Life Safety and Fire Fighting Systems – The weakest link

Unlike Backdoor , fireplace resistant cables need to work even when instantly uncovered to the fire to keep essential Life Safety and Fire Fighting gear 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 forth.
In order to classify electrical cables as hearth resistant they are required to undergo testing and certification. Perhaps the primary frequent fireplace 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 11 enhancements, revisions or new check standards introduced by British Standards for use and software of Fire Resistant cables but none of these appear to address the core concern that fireside resistant cables where tested to frequent British and IEC flame take a look at requirements usually are not required to perform to the identical fire efficiency time-temperature profiles as each different structure, system or part in a constructing. Specifically, where hearth resistant buildings, techniques, partitions, hearth doors, fire penetrations fireplace barriers, floors, partitions etc. are required to be hearth rated by building regulations, they are examined to the Standard Time Temperature protocol of BS476 parts 20 to 23 (also generally identified as ISO834-1, ASNZS1530pt4, EN1363-1 and in America and Canada ASTM E119-75).
These exams are conducted in massive furnaces to duplicate real submit flashover fireplace environments. Interestingly, Fire Resistant cable test standards 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 take a look at temperatures (than required by BS476 pts 20 to 23). Given Fire Resistant cables are prone to be uncovered in the identical fire, and are needed to make sure all Life Safety and Fire Fighting methods remain operational, this truth is probably shocking.
Contrastingly in Germany, Belgium, Australia, New Zealand, USA and Canada Fire Resistant cable methods are required to be tested to the same hearth Time Temperature protocol as all different building parts 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 fire exams carried out in the UK, Germany and the United States. The exams 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 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 know it right now and the America ASTM E119 / NFPA 251 exams likely stemmed from this time.
Image courtesy of MICC Ltd.
The curve as we see it today (see graph above) has become the standard scale for measurement of fireplace test severity and has proved related for most above floor cellulosic buildings. When components, constructions, components or methods are tested, the furnace temperatures are managed to evolve 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 beneath situations of help and loading as defined to have the ability to characterize as precisely as possible its features in service.
This Standard Time Temperature testing protocol (see graph right) is adopted by nearly all international locations around the world for fire testing and certification of just about all building structures, components, techniques and parts with the attention-grabbing exception of fireplace resistant cables (exception in USA, Canada, Australia, Germany, Belgium and New Zealand where hearth resistant cable systems are required to be examined and permitted to the Standard Time Temperature protocol, similar to all other constructing buildings, parts and components).
It is essential to understand that utility requirements from BS, IEC, ASNZS, DIN, UL etc. the place fireplace resistive cables are specified to be used, are solely ‘minimum’ requirements. We know today that fires are not all the identical and research by Universities, Institutions and Authorities around the world have identified that Underground and a few 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 very quick rise time and can attain temperatures properly above those in above floor buildings and in far much 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 fire temperatures as a lot 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 check protocols for important electric cable circuits might need to be considered by designers.
Standard Time Temperature curves (Europe and America) plotted towards widespread BS and IEC cable exams.
Of course all underground environments whether highway, rail and pedestrian tunnels, or underground public environments like shopping precincts, automotive parks and so forth. could exhibit totally different fire profiles to those in above ground buildings as a outcome of In these environments the heat generated by any fireplace can not escape as simply as it would in above ground buildings thus relying extra on warmth and smoke extraction gear.
For Metros Road and Rail Tunnels, Hospitals, Health care services, Underground public environments like shopping precincts, Very High Rise, Theaters, Public Halls, Government buildings, Airports etc. this is significantly essential. Evacuation of those public environments is usually sluggish even during emergencies, and it is our responsibility to make sure everyone is given the perfect probability of safe egress during fireplace emergencies.
It is also understood at present that copper Fire Resistant cables where put in in galvanized metal conduit can fail prematurely throughout hearth emergency due to a response between the copper conductors and zinc galvanizing inside the steel conduit. In 2012 United Laboratories (UL®) in America eliminated all certification for Fire Resistive cables the place installed in galvanized steel conduit for that reason:
UL® Quote: “A concern was dropped at our consideration related to the efficiency of these merchandise in the presence of zinc. We validated this discovering. As a result of this, we changed our Guide Information to point that each one conduit and conduit fittings that are available contact with hearth resistive cables should have an interior coating free of zinc”.
Time temperature profile of tunnel fires utilizing 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 presented the paper on the First International Symposium in Prague 2004: Safe and Reliable Tunnels.
It would seem that some Standards authorities around the globe could must evaluate the present take a look at methodology at present adopted for fire resistive cable testing and maybe align the performance of Life Safety and Fire Fighting wiring techniques with that of all the opposite hearth resistant structures, components and methods so that Architects, constructing designers and engineers know that once they need a fireplace ranking that the essential wiring system might be equally rated.
For many energy, control, communication and knowledge circuits there’s one know-how available which may meet and surpass all current fireplace checks and purposes. It is an answer which is incessantly utilized in demanding public buildings and has been employed reliably for over 80 years. MICC cable technology can present a complete and full answer to all the problems related to the fire security dangers of contemporary flexible organic polymer cables.
The metal jacket, magnesium oxide insulation and conductors of MICC cables make positive the cable is effectively hearth proof. Bare MICC cables haven’t any natural content so simply can not propagate flame or generate any smoke. The zero fuel-load of these MICC cables ensures no heat is added to the fire and no oxygen is consumed. Being inorganic these MICC cables can’t generate any halogen or poisonous gasses at all including Carbon Monoxide. MICC cable designs can meet all the present and building fire resistance efficiency requirements in all countries and are seeing a big increase in use globally.
Many engineers have previously considered MICC cable technology to be “old school’ but with the new research in fireplace performance MICC cable system at the second are proven to have far superior hearth performances than any of the newer extra fashionable versatile hearth resistant cables.
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