FIRE-ALARMS AND AUTOMATIC FIRE EXTINGUISHERS

The Romance of Modern Mechanism by Archibald Williams is part of the HackerNoon Books Series. You can jump to any chapter in this book here. CHAPTER XI

FIRE-ALARMS AND AUTOMATIC FIRE EXTINGUISHERS

Assuming that a town has a well-appointed fire brigade, equipped with the most up-to-date engines, it still cannot be considered efficiently protected against the ravages of the fire-fiend unless the outbreak of a fire can be notified immediately to the stations, and local mechanical means of suppression come into action almost simultaneously with the commencement of the conflagration. "What you do, do quickly" is the keynote of successful fire-suppression; and its importance has been practically recognised in the invention of hundreds of devices, some of which we will glance at in the following pages.

The electric circuit is the most valuable servant that we have to warn us of danger. Dotted about the streets are posts carrying at the top a circular box, which contains a knob. As soon as a fire is observed, anyone may run to such a post, smash the glass screening the knob, and pull out the latter. This action flashes the alarm to the nearest fire-station, and a few minutes later an engine is dashing to the rescue. Help may also be summoned by means of the ordinary telephone exchanges or from police-stations in direct telephonic communication with the brigade depôts.

All devices depending for their ultimate value on human initiative leave a good deal to be desired. They presuppose conditions which may be absent. For instance, an electric wire in a large factory ignites some combustible material during the night. A passer-by may happen to see flames while the fire is in an early stage. On the other hand, it is equally probable that the conflagration may be well established before the alarm is given, with the result that the fire brigade arrives too late to do much good.

What we need, therefore, is a mechanical means of calling attention to the danger automatically, with a quickness which will give the brigade or people close at hand a chance of strangling the monster almost as soon as it is born, and with a precision as to locality that will save the precious time wasted in hunting for the exact point to be attacked.

Mr. G. H. Oatway, M.I.E.E., in a valuable paper read before the International Congress of Fire Brigades in London in 1903, says that the difference between the damage resulting from a fire signalled in its early stage, and the same fire reported when it has spread to two or three floors, is often the difference between a nominal loss and a "burn out." The reformer, he continues, who aims at reducing fire waste must turn his attention primarily to hastening the alarm. The true cure of the matter is, not what quantity of gear it takes to deal with huge conflagrations, but how to concentrate at the earliest stage upon the outbreaks as they occur, and to check them before they have grown beyond control. He cites the fire record of Glasgow of 1902, from which it appears that three fires alone accounted for 40 per cent. of the year's total loss, ten fires for 73 per cent., and the other 706 for only 27 per cent., or an average of £72 per fire. Had the first three fires only been notified at an earlier stage, nearly £72,000 would have been saved. Captain Sir E. M. Shaw, late Chief of the London Fire Brigade, has put the following on record: "Having devoted a very large portion of the active period of my working life in bringing into general use mechanical and hydraulic appliances for dealing with fires after they have been discovered, I nevertheless give and have always given the highest place to the early discovery and indication of fire, and not by any means to the steam, the hydraulic, or the numerous other mechanical appliances on which the principal labours of my life have been bestowed."

A fire given fifteen minutes' start is often hard to overtake. Imagine a warehouse alight on three floors before the alarm is raised! Engines may come one after another and pour deluges of water on the flames, yet as likely as not we read next morning of "total destruction." No stitch in time has saved nine!

The sad part about fires is that they represent so much absolute waste. In commercial transactions, if one party loses the other gains; wealth is merely transferred, and still remains in the community. But in the matter of fire this is not the case. Supposing that a huge cotton mill is burnt down. The re-erection will, it is true, cause a lot of money to change hands; but what has resulted from the money that has already been put into the mill? Nothing. So many hundred thousands of pounds have been dematerialised and left nothing behind to represent them. The great Ottawa fire of a few years ago may be remembered as a terrible example of such total loss of human effort.

THE HISTORY OF FIRE-ALARMS

The first recorded specification for an automatic detecting device bears the date 1763. In that year a Mr. John Greene patented an arrangement of cords, weights, and pulleys, which, when the cord burnt through, caused the movement of an indicating semaphore arm. As this action appealed only to the eye, it might easily pass unnoticed, and we can imagine that Mr. Greene did not find a gold mine in his invention.

Twenty-four years later an advance was made when William Stedman introduced a "philosophical fire alarum." "His apparatus consisted of a pivoted bulb having an open neck, and containing mercury, spirit or other liquid. As the heat of the room increased, the expansion of the fluid caused it to spill over, release a trigger, and allow a mechanical gong to run down. This arrangement, whilst an advance upon the first referred to, is quite impracticable. Evaporation of fluid, expansion of mercury, a stiff crank, or other causes which will readily occur to you, and the thing is useless."[14]

In 1806 an automatic method for sprinkling water over a fire appeared. The idea was simplicity itself: a network of water mains, with taps controlled by cords, which burnt through and turned on the water. William Congreve patented, three years later, a sprinkler which was an improvement, in that it indicated the position of the fire in a building by dropping one of a number of weights. But string is not to be relied upon. It may "perish" and break when no fire is about, and any system of extinction depending on it might prove a double-edged weapon.

