrical cables as fireplace resistant they are required to bear testing and certification. Perhaps the primary common fire tests on cables had been IEC 331: 1970 and later BS6387:1983 which adopted a gas ribbon burner check to supply a flame by which cables have been placed.
Since the revision of BS6387 in 1994 there have been 11 enhancements, revisions or new test standards introduced by British Standards to be used and application of Fire Resistant cables but none of these seem to deal with the core problem that fireplace resistant cables the place examined to widespread British and IEC flame take a look at standards are not required to carry out to the same fireplace efficiency time-temperature profiles as each other construction, system or part in a constructing. Specifically, the place fireplace resistant structures, methods, partitions, fire doorways, fire penetrations hearth obstacles, flooring, partitions and so on. are required to be hearth rated by constructing regulations, they are tested to the Standard Time Temperature protocol of BS476 components 20 to 23 (also often known as ISO834-1, ASNZS1530pt4, EN1363-1 and in America and Canada ASTM E119-75).
These checks are conducted in massive furnaces to replicate actual submit flashover fire environments. Interestingly, Fire Resistant cable take a look at standards like BS 6387CWZ, SS299, IEC 60331 BS8343-1 and 2, BS8491 only require cables to be exposed to a flame in air and to lower last test temperatures (than required by BS476 pts 20 to 23). Given Fire Resistant cables are more likely to be uncovered in the identical fireplace, and are needed to ensure all Life Safety and Fire Fighting systems remain operational, this reality is perhaps stunning.
Contrastingly in Germany, Belgium, Australia, New Zealand, USA and Canada Fire Resistant cable systems are required to be examined to the identical fireplace Time Temperature protocol as all other building components 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 growing the standard drew on the steering given from the International Fire Prevention Congress held in London in July 1903 and the measurements of furnace temperatures made in many hearth exams carried out within the UK, Germany and the United States. The checks have been described in a sequence 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 normal 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 variations between the International ISO 834-1 check as we all know it right now and the America ASTM E119 / NFPA 251 checks likely stemmed from this time.
Image courtesy of MICC Ltd.
The curve as we see it at present (see graph above) has turn into the usual scale for measurement of fireplace check severity and has proved related for many above floor cellulosic buildings. When Unique , buildings, components or systems are tested, the furnace temperatures are managed to evolve to the curve with a set allowable variance and consideration for preliminary ambient temperatures. The standards require elements to be examined in full scale and beneath situations of assist and loading as defined so as to symbolize as precisely as possible its features in service.
This Standard Time Temperature testing protocol (see graph right) is adopted by virtually all nations all over the world for fire testing and certification of nearly all building structures, parts, systems and elements with the attention-grabbing exception of fire resistant cables (exception in USA, Canada, Australia, Germany, Belgium and New Zealand where fireplace resistant cable methods are required to be tested and accredited to the Standard Time Temperature protocol, similar to all other constructing buildings, components and components).
It is essential to understand that software requirements from BS, IEC, ASNZS, DIN, UL and so forth. the place hearth resistive cables are specified for use, are only ‘minimum’ requirements. We know at present that fires usually are not all the same and analysis by Universities, Institutions and Authorities all over the world have identified that Underground and a few Industrial environments can exhibit very totally different fireplace profiles to these in above floor cellulosic buildings. Specifically in confined underground public areas like Road and Rail Tunnels, Underground Shopping centers, Car Parks hearth temperatures can exhibit a really fast rise time and may reach temperatures properly above those in above floor buildings and in far less time. In USA right now electrical wiring methods are required by NFPA 502 (Road Tunnels, Bridges and different Limited Access Highways) to resist fire 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” where more stringent take a look at protocols for essential electric cable circuits could must be considered by designers.
Standard Time Temperature curves (Europe and America) plotted against widespread BS and IEC cable exams.
Of course all underground environments whether road, rail and pedestrian tunnels, or underground public environments like buying precincts, car parks etc. could exhibit totally different fireplace profiles to those in above ground buildings because In these environments the heat generated by any fireplace can’t escape as easily as it would in above ground buildings thus relying extra on warmth and smoke extraction tools.
For Metros Road and Rail Tunnels, Hospitals, Health care services, Underground public environments like purchasing precincts, Very High Rise, Theaters, Public Halls, Government buildings, Airports and so forth. that is particularly important. Evacuation of these public environments is often slow even throughout emergencies, and it’s our responsibility to make sure everyone seems to be given the very best chance of safe egress during fire emergencies.
It can be understood at present that copper Fire Resistant cables the place put in in galvanized metal conduit can fail prematurely throughout fireplace emergency due to a reaction between the copper conductors and zinc galvanizing inside the metallic conduit. In 2012 United Laboratories (UL®) in America removed all certification for Fire Resistive cables where installed in galvanized metal conduit for this reason:
UL® Quote: “A concern was delivered to our attention related to the performance of those products in 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 interior coating free of zinc”.
Time temperature profile of tunnel fires utilizing vehicles, HGV trailers with totally 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 around the world may have to evaluate the present take a look at methodology presently adopted for hearth resistive cable testing and perhaps align the performance of Life Safety and Fire Fighting wiring methods with that of all the opposite fire resistant constructions, components and systems in order that Architects, constructing designers and engineers know that once they want a hearth score that the important wiring system shall be equally rated.
For many energy, management, communication and information circuits there may be one know-how available which might meet and surpass all current fire checks and functions. It is an answer which is frequently used in demanding public buildings and has been employed reliably for over 80 years. MICC cable expertise can present a complete and complete reply to all the issues associated with the fire safety risks of modern flexible natural polymer cables.
The steel jacket, magnesium oxide insulation and conductors of MICC cables ensure the cable is effectively fireplace proof. Bare MICC cables don’t have any natural content so merely can not propagate flame or generate any smoke. The zero fuel-load of these MICC cables ensures no heat is added to the fireplace and no oxygen is consumed. Being inorganic these MICC cables cannot generate any halogen or toxic gasses at all together with Carbon Monoxide. MICC cable designs can meet all the present and building fire resistance efficiency standards in all nations and are seeing a big enhance in use globally.
Many engineers have previously thought-about MICC cable expertise to be “old school’ but with the brand new research in fire performance MICC cable system are now confirmed to have far superior fire performances than any of the newer more modern flexible fireplace resistant cables.
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