Unlike other cables, hearth resistant cables should work even when immediately 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 followers, Emergency Generator circuits and so on.
In order to classify electric cables as fire resistant they’re required to endure testing and certification. Perhaps the first frequent fireplace tests on cables had been IEC 331: 1970 and later BS6387:1983 which adopted a gas ribbon burner check to provide a flame during which cables were positioned.
Since the revision of BS6387 in 1994 there have been eleven enhancements, revisions or new take a look at standards launched by British Standards to be used and application of Fire Resistant cables however none of those seem to address the core problem that fireside resistant cables the place tested to frequent British and IEC flame test standards aren’t required to carry out to the identical hearth efficiency time-temperature profiles as each other structure, system or component in a building. Specifically, the place hearth resistant buildings, methods, partitions, fireplace doorways, fire penetrations fire barriers, floors, walls and so forth. are required to be hearth rated by constructing laws, they are examined to the Standard Time Temperature protocol of BS476 elements 20 to 23 (also generally recognized as ISO834-1, ASNZS1530pt4, EN1363-1 and in America and Canada ASTM E119-75).
These tests are carried out in large furnaces to duplicate real publish flashover fireplace environments. Interestingly, Fire Resistant cable test requirements like BS 6387CWZ, SS299, IEC 60331 BS8343-1 and a pair of, BS8491 only require cables to be uncovered to a flame in air and to lower ultimate test temperatures (than required by BS476 pts 20 to 23). Given Fire Resistant cables are prone to be exposed in the identical fire, and are wanted to make sure all Life Safety and Fire Fighting methods remain operational, this truth is maybe shocking.
Contrastingly in Germany, Belgium, Australia, New Zealand, USA and Canada Fire Resistant cable systems are required to be examined to the same fire Time Temperature protocol as all other 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 many fire tests carried out in 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 as nicely as these from the German Royal Technical Research Laboratory. ตัววัดแรงดัน of the ASTM standard 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 differences between the International ISO 834-1 take a look at as we know it at present and the America ASTM E119 / NFPA 251 exams doubtless stemmed from this time.
Image courtesy of MICC Ltd.
The curve as we see it at present (see graph above) has become the usual scale for measurement of fireside take a look at severity and has proved relevant for many above floor cellulosic buildings. When components, constructions, parts or techniques are examined, the furnace temperatures are managed to conform to the curve with a set allowable variance and consideration for initial ambient temperatures. The requirements require elements to be tested in full scale and under situations of help and loading as outlined to find a way to symbolize as precisely as possible its capabilities in service.
This Standard Time Temperature testing protocol (see graph right) is adopted by almost all nations all over the world for fire testing and certification of nearly all constructing buildings, 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 systems are required to be examined and accredited to the Standard Time Temperature protocol, similar to all different building constructions, elements and components).
It is essential to understand that application standards from BS, IEC, ASNZS, DIN, UL and so forth. where hearth resistive cables are specified to be used, are only ‘minimum’ necessities. We know at present that fires aren’t all the same and research by Universities, Institutions and Authorities around the world have recognized that Underground and a few Industrial environments can exhibit very completely different fireplace 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 really quick rise time and can attain temperatures well above those in above floor buildings and in far much less time. In USA right now electrical wiring methods are required by NFPA 502 (Road Tunnels, Bridges and other Limited Access Highways) to face up to 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” where more stringent take a look at protocols for important electric cable circuits might have to be thought of by designers.
Standard Time Temperature curves (Europe and America) plotted in opposition to frequent BS and IEC cable exams.
Of course all underground environments whether street, rail and pedestrian tunnels, or underground public environments like shopping precincts, car parks etc. could exhibit totally different hearth profiles to those in above ground buildings as a end result of In these environments the heat generated by any hearth can not 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 facilities, Underground public environments like buying precincts, Very High Rise, Theaters, Public Halls, Government buildings, Airports and so forth. this is significantly important. Evacuation of those public environments is usually sluggish even throughout emergencies, and it’s our accountability to make sure everyone appears to be given the perfect likelihood of protected egress during fireplace emergencies.
It can also be understood at present that copper Fire Resistant cables where put in in galvanized metal conduit can fail prematurely during fireplace emergency due to a reaction between the copper conductors and zinc galvanizing contained in the metallic conduit. In 2012 United Laboratories (UL®) in America eliminated all certification for Fire Resistive cables the place installed in galvanized metal conduit for this reason:
UL® Quote: “A concern was delivered to our consideration related to the efficiency of those products within the presence of zinc. We validated this discovering. As a result of this, we changed our Guide Information to indicate that all conduit and conduit fittings that are out there in contact with hearth resistive cables ought to have an interior coating free of zinc”.
Time temperature profile of tunnel fires using 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 at the First International Symposium in Prague 2004: Safe and Reliable Tunnels.
It would seem that some Standards authorities around the world might have to evaluation the present test methodology presently adopted for fire resistive cable testing and perhaps align the efficiency of Life Safety and Fire Fighting wiring methods with that of all the other fire resistant structures, elements and systems in order that Architects, constructing designers and engineers know that once they need a hearth rating that the important wiring system will be equally rated.
For many power, control, communication and data circuits there is one know-how out there which might meet and surpass all present fireplace exams and purposes. It is a solution which is incessantly utilized in demanding public buildings and has been employed reliably for over 80 years. MICC cable technology can provide a total and complete reply to all the problems related to the fireplace security risks of modern versatile organic polymer cables.
The metal jacket, magnesium oxide insulation and conductors of MICC cables ensure the cable is successfully fireplace proof. Bare MICC cables don’t have any organic content material so simply cannot propagate flame or generate any smoke. The zero fuel-load of those MICC cables ensures no heat is added to the fire and no oxygen is consumed. Being inorganic these MICC cables cannot generate any halogen or poisonous gasses at all together with Carbon Monoxide. MICC cable designs can meet all of the present and constructing fireplace resistance efficiency standards in all countries and are seeing a big enhance in use globally.
Many engineers have beforehand considered MICC cable expertise to be “old school’ but with the new research in fire efficiency MICC cable system are actually proven to have far superior fire performances than any of the newer extra modern versatile fireplace resistant cables.
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