Life Safety and Fire Fighting Systems – The weakest link

Unlike different cables, hearth resistant cables have to work even when instantly exposed to the fireplace 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 etc.
In order to classify electric cables as fire resistant they’re required to undergo testing and certification. Perhaps the first widespread hearth exams on cables had been IEC 331: 1970 and later BS6387:1983 which adopted a gasoline ribbon burner take a look at to supply a flame during which cables had been positioned.
Since the revision of BS6387 in 1994 there have been eleven enhancements, revisions or new test requirements launched by British Standards for use and application of Fire Resistant cables but none of these seem to handle the core problem that fireside resistant cables the place tested to frequent British and IEC flame test standards aren’t required to perform to the same fire performance time-temperature profiles as each different structure, system or element in a building. Specifically, the place fireplace resistant structures, techniques, partitions, fire doorways, hearth penetrations fire barriers, flooring, partitions etc. are required to be fire rated by constructing regulations, they’re examined to the Standard Time Temperature protocol of BS476 components 20 to 23 (also generally identified as ISO834-1, ASNZS1530pt4, EN1363-1 and in America and Canada ASTM E119-75).
These exams are carried out in massive furnaces to duplicate real publish flashover hearth environments. Interestingly, Fire Resistant cable take a look at requirements like BS 6387CWZ, SS299, IEC 60331 BS8343-1 and a pair of, BS8491 solely require cables to be exposed to a flame in air and to decrease final take a look at 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 needed to ensure all Life Safety and Fire Fighting methods remain operational, this fact is maybe stunning.
Contrastingly in Germany, Belgium, Australia, New Zealand, USA and Canada Fire Resistant cable methods are required to be examined to the same fireplace Time Temperature protocol as all other 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 guidance given from the International Fire Prevention Congress held in London in July 1903 and the measurements of furnace temperatures made in many fire checks carried out within the UK, Germany and the United States. The exams were described in a sequence 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 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 checks at Columbia University and Underwriters Laboratories in Chicago. The small time temperature differences between the International ISO 834-1 test as we all know it at present and the America ASTM E119 / NFPA 251 checks probably stemmed from this time.
Image courtesy of MICC Ltd.
The curve as we see it right now (see graph above) has turn into the standard scale for measurement of fireside test severity and has proved relevant for many above floor cellulosic buildings. When parts, buildings, components or techniques are tested, the furnace temperatures are managed to adapt to the curve with a set allowable variance and consideration for initial ambient temperatures. The requirements require parts to be examined in full scale and underneath conditions of help and loading as defined so as to characterize as accurately as potential its features in service.
This Standard Time Temperature testing protocol (see graph right) is adopted by nearly all international locations around the world for fireplace testing and certification of nearly all constructing constructions, elements, techniques and components with the attention-grabbing exception of fireplace resistant cables (exception in USA, Canada, Australia, Germany, Belgium and New Zealand where hearth resistant cable methods are required to be tested and approved to the Standard Time Temperature protocol, identical to all different building constructions, elements and components).
It is necessary to understand that utility requirements from BS, IEC, ASNZS, DIN, UL etc. where hearth resistive cables are specified for use, are only ‘minimum’ necessities. We know right now that fires aren’t 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 fireplace profiles to those 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 very quick rise time and may reach temperatures nicely above those in above ground buildings and in far less time. In USA right now electrical wiring systems are required by NFPA 502 (Road Tunnels, Bridges and other Limited Access Highways) to face up to fireplace 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 automotive parks as “Areas of Special Risk” the place more stringent check protocols for important electric cable circuits may need to be considered 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 road, rail and pedestrian tunnels, or underground public environments like shopping precincts, automotive parks and so on. may exhibit completely different fire profiles to these in above floor buildings as a end result of In these environments the heat generated by any fire can’t escape as simply as it’d in above ground buildings thus relying extra on heat and smoke extraction gear.
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 etc. this is significantly essential. Evacuation of those public environments is often slow even throughout emergencies, and it is our duty to make sure everyone appears to be given the perfect probability of secure egress during fireplace emergencies.
It is also understood at present that copper Fire Resistant cables the place put in in galvanized metal conduit can fail prematurely throughout hearth emergency due to a response between the copper conductors and zinc galvanizing contained in the metallic conduit. In 2012 United Laboratories (UL®) in America eliminated all certification for Fire Resistive cables the place installed in galvanized metal conduit for that reason:
UL® Quote: “A concern was brought to our attention related to the efficiency of these products in the presence of zinc. We validated this discovering. As a results of this, we changed our Guide Information to point that each one conduit and conduit fittings that are available contact with fire resistive cables should have an interior coating free of zinc”.
Time temperature profile of tunnel fires using cars, HGV trailers with 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 appear that some Standards authorities all over the world might need to evaluate 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 systems with that of all the opposite fireplace resistant buildings, elements and systems in order that Architects, constructing designers and engineers know that when they want a fire score that the important wiring system shall be equally rated.
For many power, control, communication and data circuits there’s one expertise obtainable which can meet and surpass all present fire tests and purposes. It is a solution which is frequently used in demanding public buildings and has been employed reliably for over 80 years. MICC cable technology can provide a total and complete reply to all the issues related to the fireplace safety dangers of modern flexible organic polymer cables.
The metal jacket, magnesium oxide insulation and conductors of MICC cables ensure the cable is effectively hearth proof. Bare MICC cables don’t have any natural content 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 fire and no oxygen is consumed. Being inorganic these MICC cables can’t generate any halogen or toxic gasses at all including Carbon Monoxide. เพรสเชอร์เกจ can meet all of the current and constructing fire resistance efficiency standards in all nations and are seeing a significant increase in use globally.
Many engineers have previously considered MICC cable expertise to be “old school’ however with the brand new research in hearth performance MICC cable system are now confirmed to have far superior hearth performances than any of the newer extra fashionable flexible fire resistant cables.
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