Life Safety and Fire Fighting Systems – The weakest link

Unlike other cables, fire resistant cables have to work even when instantly uncovered to the hearth to keep essential Life Safety and Fire Fighting tools working: Fire alarms, Emergency Lighting, Emergency Communication, Fire Sprinkler pumps, Fireman’s Lift sub-main, Smoke extraction followers, Smoke dampers, Stair pressurization followers, Emergency Generator circuits etc.
In order to classify electric cables as fireplace resistant they are required to undergo testing and certification. Perhaps the first widespread hearth tests on cables were IEC 331: 1970 and later BS6387:1983 which adopted a fuel ribbon burner take a look at to supply a flame in which cables had been positioned.
Since the revision of BS6387 in 1994 there have been 11 enhancements, revisions or new take a look at requirements launched by British Standards for use and software of Fire Resistant cables however none of those seem to address the core issue that fire resistant cables where tested to common British and IEC flame test standards aren’t required to perform to the identical hearth performance time-temperature profiles as every other construction, system or part in a building. Specifically, where fireplace resistant buildings, systems, partitions, fireplace doors, hearth penetrations fire limitations, flooring, walls and so on. are required to be hearth rated by building rules, they’re tested to the Standard Time Temperature protocol of BS476 elements 20 to 23 (also often known as ISO834-1, ASNZS1530pt4, EN1363-1 and in America and Canada ASTM E119-75).
เกจวัดแรงดันอากาศ are carried out in large furnaces to copy actual publish flashover fire environments. Interestingly, Fire Resistant cable take a look at requirements like BS 6387CWZ, SS299, IEC 60331 BS8343-1 and a pair of, BS8491 solely require cables to be uncovered to a flame in air and to decrease last check 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 methods remain operational, this reality is maybe shocking.
Contrastingly in Germany, Belgium, Australia, New Zealand, USA and Canada Fire Resistant cable methods are required to be tested to the identical fire Time Temperature protocol as all other building components 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 guidance given from the International Fire Prevention Congress held in London in July 1903 and the measurements of furnace temperatures made in many hearth tests carried out within the UK, Germany and the United States. The tests were described in a sequence of “Red Books” issued by the British Fire Prevention Committee after 1903 in addition to these from the German Royal Technical Research Laboratory. The finalization of the ASTM normal was closely 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 checks 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 today and the America ASTM E119 / NFPA 251 tests 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 fire check severity and has proved relevant for most above ground cellulosic buildings. When components, buildings, parts or methods are tested, the furnace temperatures are controlled to evolve to the curve with a set allowable variance and consideration for preliminary ambient temperatures. The standards require parts to be examined in full scale and beneath circumstances of assist and loading as outlined in order to represent as accurately as potential its functions in service.
This Standard Time Temperature testing protocol (see graph right) is adopted by nearly all nations around the globe for fireplace testing and certification of nearly all building constructions, elements, techniques and elements with the interesting exception of fireside resistant cables (exception in USA, Canada, Australia, Germany, Belgium and New Zealand the place fire resistant cable systems are required to be tested and accredited to the Standard Time Temperature protocol, just like all other building buildings, parts and components).
It is necessary to grasp that application standards from BS, IEC, ASNZS, DIN, UL and so forth. where fireplace resistive cables are specified for use, are only ‘minimum’ requirements. We know today that fires are not all the identical and research by Universities, Institutions and Authorities all over the world 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 hearth temperatures can exhibit a really fast rise time and might reach temperatures nicely above these in above floor buildings and in far much less time. In USA at present electrical wiring methods 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 test protocols for important electric cable circuits could must be considered by designers.
Standard Time Temperature curves (Europe and America) plotted towards common BS and IEC cable exams.
Of course all underground environments whether highway, rail and pedestrian tunnels, or underground public environments like shopping precincts, car parks and so on. could exhibit different fireplace profiles to those in above ground buildings because In these environments the warmth generated by any fire can not escape as easily as it might in above floor buildings thus relying extra on warmth and smoke extraction gear.
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 on. that is significantly important. Evacuation of those public environments is usually gradual even throughout emergencies, and it’s our accountability to ensure everyone seems to be given the very best likelihood of secure egress during hearth emergencies.
It can additionally 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 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 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 finding. As a results of this, we modified our Guide Information to indicate that each one conduit and conduit fittings that are available contact with hearth 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 offered the paper at the First International Symposium in Prague 2004: Safe and Reliable Tunnels.
It would appear that some Standards authorities around the world might must review the present test methodology presently adopted for hearth resistive cable testing and maybe align the performance of Life Safety and Fire Fighting wiring systems with that of all the other fireplace resistant constructions, components and methods so that Architects, building designers and engineers know that after they want a hearth rating that the important wiring system might be equally rated.
For many energy, management, communication and data circuits there is one technology obtainable which may meet and surpass all current fire exams and functions. It is a solution which is incessantly used in demanding public buildings and has been employed reliably for over 80 years. MICC cable technology can provide a complete and complete answer to all the issues associated with the fireplace security risks of modern flexible natural polymer cables.
The metal jacket, magnesium oxide insulation and conductors of MICC cables make certain the cable is successfully fire proof. Bare MICC cables haven’t any natural content so merely can’t 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 cannot generate any halogen or toxic gasses in any respect including Carbon Monoxide. MICC cable designs can meet the entire present and constructing fireplace resistance performance requirements in all nations and are seeing a significant increase in use globally.
Many engineers have beforehand thought of MICC cable expertise to be “old school’ but with the new analysis in fire efficiency MICC cable system are actually proven to have far superior fire performances than any of the newer more modern flexible fire resistant cables.
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