The nineteenth century produced hundreds of devices for alarming and extinguishing automatically. All depended upon the principle of the expansion or melting of metal in the increased temperature arising from a fire. At one time the circuit-closing thermometer was popular on account of its simplicity. "Its drawback," says Mr. Oatway, "is the smallness of its heat-collecting surface, its isolation, and, last and worst of all, its fixity of operation. In thermometer or fuse-alarm practice it is usual to place the detectors at intervals of about ten feet or so, so that a room of any size will contain a number. If a fire breaks out, the ceiling is blanketed with heat, and every detector feels its influence. Each is affected, but none can give the alarm until some one of the number absolutely reaches the set point or melts out. Having no means of varying the composition of the solder or shifting the wire, an actuating point must be selected which is high enough to give a good working margin over the maximum industrial or seasonal heat of the year; and thus it comes about that if the fire breaks out in winter, or when the room is at its lowest temperature, the amount of loss is considerably and quite unnecessarily increased. In a device set to fuse at 150° Fahrenheit, it will be clear to every one that the measure of the damage will depend upon the normal temperature of the room at the time of the outbreak. If the mercury is in the nineties, there is only some sixty degrees of a rise to wait for; whilst if it happens to be a winter's night, the alarm is held back for a rise of perhaps 120°. What chance is there in this case for a good stop?"

Mr. Oatway has examined the fuses under different conditions, and his conclusions are drawn from practical tests. Great intelligence will not be required to appreciate the force of his arguments. Inasmuch as the rise of temperature caused by a fire is relative, during the early stages at least, to the general heat of the atmosphere, it becomes obvious that an automatic fire-alarm should be one which will keep parallel, as it were, with fluctuations of natural heat. Thus, if the "danger rise" be fixed at 100°, the alarm should be given on a cold night as certainly as at midday in summer. It was the failure of early patterns in this respect that led to their being discredited by the fire-brigade authorities.

The writer already quoted has laid down the functions of a perfect alarm:—

(a) To detect the fire at a uniformly early period, under all atmospheric and industrial conditions.

(b) To give the alarm upon the premises, and simultaneously to the brigade, by a definite and unmistakable message.

(c) To facilitate the work of extinction by indicating the position of the outbreak in the building attacked.

The "May Oatway" alarm has got round the first difficulty in a most ingenious manner by adapting the principle of the compensation methods already described in connection with watches.

The alarm consists of a steel rod of a section found to be most suitable for the purpose. To the side is attached by screws entering the rod near the ends a copper wire, which is long enough to sag slightly at its centre, from which depends a silver chain carrying a carbon contact-piece. A short distance below the carbon are the two terminals of the electric circuit which, when completed by the lowering of the carbon, gives the alarm. Now if there be a very gradual change of temperature the steel rod lengthens slowly, and so does the copper wire, so that the amount of sag remains practically what it was before. But in event of a fire the copper expands much more quickly than the steel, and sags until the carbon completes the circuit. The whole thing is beautifully simple, very durable, quite consistent, and reliable. As soon as the temperature diminishes, on the extinction of the fire, the alarm automatically returns to its normal position, ready for further work.

Now for the second function, that of giving the alarm in many places at once. The closed circuit does not itself directly cause bells to ring: it works a "relay," that is, a second and more powerful circuit. In fact, it is the counterpart of the engine driver, who does not himself make the locomotive move, but merely turns on the steam. An installation has been introduced in the Poplar Workhouse—to quote an instance. Were a fire to break out, one of the 276 detectors would soon set twenty-five bells in action, one in each officer's room. Similarly, in the Warehousemen's Orphanage at Cheadle Hulme, every dormitory would be aroused, and every officer, including the Principal in his house some distance away. Messrs. Arthur and Company, of Glasgow, have [198]a warehouse fortified with 600 of these "nerve centres," all yoked to four position indicators, three of which actuate a "master" indicator connected with the central fire-station. There is no hole or corner in this huge establishment where the fire-demon could essay his fell work without being at once spied upon by a detector.

We may glance for a moment at the mechanism which sends an unmistakable message for help. At the brigade station there is a number of small tablets, each protected by a flap, on the outside of which is the word SAFE, on the inside FIRE. Normally the flap is closed. As soon as the circuit is completed, a magnet releases the flap, and a bell begins to ring. Now, it is possible that the circuit might be closed accidentally by contact somewhere between the premises it serves and the fire-station. So that the official on guard, seeing "J. Brown and Company" on the uncovered tablet, might despatch the engines to the place indicated on a wild-goose chase.

To prevent such false alarms the transmitter not only rings the station up, but automatically sends an unmistakable message. When a fire occurs an automatic printing machine is set in motion to despatch a cipher in the Morse code four times to the station. An accidental circuit could not do this; therefore, when the officer sees on the receiving tape the well-known cipher, he turns out his men with all speed.

On arriving at their destination the firemen receive valuable help from the "position indicator," which guides them to their work. On a special board is seen a row, or rows, of shutters similar to those already mentioned. Each row belongs to a floor; each unit of the row to a room. A glance suffices to tell that the trouble is, say, in the most southerly room of the second floor. No notice is therefore taken of smoke rolling out of other parts of the building, until the danger spot has been attacked.

