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 Preheat Flame Adjustment
TABLE 4-3. Oxy-Fuel Ratios/
MAPP gas is similar to acetylene and other fuel gases
Flame Condition Comparisons
because it can be made to produce a carburizing,
neutral, or oxidizing flame (Table 4-3). Flame cutting
will most likely require adjustment to a neutral flame.
Oxy-MAPP
Flame
Gas Ratio
To adjust to a slightly carburizing flame, light the
VERY
torch, then slowly increase preheat oxygen until the
2.0 TO 1
CARBURIZING
yellow flame turns blue with some yellow feathers
remaining on the end of the pre-heat cones. To adjust
SLIGHTLY
to a neutral flame, twist the oxygen valve slightly until
2.3 TO 1
CARBURIZING
the feathers disappear and the preheat cones become
sharply defined and turn a dark blue color. This flame
2.5 TO 1
NEUTRAL
will remain neutral, even with the addition of a small
amount of preheat oxygen. To adjust to an oxidizing
3.0 TO 1
OXIDIZING
flame simply give the oxygen valve a further slight
twist. The neutral flame will suddenly change color,
VERY
from dark blue to a lighter blue, and the preheat cones
3.5 TO 1
OXIDIZING
will shorten. An increase in sound will also be noted
(Figure 4-2).
Different fuel gases will produce different flames from
the same tip. MAPP gas preheat flame cones will be at
least one and one-half times longer than acetylene
4-12
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