(17) All history of the process, gas manufacture and the like have been omitted in order to give greater detail to the actual shop practice and to have the operator become familiar with his apparatus and thereby operate it with all due respect and intelligence.
(18) Oxy-acetylene welding cannot be learned by watching others work, although observation may at times assist the beginner. Actual torch practice, brain work and a power of “I will,” produce the most efficient operators. For those who earnestly apply themselves to the instructions which follow, there is every reason to believe that success will be theirs.
CHAPTER I
APPARATUS
(19) 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.
Fig. 14.—A Portable Welding Unit.
(20) 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.
Fig. 15.—Location of Mixing Chambers in Welding Torches.
(1) Shows gases mixing in the handle. (2) Has the mixing chamber in the middle of the torch. (3) Illustrates how the gases are kept separate until the head of the torch is reached. Ox. represents oxygen gas; Ac. acetylene gas; and m mixing chamber.