Life Safety and Fire Fighting Systems – The weakest link

Unlike other cables, fireplace resistant cables need to work even when instantly exposed to the hearth 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 fans, Smoke dampers, Stair pressurization fans, Emergency Generator circuits and so on.
In order to categorise electric cables as fire resistant they are required to endure testing and certification. Perhaps the first common hearth checks on cables have been IEC 331: 1970 and later BS6387:1983 which adopted a gasoline ribbon burner test to supply a flame by which cables have been placed.
Since the revision of BS6387 in 1994 there have been eleven enhancements, revisions or new check standards introduced by British Standards for use and utility of Fire Resistant cables but none of those seem to deal with the core problem that fire resistant cables where examined to widespread British and IEC flame check requirements are not required to carry out to the identical hearth performance time-temperature profiles as each different construction, system or element in a constructing. Specifically, the place hearth resistant constructions, methods, partitions, fireplace doorways, hearth penetrations hearth barriers, floors, partitions etc. 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 known as ISO834-1, ASNZS1530pt4, EN1363-1 and in America and Canada ASTM E119-75).
These checks are conducted in giant furnaces to duplicate actual publish flashover hearth environments. Interestingly, Fire Resistant cable test 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 decrease ultimate check temperatures (than required by BS476 pts 20 to 23). Given Fire Resistant cables are prone to be exposed in the identical hearth, and are wanted to make sure all Life Safety and Fire Fighting techniques 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 examined to the identical fireplace Time Temperature protocol as all other building components 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 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 tests carried out in the UK, Germany and the United States. The tests were described in a sequence 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 normal 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 tests at Columbia University and Underwriters Laboratories in Chicago. The small time temperature differences between the International ISO 834-1 test as we know it at present and the America ASTM E119 / NFPA 251 checks likely stemmed from this time.
Image courtesy of MICC Ltd.
The curve as we see it at present (see graph above) has become the usual scale for measurement of fireplace take a look at severity and has proved relevant for most above floor cellulosic buildings. When elements, constructions, parts or techniques are tested, the furnace temperatures are controlled to evolve to the curve with a set allowable variance and consideration for preliminary ambient temperatures. The standards require elements to be tested in full scale and under circumstances of help and loading as defined so as to characterize as precisely as possible its features in service.
ราคาเพรสเชอร์เกจ (see graph right) is adopted by almost all international locations around the world for fire testing and certification of nearly all building structures, parts, techniques and parts with the fascinating exception of fireside resistant cables (exception in USA, Canada, Australia, Germany, Belgium and New Zealand the place hearth resistant cable methods are required to be tested and accredited to the Standard Time Temperature protocol, similar to all different constructing structures, parts and components).
It is essential to know that software requirements from BS, IEC, ASNZS, DIN, UL etc. where hearth resistive cables are specified for use, are solely ‘minimum’ requirements. We know right now 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 different hearth profiles to these in above floor cellulosic buildings. Specifically in confined underground public areas like Road and Rail Tunnels, Underground Shopping centers, Car Parks fire temperatures can exhibit a really fast rise time and might reach temperatures well above those in above ground buildings and in far much less time. In USA at present electrical wiring techniques are required by NFPA 502 (Road Tunnels, Bridges and other Limited Access Highways) to resist fire temperatures up to 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 test protocols for essential electric cable circuits may have to be thought of by designers.
Standard Time Temperature curves (Europe and America) plotted in opposition to common BS and IEC cable checks.
Of course all underground environments whether highway, rail and pedestrian tunnels, or underground public environments like shopping precincts, automotive parks and so forth. might exhibit completely different fire profiles to those in above ground buildings as a result of In these environments the heat generated by any fire can not escape as simply as it’d in above floor buildings thus relying extra on warmth and smoke extraction equipment.
For Metros Road and Rail Tunnels, Hospitals, Health care amenities, Underground public environments like shopping precincts, Very High Rise, Theaters, Public Halls, Government buildings, Airports and so forth. this is significantly important. Evacuation of those public environments is often slow even during emergencies, and it’s our accountability to ensure everyone appears to be given the easiest probability of safe egress throughout fireplace emergencies.
It can also be understood right now that copper Fire Resistant cables where installed in galvanized steel conduit can fail prematurely throughout fireplace emergency due to a reaction between the copper conductors and zinc galvanizing contained in the steel conduit. In 2012 United Laboratories (UL®) in America removed all certification for Fire Resistive cables where put in in galvanized metal conduit for this 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 discovering. As a result of this, we modified our Guide Information to point that all conduit and conduit fittings that come in contact with hearth resistive cables ought to have an inside coating freed from zinc”.
Time temperature profile of tunnel fires utilizing vehicles, HGV trailers with different cargo and rail carriages. Graph extract: Haukur Ingason and Anders Lonnermark of the Swedish National Testing and Research Institute who introduced the paper on the First International Symposium in Prague 2004: Safe and Reliable Tunnels.
It would seem that some Standards authorities all over the world could have to review the current test methodology at present adopted for hearth resistive cable testing and maybe align the performance of Life Safety and Fire Fighting wiring systems with that of all the opposite fire resistant constructions, elements and methods so that Architects, constructing designers and engineers know that once they want a fire ranking that the essential wiring system shall be equally rated.
For many energy, control, communication and data circuits there’s one know-how out there which may meet and surpass all current fire checks and purposes. It is a solution which is frequently utilized in demanding public buildings and has been employed reliably for over eighty years. MICC cable technology can present a complete and full answer to all the problems related to the fire safety risks of contemporary flexible organic polymer cables.
The metal jacket, magnesium oxide insulation and conductors of MICC cables ensure the cable is effectively fire proof. Bare MICC cables have no organic content material so merely can not propagate flame or generate any smoke. The zero fuel-load of these MICC cables ensures no warmth is added to the fireplace 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 current and constructing fireplace resistance efficiency standards in all international locations and are seeing a significant improve in use globally.
Many engineers have previously thought-about MICC cable expertise to be “old school’ but with the new research in fire efficiency MICC cable system at the moment are proven to have far superior hearth performances than any of the newer more modern flexible fireplace resistant cables.
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