Oxy acetylene welding manual

The oxy-acetylene method of welding and cutting metals has of late been receiving considerable attention. Its tremendous power of creating, repairing and destroying the work of man has been but recently recognized in its broadest sense, and the demand for operators, skilled in the manipulation of this apparatus, which always has been far in excess of the supply, now knows no limit. Many authorities have set forth their views and theories upon this subject, in America and also in foreign countries. These have been published from time to time in many of the leading periodicals and magazines, as well as in book form. It seems the purpose of most of these works has been to advance the operators who already have a smattering knowledge of this art, or to present to the purchaser of apparatus a set of operating instructions.

Manufacturers in the metal-working world were very slow to grasp the real significance of this important process, until the operators began demonstrating some of its possibilities. At the present time, however, there is hardly a metal barrel or tank manufacturer who has not discarded the old method of producing costly leaky, riveted drums and containers, for this modern fusing process. The manufacturers of fire-proof doors and windows, cooking utensils, seamless pipe and tubing, office furniture and what not, are now virtually dependent upon the welding torch at every turn.

Cutting with the oxy-acetylene process is just the opposite from that of welding. The latter might be considered constructive and the former destructive. In the case of welding, two parts are brought to a molten condition along the line to be joined and both fused together. Whereas in cutting, one piece of metal, when brought to a red heat, is cut in two by an oxidizing flame. Cutting has not the wide scope that welding has, for it can only be applied successfully at the present day to wrought iron, rolled and cast steel. While it is limited in its scope, the speed of this process in severing large masses of metal is very spectacular and appeals forcibly to the observer.


CHAPTER I - OXY ACETYLENE WELDING APPARATUS

Oxy Acetylene welding apparatus in general consists of two regulators equipped with pressure gauges, two lengths of hose, and a welding torch. The regulators are attached to cylinders of acetylene and oxygen and are used to reduce and maintain a uniform pressure of these gases for use at the torch. The gases at reduced pressure are conveyed to the torch by the hoses. The regulators should each have a high-pressure gauge to indicate the contents of the cylinder, and also a line or working-pressure gauge to show the gas pressure on each hose. When the gases reach the torch they are there mixed and combustion takes place at the welding tip, which is fitted to the torch. Such an apparatus is called portable, on account of its movability. There are other equipments wherein one or both of the gases are generated, but these will not be discussed here.

For convenience oxy-acetylene welding apparatus may be divided into three classes, depending upon the principles used in securing the fuel gas or acetylene for the flame. Low-pressure, medium-pressure and high-pressure apparatus generally use about the same pressure of oxygen and it will be called a constant. The acetylene gas is a variable and in the low-pressure type only enough pressure is required to overcome the friction of the line until it reaches the oxygen injector, located in the torch, which acts as a syphon, drawing the acetylene gas to the point of ignition. In a medium pressure type about three-fourths as much pressure is required on the acetylene line as on the oxygen. This type is apt to verge on the injector type, as it depends to some extent upon the oxygen under pressure carrying acetylene gas to the point of ignition. In the high-pressure type equal pressure on each line is used. To further make this classification clear, a certain sized tip using, perhaps, 12 pounds of oxygen pressure can be used as an example. In a low-pressure type perhaps 2 pounds pressure or less will be needed on the acetylene line. On the medium-pressure approximately 9 pounds will be required, while on the high-pressure an equal amount, or 12 pounds will be needed. The mixing chambers for the gases may be located in the head; in the middle of the torch, or in the handle. By mixing chambers reference is made to that portion of the torch where the two gases are brought together and mixed. As can be seen with three different types of welding torches and three different locations for the mixing of the gases, the manufacturers can find a large range for producing oxy-acetylene apparatus. Some undoubtedly will fill certain requirements better than others. Much, too, will depend upon the ability of the operator in handling a torch.

Flashbacks are caused by the improper mixture of the gases, which increases the rate of flame propagation to such an extent that the flame will flash back to the mixing chamber. Acetylene in a pure state will burn very much slower than when mixed with equal parts of oxygen. When more oxygen is introduced the flame propagation is much greater, so that when an excess of oxygen is used, there is bound to be considerable trouble from back flashing. When sufficient acetylene is introduced to the mixing chamber, there is absolutely no chance for this lean mixture to occur. If the flame flashes back to the mixing chamber, both gases should be closed off immediately, at the torch, the oxygen first, and then the acetylene gas.

There are two types of regulators manufactured for the reduction of gases under high pressure, depending upon the nature of work to be done. The high-pressure regulator is employed for heavy work where a great deal of gas is used and the regulator must pass it without much effort, to prevent its freezing. This type of regulator is used on cutting or on large welding work. It differs from the low- pressure or ordinary type in four distinct features. Generally it contains a much heavier diaphragm which is smaller in diameter, making it stiffer in every respect. The tension springs which act upon this diaphragm are much heavier. The nozzle which presses against the seat is much larger, to permit the passage of a greater amount of gas. Then, too, a larger working pressure gauge must be used, in order to read this high pressure. In the welding of metals, especially in steel, the adjustment of the flame is a very important matter, and absolutely dependable regulation must be had.

This is not possible with a high-pressure regulator and is not intended to be so. The larger the diaphragm, the more sensitive the regulator, and this point should be borne in mind, and no small welding work attempted with the high pressure regulator. The reverse form of reasoning may be applied to low-pressure regulators which have been used in cutting. They are very likely to be strained and satisfactory results cannot be expected, for they are not made for that purpose. Acetylene regulators are constructed much more sensitively than the oxygen regulators, to take care of the lower pressure of gas and in a sense might be called weaker, insomuch that the larger nozzle which passes the gas is closed or regulated by springs which are not nearly as strong as in the oxygen regulator. For this reason acetylene regulators cannot be interchanged with oxygen regulators for they will not stand the pressure demanded in the first place, and in the second place, were a small quantity of acetylene gas left in the regulator and oxygen introduced, an inflammable mixture would be formed which is not advisable to have present, on account of its explosiveness. In many instances oxygen regulators are put out with the copper diaphragms, whereas another metal must be used on the acetylene regulators, because acetylene gas attacks copper and usually a German silver or rubber diaphragm is used. On account of the lower pressures used in charging the acetylene cylinders, lower pressure gauges are used than on oxygen regulators.