Life Safety and Fire Fighting Systems – The weakest link

Unlike other cables, fire resistant cables need to work even when directly uncovered to the fireplace 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 followers, Smoke dampers, Stair pressurization fans, Emergency Generator circuits etc.
In order to classify electric cables as hearth resistant they are required to endure testing and certification. Perhaps the primary widespread fireplace exams on cables were IEC 331: 1970 and later BS6387:1983 which adopted a fuel ribbon burner take a look at to supply a flame by which cables were placed.
Since the revision of BS6387 in 1994 there have been 11 enhancements, revisions or new test requirements introduced by British Standards to be used and application of Fire Resistant cables however none of these seem to deal with the core issue that fireside resistant cables where examined to widespread British and IEC flame take a look at requirements aren’t required to carry out to the identical hearth performance time-temperature profiles as every other structure, system or element in a constructing. Specifically, the place fireplace resistant constructions, techniques, partitions, fireplace doorways, fire penetrations fire barriers, floors, walls etc. are required to be hearth rated by building rules, they are examined to the Standard Time Temperature protocol of BS476 components 20 to 23 (also often recognized as ISO834-1, ASNZS1530pt4, EN1363-1 and in America and Canada ASTM E119-75).
These tests are conducted in giant furnaces to copy actual post flashover hearth environments. Interestingly, หลักการทํางานของpressuregauge like BS 6387CWZ, SS299, IEC 60331 BS8343-1 and 2, BS8491 only require cables to be uncovered to a flame in air and to lower ultimate 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 systems remain operational, this truth is maybe surprising.
Contrastingly in Germany, Belgium, Australia, New Zealand, USA and Canada Fire Resistant cable techniques are required to be tested to the same fire Time Temperature protocol as all different building elements 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 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 within the UK, Germany and the United States. The exams have been described in a series of “Red Books” issued by the British Fire Prevention Committee after 1903 as well as these 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 checks 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 at present and the America ASTM E119 / NFPA 251 checks doubtless stemmed from this time.
Image courtesy of MICC Ltd.
The curve as we see it today (see graph above) has become the standard scale for measurement of fireside test severity and has proved related for most above floor cellulosic buildings. When elements, buildings, components or systems are examined, the furnace temperatures are managed to evolve to the curve with a set allowable variance and consideration for preliminary ambient temperatures. The requirements require components to be tested in full scale and beneath circumstances of support and loading as defined to be able to represent as accurately as attainable its functions in service.
This Standard Time Temperature testing protocol (see graph right) is adopted by almost all nations around the world for fireplace testing and certification of just about all building structures, elements, systems and elements with the interesting exception of fireplace resistant cables (exception in USA, Canada, Australia, Germany, Belgium and New Zealand the place fire resistant cable techniques are required to be examined and approved to the Standard Time Temperature protocol, identical to all different building structures, parts and components).
It is necessary to understand that application requirements from BS, IEC, ASNZS, DIN, UL and so forth. where fireplace resistive cables are specified to be used, are solely ‘minimum’ requirements. We know right now that fires usually are not all the identical and analysis by Universities, Institutions and Authorities all over the world have recognized that Underground and a few Industrial environments can exhibit very different hearth profiles to these in above ground cellulosic buildings. Specifically in confined underground public areas like Road and Rail Tunnels, Underground Shopping facilities, Car Parks hearth temperatures can exhibit a very quick rise time and can attain temperatures nicely above these in above floor buildings and in far much 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 up to 1,350 Degrees C for 60 minutes and UK British Standard BS8519:2010 clearly identifies underground public areas such as car parks as “Areas of Special Risk” where more stringent take a look at protocols for important electric cable circuits might have to be thought-about by designers.
Standard Time Temperature curves (Europe and America) plotted towards widespread BS and IEC cable checks.
Of course all underground environments whether road, rail and pedestrian tunnels, or underground public environments like purchasing precincts, automobile parks and so on. may exhibit totally different fire profiles to these in above floor buildings because In these environments the heat generated by any fire can not escape as easily as it would in above floor buildings thus relying more on heat and smoke extraction gear.
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 and so on. that is particularly necessary. Evacuation of these public environments is often sluggish even during emergencies, and it is our accountability to make sure everyone seems to be given the very best probability of safe egress throughout fire emergencies.
It is also understood today that copper Fire Resistant cables the place installed in galvanized steel conduit can fail prematurely throughout fireplace emergency due to a reaction between the copper conductors and zinc galvanizing inside the metal 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 dropped at our consideration associated to the efficiency of those products in the presence of zinc. We validated this finding. As a result of this, we modified our Guide Information to point that all conduit and conduit fittings that are obtainable in contact with fireplace resistive cables should have an interior coating freed from zinc”.
Time temperature profile of tunnel fires utilizing automobiles, 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 at the First International Symposium in Prague 2004: Safe and Reliable Tunnels.
It would seem that some Standards authorities around the world may have to review the current check methodology presently adopted for hearth resistive cable testing and maybe align the performance of Life Safety and Fire Fighting wiring methods with that of all the other fireplace resistant constructions, components and systems in order that Architects, constructing designers and engineers know that once they need a hearth ranking that the essential wiring system might be equally rated.
For many power, management, communication and knowledge circuits there may be one expertise obtainable which may meet and surpass all present fire exams and applications. It is an answer which is regularly used in demanding public buildings and has been employed reliably for over 80 years. MICC cable expertise can provide a total and complete answer to all the issues associated with the hearth safety dangers of contemporary flexible organic polymer cables.
The metal jacket, magnesium oxide insulation and conductors of MICC cables ensure the cable is successfully fireplace 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 heat 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 including Carbon Monoxide. MICC cable designs can meet the entire current and building hearth resistance performance requirements in all nations and are seeing a major improve in use globally.
Many engineers have previously thought of MICC cable technology to be “old school’ but with the new research in fire efficiency MICC cable system at the second are proven to have far superior fireplace performances than any of the newer extra modern versatile fireplace resistant cables.
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