acetylene lighting



acetylene lighting defined in 1909 year

acetylene lighting - acetylene lighting;
acetylene lighting -

THE ARRANGEMENT OF AN ACETYLENE LIGHTING INSTALLATION

Acetylene can now be made (given a proper generator) by a lad or any unskilled person, without supervision and with no risk; and it can be had at a cost that compares equally with good coal-gas at about 3s. 6d. per 1000 ft. for a given candle-power or brilliancy of illumination. This is after allowing for wear and tear and interest on outlay. Should the present price of carbide go down, or should its gas-yielding qualities be increased, then acetylene will compare, of course, more favourably still.

The present cost of the gas, however, is no obstacle to its free adoption, for it is in very few country places that coal-gas costs less than 3s. 6d. per 1000 ft., and in many districts it exceeds this greatly. Probably most people would rather pay a little more for coal-gas supplied by a gas company, as the trouble of making the acetylene, small as it is or should be, is still a trouble, and the outlay for the apparatus has to be considered. Therefore acetylene is unlikely to displace coal-gas where the latter exists ; but it is already a possible and strong rival to coal-gas, if it should be a question of which gas plant shall be laid down to light a village. For isolated residences acetylene has nothing to fear from coal-gas. Its possible rival at this moment is petrol.

As to how acetylene compares with paraffin oil in cost, there is much uncertainty. One authority puts oil as costing double as much as acetylene for a given light, whilst another says oil costs little more than half as much. There can be no doubt of the former being correct for a given light, but it is not quite the correct way to compare the two. When oil is used a comparatively dull light is obtained, and this is considered satisfactory for oil: If an acetylene plant is then substituted, the degree of light given by the lamp is considered insufficient, and a much more brilliant effect is looked for and insisted on. Then the second authority quoted comes nearer truth; and from inquiries made by the writer from the users of the many acetylene apparatus he has erected, it may be stated that the average of these shows that acetylene costs about 20 per cent, more than oil, but a superior degree of illumination is obtained. Acetylene, however, can show a saving of labour, for the apparatus the writer uses only takes about five minutes per day for recharging— equivalent to the time taken on two lamps in wick-trimming and refilling. It may also be mentioned that the lamp room of a large country house is a far greater menace to its safety that an acetylene generator in its hut outside. To give an outline of acetylene gas production and consumption for those-whose experience is limited, the manufacture of the carbide need not be considered. The carbide (carbide of calcium) consists of lime and carbon fused together, and is to be readily purchased in any quantities from the different factors now stocking it. This carbide is a dry, grey material much resembling ordinary gas coke, but is denser and heavier. While it is kept dry it remains unchanged, and is perfectly safe even if fire should attack it. The change comes when water is brought in contact, and the carbide is so susceptible to this, and so greedily absorbs moisture, that the little water-vapour there is in the atmosphere is quite sufficient to attack it and start gas production. It is therefore important that carbide be kept in air-tight drums, or vessels, and these should be kept in as dry a place as possible in case of a fissure or- loose lid.

When water is brought in contact with carbide an immediate change occurs. The lime is slaked, hydrogen gas is given off, and this carries carbon with it. In other words the resulting gas is carburetted hydrogen, and the spirit material left behind is slaked lime. It will therefore be seen that the manufacture (if this is not too great a word) of acetylene gas is simplicity itself—either some carbide thrown into water, or some water brought to the carbide.

For the details of acetylene generation reference should be made to a standard work, and for this description it may be assumed that a generator is chosen and it is necessary to fix it. A hut or house is prepared to receive it, outside the building which is to be lighted. The generator must not be fixed in a room or cellar beneath the house;. The generator house must be very sheltered, or preferably heated by hot water or steam to prevent frost attacking the water in the plant. Whatever kind of generating apparatus .is used, water is in. it somewhere, and trouble must ensue if this freezes. Some consider that a brick-built generator house, with the doors lined with felt, can be protected by a good sized box of fresh horn; manure (in which fermentation and heat wet up). The writer has not had occasion to try this, but it sounds feasible.

