Life Safety and Fire Fighting Systems – The weakest link

Unlike different cables, hearth resistant cables should work even when instantly exposed to the hearth to maintain important 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 categorise electrical cables as fire resistant they’re required to endure testing and certification. Perhaps the primary frequent hearth checks on cables have been IEC 331: 1970 and later BS6387:1983 which adopted a gas ribbon burner test to produce a flame during which cables had been placed.
Since เพรสเชอร์เกจ4นิ้ว of BS6387 in 1994 there have been eleven enhancements, revisions or new take a look at requirements launched by British Standards to be used and software of Fire Resistant cables but none of these seem to handle the core concern that fireplace resistant cables where tested to frequent British and IEC flame test standards usually are not required to perform to the same hearth efficiency time-temperature profiles as each different construction, system or part in a building. Specifically, where hearth resistant buildings, systems, partitions, fireplace doorways, fire penetrations hearth barriers, floors, walls and so forth. are required to be hearth rated by building rules, they are examined 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).
These exams are conducted in large furnaces to replicate real post flashover fire 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 check temperatures (than required by BS476 pts 20 to 23). Given Fire Resistant cables are likely to be uncovered in the same fireplace, and are needed to make sure all Life Safety and Fire Fighting techniques remain operational, this fact is probably surprising.
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 different 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 creating the usual drew on the steering given from the International Fire Prevention Congress held in London in July 1903 and the measurements of furnace temperatures made in plenty of fireplace tests carried out in the UK, Germany and the United States. The tests had been described in a sequence of “Red Books” issued by the British Fire Prevention Committee after 1903 as nicely as those from the German Royal Technical Research Laboratory. The finalization 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 exams at Columbia University and Underwriters Laboratories in Chicago. The small time temperature differences between the International ISO 834-1 check as we know it at present and the America ASTM E119 / NFPA 251 exams probably stemmed from this time.
Image courtesy of MICC Ltd.
The curve as we see it at present (see graph above) has become the standard scale for measurement of fireplace test severity and has proved related for many above ground cellulosic buildings. When components, structures, parts or methods are examined, the furnace temperatures are controlled to adapt to the curve with a set allowable variance and consideration for initial ambient temperatures. The requirements require components to be tested in full scale and under circumstances of help and loading as outlined to have the ability to represent as precisely as potential its features in service.
This Standard Time Temperature testing protocol (see graph right) is adopted by virtually all nations all over the world for fire testing and certification of just about all building constructions, elements, techniques and elements with the attention-grabbing exception of fire resistant cables (exception in USA, Canada, Australia, Germany, Belgium and New Zealand the place fireplace resistant cable systems are required to be examined and approved to the Standard Time Temperature protocol, just like all other building constructions, parts and components).
It is necessary to know that utility requirements from BS, IEC, ASNZS, DIN, UL and so forth. the place hearth resistive cables are specified for use, are solely ‘minimum’ necessities. We know at present that fires aren’t all the same and analysis by Universities, Institutions and Authorities around the world have identified that Underground and a few Industrial environments can exhibit very totally different fire 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 can attain temperatures properly above those in above floor buildings and in far less time. In USA today electrical wiring methods are required by NFPA 502 (Road Tunnels, Bridges and different Limited Access Highways) to resist fireplace temperatures up to 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 important electrical cable circuits may must be considered by designers.
Standard Time Temperature curves (Europe and America) plotted in opposition to frequent BS and IEC cable checks.
Of course all underground environments whether highway, rail and pedestrian tunnels, or underground public environments like shopping precincts, car parks etc. might exhibit totally different fire profiles to these in above ground buildings as a outcome of In these environments the warmth generated by any fire cannot escape as simply as it would in above ground buildings thus relying extra on heat 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 notably essential. Evacuation of those public environments is usually slow even throughout emergencies, and it’s our responsibility to make sure everyone is given the perfect likelihood of secure egress throughout hearth emergencies.
It is also understood at present that copper Fire Resistant cables the place installed in galvanized metal conduit can fail prematurely during fire emergency due to a reaction 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 metal conduit because of this:
UL® Quote: “A concern was brought to our attention associated to the performance of these products within the presence of zinc. We validated this discovering. As a results of this, we modified our Guide Information to point that all conduit and conduit fittings that come in contact with hearth 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 offered the paper on the First International Symposium in Prague 2004: Safe and Reliable Tunnels.
It would seem that some Standards authorities all over the world may need to review the present check methodology currently adopted for fire resistive cable testing and perhaps align the performance of Life Safety and Fire Fighting wiring techniques with that of all the opposite hearth resistant constructions, parts and techniques so that Architects, constructing designers and engineers know that when they want a fire rating that the essential wiring system shall be equally rated.
For many energy, management, communication and information circuits there might be one expertise obtainable which may meet and surpass all present hearth exams and purposes. It is a solution which is regularly utilized in demanding public buildings and has been employed reliably for over 80 years. MICC cable know-how can present a complete and complete answer to all the problems associated with the fire security dangers of recent versatile natural polymer cables.
The metal jacket, magnesium oxide insulation and conductors of MICC cables make sure the cable is successfully hearth proof. Bare MICC cables have no natural content so merely can’t propagate flame or generate any smoke. The zero fuel-load of these MICC cables ensures no heat is added to the fireplace and no oxygen is consumed. Being inorganic these MICC cables cannot generate any halogen or poisonous gasses in any respect including Carbon Monoxide. MICC cable designs can meet all of the current and constructing fireplace resistance efficiency standards in all nations and are seeing a big increase in use globally.
Many engineers have beforehand thought of MICC cable expertise to be “old school’ but with the brand new analysis in fireplace performance MICC cable system are actually proven to have far superior hearth performances than any of the newer more trendy versatile hearth resistant cables.
For further data, go to www.temperature-house.com
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