ELECTRIC FIRES—THEIR CAUSE AND PREVENTION.

ELECTRIC FIRES—THEIR CAUSE AND PREVENTION.

The general classes of wiring we have to meet in electrical inspection work, and which will appeal to you, men, broadly speaking, are two, namely: (1) The system by which the wires are fastened on and separated by porcelain insulators throughout; and (2) the conduit system, by which the wires are inclosed in tubes. The first is placed in that order, because it is the first one used extensively. Of course, at the very first inception of the business, the wires were attached to wooden cleats; but it was soon found to be impracticable, and then porcelain insulators were substituted with the wires attached thereto. Porcelain presents a perfect insulator, and, so long as the entire system of a building is kept clear of woodwork, iron-work, or gas pipes, there is no danger from leakage of current from the wires thus protected. Therefore, that would seem at first blush to be the ideal system; but experience demonstrates it has one great fault—viz: The wires thus attached are subject to displacement and may become crossed, and in the latter event cause shortcircuits, with which you are all familiar. And right here I might pause to say that how great a flame a little fire will kindle is illustrated in these electrical fires. It is almost a little flash at the start, although there are cases where, with the large wires, there are not little flashes at the start. But we have records to show that fires have been caused bv wires becoming shortcircuited and with only a little flash at the start. This may occur in dwellings or other buildings, where the wires are carried under floors and in walls, the short-circuit occurring inside and out of sight and setting fire to shavings left there by the builder, and this fire, not being discovered at that stage, smoulders a long while, gathering force and headway before manifesting itself, and, when it breaks forth so as to be seen, and an alarm is sent in, it has reached such proportions as often to give considerable trouble. It is probable that a large percentage of our electrical fires have occurred just in that way. But it is also said, and I may give a word of warning here, that it is not quite fair to charge all fires that are mysterious in their origin to an electrical origin. That charge has probably been overdone, and we know, as a matter of fact, that other fires do start from other causes, and I think the matter of charging mysterious fires to electricity is excessive. 1 know it is somewhat natural in the layman’s mind so to charge it, and I confess it was the same with me until I had studied the subject thoroughly. 1 will now speak a word in behalf of the system of electrical wiring which is at this time coming into vogue, and in some localities almost to the exclusion of the porcelain insulator system first generally adopted. That method is the putting of wires in iron conduits. This is the ideal method, if properly carried out from start to finish, for the materials supplied by the trade for the purpose are perfect, and we have nothing further to ask from that source. The matter of workmanship is the only weak spot. 1 want to impress that fact upon your minds. If there is a chance to advocate the iron conduit system in your towns, cities and States, advocate it: but look after the workmanship and see that it is firstclass. See that the architect inserts in his specifications a full set of requirements on the subject, which he can secure by writing to the National Board of hire Underwriters, as they will gladly send him a copy of their code of rules. For, if the iron conduit system is put in, it must be put in thoroughly throughout. I will explain it briefly: The wires are contained in iron pipes, as you all know, and these pipes are looped from one point to another. Starting where the wires enter the basement, they are led into an iron pipe on to the distributing board, which is roughly spoken of as a switchboard—but distributing board is the proper and expressive term. Of course, that distributing board is located in the basement in case of an underground system. From that distributing board the wires are led in iron pipes to smaller cabinets, and through those cabinets the smaller wires still are led un to lights in the different portions of the building. Now, bear in mind that the safety of the iron conduit system lies in its continuity. It must be a continuous system from the point where it enters the building to the last light. On that depends the safety from fire. That should be located to begin at the cellar wall, if it is an underground system, as is almost always the case in our cities The cabinet should be constructed there, lined, preferably with 1-8-in. iron or steel plate, although the rules permit 1-16-in. in thickness. And my preference is for yi-in. or ¾-in. in cast of the larger installation. From the outside line the house-main begins, and that is a most important point with wires supplied by the Edison system. When the wires are brought into the cut-out block, it will melt out in case of trouble. In some instances, however, it is no exaggeration to say that there is 100,000-h. p. of energy behind it when that fuse blows out. That is an almost inconceivable amount of energy to be manifested in the form of heat. If the cabinet is not such as to contain a quick, hot flash, it may set something on fire. It does not last for but an instant; being a quick, hot flash from the burning fuse, it is instantly over. It has been said that the progress of the art has given us a fuse that is safe. When I speak of a modern, safe, electrical fuse, I mean when care is exercised to arrange it as has been intended. We have a fuse which is incased in a hard-fibre tube. That tube is of paper; but it is as hard as metal, and very thick, and this flash, although intensely hot, is quickly over, and, after a searching test, these paper tubes have been found to permit of very little escape from them. But bear in mind that these tubes are no flimsy construction; and, in case of the large fuses, they are massive and of heavy construction. There is another point of danger right at that spot—where wires enter a building. If the insulation breaks down, it produces an arc. That arc is, of course, intensely hot; and, mind you, it is back of the protective fuses. It is towards the