How Electricity Causes Fires.

How Electricity Causes Fires.

Supt. Rickwood, of the Adelaide. Fire Brigade, submitted to the Australian Fire Brigades’ Conference, held at Adelaide, May 1 to 4, a paper of exceptional interest on the subject of “Electricity as a Fire Risk.” It was due to ignorance or the careless use of rules that, he said a great number of fires occurred. Circuits were wired irrespective of the loads they had to carry, lamps were added to circuits already overloaded, and as there was a limit to the carrying capacity of conductors, which, when exceeded, caused overheating, in many cases serious results followed if the circuit was not properly protected. such as burning out of lamps, ignition of insulation and any inflammable material in contact with same. Want of proper fuse protection, he continued, is the cause of numerous outbreaks of fire, showing the necessity of strict supervision of all installations by the fire underwriters. The insulation of circuits is probably the most important factor in electrical installations, because should two wires of difference of potentials having small resistance come in contact with one another, due to faulty insulation, a short circuit will be formed, and if no automatic cut out or fuse is in the circuit the danger of a fire occurring is always present. In all cases, where possible, t h e negative main should be connected to earth by means of an earth plate, and with armored cable circuits the armoring should be bonded to the negative return to minimize electrolysis. It has been stated by fire brigade authorities that the conduit system is responsible for electrolysis, and is the cause of many fires and explosions. This appears to be impossible if the proper bonding o f negative and earthing of conduit be carried out. While on the subject of electrolysis. I should like an expression of opinion on a very important matter—the bonding of gas and water mains to all negative returns. tints bringing all earthed metal to zero potential, and by such means providing ample metallic paths for stray return currents without danger to the pipes. Naturally if the water pipe only is used for earthing, and there is a gaspipe in close proximity to it, the difference in potential is such that an action takes place between the two, and as the point at which the current leaves a gaspipe is the most seriously affected, the corrosion is liable to cause trouble at any time through leakage of gas and consequent fire or explosion. But if both water and gas pipes are bonded to the return, then the potential in each is the same, and electrolysis does not take place. In all cases there must be a difference of potential to cause an electrical current to flow or set up an action between two metals. Where high tension work is in use special precautions should be taken in the insulation of circuits, as the danger of arcing exists unless this is carried out. Strict supervision is necessary where joints in wires and cables are made, because if a bad joint has to carry a heavy current heating takes place, which may endanger any surrounding property. All buildings with complete electrical installations should be adequately protected from lightning by suitable arrestors, as the low resistance offered by conductors presents a ready path for the lightning to flow to earth, and in doing so endangers not only property, but life as well. Conduit versus casing for electric circuits is largely a matter to be decided by local conditions. Where extreme safety and protection are required, screwed metal conduit should in all cases be used, particularly when in contact with wood; wood casing, if carefully installed for internal circuits, can be used with safety; in both wood casing and conduit the principal danger lies in the junctions and bad workmanship. In installing electric circuits efficient wiremen should in all cases be employed, as faulty installations may be the cause of serious loss by fire. It is not uncommon to see men hauling wires through small conduit and stripping the insulation in doing so. All conduit systems should be earthed at intervals, and well bonded with adjacent pipes. The danger of electrical shock to firemen from these electric wires is increasing daily, and to minimize this danger it is necessary for brigades to get all information possible as to voltage used, position of main switch, leads for lift power, etc., and to have the means at band for disconnecting any wires which are a menace to the firemen. Rubber gloves are not reliable for high voltage work, as a pin prick is sufficient to render them dangerous. Insulated pliers are useful if capable of cutting large wires. Tramway overhead wires are dangerous if in narrow streets, as in getting to work with ladders there is always the risk of “shorting” through the ladder and so endangering the men’s lives. All telephone and alarm wires in the vicinity of tramway overhead lines should be amply protected, for should one of the former break and come in contact with the overhead line burning out of coils and in some cases ignition of woodwork will result. The danger to branchmen from the standard voltage, 600 volts, is very slight, the theory of the current being conveyed through the water jet to the man holding the branch and giving severe shocks not being borne out in practice. With a 600-volt line it is possible to hold the branch within 2 feet of a wire without the slightest inconvenience. In dealing with electrical fires the most important thing is to communicate with the power house to switch off power.

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