Torch safety

Hi Liss,

I always light the torch by lighting the propane first and then add
the oxygen. When finished I cut the propane so there is no fuel to
burn and then the oxygen. I learnt to do that when I was taught gas
welding many years ago and I do the same with my jewellers torch.

All the best
Jen

Hi Liss,

I think perhaps I’m misreading you.

You state that you were taught to turn on the propane, light the
torch, and then dial in the oxygen. (This is correct) But you then
state that the welding instructor said “A before O” which I
interpret to mean turn on the acetylene, light it, and then dial in
the oxygen. (correct, and functionally identical to the procedure
with the propane torch.) To turn off either torch, you turn off the
O2, then turn off the fuel gas, whatever it is.

Some welders like to turn of the acetylene first, to deliberately
cause a “pop” during shutdown. My understanding of this from years
of being around welders is that it’s largely tradition among them.

If asked (and I have) they’ll generally say that the ‘pop’ blows out
the acetylene soot that can build up in the tip. (which it can, so
other than startling people, I don’t see any reason not to do it.)
Propane torches don’t build up soot as badly as acetylene torches do,
and have no need for a ‘pop’ to blow the (nonexistent) soot out.

Regards,
Brian

Always turn on the gas first then ox. When shutting down turn off
the gas first then the ox. Prevents blowback of the gas into the gas
tank when you turn it off. thus saving you and shop from being blown
into small pieces. Also the reason to invest into flame arrestor for
your torches…

I don’t understand your query. First you say that you were taught to
light the propane before adding O2, then the welding instructor
contradicted that by saying “A before O, or up you go”. Surely they
are the same: add the O2 AFTER lighting the gas.

Lighting the O2 is a recipe for disaster.

I was taught fuel on then oxygen and oxygen off then fuel off and
given the rational that it prevents the pop and is safer due to
issues with flash back. Well after going through several of these
disagreements that seem to crop up on this subject I decided to do
some research. So I went to the instructions provided by various
torch manufacturers and lo and behold even the torch manufacturers
differ on whether to turn off the oxygen or the fuel first. After
doing some more digging it appears that if you have flashback
arrestors on your torch and/or regulator there is not much issue with
which one you turn off first with some exceptions. On larger multi
orifice heating tips (rosebuds) you can have enough volume of gas in
the tube and tip to damage the tip if you shut the fuel off first and
you get a detonation of the fuel and oxygen inside the tip but on
smaller torches no big deal. However I did find and interesting
reason to use the oxygen off first then fuel off routine. If you have
a leaky valve on the oxygen side as you turn the fuel off you will
get a little bang. This is a clue that you want to get the oxygen
valve serviced. Also it allows you to see if you have a leak in the
fuel valve because the flame will not totally go out due to leaking
fuel and again a clue to get the valve serviced.

James Binnion

This is why I use a blowback resistor that should only allow gas
flow in one direction on all of my fuel lines.

They are inexpensive but I don’t know how reliable. If you do this
and always remember that propane, if leaking, can sink to the floor
and accumulate in small spaces, and thus ignite at some point into a
pretty big fireball… you should be fine. (So if possible, store
your propane tank outside so that if it leaked, it would not sink to
the floor inside a room).

Rick

Thank you all for your comments and replies! I apologise if I my
question seemed a bit vague to some (I can be a bit wordy), but I do
appreciate hearing from so many of you.

I will be printing all the replies, and will have a discussion with
my welding teacher about this, as well as continuing to research this
further - both from other jewellers, and industry contacts. If I
EVER figure out a standard answer, I will post it here, for anyone
else that is curious about it.

Regards,
Liss.