Unlike different cables, hearth resistant cables should work even when directly exposed to the hearth 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 fans, Smoke dampers, Stair pressurization fans, Emergency Generator circuits etc.
In order to classify electrical cables as fireplace resistant they’re required to undergo testing and certification. Perhaps the first common fire checks on cables were IEC 331: 1970 and later BS6387:1983 which adopted a fuel ribbon burner check to supply a flame by which cables had been placed.
Since the revision of BS6387 in 1994 there have been eleven enhancements, revisions or new take a look at standards introduced by British Standards for use and utility of Fire Resistant cables however none of those appear to deal with the core problem that fireside resistant cables the place tested to widespread British and IEC flame take a look at requirements are not required to perform to the same hearth performance time-temperature profiles as every different construction, system or part in a building. Specifically, the place hearth resistant structures, systems, partitions, hearth doors, fire penetrations hearth barriers, flooring, walls etc. are required to be fireplace rated by building rules, they’re 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 copy real submit flashover fire environments. Interestingly, Fire Resistant cable take a look at 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 last take a look at temperatures (than required by BS476 pts 20 to 23). Given Fire Resistant cables are more probably to be exposed in the same fire, and are wanted to make sure all Life Safety and Fire Fighting systems stay operational, this fact is maybe surprising.
Contrastingly in Germany, Belgium, Australia, New Zealand, USA and Canada Fire Resistant cable techniques are required to be examined to the same fireplace Time Temperature protocol as all different constructing components 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 steering given from the International Fire Prevention Congress held in London in July 1903 and the measurements of furnace temperatures made in plenty of fire tests carried out in the UK, Germany and the United States. The exams have been described in a series 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 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 variations between the International ISO 834-1 check as we all know it today and the America ASTM E119 / NFPA 251 tests likely 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 fire take a look at severity and has proved related for many above floor cellulosic buildings. When elements, buildings, components or methods are examined, 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 under situations of assist and loading as outlined in order to symbolize as accurately 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 just about all constructing structures, components, systems and components with the fascinating exception of fireplace resistant cables (exception in USA, Canada, Australia, Germany, Belgium and New Zealand where fire resistant cable methods are required to be examined and accredited to the Standard Time Temperature protocol, identical to all different constructing constructions, components and components).
It is essential to grasp that utility requirements from BS, IEC, ASNZS, DIN, UL and so forth. the place hearth resistive cables are specified to be used, are solely ‘minimum’ requirements. We know at present that fires usually are not all the identical and analysis by Universities, Institutions and Authorities all over the world have identified that Underground and some Industrial environments can exhibit very totally different hearth profiles to these in above floor cellulosic buildings. Specifically in confined เกจ์แรงดัน like Road and Rail Tunnels, Underground Shopping facilities, Car Parks hearth temperatures can exhibit a really quick rise time and may reach temperatures nicely above those in above ground buildings and in far much less time. In USA at present electrical wiring methods are required by NFPA 502 (Road Tunnels, Bridges and other Limited Access Highways) to face up to fireplace temperatures up to 1,350 Degrees C for 60 minutes and UK British Standard BS8519:2010 clearly identifies underground public areas corresponding to automobile parks as “Areas of Special Risk” where more stringent check protocols for essential electric cable circuits might have to be considered by designers.
Standard Time Temperature curves (Europe and America) plotted in opposition to widespread BS and IEC cable checks.
Of course all underground environments whether street, rail and pedestrian tunnels, or underground public environments like buying precincts, car parks and so forth. could exhibit totally different fireplace profiles to these in above floor buildings as a result of In these environments the warmth generated by any fire can’t escape as simply as it might in above floor buildings thus relying more on heat and smoke extraction equipment.
For Metros Road and Rail Tunnels, Hospitals, Health care amenities, Underground public environments like buying precincts, Very High Rise, Theaters, Public Halls, Government buildings, Airports and so on. this is significantly essential. Evacuation of those public environments is commonly sluggish even throughout emergencies, and it is our responsibility to ensure everyone is given the perfect chance of protected egress throughout fire emergencies.
It is also understood right now that copper Fire Resistant cables the place installed in galvanized metal conduit can fail prematurely during hearth emergency due to 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 where put in in galvanized steel conduit because of this:
UL® Quote: “A concern was delivered to our attention associated to the efficiency of those products within the presence of zinc. We validated this finding. As a results of this, we changed our Guide Information to point that each one conduit and conduit fittings that are available contact with fire resistive cables should 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 presented the paper at the First International Symposium in Prague 2004: Safe and Reliable Tunnels.
It would appear that some Standards authorities around the globe might need to evaluate the current check methodology at present adopted for hearth resistive cable testing and maybe align the efficiency of Life Safety and Fire Fighting wiring methods with that of all the opposite fire resistant constructions, elements and methods in order that Architects, constructing designers and engineers know that once they want a hearth ranking that the important wiring system will be equally rated.
For many energy, management, communication and data circuits there’s one expertise available which may meet and surpass all present fire checks and applications. It is an answer which is frequently utilized 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 associated with the fireplace security risks of recent flexible organic polymer cables.
The steel jacket, magnesium oxide insulation and conductors of MICC cables ensure the cable is effectively hearth proof. Bare MICC cables have no natural content material so merely can not propagate flame or generate any smoke. The zero fuel-load of those MICC cables ensures no warmth is added to the fire and no oxygen is consumed. Being inorganic these MICC cables can not generate any halogen or toxic gasses in any respect including Carbon Monoxide. MICC cable designs can meet all of the current and building hearth resistance efficiency standards in all countries and are seeing a significant increase in use globally.
Many engineers have previously considered MICC cable technology to be “old school’ however with the model new analysis in hearth efficiency MICC cable system are now confirmed to have far superior fireplace performances than any of the newer more modern flexible fire resistant cables.
For additional data, go to www.temperature-house.com
Share this:
Share