บทความ เกจวัดแรงดัน

Life Safety and Fire Fighting Systems – The weakest link

Unlike other cables, fire resistant cables need to work even when immediately exposed to the fireplace to maintain important Life Safety and Fire Fighting equipment 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 forth.
In order to categorise electric cables as fireplace resistant they’re required to bear testing and certification. Perhaps the first frequent fireplace exams on cables have been IEC 331: 1970 and later BS6387:1983 which adopted a fuel ribbon burner take a look at to provide a flame by which cables have 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 those seem to address the core concern that fireplace resistant cables where tested to widespread British and IEC flame take a look at standards are not required to perform to the same fire performance time-temperature profiles as every other construction, system or part in a building. Specifically, where fireplace resistant buildings, methods, partitions, fire doorways, fire penetrations fireplace obstacles, floors, partitions and so on. are required to be fireplace rated by constructing regulations, they are 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 duplicate real publish flashover hearth environments. Interestingly, Fire Resistant cable test standards like BS 6387CWZ, SS299, IEC 60331 BS8343-1 and a pair of, BS8491 only require cables to be uncovered to a flame in air and to lower ultimate check temperatures (than required by BS476 pts 20 to 23). Given เกจวัดแรงลม are more probably to be uncovered in the identical fireplace, and are wanted to make sure all Life Safety and Fire Fighting techniques remain operational, this truth is perhaps surprising.
Contrastingly in Germany, Belgium, Australia, New Zealand, USA and Canada Fire Resistant cable techniques are required to be examined to the identical fireplace Time Temperature protocol as all other building elements 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 steering given from the International Fire Prevention Congress held in London in July 1903 and the measurements of furnace temperatures made in plenty of hearth checks carried out within 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 as properly as those from the German Royal Technical Research Laboratory. The finalization of the ASTM commonplace 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 variations between the International ISO 834-1 check as we all know it at present and the America ASTM E119 / NFPA 251 tests probably stemmed from this time.
Image courtesy of MICC Ltd.
The curve as we see it right now (see graph above) has become the standard scale for measurement of fireside check severity and has proved related for many above ground cellulosic buildings. When elements, buildings, elements or techniques are examined, the furnace temperatures are managed to evolve to the curve with a set allowable variance and consideration for initial ambient temperatures. The requirements require elements to be tested in full scale and beneath conditions of help and loading as outlined to have the ability to characterize as precisely as attainable its capabilities in service.
This Standard Time Temperature testing protocol (see graph right) is adopted by almost all nations around the globe for fireplace testing and certification of just about all constructing structures, components, methods and elements with the fascinating exception of fireplace resistant cables (exception in USA, Canada, Australia, Germany, Belgium and New Zealand the place hearth resistant cable techniques are required to be examined and permitted to the Standard Time Temperature protocol, identical to all other building constructions, components and components).
It is important to understand that software requirements from BS, IEC, ASNZS, DIN, UL etc. the place fireplace resistive cables are specified to be used, are only ‘minimum’ requirements. We know at present that fires are not all the identical and research by Universities, Institutions and Authorities all over the world have recognized that Underground and some Industrial environments can exhibit very totally different fireplace profiles to these in above floor cellulosic buildings. Specifically in confined underground public areas like Road and Rail Tunnels, Underground Shopping centers, Car Parks fireplace temperatures can exhibit a really fast rise time and may reach temperatures properly above those in above floor buildings and in far less time. In USA at present electrical wiring techniques are required by NFPA 502 (Road Tunnels, Bridges and different Limited Access Highways) to withstand fire 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 take a look at protocols for essential electrical cable circuits could must 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 street, rail and pedestrian tunnels, or underground public environments like shopping precincts, car parks etc. could exhibit completely different hearth profiles to these in above floor buildings because In these environments the warmth generated by any fire can’t escape as simply as it’d in above floor buildings thus relying extra on warmth and smoke extraction gear.
For Metros Road and Rail Tunnels, Hospitals, Health care amenities, Underground public environments like buying precincts, Very High Rise, Theaters, Public Halls, Government buildings, Airports and so on. this is notably important. Evacuation of these public environments is often gradual even during emergencies, and it is our duty to ensure everyone is given the very best probability of protected egress throughout fireplace emergencies.
It can also be understood at present that copper Fire Resistant cables the place put in in galvanized metal conduit can fail prematurely during fire emergency because of 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 where put in in galvanized metal conduit for this reason:
UL® Quote: “A concern was brought to our consideration related to the performance of these merchandise in the presence of zinc. We validated this discovering. As a result of this, we modified our Guide Information to indicate that all conduit and conduit fittings that are out there in contact with hearth resistive cables should have an inside coating free of zinc”.
Time temperature profile of tunnel fires utilizing vehicles, HGV trailers with different cargo and rail carriages. Graph extract: Haukur Ingason and Anders Lonnermark of the Swedish National Testing and Research Institute who offered the paper at the First International Symposium in Prague 2004: Safe and Reliable Tunnels.
It would seem that some Standards authorities all over the world might have to evaluate the current take a look at methodology currently adopted for hearth resistive cable testing and perhaps align the efficiency of Life Safety and Fire Fighting wiring methods with that of all the other fireplace resistant buildings, parts and techniques in order that Architects, building designers and engineers know that after they want a fire ranking that the important wiring system might be equally rated.
For many power, management, communication and data circuits there may be one expertise available which can meet and surpass all current hearth checks and functions. It is an answer which is incessantly utilized in demanding public buildings and has been employed reliably for over 80 years. MICC cable expertise can present a complete and complete answer to all the problems related to the fireplace security dangers of contemporary flexible natural polymer cables.
The metallic jacket, magnesium oxide insulation and conductors of MICC cables ensure the cable is successfully fire proof. Bare MICC cables don’t have any natural content so simply can’t propagate flame or generate any smoke. The zero fuel-load of those MICC cables ensures no warmth is added to the hearth and no oxygen is consumed. Being inorganic these MICC cables can not generate any halogen or poisonous gasses in any respect together with Carbon Monoxide. MICC cable designs can meet all the current and building hearth resistance performance standards in all countries and are seeing a major increase in use globally.
Many engineers have beforehand thought of MICC cable expertise to be “old school’ but with the new research in fireplace performance MICC cable system at the moment are proven to have far superior fireplace performances than any of the newer more modern versatile fireplace resistant cables.
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