Life Safety and Fire Fighting Systems – The weakest link

Unlike other cables, fireplace resistant cables need to work even when directly exposed to the fireplace 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 fans, Emergency Generator circuits etc.
In order to classify electric cables as fireplace resistant they’re required to endure testing and certification. Perhaps the primary common fireplace tests on cables had been IEC 331: 1970 and later BS6387:1983 which adopted a fuel ribbon burner check to supply a flame during which cables were positioned.
Since the revision of BS6387 in 1994 there have been eleven enhancements, revisions or new check requirements introduced by British Standards for use and application of Fire Resistant cables but none of these seem to handle the core concern that fire resistant cables where tested to common British and IEC flame check requirements are not required to carry out to the same hearth performance time-temperature profiles as each different structure, system or part in a constructing. Specifically, where fire resistant constructions, systems, partitions, fireplace doorways, hearth penetrations fire limitations, floors, partitions and so on. are required to be fireplace rated by constructing regulations, they’re tested to the Standard Time Temperature protocol of BS476 parts 20 to 23 (also generally recognized as ISO834-1, ASNZS1530pt4, EN1363-1 and in America and Canada ASTM E119-75).
These checks are carried out in massive furnaces to replicate actual publish flashover fireplace environments. Interestingly, Fire Resistant cable check standards like BS 6387CWZ, SS299, IEC 60331 BS8343-1 and a pair of, BS8491 only require cables to be exposed to a flame in air and to decrease ultimate take a look at temperatures (than required by BS476 pts 20 to 23). Given Fire Resistant cables are prone to be exposed in the same fire, and are needed to make sure all Life Safety and Fire Fighting systems remain operational, this reality is maybe stunning.
Contrastingly in Germany, Belgium, Australia, New Zealand, USA and Canada Fire Resistant cable systems are required to be examined to the identical hearth Time Temperature protocol as all different building 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 growing the usual 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 lots of fireplace checks carried out within the UK, Germany and the United States. The checks had been described in a collection 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 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 variations between the International ISO 834-1 take a look at as we all know it today and the America ASTM E119 / NFPA 251 exams probably stemmed from this time.
Image courtesy of MICC Ltd.
The curve as we see it today (see graph above) has turn into the usual scale for measurement of fire test severity and has proved related for most above floor cellulosic buildings. When elements, structures, parts or techniques 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 elements to be tested in full scale and under situations of support and loading as outlined in order to characterize as accurately as attainable its features in service.
เกจวัดแรงกด (see graph right) is adopted by virtually all international locations around the globe for fireplace testing and certification of just about all building buildings, components, systems and elements with the attention-grabbing exception of fire resistant cables (exception in USA, Canada, Australia, Germany, Belgium and New Zealand where fire resistant cable techniques are required to be examined and permitted to the Standard Time Temperature protocol, similar to all other constructing constructions, elements and components).
It is important to know that application standards from BS, IEC, ASNZS, DIN, UL and so forth. where fire resistive cables are specified for use, are solely ‘minimum’ requirements. We know at present that fires are not all the same and analysis by Universities, Institutions and Authorities around the globe have recognized that Underground and some Industrial environments can exhibit very completely 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 fire temperatures can exhibit a really quick rise time and can attain temperatures well 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 resist hearth temperatures as much as 1,350 Degrees C for 60 minutes and UK British Standard BS8519:2010 clearly identifies underground public areas similar to car parks as “Areas of Special Risk” where more stringent test protocols for important electrical cable circuits may have to be thought-about by designers.
Standard Time Temperature curves (Europe and America) plotted against frequent BS and IEC cable checks.
Of course all underground environments whether or not road, rail and pedestrian tunnels, or underground public environments like buying precincts, car parks etc. could exhibit totally different fire profiles to those in above floor buildings as a result of In these environments the heat generated by any fireplace can’t escape as simply as it would in above floor buildings thus relying extra on warmth and smoke extraction equipment.
For Metros Road and Rail Tunnels, Hospitals, Health care amenities, Underground public environments like purchasing precincts, Very High Rise, Theaters, Public Halls, Government buildings, Airports and so on. that is notably essential. Evacuation of those public environments is usually slow even during emergencies, and it is our responsibility to make sure everyone is given the easiest probability of secure egress throughout fireplace emergencies.
It can be understood at present that copper Fire Resistant cables the place installed in galvanized steel conduit can fail prematurely throughout fire emergency due to a reaction between the copper conductors and zinc galvanizing inside the steel conduit. In 2012 United Laboratories (UL®) in America removed all certification for Fire Resistive cables where put in in galvanized metal conduit for this reason:
UL® Quote: “A concern was dropped at our attention associated to the efficiency of these products within the presence of zinc. We validated this finding. As a results of this, we changed our Guide Information to point that all conduit and conduit fittings that are obtainable in contact with fireplace resistive cables ought to have an interior 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 at the First International Symposium in Prague 2004: Safe and Reliable Tunnels.
It would appear that some Standards authorities around the globe may must review the present take a look at methodology at present adopted for fireplace resistive cable testing and perhaps align the performance of Life Safety and Fire Fighting wiring methods with that of all the other hearth resistant buildings, elements and methods so that Architects, building designers and engineers know that when they need a fire rating that the essential wiring system shall be equally rated.
For many power, control, communication and knowledge circuits there may be one technology available which can meet and surpass all present fire checks and functions. It is an answer which is regularly used in demanding public buildings and has been employed reliably for over eighty years. MICC cable technology can present a complete and full reply to all the problems related to the fire security dangers of contemporary flexible natural polymer cables.
The metal jacket, magnesium oxide insulation and conductors of MICC cables make certain the cable is effectively hearth proof. Bare MICC cables haven’t any organic content material so simply 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 can not generate any halogen or poisonous gasses in any respect together with Carbon Monoxide. MICC cable designs can meet all the present and building fire resistance performance standards in all international locations and are seeing a big enhance in use globally.
Many engineers have previously thought-about MICC cable know-how to be “old school’ but with the new analysis in fire performance MICC cable system at the moment are proven to have far superior hearth performances than any of the newer more modern flexible fireplace resistant cables.
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