Life Safety and Fire Fighting Systems – The weakest link

Unlike different cables, hearth resistant cables need to work even when directly exposed to the fireplace to maintain important Life Safety and Fire Fighting tools working: Fire alarms, Emergency Lighting, Emergency Communication, Fire Sprinkler pumps, Fireman’s Lift sub-main, Smoke extraction followers, Smoke dampers, Stair pressurization followers, Emergency Generator circuits etc.
In order to categorise electrical cables as hearth resistant they are required to undergo testing and certification. Perhaps the first common hearth exams on cables were IEC 331: 1970 and later BS6387:1983 which adopted a gas ribbon burner take a look at to supply a flame during which cables had been placed.
Since the revision of BS6387 in 1994 there have been 11 enhancements, revisions or new test standards launched by British Standards to be used and application of Fire Resistant cables however none of those appear to deal with the core issue that fireplace resistant cables where examined to common British and IEC flame test standards usually are not required to perform to the identical hearth efficiency time-temperature profiles as every other construction, system or part in a building. Specifically, the place fire resistant buildings, methods, partitions, fire doorways, fireplace penetrations fireplace limitations, floors, partitions etc. are required to be fireplace rated by constructing laws, they are examined to the Standard Time Temperature protocol of BS476 parts 20 to 23 (also often known as ISO834-1, ASNZS1530pt4, EN1363-1 and in America and Canada ASTM E119-75).
These tests are carried out in large furnaces to copy actual publish flashover fireplace environments. Interestingly, Fire Resistant cable take a look at standards like BS 6387CWZ, SS299, IEC 60331 BS8343-1 and a couple of, BS8491 only require cables to be uncovered to a flame in air and to lower final check temperatures (than required by BS476 pts 20 to 23). Given Fire Resistant cables are likely to be exposed in the same hearth, and are needed to make sure all Life Safety and Fire Fighting techniques stay operational, this fact is maybe shocking.
Contrastingly in Germany, Belgium, Australia, New Zealand, USA and Canada Fire Resistant cable methods are required to be examined to the identical fire Time Temperature protocol as all other constructing parts 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 steering given from the International Fire Prevention Congress held in London in July 1903 and the measurements of furnace temperatures made in lots of hearth exams carried out within the UK, Germany and the United States. The checks were described in a collection of “Red Books” issued by the British Fire Prevention Committee after 1903 in addition to 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 check as we know it at present and the America ASTM E119 / NFPA 251 exams probably stemmed from this time.
Image courtesy of MICC Ltd.
The curve as we see it right now (see graph above) has turn out to be the standard scale for measurement of fireside check severity and has proved related for many above floor cellulosic buildings. When elements, buildings, components or systems 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 parts to be examined in full scale and under conditions of assist and loading as defined to find a way to represent as accurately as potential its functions in service.
This Standard Time Temperature testing protocol (see graph right) is adopted by almost all countries around the globe for hearth testing and certification of virtually all constructing constructions, components, techniques and elements with the interesting 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 permitted to the Standard Time Temperature protocol, identical to all different constructing structures, elements and components).
It is necessary to know that utility standards from BS, IEC, ASNZS, DIN, UL etc. the place hearth resistive cables are specified to be used, are solely ‘minimum’ requirements. We know today that fires usually are not all the identical and research by Universities, Institutions and Authorities all over the world have recognized that Underground and a few Industrial environments can exhibit very different fire 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 very quick rise time and may attain temperatures nicely above these in above ground buildings and in far much less time. In USA right now electrical wiring systems 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 automobile parks as “Areas of Special Risk” the place extra stringent check protocols for essential electrical cable circuits could need to be thought-about by designers.
Standard Time Temperature curves (Europe and America) plotted in opposition to widespread BS and IEC cable tests.
Of course all underground environments whether or not road, rail and pedestrian tunnels, or underground public environments like buying precincts, automotive parks etc. could exhibit totally different fireplace profiles to these in above ground buildings as a outcome of In these environments the warmth generated by any hearth cannot escape as easily as it’d in above floor buildings thus relying more on warmth and smoke extraction equipment.
For Metros Road and Rail Tunnels, Hospitals, Health care services, Underground public environments like shopping precincts, Very High Rise, Theaters, Public Halls, Government buildings, Airports etc. that is notably essential. Evacuation of these public environments is usually gradual even during emergencies, and it’s our accountability to make sure everyone is given the easiest probability of safe egress during fire emergencies.
It is also understood at present that copper Fire Resistant cables where installed in galvanized steel conduit can fail prematurely during fire emergency due to a response between the copper conductors and zinc galvanizing inside the steel conduit. In 2012 United Laboratories (UL®) in America removed 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 consideration associated to the efficiency of those products 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 come in contact with fireplace resistive cables should have an interior coating freed from 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 introduced the paper at the First International Symposium in Prague 2004: Safe and Reliable Tunnels.
It would appear that some Standards authorities around the world may have to evaluation the current take a look at methodology presently adopted for fireplace resistive cable testing and maybe align the efficiency of Life Safety and Fire Fighting wiring methods with that of all the other hearth resistant structures, parts and systems so that Architects, constructing designers and engineers know that after they want a fire rating that the important wiring system shall be equally rated.
For many power, management, communication and knowledge circuits there’s one expertise available which can meet and surpass all current fire checks and functions. It is an answer which is regularly used in demanding public buildings and has been employed reliably for over 80 years. MICC cable technology can present a total and complete answer to all the issues related to the hearth security dangers of modern 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 don’t have any natural content so simply can not 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 cannot generate any halogen or poisonous gasses in any respect together with Carbon Monoxide. เกจปรับแรงดันแก๊ส can meet all the present and building fire resistance efficiency standards in all international locations and are seeing a significant enhance in use globally.
Many engineers have beforehand thought-about MICC cable know-how to be “old school’ but with the brand new analysis in fire performance MICC cable system at the moment are confirmed to have far superior fire performances than any of the newer more modern flexible fire resistant cables.
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