Life Safety and Fire Fighting Systems – The weakest link

Unlike different cables, fireplace resistant cables have to work even when immediately exposed to the hearth to keep essential 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 etc.
In order to categorise electrical cables as fireplace resistant they are required to undergo testing and certification. Perhaps the first widespread fire tests on cables were IEC 331: 1970 and later BS6387:1983 which adopted a gas ribbon burner test to supply a flame during which cables have been positioned.
Since the revision of BS6387 in 1994 there have been eleven enhancements, revisions or new take a look at standards launched by British Standards to be used and software of Fire Resistant cables however none of these seem to deal with the core concern that fireplace resistant cables where examined to widespread British and IEC flame check standards are not required to perform to the identical hearth performance time-temperature profiles as every different structure, system or component in a constructing. Specifically, the place fire resistant buildings, systems, partitions, hearth doorways, fire penetrations hearth limitations, flooring, partitions etc. are required to be hearth rated by building laws, they’re examined to the Standard Time Temperature protocol of BS476 elements 20 to 23 (also known as ISO834-1, ASNZS1530pt4, EN1363-1 and in America and Canada ASTM E119-75).
These tests are carried out in massive furnaces to replicate actual publish flashover hearth 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 probably to be uncovered in the identical fire, and are needed to make sure all Life Safety and Fire Fighting methods stay operational, this fact is probably stunning.
Contrastingly in Germany, Belgium, Australia, New Zealand, USA and Canada Fire Resistant cable methods are required to be tested to the identical fire Time Temperature protocol as all different 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 creating 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 plenty of fire tests carried out in the UK, Germany and the United States. The tests have been described in a series 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 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 test as we all 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 right now (see graph above) has turn into the usual scale for measurement of fireplace test severity and has proved relevant for most above floor cellulosic buildings. When elements, buildings, components or methods are examined, the furnace temperatures are controlled to conform to the curve with a set allowable variance and consideration for initial ambient temperatures. The standards require elements to be tested in full scale and beneath circumstances of support and loading as defined so as to characterize as accurately as possible its features in service.
This Standard Time Temperature testing protocol (see graph right) is adopted by virtually all countries around the globe for fireplace testing and certification of virtually all constructing buildings, elements, techniques and parts with the interesting exception of fireside resistant cables (exception in USA, Canada, Australia, Germany, Belgium and New Zealand the place fire resistant cable systems are required to be examined and permitted to the Standard Time Temperature protocol, just like all other building buildings, components and components).
It is important to grasp that application requirements from BS, IEC, ASNZS, DIN, UL etc. the place hearth resistive cables are specified to be used, are solely ‘minimum’ necessities. We know today that fires aren’t all the same and analysis by Universities, Institutions and Authorities all over the world have identified that Underground and a few 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 fast rise time and can reach temperatures well above these in above floor buildings and in far much less time. In USA today electrical wiring techniques are required by NFPA 502 (Road Tunnels, Bridges and different Limited Access Highways) to resist fireplace temperatures as a lot as 1,350 Degrees C for 60 minutes and UK British Standard BS8519:2010 clearly identifies underground public areas corresponding to automobile parks as “Areas of Special Risk” where more stringent check protocols for essential electrical cable circuits may have to be considered 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 road, rail and pedestrian tunnels, or underground public environments like purchasing precincts, automobile parks and so forth. could exhibit different fire profiles to those in above ground buildings as a outcome of In these environments the warmth generated by any fire can not escape as easily as it would in above floor buildings thus relying extra on heat and smoke extraction gear.
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. that is particularly essential. Evacuation of these public environments is usually slow even during emergencies, and it is our duty to make sure everyone is given the easiest chance of secure egress throughout fire emergencies.
It can additionally be understood at present that copper Fire Resistant cables the place put in in galvanized steel conduit can fail prematurely during hearth emergency because of a reaction between the copper conductors and zinc galvanizing contained in the metal conduit. In 2012 United Laboratories (UL®) in America eliminated all certification for Fire Resistive cables the place installed in galvanized steel conduit for this reason:
UL® Quote: “A concern was dropped at our consideration associated to the performance of these merchandise within the presence of zinc. We validated this discovering. 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 should have an interior coating freed from zinc”.
Time temperature profile of tunnel fires using vehicles, HGV trailers with totally different cargo and rail carriages. Graph extract: Haukur Ingason and Anders Lonnermark of the Swedish National Testing and Research Institute who presented the paper on the First International Symposium in Prague 2004: Safe and Reliable Tunnels.
It would appear that some Standards authorities around the globe may need to review the present test methodology at present 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 fire resistant constructions, elements and systems in order that Architects, constructing designers and engineers know that after they need a fire score that the essential wiring system shall be equally rated.
For เกจแรงดันลม , control, communication and data circuits there’s one expertise obtainable which might meet and surpass all current fireplace exams and applications. It is a solution which is frequently used in demanding public buildings and has been employed reliably for over eighty years. MICC cable technology can present a total and full reply to all the problems related to the hearth safety risks of contemporary versatile natural polymer cables.
The metallic jacket, magnesium oxide insulation and conductors of MICC cables ensure the cable is effectively fireplace proof. Bare MICC cables have no organic content so simply can’t 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 can’t generate any halogen or toxic gasses in any respect including Carbon Monoxide. MICC cable designs can meet all the current and building fire resistance performance standards in all countries and are seeing a big enhance in use globally.
Many engineers have previously thought-about MICC cable technology to be “old school’ but with the new analysis in fire efficiency MICC cable system at the second are confirmed to have far superior hearth performances than any of the newer more modern versatile fireplace resistant cables.
For additional info, go to www.temperature-house.com
Share this:
Share

Leave a Comment