Life Safety and Fire Fighting Systems – The weakest link

Unlike different cables, fireplace resistant cables have to work even when directly exposed to the hearth to keep important 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 and so on.
In order to classify electric cables as hearth resistant they are required to endure testing and certification. Perhaps the primary common hearth exams on cables had been IEC 331: 1970 and later BS6387:1983 which adopted a gasoline ribbon burner test to provide a flame by which cables have been placed.
Since the revision of BS6387 in 1994 there have been 11 enhancements, revisions or new check standards introduced by British Standards to be used and software of Fire Resistant cables but none of those seem to deal with the core issue that fire resistant cables the place tested to frequent British and IEC flame check standards aren’t required to perform to the same fire efficiency time-temperature profiles as every different construction, system or part in a building. Specifically, the place fire resistant buildings, methods, partitions, fire doorways, fire penetrations hearth obstacles, flooring, walls and so forth. are required to be fireplace rated by constructing rules, they’re tested to the Standard Time Temperature protocol of BS476 components 20 to 23 (also known as ISO834-1, ASNZS1530pt4, EN1363-1 and in America and Canada ASTM E119-75).
These tests are performed in large furnaces to replicate actual post flashover hearth environments. Interestingly, Fire Resistant cable take a look at standards 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 check temperatures (than required by BS476 pts 20 to 23). Given Fire Resistant cables are likely to be exposed in the identical fire, and are needed to make sure all Life Safety and Fire Fighting methods remain operational, this truth is probably stunning.
Contrastingly in Germany, Belgium, Australia, New Zealand, USA and Canada Fire Resistant cable techniques are required to be tested to the identical hearth 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 standard 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 hearth exams carried out within the UK, Germany and the United States. The tests had been described in a collection 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 normal 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 variations between the International ISO 834-1 check as we all know it today and the America ASTM E119 / NFPA 251 tests probably 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 fireplace check severity and has proved relevant for most above floor cellulosic buildings. When elements, constructions, components or methods are examined, the furnace temperatures are managed to conform to the curve with a set allowable variance and consideration for preliminary ambient temperatures. The standards require elements to be examined in full scale and underneath conditions of support and loading as outlined so as to characterize as accurately as potential its capabilities in service.
This Standard Time Temperature testing protocol (see graph right) is adopted by nearly all countries all over the world for fire testing and certification of just about all constructing buildings, elements, systems and components with the interesting exception of fireplace resistant cables (exception in USA, Canada, Australia, Germany, Belgium and New Zealand the place hearth resistant cable techniques are required to be examined and accredited to the Standard Time Temperature protocol, similar to all different building structures, elements and components).
It is necessary to grasp that application requirements from BS, IEC, ASNZS, DIN, UL and so on. where hearth resistive cables are specified for use, are solely ‘minimum’ necessities. We know at present that fires aren’t all the identical and research by Universities, Institutions and Authorities around the globe have identified that Underground and some Industrial environments can exhibit very totally different fire profiles to these in above floor cellulosic buildings. Specifically in confined underground public areas like Road and Rail Tunnels, Underground Shopping facilities, Car Parks fire temperatures can exhibit a very quick rise time and might attain temperatures nicely above these 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 withstand fire temperatures as a lot as 1,350 Degrees C for 60 minutes and UK British Standard BS8519:2010 clearly identifies underground public areas such as automobile parks as “Areas of Special Risk” the place extra stringent test protocols for important electrical cable circuits could must 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 purchasing precincts, automobile parks and so forth. might exhibit totally different fire profiles to those in above ground buildings as a result of In these environments the warmth generated by any fireplace can’t escape as easily as it’d in above floor buildings thus relying more on heat and smoke extraction gear.
For เกวัดแรงดัน and Rail Tunnels, Hospitals, Health care facilities, Underground public environments like purchasing precincts, Very High Rise, Theaters, Public Halls, Government buildings, Airports etc. this is particularly essential. Evacuation of these public environments is often sluggish even throughout emergencies, and it’s our responsibility to make sure everyone is given the easiest likelihood of protected egress throughout fire emergencies.
It is also understood today that copper Fire Resistant cables where installed in galvanized steel conduit can fail prematurely throughout 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 the place installed in galvanized steel conduit for that reason:
UL® Quote: “A concern was brought to our consideration related to the performance of these products in the presence of zinc. We validated this finding. As a results of this, we changed our Guide Information to indicate that every one conduit and conduit fittings that are obtainable in contact with fireplace resistive cables should have an inside coating freed from 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 offered the paper on the First International Symposium in Prague 2004: Safe and Reliable Tunnels.
It would appear that some Standards authorities around the globe might must evaluate the current test methodology at present adopted for hearth resistive cable testing and perhaps align the efficiency of Life Safety and Fire Fighting wiring techniques with that of all the other hearth resistant constructions, parts and techniques in order that Architects, constructing designers and engineers know that when they want a fireplace ranking that the important wiring system shall be equally rated.
For many energy, control, communication and knowledge circuits there could be one technology available which may meet and surpass all present fireplace tests and applications. It is a solution which is incessantly used in demanding public buildings and has been employed reliably for over 80 years. MICC cable expertise can present a complete and full answer to all the issues associated with the hearth safety dangers of recent versatile natural polymer cables.
The metal jacket, magnesium oxide insulation and conductors of MICC cables make sure the cable is successfully fire proof. Bare MICC cables don’t have any natural content so simply cannot propagate flame or generate any smoke. The zero fuel-load of these MICC cables ensures no warmth is added to the fire and no oxygen is consumed. Being inorganic these MICC cables can’t generate any halogen or poisonous gasses in any respect together with Carbon Monoxide. MICC cable designs can meet all of the present and constructing fireplace resistance efficiency standards in all nations and are seeing a significant enhance in use globally.
Many engineers have previously thought of MICC cable know-how to be “old school’ but with the brand new analysis in fire efficiency MICC cable system at the second are confirmed to have far superior hearth performances than any of the newer extra trendy versatile fireplace resistant cables.
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