Life Safety and Fire Fighting Systems – The weakest hyperlink

Unlike different cables, fire resistant cables need to work even when directly 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 forth.
In order to classify electrical cables as fire resistant they are required to endure testing and certification. Perhaps the primary widespread fireplace checks on cables were IEC 331: 1970 and later BS6387:1983 which adopted a gas ribbon burner check to supply a flame by which cables had been 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 software of Fire Resistant cables however none of those appear to handle the core concern that fireside resistant cables the place tested to widespread British and IEC flame test standards aren’t required to carry out to the same hearth performance time-temperature profiles as every other construction, system or component in a constructing. Specifically, the place hearth resistant structures, techniques, partitions, hearth doors, fireplace penetrations fire obstacles, flooring, partitions etc. are required to be fireplace rated by building laws, they are tested to the Standard Time Temperature protocol of BS476 components 20 to 23 (also known as ISO834-1, ASNZS1530pt4, EN1363-1 and in America and Canada ASTM E119-75).
These exams are performed in massive furnaces to duplicate real publish flashover hearth 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 exposed to a flame in air and to lower last take a look at temperatures (than required by BS476 pts 20 to 23). Given Fire Resistant cables are more likely to be exposed in the same fireplace, and are wanted to ensure all Life Safety and Fire Fighting techniques stay operational, this reality is perhaps stunning.
Contrastingly in Germany, Belgium, Australia, New Zealand, USA and Canada Fire Resistant cable methods are required to be examined to the same 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 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 many fireplace tests carried out within the UK, Germany and the United States. The checks had been described in a sequence of “Red Books” issued by the British Fire Prevention Committee after 1903 as nicely as 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 differences between the International ISO 834-1 check as we all know it right now and the America ASTM E119 / NFPA 251 exams doubtless stemmed from this time.
Image courtesy of MICC Ltd.
The curve as we see it today (see graph above) has turn out to be the standard scale for measurement of fireside check severity and has proved related for many above floor cellulosic buildings. When parts, buildings, components or methods are tested, the furnace temperatures are managed to conform to the curve with a set allowable variance and consideration for initial ambient temperatures. The standards require parts to be examined in full scale and beneath circumstances of assist and loading as defined so as to symbolize as precisely as possible its functions in service.
This Standard Time Temperature testing protocol (see graph right) is adopted by almost all nations around the world for fireplace testing and certification of just about all building constructions, elements, systems and components with the attention-grabbing exception of fire resistant cables (exception in USA, Canada, Australia, Germany, Belgium and New Zealand where fireplace resistant cable techniques are required to be tested and approved to the Standard Time Temperature protocol, similar to all different building constructions, parts and components).
It is necessary to know that application standards from BS, IEC, ASNZS, DIN, UL and so on. the place fire resistive cables are specified to be used, are solely ‘minimum’ necessities. We know today that fires usually are not all the identical and research by Universities, Institutions and Authorities around the world have identified that Underground and some Industrial environments can exhibit very completely different hearth profiles to those 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 very quick rise time and may 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 a lot as 1,350 Degrees C for 60 minutes and UK British Standard BS8519:2010 clearly identifies underground public areas corresponding to car parks as “Areas of Special Risk” the place extra stringent check protocols for essential electrical cable circuits could need to be thought-about by designers.
Standard Time Temperature curves (Europe and America) plotted against frequent 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 and so on. could exhibit completely different hearth profiles to those in above ground buildings as a end result of In these environments the warmth generated by any fireplace cannot escape as easily as it’d in above floor buildings thus relying extra on heat and smoke extraction gear.
For Metros Road and Rail Tunnels, Hospitals, Health care facilities, Underground public environments like buying precincts, Very High Rise, Theaters, Public Halls, Government buildings, Airports and so forth. that is significantly essential. Evacuation of those public environments is often slow even throughout emergencies, and it’s our duty to make sure everyone is given the perfect probability of protected egress during fireplace emergencies.
It is also understood right now that copper Fire Resistant cables the place put in in galvanized steel conduit can fail prematurely throughout fire emergency due to a response between the copper conductors and zinc galvanizing inside the metal conduit. In 2012 United Laboratories (UL®) in America eliminated all certification for Fire Resistive cables the place installed in galvanized steel conduit for this reason:
UL® Quote: “A concern was brought to our consideration associated to the efficiency of these merchandise in the presence of zinc. เกจวัดแรงดันน้ำมันเครื่อง validated this discovering. As a result of this, we changed our Guide Information to point that all conduit and conduit fittings that are available contact with fireplace resistive cables should have an inside coating free of zinc”.
Time temperature profile of tunnel fires using automobiles, HGV trailers with completely 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 seem that some Standards authorities around the world may need to review the current test methodology currently adopted for hearth resistive cable testing and perhaps align the performance of Life Safety and Fire Fighting wiring methods with that of all the other fireplace resistant structures, components and systems in order that Architects, building designers and engineers know that when they need a fireplace rating that the important wiring system shall be equally rated.
For many power, control, communication and information circuits there’s one know-how out there which may meet and surpass all current fireplace exams and applications. It is an answer which is incessantly used in demanding public buildings and has been employed reliably for over eighty years. MICC cable expertise can present a complete and full reply to all the problems related to the fire safety risks of modern flexible natural polymer cables.
The metallic jacket, magnesium oxide insulation and conductors of MICC cables ensure the cable is effectively fire proof. Bare MICC cables have no organic content material 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 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 present and constructing fire resistance efficiency standards in all nations and are seeing a major enhance in use globally.
Many engineers have beforehand considered MICC cable expertise to be “old school’ however with the new analysis in fireplace efficiency MICC cable system at the second are proven to have far superior hearth performances than any of the newer extra fashionable versatile fire resistant cables.
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