Unlike other cables, fire resistant cables have to work even when directly exposed to the fireplace to keep essential Life Safety and Fire Fighting equipment working: Fire alarms, Emergency Lighting, Emergency Communication, Fire Sprinkler pumps, Fireman’s Lift sub-main, Smoke extraction followers, Smoke dampers, Stair pressurization fans, Emergency Generator circuits and so on.
In order to classify electrical cables as hearth resistant they are required to undergo testing and certification. Perhaps the primary widespread fire checks on cables were IEC 331: 1970 and later BS6387:1983 which adopted a fuel ribbon burner check to provide 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 launched by British Standards for use and application of Fire Resistant cables but none of those appear to deal with the core concern that fire resistant cables where tested to frequent British and IEC flame take a look at standards usually are not required to perform to the same fireplace performance time-temperature profiles as every other construction, system or component in a building. Specifically, where fire resistant buildings, systems, partitions, hearth doorways, fire penetrations fireplace limitations, floors, walls and so forth. are required to be fireplace rated by constructing laws, they’re examined to the Standard Time Temperature protocol of BS476 elements 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 duplicate actual submit flashover hearth environments. Interestingly, Fire Resistant cable check requirements like BS 6387CWZ, SS299, IEC 60331 BS8343-1 and 2, BS8491 solely require cables to be exposed to a flame in air and to decrease ultimate test temperatures (than required by BS476 pts 20 to 23). Given Fire Resistant cables are more probably to be exposed in the same hearth, and are wanted to make sure all Life Safety and Fire Fighting methods stay operational, this truth is maybe 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 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 developing 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 many fireplace exams carried out in the UK, Germany and the United States. The tests were described in a collection 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 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 variations between the International ISO 834-1 take a look at as we know it right now and the America ASTM E119 / NFPA 251 tests doubtless stemmed from this time.
Image courtesy of MICC Ltd.
The curve as we see it right now (see graph above) has become the usual scale for measurement of fireside test severity and has proved related for many above floor cellulosic buildings. When parts, constructions, elements or techniques are examined, the furnace temperatures are controlled to adapt to the curve with a set allowable variance and consideration for preliminary ambient temperatures. The standards require components to be examined in full scale and under situations of help and loading as outlined so as to symbolize as precisely as potential its features in service.
This Standard Time Temperature testing protocol (see graph right) is adopted by virtually all international locations all over the world for fire testing and certification of just about all building buildings, components, systems 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 methods are required to be tested and accredited to the Standard Time Temperature protocol, just like all different building structures, components and components).
It is important to grasp that utility standards from BS, IEC, ASNZS, DIN, UL and so forth. where fire resistive cables are specified for use, are only ‘minimum’ requirements. We know today that fires are not all the identical and research by Universities, Institutions and Authorities around the world have identified that Underground and a few Industrial environments can exhibit very totally different fireplace profiles to these in above floor cellulosic buildings. Specifically in confined underground public areas like Road and Rail Tunnels, Underground Shopping facilities, Car Parks hearth temperatures can exhibit a really quick rise time and may reach temperatures properly above these in above ground buildings and in far less time. In USA at present electrical wiring methods are required by NFPA 502 (Road Tunnels, Bridges and different Limited Access Highways) to resist fireplace 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” where more stringent take a look at protocols for important electrical cable circuits could need to be thought of by designers.
Standard Time Temperature curves (Europe and America) plotted against frequent BS and IEC cable tests.
Of course all underground environments whether highway, rail and pedestrian tunnels, or underground public environments like buying precincts, automotive parks etc. may exhibit completely different hearth profiles to those in above ground buildings as a end result of In these environments the warmth generated by any fireplace can’t escape as simply as it would in above floor buildings thus relying more on heat and smoke extraction equipment.
For Metros Road and Rail Tunnels, Hospitals, Health care services, Underground public environments like buying precincts, Very High Rise, Theaters, Public Halls, Government buildings, Airports etc. that is particularly important. Evacuation of those public environments is commonly sluggish even throughout emergencies, and it’s our responsibility to make sure everyone is given the very best chance of protected egress throughout fire emergencies.
It can additionally be understood right now that copper Fire Resistant cables the place put in in galvanized metal conduit can fail prematurely throughout fireplace emergency because of a reaction between the copper conductors and zinc galvanizing contained in the metal conduit. In 2012 United Laboratories (UL®) in America eliminated all certification for Fire Resistive cables the place put in in galvanized metal conduit because of this:
UL® Quote: “A concern was delivered to our attention related to the efficiency of those merchandise within the presence of zinc. We validated this discovering. As a result of this, we modified our Guide Information to indicate that each one conduit and conduit fittings that are available contact with fireplace resistive cables should have an inside coating free of zinc”.
Time temperature profile of tunnel fires utilizing 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 offered the paper at the First International Symposium in Prague 2004: Safe and Reliable Tunnels.
diaphragm seal would seem that some Standards authorities all over the world might have to review the present take a look at methodology presently adopted for hearth resistive cable testing and perhaps align the performance of Life Safety and Fire Fighting wiring methods with that of all the opposite fire resistant constructions, elements and systems so that Architects, constructing designers and engineers know that after they need a fire rating that the essential wiring system will be equally rated.
For many energy, control, communication and knowledge circuits there is one expertise obtainable which might meet and surpass all current fireplace tests and applications. It is a solution which is incessantly used in demanding public buildings and has been employed reliably for over eighty years. MICC cable technology can present a total and complete answer to all the problems related to the fireplace security risks of modern flexible organic polymer cables.
The metallic jacket, magnesium oxide insulation and conductors of MICC cables ensure the cable is successfully hearth proof. Bare MICC cables have no organic content material so simply 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 can’t generate any halogen or toxic gasses at all together with Carbon Monoxide. MICC cable designs can meet the entire present and building fireplace resistance performance standards in all international locations and are seeing a major increase in use globally.
Many engineers have previously thought of MICC cable know-how to be “old school’ but with the brand new analysis in hearth performance MICC cable system are actually proven to have far superior fire performances than any of the newer extra fashionable flexible hearth resistant cables.
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