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 Preheat Flame Adjustment (Continued)
preheat cones. Operators accustomed to acetylene and
oxidizing flame to obtain a fast start. As soon as the
cut is started, drop to the "low" position and continue
given a one-piece MAPP gas tip tend to adjust the
the cut with the neutral flame.
flame as if they were using acetylene and may think
the gas is too cold. In fact, such a setting with MAPP
An "oxidizing flame" may be used for beveling. When
gas will not have sufficient fuel volume to produce
enough heat for the job at hand.
the tip is at an angle to the surface it is not using all of
its preheat flames to make the bevel cut, therefore, an
Neutral flame adjustments are used for most cutting.
oxidizing flame is used to get maximum heat from the
Carburizing and oxidizing flames are used in special
small portion of the preheat flame actually heating the
applications.
critical area.
Do not use "very oxidizing" flames for fast starts. An
Use a "slightly carburizing" flame to stack cut light
material because slag formation is minimal. If a
overly oxidizing flame actually increases starting
time. The extra oxygen flow does not contribute to
strongly oxidizing flame is used, slag produced in the
combustion, but instead cools the flame and oxidizes
kerf may be enough to weld the plates together and
the steel surface.
slag-welded plates often cannot be separated after the
cut is completed.
Oxygen Pressure
For cutting or piercing, use a "moderately oxidizing"
The term flame-cutting oxygen pressure always refers
flame for fast starts because it produces a slightly
to the pressure at the torch, not at some remotely
hotter flame temperature, and higher burning velocity
than a neutral flame. An oxidizing flame is commonly
located regulator. Reasons for this are discussed in
used with a "high-low" device. Use a large "high"
detail in the Oxygen Supply paragraph on page 4-23.
4-13
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