Figure 5-1.An oxygas welding outfit.
The low-pressure torch is also known as an injector
torch. The fuel-gas pressure is 1 psi (pound per square
inch) or less. The oxygen pressure ranges between 10 to
40 pounds, depending on the size of the torch tip. A jet
of relatively high-pressure oxygen produces the suction
necessary to draw the fuel gas into the mixing head. The
welding tips may or may not have separate injectors in
the tip. Atypical mixing head for the low-pressure (or
injector) torch is shown in figure 5-3.
Medium-pressure torches are often called balanced-
pressure or equal-pressure torches because the fuel gas
and the oxygen pressure are kept equal. Operating pres-
sures vary, depending on the type of tip used.
If acetylene is used as the fuel gas, the
pressure must never be allowed to exceed 15 psi
because acetylene becomes very dangerous at
15 psi and self-explosive at 29.4 psi.
Figure 5-2.A portable oxygas welding and cutting outfit,