34.
Which method of precleaning containers that have held flammable liquids is
considered the safest by military personnel?
a.
Hot chemical solution
b.
Carbon tetrachloride
c.
Steam cleaning
35.
Which solution should be used on aluminum using the steam cleaning method?
a.
Soda detergents
b.
Soda ash
c.
Chlorinated hydrocarbons
SECTION III.
INTRODUCTION TO OXYGEN-ACETYLENE WELDING
9. GENERAL. Welding processes may be broken down into many categories and
various methods and materials may be used to accomplish good welding practices. In
the oxyacetylene welding process, heat is supplied by the combustion of acetylene
and pure oxygen. These gases are mixed in a welding torch and regulated to produce
a flame that has the desired welding characteristics. Acetylene and oxygen are the
gases most widely used. This lesson will deal only with the oxyacetylene welding
process. A chart reflecting many welding processes is shown in figure 1.
10. SCOPE. In principle, oxyacetylene welding is a fundamentally simple,
nonpressure process. The phrase "nonpressure process" means that no pressure is
required to make a fusion weld; e.g., two pieces of metal brought together with
their edges in contact are melted and fused by the heat of the flame with or
without the addition of molten metal from a welding rod. The molten edges will
flow together until each is completely fused with the other and, after the metal
has cooled, there is a single continuous piece. In fusion welding, the base metal
and welding rod generally have essentially the same composition. Plain carbon
steel, alloy steel, and stainless steel can all be joined by the oxyacetylene
fusion welding process.
11. EQUIPMENT. Oxyacetylene welding outfits can be stationary or portable.
The portable outfit is most commonly used by the military and will be the system
covered by this lesson. The portable oxyacetylene welding outfit consists of an
oxygen cylinder and acetylene cylinder with attached valves, regulators, gages, and
hoses (fig 2). This equipment may be temporarily secured on the floor or mounted
on a two-wheel, all-welded, steel truck equipped with a platform which will support
two large size cylinders. The cylinders are secured by chains attached to the
truck frame. A metal toolbox, welded to the frame, provides storage space for
torch tips, gloves: fluxes, goggles, and necessary wrenches.
a. Oxygen cylinders.
(1) The oxygen cylinder is a seamless, drawn steel bottle with walls about
one-half inch in thickness but thicker at the top and bottom.
(2) The cylinder contains approximately 220 cubic feet of oxygen at a
pressure of 2,000 PSI at a temperature of 70F.
(3) Attached equipment consists of an outlet valve, a removable metal cap
for the protection of the valve, and a low melting point safety fuse plug and disk.
104
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