It is
well known that flame travels through any inflammable gas at a certain
definite rate of speed, depending on the degree of inflammability of the
gas. The easier and quicker the gas burns, the faster will the flame travel
through it.
If the gas in the nozzle and mixing chamber stood still, the flame would
immediately travel back into these parts and produce an explosion of more
or less violence. The speed with which the gases issue from the nozzle
prevent this from happening because the flame travels back through the gas
at the same speed at which the gas issues from the torch tip. Should the
velocity of the gas be greater than the speed of flame propagation through
it, it will be impossible to keep the flame at the tip, the tendency being
for a space of unburned gas to appear between tip and flame. On the other
hand, should the speed of the flame exceed the velocity with which the gas
comes from the torch there will result a flash back and explosion.
_Care of Torches._--An oxy-acetylene torch is a very delicate and
sensitive device, much more so that appears on the surface. It must be
given equally as good care and attention as any other high-priced piece of
machinery if it is to be maintained in good condition for use.
It requires cleaning of the nozzles at regular intervals if used regularly.
This cleaning is accomplished with a piece of copper or brass wire run
through the opening, and never with any metal such as steel or iron that is
harder than the nozzle itself, because of the danger of changing the size
of the openings.
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