nuts enough to prevent leakage. Never use vice grips, 10. Adjust the working pressures. A standard,
pliers, adjustable wrenches, and so on to open or close working pressure of 20 to 25 psi oxygen and 5 to 7 psi
gas cylinder valves or to tighten equipment fittings. You acetylene is recommended. The acetylene pressure is
will only ruin the valve stem and damage equipment, adjusted by turning the regulator screw to the right until
making it impossible to open or close the equipment in the desired pressure is attained. (Due to the instability
an emergency. of acetylene at high pressures, you should never exceed
4. Connect the red hose to the acetylene regulator
15 psig on the regulator gauge.)
and the green hose to the oxygen regulator. Tighten the 11. Light and adjust the welding flame. Open the
connecting nuts enough to prevent leakage. oxygen needle valve a very slight amount and then the
5. Back off on the regulator screws, and then open
acetylene needle valve considerably more than the
the cylinder valves slowly. Open the acetylene valve
oxygen needle valve. Light the flame with a friction
one-fourth to one-half turn. This will allow an adequate
igniter. Make sure that the flame path is pointed in a safe
flow of acetylene, and the valve can be turned off
direction and that your hands are not in front of the torch
quickly in an emergency. (NEVER open the acetylene
tip. Adjust the oxygen and acetylene needle valves as
cylinder valve more than 1 1/2 turns.) The oxygen
necessary to get a proper flame.
cylinder valve should be opened all the way to eliminate
leakage around the stem. (Oxygen valves are
ADJUSTING THE FLAME
double-seated or have diaphragms to prevent leakage
when they are open.) Read the high-pressure gauge to
A pure acetylene flame is long and bushy and has
check the pressure of each cylinder.
a yellowish color, as shown in figure 8-8. It is burned
by the oxygen in the air, which is not sufficient to bum
6. Blow out the oxygen hose by turning the the acetylene completely; therefore, the flame is
regulator screw in and then back out again. If it is smoky, producing a soot of fine, unburned carbon. The
necessary to blow out the acetylene hose, do it ONLY in pure acetylene flame is unsuitable for welding. When
a well-ventilated place that is free from sparks, flames, the oxygen valve is opened, the mixed gases burn in
or other possible sources of ignition.
contact with the tip face. The flame changes to a
7. Connect the hose to the torch. The torch hose
bluish-white color and forms a bright inner cone
connections should be marked with a small “ac” or
surrounded by an outer flame envelope. The inner cone
“acet” for acetylene or “ox” for oxygen stamped on the
develops the high temperature required for welding.
connection or the needle valve. Also, to prevent you
from cross-connecting hoses or equipment, all acetylene
There are three types of flame commonly used for
connections have left-hand threads and all oxygen
welding. These are neutral, reducing or carburizing,
connections have right-hand threads.
and oxidizing flames. (See fig. 8-8.) The NEUTRAL
8. Test all oxyaceteylene connections for leaks.
flame is produced by burning one part of oxygen to one
There are several ways to test oxyacetylene connections
part of acetylene. Together with the oxygen in the air,
for leaks after the system has been pressurized. The
it produces complete combustion of the acetylene. The
preferred method is to coat all connections with a soapy
luminous white cone is well defined and there is no
water solution and check for the formation of small
greenish tinge of acetylene at its tip, nor is there an
bubbles. The formation of small bubbles at the
excess of oxygen. The welding flame should always
connection indicates leaking gas and you should
be adjusted to neutral before either the oxidizing or
retighten the connection as needed. Another way to
carburizing flame mixture is set. A neutral flame is
check fittings for leakage is to secure the system at the
obtained by gradually opening the oxygen valve to
cylinder by closing the cylinder valve and check for a
shorten the acetylene flame until a clearly defined
pressure drop on the regulator gauges. Any drop in
inner luminous cone is visible. The neutral flame is
pressure, on the gauges, indicates a loose connection and
used for most welding and for the preheating flames
you should retighten all connections.
during cutting operations. The temperature at the tip
of the inner cone is about 5900°F, while at the
9. Adjust the tip. Screw the tip into the mixing
extreme-end of the outer cone it is only about 2300°F.
head and assemble in the torch body. Tighten by hand
This gives you a chance to exercise some temperature
and adjust to the proper angle. Secure this adjustment
control by moving the torch closer or farther from the
by tightening with the wrench provided with the torch.
work. When steel is welded with this flame, the puddle
8-7
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