Life Safety and Fire Fighting Systems – The weakest hyperlink

Unlike different cables, fireplace resistant cables have to work even when immediately uncovered to the hearth to keep important 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 categorise electric cables as fire resistant they are required to undergo testing and certification. Perhaps the primary frequent fireplace checks on cables were IEC 331: 1970 and later BS6387:1983 which adopted a fuel ribbon burner take a look at to produce a flame in which cables had been positioned.
Since the revision of BS6387 in 1994 there have been 11 enhancements, revisions or new check standards introduced by British Standards for use and application of Fire Resistant cables but none of those appear to address the core issue that fire resistant cables the place examined to frequent British and IEC flame check standards usually are not required to perform to the identical fire efficiency time-temperature profiles as each different structure, system or element in a building. Specifically, the place hearth resistant constructions, techniques, partitions, hearth doorways, fireplace penetrations fireplace barriers, flooring, walls etc. 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 generally identified as ISO834-1, ASNZS1530pt4, EN1363-1 and in America and Canada ASTM E119-75).
These tests are performed in large furnaces to replicate real post flashover hearth environments. Interestingly, Fire Resistant cable take a look at standards like BS 6387CWZ, SS299, IEC 60331 BS8343-1 and a pair of, BS8491 solely require cables to be uncovered to a flame in air and to lower ultimate take a look at temperatures (than required by BS476 pts 20 to 23). Given Fire Resistant cables are prone to be uncovered in the same fire, and are needed to make sure all Life Safety and Fire Fighting systems stay operational, this fact is maybe shocking.
Contrastingly in Germany, Belgium, Australia, New Zealand, USA and Canada Fire Resistant cable techniques are required to be tested to the identical fireplace 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 standard 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 fire tests carried out in 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 in addition to those 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 take a look at as we all know it today and the America ASTM E119 / NFPA 251 checks probably stemmed from this time.
Image courtesy of MICC Ltd.
The curve as we see it today (see graph above) has turn into the standard scale for measurement of fireside take a look at severity and has proved related for most above ground cellulosic buildings. When parts, constructions, elements or techniques are examined, the furnace temperatures are managed to conform to the curve with a set allowable variance and consideration for initial ambient temperatures. The standards require components to be examined in full scale and under conditions of assist and loading as defined to have the ability to symbolize as accurately as attainable its features in service.
This Standard Time Temperature testing protocol (see graph right) is adopted by almost all international locations around the globe for hearth testing and certification of nearly all building buildings, components, techniques and components with the interesting exception of fireplace resistant cables (exception in USA, Canada, Australia, Germany, Belgium and New Zealand where fire resistant cable methods are required to be tested and approved to the Standard Time Temperature protocol, just like all other constructing structures, parts and components).
It is essential to grasp that utility standards from BS, IEC, ASNZS, DIN, UL etc. where fireplace resistive cables are specified to be used, are only ‘minimum’ requirements. We know at present that fires are not all the same and analysis by Universities, Institutions and Authorities around the globe have identified that Underground and some Industrial environments can exhibit very different fire profiles to these in above floor cellulosic buildings. Specifically in confined ที่วัดแรงดันน้ำ like Road and Rail Tunnels, Underground Shopping facilities, Car Parks hearth temperatures can exhibit a really quick rise time and might reach temperatures nicely above those in above floor buildings and in far much less time. In USA right now electrical wiring systems are required by NFPA 502 (Road Tunnels, Bridges and different Limited Access Highways) to resist hearth 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 automotive parks as “Areas of Special Risk” where more stringent test protocols for important electric cable circuits might need to be thought-about by designers.
Standard Time Temperature curves (Europe and America) plotted in opposition to common BS and IEC cable tests.
Of course all underground environments whether or not street, rail and pedestrian tunnels, or underground public environments like shopping precincts, automobile parks and so forth. may exhibit totally different fire profiles to these in above floor buildings because In these environments the warmth generated by any fire can not escape as simply as it’d in above ground buildings thus relying more on heat and smoke extraction equipment.
For Metros Road and Rail Tunnels, Hospitals, Health care services, Underground public environments like purchasing precincts, Very High Rise, Theaters, Public Halls, Government buildings, Airports etc. this 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 likelihood of safe egress during fire emergencies.
It can be understood at present that copper Fire Resistant cables where put in in galvanized steel conduit can fail prematurely throughout fireplace emergency due to a response between the copper conductors and zinc galvanizing contained in the steel 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 brought to our attention related to the efficiency of those products within the presence of zinc. We validated this finding. As a results of this, we modified our Guide Information to point that all conduit and conduit fittings that are available in contact with fireplace resistive cables ought to have an interior coating free of 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 globe could need to evaluate the current take a look at methodology presently adopted for hearth resistive cable testing and perhaps align the efficiency of Life Safety and Fire Fighting wiring systems with that of all the opposite fire resistant constructions, parts and systems in order that Architects, constructing designers and engineers know that once they want a hearth score that the essential wiring system might be equally rated.
For many energy, management, communication and knowledge circuits there could be one expertise obtainable which might meet and surpass all current fire tests and purposes. It is a solution which is frequently used in demanding public buildings and has been employed reliably for over eighty years. MICC cable know-how can present a total and full answer to all the problems related to the fire safety risks of modern flexible natural polymer cables.
The metallic jacket, magnesium oxide insulation and conductors of MICC cables ensure the cable is effectively fire proof. Bare MICC cables have no 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 can not generate any halogen or toxic gasses at all together with Carbon Monoxide. MICC cable designs can meet the entire present and building hearth resistance performance requirements in all international locations and are seeing a major increase in use globally.
Many engineers have beforehand thought of MICC cable technology to be “old school’ but with the new analysis in fireplace efficiency MICC cable system are now proven to have far superior hearth performances than any of the newer more fashionable flexible hearth resistant cables.
For further info, go to www.temperature-house.com
Share this:
Shareg

Leave a Comment