บทความ เกจวัดแรงดัน

Life Safety and Fire Fighting Systems – The weakest link

Unlike other cables, fire resistant cables need to work even when directly exposed to the fireplace to maintain 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 and so on.
In order to classify electrical cables as fireplace resistant they’re required to endure testing and certification. Perhaps เกจวัดแรงดันแก๊ส on cables had been IEC 331: 1970 and later BS6387:1983 which adopted a fuel ribbon burner test to supply a flame during which cables were positioned.
Since the revision of BS6387 in 1994 there have been 11 enhancements, revisions or new check standards launched by British Standards for use and software of Fire Resistant cables but none of these appear to handle the core concern that fireside resistant cables the place tested to frequent British and IEC flame take a look at standards aren’t required to carry out to the same hearth performance time-temperature profiles as every other structure, system or element in a building. Specifically, the place fire resistant structures, techniques, partitions, fireplace doorways, fireplace penetrations fireplace limitations, flooring, partitions etc. are required to be hearth rated by constructing regulations, they’re tested to the Standard Time Temperature protocol of BS476 components 20 to 23 (also generally recognized 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 fireplace environments. Interestingly, Fire Resistant cable check requirements 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 decrease final take a look at temperatures (than required by BS476 pts 20 to 23). Given Fire Resistant cables are likely to be uncovered in the identical fire, and are needed to make sure all Life Safety and Fire Fighting methods stay operational, this reality is perhaps stunning.
Contrastingly in Germany, Belgium, Australia, New Zealand, USA and Canada Fire Resistant cable techniques are required to be examined to the identical hearth 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 growing 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 checks carried out within the UK, Germany and the United States. The tests had been 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 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 tests at Columbia University and Underwriters Laboratories in Chicago. The small time temperature differences between the International ISO 834-1 check as we all know it at present and the America ASTM E119 / NFPA 251 tests doubtless stemmed from this time.
Image courtesy of MICC Ltd.
The curve as we see it at present (see graph above) has become the usual scale for measurement of fireplace test severity and has proved relevant for most above ground cellulosic buildings. When parts, constructions, components or methods are examined, the furnace temperatures are controlled to evolve to the curve with a set allowable variance and consideration for preliminary ambient temperatures. The standards require components to be examined in full scale and underneath situations of support and loading as outlined to find a way to characterize as precisely as potential its features in service.
This Standard Time Temperature testing protocol (see graph right) is adopted by virtually all nations around the world for fire testing and certification of nearly all constructing buildings, components, methods and components with the attention-grabbing exception of fireplace resistant cables (exception in USA, Canada, Australia, Germany, Belgium and New Zealand the place fireplace resistant cable systems are required to be tested and accredited to the Standard Time Temperature protocol, identical to all other building buildings, parts and components).
It is essential to grasp that software requirements from BS, IEC, ASNZS, DIN, UL etc. where hearth resistive cables are specified to be used, are only ‘minimum’ necessities. We know today that fires usually are not all the identical and research by Universities, Institutions and Authorities around the world have identified that Underground and some Industrial environments can exhibit very completely different hearth profiles to those in above ground cellulosic buildings. Specifically in confined underground public areas like Road and Rail Tunnels, Underground Shopping centers, Car Parks hearth temperatures can exhibit a really fast rise time and may attain temperatures well above those in above floor buildings and in far less time. In USA today electrical wiring methods are required by NFPA 502 (Road Tunnels, Bridges and other Limited Access Highways) to face up to fireplace temperatures up to 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 test protocols for essential electrical cable circuits might have to be considered by designers.
Standard Time Temperature curves (Europe and America) plotted against frequent BS and IEC cable tests.
Of course all underground environments whether or not highway, rail and pedestrian tunnels, or underground public environments like shopping precincts, automobile parks and so forth. may exhibit different fireplace profiles to these in above ground buildings as a result of In these environments the heat generated by any fire can’t escape as simply as it would in above ground buildings thus relying extra on warmth 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 and so on. this is significantly necessary. Evacuation of those public environments is usually slow even throughout emergencies, and it’s our duty to ensure everyone is given the very best likelihood of safe egress during fireplace emergencies.
It is also understood right now that copper Fire Resistant cables where put in in galvanized steel conduit can fail prematurely during fire emergency because of a response between the copper conductors and zinc galvanizing contained in the metal conduit. In 2012 United Laboratories (UL®) in America removed all certification for Fire Resistive cables where installed in galvanized steel conduit for this reason:
UL® Quote: “A concern was dropped at our attention associated to the performance of these merchandise in the presence of zinc. We validated this discovering. As a result of this, we changed our Guide Information to point 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 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 on the First International Symposium in Prague 2004: Safe and Reliable Tunnels.
It would appear that some Standards authorities around the globe could have to evaluation the present check methodology at present adopted for fireplace resistive cable testing and maybe align the performance of Life Safety and Fire Fighting wiring methods with that of all the other fireplace resistant buildings, elements and techniques so that Architects, building designers and engineers know that once they need a fireplace rating that the essential wiring system might be equally rated.
For many power, control, communication and information circuits there might be one expertise available which can meet and surpass all current fire exams and purposes. It is a solution which is frequently utilized in demanding public buildings and has been employed reliably for over 80 years. MICC cable know-how can provide a total and complete reply to all the issues associated with the hearth safety dangers of recent flexible organic polymer cables.
The steel jacket, magnesium oxide insulation and conductors of MICC cables ensure the cable is successfully fireplace proof. Bare MICC cables have no organic content material so simply can not propagate flame or generate any smoke. The zero fuel-load of those MICC cables ensures no warmth is added to the fire and no oxygen is consumed. Being inorganic these MICC cables can not generate any halogen or poisonous gasses at all together with Carbon Monoxide. MICC cable designs can meet the entire present and building hearth resistance efficiency standards in all international locations and are seeing a significant increase in use globally.
Many engineers have beforehand thought of MICC cable expertise to be “old school’ however with the new research in fire performance MICC cable system are actually confirmed to have far superior fire performances than any of the newer extra trendy flexible hearth resistant cables.
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