Having made the necessary water connections to, and the gas connections from the generator, it has to be considered whether the gas shall be purified. In any case, whatever the gas is used for, it should pass through water first, and the majority of generating apparatus provide for this. The evolution of the gas is accompanied by heat, much the same as when ordinary quicklime is slaked, and the gas whilst warm carries vapours that can well be dispensed with. Condensation of these vapours is easily effected by passing the gas through cold water.

The condensation of condensible vapours, however, is not complete purification, and for residence work, or anything other than, say, such places as brick works or comparatively open factories, a purifier must be used. This appliance removes the gaseous impurities which pass unchanged through the condensing process, but which, if burned, cause a haze and an odour which cannot be borne in rooms. It is peculiar that in trying an apparatus minus a purifier, there may be no haze or smell for several days ; then there comes a bad day, which shows how I necessary the purifier is. It also shows ! that some of the carbide is good enough to yield a pure gas, and a purifier is chiefly necessary therefore to deal with occasional bad pieces or quantities of material.

If a purifier is used, and fully three-fourths of the works erected need one, the gas service is taken from the holder directly to it, with perhaps no more than 2 or 3 ft. of pipe between. If there are washers, or water chambers for condensing, in the generating apparatus, the gas would, on leaving the generating chambers, first go through these, then proceed to the holder. As the gas leaves the holder it next has to pass through the purifier, and then passes directly to the house. It is best not to put the purifier between the generator and holder, although at first thought it might be considered correct to do so. A purifier gives best results if the gas passes through it slowly and as regularly as possible. This result is best attained on the house side of the holder. If placed between generator arid holder the gas passes through more in rushes and the general effect is not so satisfactory.

The service piping is arranged much the same as ordinary gas piping is, except that the pipes may be much smaller. At the lowest point in the piping, usually where the gas first (inters the house there should be a syphon-box, or some such provision, to receive the water that will collect in gas pipes. This is an ordinary provision with any gas-piping system, to (1ispose of ''water in the pipes"as it is called.

An appliance that should appear in all but the smallest installations is a "governor" or pressure regulator which automatically controls the pressure of gas in the house services.

This is of greater advantage with acetylene than with coal-gas, as any extravagance with the former means a greater waste of money than with 1110 latter. It takes approximately fifteen times the volume of coal-gas an it does acetylene to afford a given light for a given time, therefore in the case of waste, a certain amount of acetylene, say a cubic foot, being wasted is equal to losing 15 cubic ft of coal-gas. In other words it is, as regards monetary loss, much more desirable to prevent waste of acetylene than coal-gas. The governor will do this quite satisfactorily.

Having described the general arrangement of the various appliances included in a complete plant, a sketch, Fig. 1, is given to make the description more readily understood by those new to the work. No shape or form is given to the generator, as no particular make can be inserted here. The sketch is merely to show the order in which the parts come. They need not necessarily be in a line, but as a rule they are all in the generator house. Quite usually the generating chamber and washer are attached to the gas holder.

As regards leaks in pipes, a slight issue of gas may not be considered any more dangerous than such a leakage of coal-gas, but it represents a greater monetary loss. As just stated, if a cubic foot of acetylene leaks from a fissure in one hour, the cost is equal to about fifteen such leaks in coal-gas piping.

Respecting the sizes of gas services, the following are those customarily used, allowing for the pressure being reduced by the governor. With higher pressures, smaller pipes would suffice, but higher than normal pressures are distinctly bad in results.

Ordinary iron gas tube is used, also compo pipe, but the latter would not appear in good work. The pipe should be given a rise all the way from its starting point, or from the syphon-box previously alluded to. This is the customary provision with all gas piping systems.

The brackets, pendants and fittings can be of ordinary good quality, but there are now special fittings being made and it is desirable to use them. Acetylene is described as a searching gas, meaning that it will find (pass through) a smaller and less important leak than coal-gas ; consequently a badly made fitting, or the wear and tear to ordinary fittings, is sooner brought to notice. The special fittings are made so that they are being perpetually ground in as they are used, and this keeps them sound much longer. This applies to the wearing parts, of course—the cocks, bracket joints, and cup and ball joints.

