Life Safety and Fire Fighting Systems – The weakest link

Unlike different cables, fire resistant cables should work even when immediately exposed to the fire to maintain important 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 forth.
In order to categorise electrical cables as fire resistant they’re required to endure testing and certification. Perhaps the first widespread fire exams on cables have been IEC 331: 1970 and later BS6387:1983 which adopted a gas ribbon burner check to produce a flame by which cables have been placed.
Since the revision of BS6387 in 1994 there have been eleven enhancements, revisions or new test standards introduced by British Standards for use and application of Fire Resistant cables but none of those seem to deal with the core issue that fireside resistant cables the place examined to widespread British and IEC flame test requirements usually are not required to carry out to the identical hearth performance time-temperature profiles as each different structure, system or part in a building. Specifically, where hearth resistant structures, techniques, partitions, hearth doorways, fire penetrations fireplace limitations, floors, walls and so on. are required to be hearth rated by building laws, they’re examined to the Standard Time Temperature protocol of BS476 parts 20 to 23 (also known as ISO834-1, ASNZS1530pt4, EN1363-1 and in America and Canada ASTM E119-75).
These checks are conducted in large furnaces to replicate real post flashover fireplace environments. Interestingly, Fire Resistant cable take a look at requirements like BS 6387CWZ, SS299, IEC 60331 BS8343-1 and a couple of, BS8491 solely require cables to be uncovered to a flame in air and to lower last test temperatures (than required by BS476 pts 20 to 23). Given Fire Resistant cables are more doubtless to be exposed in the identical fire, and are wanted to make sure all Life Safety and Fire Fighting methods remain operational, this reality is maybe stunning.
Contrastingly in Germany, Belgium, Australia, New Zealand, USA and Canada Fire Resistant cable systems are required to be tested to the identical fireplace Time Temperature protocol as all different constructing 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 steering given from the International Fire Prevention Congress held in London in July 1903 and the measurements of furnace temperatures made in many hearth exams carried out within the UK, Germany and the United States. The exams 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. เกจวัดแรงดันลม 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 tests at Columbia University and Underwriters Laboratories in Chicago. The small time temperature differences between the International ISO 834-1 take a look at 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 at present (see graph above) has turn into the usual scale for measurement of fireside check severity and has proved related for many above ground cellulosic buildings. When parts, structures, parts or methods are tested, the furnace temperatures are controlled to conform to the curve with a set allowable variance and consideration for initial ambient temperatures. The standards require components to be tested in full scale and underneath circumstances of help and loading as defined to be able to represent as precisely as attainable 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 nearly all building structures, parts, techniques and elements with the fascinating exception of fire resistant cables (exception in USA, Canada, Australia, Germany, Belgium and New Zealand where fire resistant cable techniques are required to be tested and accredited to the Standard Time Temperature protocol, identical to all different constructing buildings, elements and components).
It is important to grasp that application standards from BS, IEC, ASNZS, DIN, UL etc. where fire resistive cables are specified for use, are only ‘minimum’ requirements. We know at present that fires aren’t all the identical and analysis by Universities, Institutions and Authorities around the world have recognized that Underground and some Industrial environments can exhibit very totally different fireplace profiles to those 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 very quick rise time and may reach temperatures nicely above those in above floor buildings and in far less time. In USA right now electrical wiring methods are required by NFPA 502 (Road Tunnels, Bridges and different Limited Access Highways) to withstand fire temperatures up to 1,350 Degrees C for 60 minutes and UK British Standard BS8519:2010 clearly identifies underground public areas corresponding to automotive parks as “Areas of Special Risk” where more stringent check protocols for essential electrical cable circuits may need to be thought-about by designers.
Standard Time Temperature curves (Europe and America) plotted in opposition to frequent BS and IEC cable tests.
Of course all underground environments whether street, rail and pedestrian tunnels, or underground public environments like buying precincts, automobile parks etc. could exhibit totally different fire profiles to these in above ground buildings because In these environments the warmth generated by any fireplace can not escape as simply as it would in above ground buildings thus relying more on warmth and smoke extraction tools.
For Metros Road and Rail Tunnels, Hospitals, Health care facilities, Underground public environments like buying precincts, Very High Rise, Theaters, Public Halls, Government buildings, Airports etc. this is significantly necessary. Evacuation of those public environments is often gradual even throughout emergencies, and it’s our duty to ensure everyone is given the perfect probability of safe egress throughout fireplace emergencies.
It can also be understood right now that copper Fire Resistant cables the place put in in galvanized steel conduit can fail prematurely during hearth emergency due to a reaction between the copper conductors and zinc galvanizing inside the metal conduit. In 2012 United Laboratories (UL®) in America eliminated all certification for Fire Resistive cables the place installed in galvanized metal conduit for this reason:
UL® Quote: “A concern was brought to our attention associated to the performance of these merchandise in the presence of zinc. We validated this finding. As a results of this, we modified our Guide Information to indicate that all conduit and conduit fittings that are available contact with fire resistive cables ought to have an interior 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 introduced the paper at the First International Symposium in Prague 2004: Safe and Reliable Tunnels.
It would seem that some Standards authorities around the world might must review the current check methodology at present 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 hearth resistant buildings, components and techniques so that Architects, constructing designers and engineers know that when they need a hearth rating that the essential wiring system will be equally rated.
For many power, management, communication and knowledge circuits there could be one know-how obtainable which can meet and surpass all current hearth exams and applications. It is an answer which is regularly used in demanding public buildings and has been employed reliably for over eighty years. MICC cable technology can provide a complete and full reply to all the problems related to the hearth safety dangers of recent versatile organic polymer cables.
The metallic jacket, magnesium oxide insulation and conductors of MICC cables ensure the cable is successfully fire proof. Bare MICC cables haven’t any natural content material so simply cannot propagate flame or generate any smoke. The zero fuel-load of those MICC cables ensures no heat is added to the hearth and no oxygen is consumed. Being inorganic these MICC cables can not generate any halogen or toxic gasses in any respect together with Carbon Monoxide. MICC cable designs can meet the entire current and building fire resistance performance requirements in all countries and are seeing a big improve in use globally.
Many engineers have previously thought of MICC cable know-how to be “old school’ however with the model new research in hearth efficiency MICC cable system at the moment are proven to have far superior fire performances than any of the newer extra fashionable flexible hearth resistant cables.
For further information, go to www.temperature-house.com
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