EoW July 2012

Technologynews

Howmuch time does cable have in an emergency?

TO ensure safe evacuation of a building in the event of a fire, there are a combination of active fire systems such as emergency lighting, smoke control and extraction, gaseous fire extinguishing and firefighter support systems that need to be factored in. Many of these systems require electrical power supplies and control circuitry to remain fully functional throughout a potentially serious fire lasting many hours. An example would be in a high rise building where it is vital that power supplies for fire-fighting lifts, smoke extract systems and emergency lighting remain intact for a prolonged period to ensure safe evacuation and effective fire fighting. There are two different types of cable on the market. Those that, when subjected to fire, have low smoke emissions and are flame retardant, and those that are fire resistant, which will continue to operate for a certain period of time. Normal armoured power distribution cables such as BS5467 or BS6724 have limited performance against a sustained fire attack. Cables which need to remain operational throughout the fire need to be robust not only to fire, but also to ‘shock’ damage from falling items of building structure and resistant to the effects of water spray from sprinklers or from fire fighting activities. Some well-established cable types, such as mineral insulated cables to BSEN 60702-1, remain very effective under such circumstances and are usually smaller in diameter than the equivalent armoured cable. A new cable fire test, BS8491, has been developed to provide assessment of cables larger than 20mm diameter. The test incorporates direct fire attack, mechanical attack and water spray, over a variable time up to two hours. The enhanced performance categories are classified as F30, F60 or F120, reflecting the length of time in minutes of the BS8491 fire test. BASEC recommends that specifiers choose BS7846 F120 to ensure such cable has been tested to withstand up to two hours of fire. Gaining BASEC product approval for a fire performance cable is a prestigious mark

▲ ▲ Testing cables to keep you safe

BASEC conducts a full range of tests on each cable type, including electrical, mechanical, materials, chemical and fire tests as specified in the cable standard and in all the subsidiary standards referred to.

of quality for a cable manufacturer. BASEC approval includes all the tests specified for a cable type and its constituent materials, not just a single fire test. A cable may be seen to pass a single fire test, but if its construction is incorrect or its materials do not last very long this would be a poor value product.

BASEC – UK Website : www.basec.org.uk

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