station from which is flowing, and means a tremendous amount of energy, which is capable of being manifested as heat at that point. Now, poor workmanship at that point will produce a breakdown of insulation in a short time. Good workmanship and materials will make that point safe—not for all time, perhaps, but for a very long period. The principles 1 have mentioned as applying to this point where the wires enter the building, will apply to all points; and that is why I say the iron-conduit system, to be safe, must be of good and safe construction throughout. I will speak now of large installations, containing 4,000, 6,000, or 8,000 lights, with motors to correspond, for various purposes. The conduit should run from the street service to the distributing board in a fireproof room. There is no question that this point is of almost equal importance to safeguarding the service entrance wire. The distributing board will be of a size to accommodate the wires, with fuses to protect the separate circuits, so that, if one gets in trouble and the fuse blows out, it will not put the others out of business. And there is no way to safeguard that positively, without putting the distributing board in a fireproof room. It requires a room by itself, because it must afford ample space for a man to walk round. That is a recommendation that ought to be strongly insisted upon. Starting from this point, the conduits should be continuous to the different distributing cabinets on the different floors of the building. These cabinets are small in size, and the amount of energy tc reach any one of them is not so great, lienee, they are lined with Id-in. or 1/2-in. slate, which is ample. They are often provided with doors to close, with glass. The smaller switches in these cases make a handsome appearance. This glass being 1/8-in. in thickness is usually ample to keep any flash within. Thecauses of fire in the older classes of installation, I will run over very briefly. The most frequent cause is the short-circuit, which is where two wires get together. The current flows from one to the other and causes a flash. Another cause is where the wire becomes corroded. If the two ends of the wire do not separate but a very little distance an arc will be produced—in other words, the current will continue to pass through the ‘atmo sphere, and that short passage through the atmosphere brings on a flash. That sets up a dangerous condition, because there is nothing to stop it. and it will continue to pass through, until the wires fall apart in the case of crossed wires, or until the two ends of a wire thus slightly separated get too far apart to carry the circuit. Two men of the board once investigated a case of this kind. It was an important matter, and I assigned two men to it. The building in question was of rough construction, being for pleasure-resort purposes on the shore, and was open-work construction, so that it could be easily seen. Perhaps the wire had been stretched tightly when put in; but 1 imagine the building had sagged, or, at any rate, something broke the copper wire inside the insulation, and an arc was set up. Our men smelled burning rubber at the point, and began to search for the cause, and happened to be there in time to watch the whole proceeding. The arc. continued, the covering of rubber ignited and burned until the wires fell apart, and, in falling, one was slapped out; but the other one hung there and continued to burn up following along the insulation. They being there, of course, could, and did put it out. But that was a demonstration of what may happen. Now, very briefly, we will refer to the flexible-cord hazard, where flexible lamp-cords are carried all round the room and hung on nails, and corroded off in time bv dirt and moisture. I had better say right here, that moisture is one of the worst enemies of installation that we have to contend with. The fuses, as I have mentioned before, should always be inclosed in a fireproof cabinet. There is no possible question that that is one of the greatest safeguards we can have; because, when a fuse melts out, and that is its purpose, it protects things. When there is trouble on a circuit, the fuse will melt out and cause a flash, especially if the fuse is not up to the standard, and a fireproof cabinet makes everything safe. The electrical pressing-iron is another hazard. They are used in the large houses, and in many private houses. It is thought the fire in John Wanatnaker’s house, near Philadelphia, was caused by a pressingiron being left, with the current turned on, on the cloth pad, until the heat arose to the point where it set fire to the ironing table There is very little doubt that the cause of that $5,000, 000 fire arose in that way. And there is the hazard of the electrical motor. It is a pretty safe proposition, and a good deal safer than many other sources of motive power we use, nevertheless, it is a source offire. In printing establishments and other like places, the motor should be inclosed. In that way, the danger is minimised. They are a little more expensive when inclosed, and, hence, not as popular nor used so much where economy is in view, as they should be: but it is important that the inclosed type should be used. The rheostat used in the Edison systems is a source of danger; but we believe we have gotten to the root of that. The newer ones are pretty safe. Another point of hazard is show-window lighting. It has caused fires, and, perhaps, quite numerous ones. In show-window decorations the flexible cord is carried round wherever the bulb may he needed, and the electric lamps are covered with all sorts of combustible material. It is a wellknown fact that, if you put a light in a cigar-hox packed with waste, it will not he so very long before the box will be gone and the lamp likewise. If you want to try it, do so, and the result will he apparent so quickly that il will not take long to experiment. Now in show-window decorating the lamps arc very easily disarranged, especially if one has to go in there for anything, and, inasmuch as there is much flimsy and combustible stuff all round, if the lamps do get disarranged, there is strong probability of a fire being caused.

tlonal Association of Fire Engineers, Washington, D. C.. October, 1907. Address made at the Convention of the Intema-

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