Life Safety and Fire Fighting Systems – The weakest link

Unlike other cables, hearth resistant cables should work even when immediately exposed to the fire 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 followers, Emergency Generator circuits and so on.
In order to classify electric cables as fireplace resistant they’re required to bear testing and certification. Perhaps the first widespread fireplace exams on cables had been IEC 331: 1970 and later BS6387:1983 which adopted a gas ribbon burner take a look at to provide a flame during which cables had been placed.
Since เครื่องมือที่ใช้วัดความดันเลือด of BS6387 in 1994 there have been eleven enhancements, revisions or new test standards introduced by British Standards to be used and application of Fire Resistant cables however none of these appear to handle the core problem that fireside resistant cables the place examined to common British and IEC flame check requirements are not required to perform to the identical fireplace performance time-temperature profiles as each different construction, system or part in a constructing. Specifically, the place hearth resistant constructions, systems, partitions, fireplace doorways, fire penetrations hearth limitations, floors, partitions and so forth. are required to be fireplace rated by building laws, they are tested to the Standard Time Temperature protocol of BS476 parts 20 to 23 (also often recognized as ISO834-1, ASNZS1530pt4, EN1363-1 and in America and Canada ASTM E119-75).
These checks are performed in giant furnaces to duplicate real post flashover hearth environments. Interestingly, Fire Resistant cable check requirements 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 decrease last check temperatures (than required by BS476 pts 20 to 23). Given Fire Resistant cables are more doubtless to be uncovered in the identical fire, and are wanted to make sure all Life Safety and Fire Fighting systems remain operational, this reality is maybe surprising.
Contrastingly in Germany, Belgium, Australia, New Zealand, USA and Canada Fire Resistant cable techniques are required to be tested to the identical fireplace 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 growing the usual drew on the steerage 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 in the UK, Germany and the United States. The exams had been described in a sequence of “Red Books” issued by the British Fire Prevention Committee after 1903 as well as 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 exams 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 likely stemmed from this time.
Image courtesy of MICC Ltd.
The curve as we see it today (see graph above) has become the usual scale for measurement of fireside check severity and has proved related for most above ground cellulosic buildings. When components, structures, parts or techniques are tested, the furnace temperatures are controlled to adapt to the curve with a set allowable variance and consideration for preliminary ambient temperatures. The requirements require parts to be tested in full scale and underneath situations of support and loading as outlined so as to characterize as precisely as attainable its functions in service.
This Standard Time Temperature testing protocol (see graph right) is adopted by nearly all international locations around the globe for fire testing and certification of nearly all building buildings, components, techniques and parts with the fascinating exception of fireside resistant cables (exception in USA, Canada, Australia, Germany, Belgium and New Zealand the place fireplace resistant cable methods are required to be examined and permitted to the Standard Time Temperature protocol, similar to all other constructing structures, parts and components).
It is necessary to understand that software requirements from BS, IEC, ASNZS, DIN, UL etc. the place fire resistive cables are specified to be used, are solely ‘minimum’ requirements. We know at present that fires are not all the same and research by Universities, Institutions and Authorities all over the world have identified that Underground and a few Industrial environments can exhibit very totally different hearth profiles to these in above ground cellulosic buildings. Specifically in confined underground public areas like Road and Rail Tunnels, Underground Shopping facilities, Car Parks fireplace temperatures can exhibit a really fast rise time and may reach temperatures properly above those in above floor buildings and in far much less time. In USA right now electrical wiring techniques are required by NFPA 502 (Road Tunnels, Bridges and other Limited Access Highways) to withstand fireplace 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 automotive parks as “Areas of Special Risk” the place more stringent take a look at protocols for important electrical cable circuits may have to be thought of by designers.
Standard Time Temperature curves (Europe and America) plotted towards common BS and IEC cable exams.
Of course all underground environments whether or not road, rail and pedestrian tunnels, or underground public environments like purchasing precincts, automotive parks etc. could exhibit different hearth profiles to those in above ground buildings as a end result of In these environments the warmth generated by any hearth cannot escape as easily as it might in above ground buildings thus relying more on warmth and smoke extraction tools.
For Metros Road and Rail Tunnels, Hospitals, Health care services, Underground public environments like purchasing precincts, Very High Rise, Theaters, Public Halls, Government buildings, Airports etc. that is notably essential. Evacuation of those public environments is often slow even during emergencies, and it’s our responsibility to make sure everyone is given the very best likelihood of safe egress throughout hearth emergencies.
It can be understood at present that copper Fire Resistant cables the place put in in galvanized steel conduit can fail prematurely during fire emergency because of a reaction between the copper conductors and zinc galvanizing inside the metallic conduit. In 2012 United Laboratories (UL®) in America removed all certification for Fire Resistive cables the place put in in galvanized metal conduit for that reason:
UL® Quote: “A concern was delivered to our attention associated to the performance of these merchandise within the presence of zinc. We validated this finding. As a results of this, we changed our Guide Information to point that every one conduit and conduit fittings that are available contact with fireplace resistive cables should have an inside coating freed from zinc”.
Time temperature profile of tunnel fires utilizing 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 offered 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 need to review the current test methodology currently 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 fire resistant buildings, elements and systems so that Architects, building designers and engineers know that after they need a fire ranking that the important wiring system shall be equally rated.
For many power, management, communication and information circuits there’s one expertise obtainable which can meet and surpass all current hearth checks and applications. It is a solution which is incessantly utilized in demanding public buildings and has been employed reliably for over eighty years. MICC cable technology can present a total and complete reply to all the issues associated with the fireplace safety risks of recent versatile organic polymer cables.
The metal jacket, magnesium oxide insulation and conductors of MICC cables make certain the cable is successfully fire proof. Bare MICC cables don’t have any organic 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 fire and no oxygen is consumed. Being inorganic these MICC cables cannot generate any halogen or toxic gasses in any respect together with Carbon Monoxide. MICC cable designs can meet the entire present and constructing hearth resistance efficiency requirements in all nations and are seeing a major enhance in use globally.
Many engineers have previously thought-about MICC cable know-how to be “old school’ however with the model new analysis in fireplace performance MICC cable system are now proven to have far superior hearth performances than any of the newer more trendy versatile fire resistant cables.
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