In the majority of cases welding does away with a lot of preparatory work, caulking of edges, pulling apart of rivets and other fastenings, operations always expensive, and which are always to be avoided if possible.

Take, for instance, the case of a cylindrical tank with riveted bottom and head. If this tank is not of a sufficient diameter, and is not provided with a manhole, it will be necessary to make it with at least a convex bottom or head. Anyway its making requires a riveted cylindrical shell with two drawn heads at the ends to permit the riveting of bottom and head and caulked edges.

The same tank can be made by welding with solid welded heads.

It may be mentioned that welding has rendered possible the making, volume and resistance being equal, of tanks less cumbersome and lighter than those before its advent, in that it has made possible the building of tanks with two convex bottoms without regard to the diameter and absolutely free of the double thickness of plates necessitated by riveted coverings.

Nearly all the tanks built to contain gases under pressure or any liquids, such as petroleum, are now welded, because, apart from the advantages of weight, bulk, and price which they have over the riveted tanks, they do not leak, a quality which is difficult to obtain by riveting, and even with subsequent tin soldering, particularly when these tanks are supposed to travel and are, consequently, subject to continual rough handling.

Besides the saving which may be realised by welding over riveting by doing away, in a large measure, with preparatory forge work, the economy of the process in itself should be considered.

Take, for instance, the case of the ordinary riveting together of two plates of 1/4-in. thickness, as given by The Boiler Maker.

Riveting (one line of rivets), diameter of rivets 1/2 in., number of rivets per foot, eight.

Price paid to the workman per foot of joint: -

This cost does not include the general expenses arising from the necessary power, keeping, etc., of the machinery, and heating of the rivets.

This shows conclusively that acetylene welding is more economical than riveting.

To complete the comparison, consider the case of the building of a vertical tubular trailer by acetylene welding and by riveting. Those operations, which are similar in both processes of manufacture, are not considered : shearing and laying out of the plates, boring holes, assembling and expanding of tubes, etc.

The above prices of riveting are taken on the supposition that the chamfering and caulking are executed by compressed air (except for the heads, which require some hand work). They do not include the general expenses (material, coal, and coke necessary for welding the charger, and for the various forge work).

These results show the considerable saving obtained by judiciously using acetylene welding in boiler-making.

The cost price may also be made lower by a preliminary heating of the parts to be welded, using a less expensive combustible than the acetylene or hydrogen mixture.

It is evident that in every instance where the method of manufacture, the shape of the pieces, the place where the work is to be done, will admit of such a previous heating, a great advantage will result by bringing the parts to be welded to the highest practicable degree of heat. The more expensive temperature from the blowpipe is thus used only for the actual welding, which the cheaper way of heating cannot effect.

Probably one of the widest fields for the adoption of the autogenous welding is in keeping down the heap. There are many instances, particularly in pressed steel work, where, owing to the development of a small split or the opening of a seam, a large and valuable piece of work has to be scrapped. A few minutes' application of the blowpipe will, at an almost insignificant cost, in most cases enable such a flaw to be repaired and the piece put into use.