A torch that has backfired can be relighted
at once. It may even relight itself,
if the flow of gas is directed against
molten or hot metal. If a torch backfires repeatedly, however, without evident
contact with the work, the cause
should be investigated. Backfiring may be due to use of improper operating pressures,
or to a loose tip or nozzle
in the torch, or to dirt on the cutting nozzle seats. If
the flame goes out and burns back within the torch, which usually produces a pronounced
hissing or squealing
noise, immediately shut off the torch. This is termed a flashback
and is always a sign that there is something
wrong with the torch or with your operation of it. After a flashback,
always allow the torch to cool before
attempting to relight it.
Always check your operating pressures before attempting
to relight it. Further, before relighting,
allow oxygen (NOT acetylene) to flow through the torch for several seconds to
help clear out soot which may
have accumulated within the torch. Then relight, following the usual procedure.
If what appears to be normal flame,
or flames, is produced, proceed with your work, but be prepared to shut the torch
off instantly if the flame goes
out and that characteristic flashback sound is heard again. If there is a second
flashback, remove the torch from
service and return it to an approved repair station for check and necessary repair.
Fig 6-8. Always use a friction lighter
when lighting a torch
Be ready to adjust the torch acetylene valve immediately
after flame is lit.