Page:EB1922 - Volume 32.djvu/1002

at B. The acetylene, at less than i-lb. pressure, goes to chamber C, from which it is sucked by the oxygen, under 5 to 3O-lb. pressure, pouring out of nozzle D, and is carried along with the oxygen into the mixing chamber E. The thoroughly mixed gases issue from the nozzle of the torch, where they are burned.

Carbureting device which positively and r intimately mixes the two gases in proper proportion ^- /OXYGEN

Oxygen needle Valvej

Acetylene needle Valve

\ACETYLENE The two gases strike together at right angles creating a vortex which insures intimate mixture

The diameters of the parts in the carbureting device are proportioned to each size of lip, to deliver proper volumes of gas for each size of flame produced

| luminous Cone of Flame

Secondary reaction. Hydrogen and carbon monoxide burn, taking the necessary oxygen from the air and produce water vapor and carbon dioxide.

FIG. 3. A typical positive-pressure gas torch

The positive-pressure torch principle is illustrated in fig. 2. Here the oxygen, at from I to 14-lb. pressure, enters at A, and the acety- lene, at from I to 24-lb. pressure, enters at B. The oxygen enters the small chamber C and thence out through the centre hole. The acetylene goes to chamber D and also out through the centre hole. The two gases start to mix at E and are thoroughly mixed in the channel F in the torch nozzle G. A typical positive-pressure torch is shown in fig. 3. Torches are made with tips set at various angles from 90 to straight, the latter being principally used in welding and cutting machines. Where the work is heavy the tips are water- cooled. In welding very thin metal the edges are often turned up or " flanged " and the torch used to fuse them together without using any additional metal. On heavier work the edges to be welded are V-eed out at an angle of from 60" to 90", and this channel is filled in by using a welding rod or wire, care being taken to obtain perfect fusion between the old metal and new. Welding of this kind is progressive, as the welder gradually works along the channel, filling

Oxygen Tank Valve

OXYGEN REGULATOR

^.--Tankor High- Pressure Gage

Tank or High-

Pressure Gage

Connecting Nut---

Adapter ;

Safety Valve-

Outlet Connection

V- Gutting Nozzle

-Torch Head

TORCH Cutting Valve

Acetylene Hose_.--

FIG. 4. Typical oxy-acetylene cutting unit

as he goes. The torch is given a weaving motion from side to side in order to fuse the sides of the V and to puddle in the added metal from the rod. On all torch welding work allowance must be made for expansion and contraction, and on repair work of complicated design, like an automobile cylinder, preheating with charcoal, gas- and-air torches, or other means is usually necessary. Preheating is also sometimes resorted to in order to save the more expensive gases. Nearly all of the common medals may be welded with the gas torch, though some are more difficult than others. Steel ship or boiler plate

is about the easiest, though aluminium, cast iron, copper, and many alloys present no serious difficulties.

The set-up for a welding outfit is practically the same as that of the one for cutting shown in fig. 4. A cutting torch, however, differs from a welding torch in that it has a separate high-pressure oxygen vent. The cutting of steel and wrought iron is based on the fact that a jet of oxygen directed on to a previously heated spot of steel causes it to ignite and burn away rapidly in the form of iron oxide. The oxide runs or is blown out of the cut or " kerf," in a stream, provided the torch is fed along properly. The tips used for cutting may have one or several heating jets preceding or surrounding the cutting oxygen jet. Only steel or wrought-iron can be successfully cut on a commercial scale, though channels or slots may be melted in any metal. A typical job of steel plate cutting is shown in fig. 5, and a typical cutting torch in fig. 6. Cast iron is cut with difficulty, and only by using a special tip and highly preheating the oxygen in a positive-pressure torch or by using an excess of acetylene and an unusually large tip on the low-pressure types.

FIG. 5. Cutting through a steel plate

CUTTING OXYGEN

CONICAL

GROUND SEAT

COPPER TIP

CUTTING . JET OF ?M OXYGEN ,',

? ACETYLENE ;

'REHEA' OXYGEN

y. OXYGEN CUTTING Si

SET TRIGGER VALVE

OXYGEN CUTTING

PREHEATING PACK ' NG FLAME

' PACKING CUTTING VALVE NUT

TRIGGER (Remains in Open Position)

PREHEATING ,OXYGEN VALVE

OXYGEN ACETYLENE

ACETYLENE VALVE

VALVE

REMOVABLE PLUS SPRING

FIG. 6. A typical cutting torch

The same sources of gas supply are used in cutting as in welding. These are commonly cylinders or drums containing the gases under pressure up to 225 Ib. per sq. in. and from 100 to 300 cu. ft. capac- ity for acetylene, and 1,800 Ib. per sq. in. and from loo to 200 cu. ft. capacity for oxygen or hydrogen. Acetylene, however, may be generated on the premises, in which case the pressure must not exceed 15 Ib. per square inch. Obviously pressure as great as that mentioned for cylinders must be reduced for use in the torch and for this pur- pose regulators are used which automatically keep the gases supplied to the torch close to the pressure for which they are set. Gas-torch welding machines that are practically automatic are in use in many large plants for straight or circular seam welding of drums, cylinders, tubes, kettles and the like. Cutting machines are much more commonly used than welding machines. The cutting machines range from the simple, hand-fed, straight-line cutters to complicated motor-driven automatic machines that will cut rounds, squares, ovals or other patterns. One type of cutting machine is made on the panto- graph principle, and by following a template or pattern the operator can use two torches and cut two separate steel plates at once. A cutting machine will, as a rule, cut a narrower and more even kerf than can be done by hand. Under favourable conditions a machine can be made to cut a kerf not over -fa in. wide, while a careless or inexperienced operator with a hand torch may cut a kerf J in. or more in width. (E. Vi.)

WELFARE WORK IN INDUSTRY. Human beings possess intelligence, and their well-being depends on psychological as well as on physiological make-up. Mental and physical activity are necessary to health. From the industrial point of view both require to be maintained in order to ensure the efficiency which represents for the employer a contented personnel, and for the employed not merely physical health, but a "worth while" life.