The theoretical temperature of the Oxy-Acetylene flame, as used in the Oxy-Acetylene Welding and Metal Cutting processes, is approximately 4,000 degrees Centigrade, a heat sufficiently above the melting point of steel to reduce it to fluidity by local application and so produce the required conditions for autogenous welding.

Many metals, however, possess a far lower melting point than steel, and in many jointing operations autogenous welding is either unnecessary or impracticable.

Such operations include the common practices of brazing, soldering, plumbing and lead-jointing.

In the case of brazing, it is important that the heat applied should be neither high enough to produce actual melting, nor so low as to require greater expenditure of time or fuel than economy will permit.

Air- Acetylene

Acetylene possesses the highest calorific value of all fuel gases, and compared with others, gives with air alone to support combustion a flame temperature sufficiently in excess to provide the requisite bulk of flame with a relatively low consumption of gas. It has, therefore, been round that the use of Acetylene mixed with atmospheric air in a blowpipe provides the ideal conditions noted above, as is shown in the following table of comparative temperatures and heating values :-

No Air Bellows Or Oxygen

In order to arrive at an adequate velocity and bulk of flame, it has been found necessary with fuels other than Acetylene to use some auxiliary, such as compressed air or oxygen. This is necessary with coal gas on account of its relatively low supply pressure, increased velocity being obtained from the energy of the auxiliary. With Dissolved Acetylene no auxiliary is needed, the pressure under which this gas is stored, combined with its high calorific value, being sufficient to give it the required velocity and heating power.

This fact is indicated in the table above, in which it is shown that the flame temperature of Acetylene, when consumed with atmospheric air, is notably higher than that of other fuel gases, even under the best conditions, i.e., mixed with Oxygen.

In the case of Dissolved Acetylene, therefore, all hand pumps blowers, compressors, foot-bellows, vaporisers or other extraneous means of producing a suitable flame are entirely eliminated.

In addition to the Gas supply and Blowpipe, the apparatus is confined to a piece of flexible tubing of suitable length for the purpose in hand.

Gas Supply

Unlike Oxy-Acetylene Welding and Metal Cutting, where almost invariably Dissolved Acetylene cylinders of the larger capacities are used, there are numerous cases in which Air-Acetylene Blowpipes may be employed with equal efficiency and greater convenience with Acetylene cylinders of smaller size. The user, therefore, should select the size of cylinder (the range of which is from 6 cubic feet to 250 cubic feet capacity) best suited to his individual needs.

The Apparatus

Careful experiments, spread over a number of years, made with Blowpipes of all types have been the means of developing a series of instruments designed on the Bunsen principle, with the object of producing the blowpipe flame in the form most efficient for each particular purpose, and of giving in every case the requisite temperature and bulk of flame with the lowest practical consumption of gas.

Individual requirements occasionally demand a variation from standard products, and the manufacturers are therefore willing at all times to study the special needs of their customers, and are continually conducting experiments at their own Research Laboratories with this end in view.

The Air-Acetylene Blowpipe was first used as a means of heating to incandescence a pastille of non-combustible material for the purpose of illumination in a lantern or searchlight projector. In this, its prime object was that of a heating agent, and the various Air-Acetylene instruments have been-with one exception (the High Temperature type of Blowpipe)-developed from this original (Messrs. Allen Liversidge. Ltd.)

Oxy - Acetylene Welding and Metal Cutting for Blacksmiths, Farriers, Wheelwrights, etc.-It is not too much to say that the use of the Oxy-Acetylene Process opens up for Blacksmiths, Farriers, and all those engaged from time to time upon repairs to Agricultural Machinery and the like, an entirely new field of valuable work. Moreover, Oxy-Acetylene welding can be applied, with greater speed and economy, to many jobs for which hitherto the forge alone has not offered sufficient facilities.

The modern blacksmith, farrier or wheelwright, uses both Forge and Blowpipe and thus not only preserves his strength for work in which the muscles of his arm are the most important factor, but makes possible, in and outside his smithy, a very great variety of jobs which, were it not for the presence in his forge of blowpipe and burner, would have been sent to the foundry or elsewhere.

With Dissolved Acetylene the gas is paid for as it is used ; there is no waste gas for which to make allowances, the gas is always ready for use whenever required, and the user has therefore at his immediate command the most economical outfit for the intermittent work which comes his way.

It is admitted that the cost of Dissolved Acetylene is higher than that of gas generated direct from carbide and water, but in considering the cost of any given job the amount of gas consumed must be taken into account, and in most intermittent work such as that done in the smithy the amount of Acetylene consumed is so small and the difference in cost so trifling that the convenience of pure gas, ready for use, far more than compensates for that difference.

Not less important is the factor of time, and it is frequently found that when acetylene generating plant has been lying idle for some days it is full of " sludge " with even the gas conduits choked up, so that valuable time must be spent in cleaning out. Dissolved Acetylene equipment on the other hand is always ready for use-and always clean.