That the firemen appreciate such an ally goes without saying. Every fire extinguished is a point to their credit. Also, the risks they run are greatly diminished, while the wear and tear of tackle is proportionately reduced. The fireman is noted for his courage and unflinching performance of duty. The discomforts of his profession are sometimes severe, and its dangers as certain as they are at times appalling. Therefore we welcome any mechanical method which at once shortens his work, lessens his peril, and protects property from damage.

Mr. Oatway draws special attention to the need for simultaneous warning on the premises and at the fire-station. "I remember," he says, "many cases, but perhaps no better illustration need be looked for than the case of a cotton mill in Lancashire about two years ago (1901). The fire was seen to start at a few minutes past seven; a fuse blew out, and sparked some cotton; but it looked such a simple job that the operatives elected to deal with it. At twenty minutes to eight it dawned upon somebody that the brigade had better be sent for, because the fire was getting away; and in due course they arrived; but the mill, already doomed, became a total loss. In every centre similar instances can be quoted. There is nothing in any automatic system to discourage individual effort. Inmates can put the fire out, if able; but in any case the brigade gets timely and definite notice, and if on their arrival they find the fire extinguished, as Chief Superintendent Thomas put it when we opened the Dingle Station after the fatal train-burning, 'So much the better, we shall get to our beds all the quicker.' This is the common-sense view of it. Helpers work none the less intelligently because they know the brigade is coming; and it is necessary to provide some automatic method of calling them, because you can never rely upon anybody who is unfamiliar with fire doing the right thing at the proper time."

Messrs. May and Oatway, who give their name to the alarm described above, first introduced their apparatus in New Zealand, from which country it has spread over the British Empire. The largest installation is at Messrs. Clark and Company's Anchor Mills, Paisley. The whole of the immense block of buildings, the greater part of which was previously protected by "sprinklers" only, is now electrically protected also; and connected up with the fire brigade, and through their station with the sleeping quarters of every fireman. Some figures will be interesting here. There are 119 miles of internal alarm circuits; 514 miles of underground cable between buildings; 19 automatic telegraphs; 21 automatic position indicators; 20 alarm gongs a foot in diameter.

Early in January, 1905, a fire broke out in these buildings during the dinner hour, when most of the works' firemen were at their midday meal. The alarm sounded simultaneously at the works' fire-station and at the firemen's houses, which are situated on the other side of the street from the mill. The firemen were on the spot immediately, and were enabled to subdue the flames, which had broken out in the building occupied as warehouse and office, before it had got a firm hold of the inflammable material, although not before one of the large stacks of finished thread was ablaze. The brigade, however, were soon masters of the situation, and the damage done was under £100. There is little doubt, had the alarm been left to the ordinary course, the building would have been totally destroyed.[15]

In those few minutes the installation saved its entire cost many times over. Truly

"A little fire is quickly trodden out,
Which, being suffered, rivers cannot quench."

Here, in a Shakespearean nutshell, is the whole science of fire protection.

AUTOMATIC SPRINKLERS

As these have been referred to several times a short description may appropriately be given. The building which they protect is fitted with a network of mains and branches ramifying into each room. At the end of each branch is a nozzle, the mouth of which is bridged over by a metal arch carrying a small plate. Between the bridge and a glass plug closing the nozzle is a bar of easily fusible solder. When the temperature has risen to danger point the solder melts, and the plug is driven out by the water, which strikes the plate and scatters in all directions.

This device has proved very valuable on many occasions. The Encyclopædia Britannica (Tenth Edition) states that, in the record of the American Associated Factory Mutual companies for the 512 years ending January 1, 1900, it [appears that out of 563 fires where sprinklers came into play 129 were extinguished by one jet; 83 by two jets; 61 by three; 44 by four; 40 by five.

The fire-bucket is the simplest device we have as a first aid; and very effective it often proves. Insurance statistics show that more fires are put out by pails than by all other appliances put together. The important point to be remembered in connection with them is that they should always be kept full; so that, at the critical moment, there may be no hurried rushing about to find the two gallons of liquid which each is supposed to contain permanently. In Cassier's Magazine (vol. xx. p. 85) is given an account of the manner in which an ingenious mill superintendent ensured the pails on the premises being ready for duty. The hooks carrying the pails were fitted up with pieces of spring steel strong enough to lift the pail when nearly empty, but not sufficiently so to lift a full pail. Just over each spring, in such a position as to be out of the way of the handle of the pail, was set a metal point, connected with a wire from an open-circuit battery. So long as the pails were full, their weight, when hung on their hooks, kept the springs down, but as soon as one was removed, or lost a considerable part of its contents by evaporation or otherwise, the spring on its hook would rise, come into contact with the metal point, thus close the battery circuit and ring a bell in the manager's office, at the same time showing which was the bucket at fault. The bell continued to ring till the deficiency had been made right; and by this simple contrivance the buckets were protected from misuse or lack of attention.

FOOTNOTES:

14. Mr. W. H. Oatway.

15. Glasgow Evening News.

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