reducing the fire hazard ofelectrical cable installations
By
geoff williams
the use of electric cables, to transmitpower, exercise control and provide communication has multiplied in the past 20years by ten, twenty and in some instances even by thirty times. economicpressures have forced reductions in labour content resulting in an enormousdependence in automatic and remote control. the increase in the use of electriccables has brought about a considerable increase of fire hazards, especiallywhere cables are concentrated in large numbers. research into the cause offires in buildings has shown that up to 40% of the fires globally have been,cable related, due to short circuit, or insulation malfunction.
it may be safely assumed that theperformance of electric cables in key buildings like, hospitals, airports,metro systems, petrochemicals, power stations, nuclear and high-rise buildingsfor power, communication and control is of paramount importance. cables are takeneverywhere, in great bundles, on trays and racks, passing from room to room,level to level, supplying power, maintaining control and transmittingcommunication. this creates a high fire risk in cable related fires of firespread, necessitating predictable fire protection and security of supply toessential services.
for the most part, cables consist of metalconductors insulated by plastic materials and covered by a plastic sheath. formany years the plastic industry and cable manufacturers have attempted todevelop an insulating and sheath material for electric cables which does notburn. to date no completely satisfying solution has been found as mostimprovements have appeared in retardation of combustion of cable polymers that seemto lead to the loss or retardation of another needed component. the current designsof fire resistant cable have specific limitations in regard to theirperformance in fire. furthermore, the dynamics of a fire bring together fire,water and mechanical shock simultaneously, which creates premature failure in fireconditions.
from a fire survival point of view theideal cable would be micc [mineral insulated copper cable] which is a cablewidely used in buildings for essential and emergency circuits of a criticalnature. the conductors are embedded in an inorganic powder known as magnesiumoxide. the cable will continue to operate up to the melting point of copper. itis both fireproof and watertight. it might appear to be more expensive comparedwith other types, on purchase cost, but is competitive with frc types on installed cost. its record as afire survival cable remains unquestioned and provides value for money. itsspecific use is to maintain a security of supply to rising main services andfire fighting applications, especially in high-rise buildings that present ahigh risk to life.
geoff williams
June 2013
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