crb wrote:
I recently invested in a new Portaflame MAPP/Oxygen gas welder.
Results to date have been encouraging, and I am slowly improving my
technique. The only problem I have is that on shutting down, by
closing the torch controls for the MAPP and the oxygen a little at a
time in turn, I always end up with a loud and unsettling high-pitched
POP as the flame extinguishes. Can anyone give guidance on why this is
happening, and whether it is likely to cause damage/injury?

The oxygen and fuel mix inside the burner head, but they burn outside.
What's actually happening is that the flame-front is continually trying
to move back into the burner head, but the outward flow of the
gas/oxygen mixture prevents it from doing that.

In operation, it settles into a stable situation where the flame is
"attached" to the rim of the burner. The rate of burning exactly
balances the rate of feed, and you have a stable flame.

When you turn the gas and oxygen right down, this balance no longer
holds. The flame front strikes back into the burner head, and the whole
volume inside the head burns all at once - pop.

If it just pops and blows itself out, then it really is mostly harmless.
You're turning the torch off anyway so it's self-limiting. The situation
to avoid is where the gas continues to burn inside the burner... so
don't do that.


--
Ian White