No fittings or tubes or any other parts should he of copper. Brass, although it in an alloy of copper, may be used freely. The burners used for acetylene are specially made for this gas, and they should be kept of one candle-power or size as far as possible, because burners of different candle-powers require different pressures of gas to give the best results. Burners varying five or even ten candle-power do not show any difference to speak of, and this degree of variation is permissible ; but to have 20 and 50 candle-power burners on the same piping must result in one or the other being less effective or less economical than it should be, unless the governor is adjusted for the large burners and the bracket taps are carefully adjusted for each smaller one. It is better in such a case to have double burners for the large ones, a burner that gives two 25 candle-power flames. This would reduce the variation in size of burners to the permissible limits.

A f foot burner is the size generally used for residence work, or any living rooms, and this is the most desirable size as a rule ; but there remains the fact that the larger the burner the more economical of gas it is, or perhaps it should be said the more candle-power you get per cubic foot of gas burned. Therefore, if an installation required a number of 1 foot burners, then it would be the most economical to use these and trust to the bracket taps being regulated for the smaller ones. Or, better still, try and arrange for all the small burners to be on a separate service, and put a separate governor to them.

For ordinary purposes a 25 candle-power flame is allowed to each 100 superficial feet of floor space, for lighting living rooms. It will be noticed that a 25 candle-power lighting flame, not burner, is mentioned, for burners vary much in their rated candle-power and the candle-power of the flame they give.

When the apparatus is thus completed it has to be tested, and this is done from the house side of the governor, as the test must be of a higher pressure than the governor would allow unless its inner mechanism were removed. The appliance or gauge used for this is as Fig. 2; it need not be purchased as it can be readily made. It is customary to test with a pressure of 10 in. of water, and good work should not only bear this but much more. After testing, the gas can be turned on and the working pressure is then fixed by attaching the testing apparatus to a bracket, and then adjusting the weights of the governor until the pressure is obtained there. A 2½ pressure gives the best results with f foot burners, but with burners of higher power 3-in. and 4-in. pressures are needed.

Before applying lights to the burners of the completed apparatus, it is as well to make certain that there is no air in the apparatus. Air mixed with the gas is, of course, an explosive mixture, and this should be discharged before lighting up, by allowing part of the first volume of gas to waste, to make sure of all the air being got out of the apparatus.

Having started the generating apparatus, it only remains to give the future attendant his directions as to re-charging. One important thing is to caution everyone against taking artificial lights to the gas house. An electric hand lamp would be permissible but nothing else. No such light should be needed, as recharging can be done in daytime. A conspicuous notice of these things should be attached to the door of the generator house.

The store of carbide can be kept in 1,110 same house as the generator, or in any adjacent dry place. It must not be kept on or under the building that is lighted, or any insured building. In every case the Fire Insurance Company must be apprised, and their rules (if they issue any) adhered to.

The spent material should be white, or very nearly so, and odourless. It then consists of slaked lime with a little excess water, and it may be used for practically any purpose that such lime can be put to. It may be used for walls, trees, etc. It will not pay, however, to attempt to dry it for any purpose. If the spent material gives off any odour of gas, it shows either that the apparatus does not use up the carbide properly or that the attendant is careless in re-charging before it is quite necessary. At the same time there are generators made with which it is difficult to wait until the carbide is all spent, as this might be after dark, when re-charging is awkward or impossible, and when the gas is needed for use. Such a generator is not the best one to use for private residence work ; but if one exists, then when re-charging, the attendant has to sort the contents of the generating chamber, picking out the partially decomposed pieces and putting them back with the charge of new material. It is not a convenient arrangement, yet it must be done in such cases to admit of daylight recharging. With such generators it is difficult to get a sludge odourless and free of gas, therefore the spent material should be dumped into a tub or pit containing water. (F. Dye.)

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