first welded from the outside, and then reinforced from
the back side with a seal bead.
Acetylene Safety Precautions
Acetylene safety precautions should be rigidly
observed and enforced. Some of the more important
precautions to remember are as follows:
1. Store acetylene cylinders in an upright
position. They must be securely fastened to prevent
shifting or falling. Do not lay on sides, drop, or handle
roughly. If horizontal stowage is necessary, or an
acetylene cylinder is inadvertently left lying in a
horizontal position, it must be placed in an upright
position for a minimum of 2 hours before it can be used.
(Otherwise, acetone in which the acetylene is dissolved
will be drawn out with the gas. ) Avoid damaging the
valves or fuse plugs to prevent leakage.
2. Store acetylene cylinders in a well-protected,
well-ventilated, dry place, away from heating devices or
3. Use acetylene from cylinders only through
pressure-reducing regulators. Do not use acetylene at
pressures greater than 15 psi.
4. Open the acetylene valve slowly, 1/4 to 1/2
turn. This will permit an adequate flow of gas. Never
open the valve more than 1 1/2 turns of the spindle.
5. Keep sparks, flames, and heat away
6. Turn the acetylene cylinder so that the
outlet will point away from the oxygen cylinder.
7. Do not interchange hose, regulators, or
apparatus intended for oxygen with those intended for
8. Use only approved hoses and fittings with
acetylene equipment. Pure copper, or copper alloys
containing 67 to 99 percent copper, must not be used in
piping or fittings for handling acetylene (except
blowpipe or torch tips).
9. Test for leaks with soapy waternot with an
10. Make no attempt to transfer acetylene from one
cylinder to another, refill an acetylene cylinder, or mix
any other gas or gases with acetylene.
11. Keep valves closed on empty cylinders.
12. Should an acetylene cylinder catch fire, use a
wet blanket to extinguish the fire. If this fails, spray a
stream of water on the cylinder to keep it cool.
13. Crack each cylinder valve for an instant to blow
dirt out of the nozzles before attaching the pressure
regulator. Do not stand in front of the valve when
14. Learn to identify standard Navy cylinders by
color and decals.
GAS TUNGSTEN-ARC WELDING
Gas tungsten-arc (GTA) welding is an arc welding
process that produces coalescence of metals by heating
them with an electric arc between a nonconsumable
tungsten electrode and the base metal. The weld pod,
arc, electrode, and the heated section of the work pieces
are protected from atmospheric contamination by a
gaseous shield; otherwise, atmospheric oxygen and
nitrogen will combine with the molten weld metal and
result in a weak, porous weld. The shielding gas is
usually an inert gas, such as helium, argon, or a mixture
The electrode used in GTA welding is generally
tungsten or a tungsten alloy because other refractory
metals would erode too rapidly at the high arc
GTA welds are stronger, more ductile, and more
corrosion-resistant than other types of arc welds. The
weld zone has 100-percent protection from the
atmosphere; therefore, no flux is required. Since no flux
is required, it eliminates flux or slag inclusions in the
weld, and there are no sparks, fumes, or spatter. With
GTA welding, the welding heat, amount of penetration,
and bead shape can be very accurately controlled, and
the bead surface is smooth and uniform.
Any standard dc or ac welding machine can be used
to supply the current for gas tungsten-arc welding.
However, it is important that the generator or
transformer have good current control in the low range.
This is necessary to maintain a stable arc, especially
when welding thin gauge materials. Specially designed
machines with all of the necessary controls are available
for gas tungsten-arc welding. Many of the power supply
units are made to produce both ac and dc current.
The choice of an ac or dc machine depends on what
weld characteristics may be required. Some metals are