Life Safety and Fire Fighting Systems – The weakest link

Unlike different cables, hearth resistant cables need to work even when instantly exposed 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 etc.
In order to categorise electrical cables as fire resistant they’re required to undergo testing and certification. Perhaps the first frequent fireplace tests on cables were IEC 331: 1970 and later BS6387:1983 which adopted a gas ribbon burner test to supply a flame in which cables have been placed.
Since the revision of BS6387 in 1994 there have been 11 enhancements, revisions or new test standards launched by British Standards for use and utility of Fire Resistant cables however none of these seem to deal with the core issue that fireside resistant cables the place examined to common British and IEC flame take a look at requirements aren’t required to carry out to the same hearth efficiency time-temperature profiles as each other construction, system or part in a building. Specifically, the place hearth resistant constructions, systems, partitions, fire doors, fireplace penetrations fire barriers, floors, walls and so forth. are required to be fire rated by building laws, they are examined to the Standard Time Temperature protocol of BS476 components 20 to 23 (also generally known as ISO834-1, ASNZS1530pt4, EN1363-1 and in America and Canada ASTM E119-75).
These tests are carried out in giant furnaces to duplicate real submit flashover fire environments. Interestingly, Fire Resistant cable take a look at requirements like BS 6387CWZ, SS299, IEC 60331 BS8343-1 and 2, BS8491 only require cables to be uncovered to a flame in air and to decrease last test temperatures (than required by BS476 pts 20 to 23). Given Fire Resistant cables are likely to be exposed in the same fireplace, and are wanted to ensure all Life Safety and Fire Fighting methods stay operational, this reality is probably shocking.
Contrastingly in Germany, Belgium, Australia, New Zealand, USA and Canada Fire Resistant cable methods are required to be examined to the identical fire Time Temperature protocol as all different building elements 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 steering 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 within the UK, Germany and the United States. The checks had been described in a series 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 standard 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 checks at Columbia University and Underwriters Laboratories in Chicago. The small time temperature differences between the International ISO 834-1 check as we know it today and the America ASTM E119 / NFPA 251 checks doubtless stemmed from this time.
Image courtesy of MICC Ltd.
The curve as we see it right now (see graph above) has turn into the standard scale for measurement of fireplace check severity and has proved related for many above ground cellulosic buildings. When parts, structures, elements or systems are tested, the furnace temperatures are managed to evolve to the curve with a set allowable variance and consideration for initial ambient temperatures. เกจวัดแรงดันpressuregauge require components to be examined in full scale and underneath conditions of support and loading as outlined in order to characterize as accurately as potential its capabilities in service.
This Standard Time Temperature testing protocol (see graph right) is adopted by almost all international locations all over the world for fire testing and certification of just about all constructing buildings, elements, techniques and elements with the interesting exception of fireside resistant cables (exception in USA, Canada, Australia, Germany, Belgium and New Zealand the place fire resistant cable methods are required to be tested and accredited to the Standard Time Temperature protocol, similar to all different building constructions, elements and components).
It is necessary to know that application requirements from BS, IEC, ASNZS, DIN, UL and so forth. the place fire resistive cables are specified for use, are solely ‘minimum’ requirements. We know at present that fires are not all the identical and research by Universities, Institutions and Authorities around the globe have recognized that Underground and a few Industrial environments can exhibit very different fire profiles to these in above floor cellulosic buildings. Specifically in confined underground public areas like Road and Rail Tunnels, Underground Shopping centers, Car Parks fireplace temperatures can exhibit a very quick rise time and may attain temperatures nicely 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 withstand fire temperatures as much 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 more stringent check protocols for important electrical cable circuits may need to be considered by designers.
Standard Time Temperature curves (Europe and America) plotted towards widespread BS and IEC cable exams.
Of course all underground environments whether or not highway, rail and pedestrian tunnels, or underground public environments like purchasing precincts, car parks and so forth. may exhibit totally different fireplace profiles to those in above floor buildings because In these environments the heat generated by any hearth can’t escape as easily as it might in above ground buildings thus relying more on warmth and smoke extraction gear.
For Metros Road and Rail Tunnels, Hospitals, Health care amenities, Underground public environments like purchasing precincts, Very High Rise, Theaters, Public Halls, Government buildings, Airports and so on. this is particularly necessary. Evacuation of these public environments is commonly sluggish even during emergencies, and it is our accountability to make sure everyone seems to be given the very best chance of protected egress during fire emergencies.
It is also understood today that copper Fire Resistant cables the place put in in galvanized metal conduit can fail prematurely throughout fireplace 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 the place put in in galvanized steel conduit for that reason:
UL® Quote: “A concern was dropped at our attention related to the efficiency of those merchandise within the presence of zinc. We validated this discovering. As a results of this, we modified our Guide Information to indicate that each one conduit and conduit fittings that come in contact with hearth resistive cables ought to have an inside coating free of zinc”.
Time temperature profile of tunnel fires using cars, 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 presented the paper on the First International Symposium in Prague 2004: Safe and Reliable Tunnels.
It would seem that some Standards authorities around the world may must evaluate the present take a look at methodology currently adopted for fireplace resistive cable testing and maybe align the efficiency of Life Safety and Fire Fighting wiring techniques with that of all the opposite fire resistant structures, components and techniques so that Architects, building designers and engineers know that once they want a fireplace score that the important wiring system shall be equally rated.
For many power, management, communication and data circuits there could be one know-how out there which might meet and surpass all current hearth exams and purposes. It is an answer which is regularly used in demanding public buildings and has been employed reliably for over 80 years. MICC cable technology can present a total and complete reply to all the issues related to the fire security risks of contemporary flexible organic polymer cables.
The steel jacket, magnesium oxide insulation and conductors of MICC cables make sure the cable is effectively hearth proof. Bare MICC cables don’t have any natural content material so simply can not propagate flame or generate any smoke. The zero fuel-load of those MICC cables ensures no warmth is added to the hearth and no oxygen is consumed. Being inorganic these MICC cables can not generate any halogen or toxic gasses at all together with Carbon Monoxide. MICC cable designs can meet all of the present and constructing fire resistance performance standards in all countries and are seeing a big improve in use globally.
Many engineers have previously thought of MICC cable expertise to be “old school’ however with the new analysis in fire performance MICC cable system are actually proven to have far superior hearth performances than any of the newer extra trendy versatile fire resistant cables.
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