"Andrew Mawson" wrote:


"Matt" wrote in message
.. .
"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?

Turn off the oxy first, then the fuel.

No!

Fuel gas on first AND off first to avoid the explosions. I was taught
that the only time you should turn the oxygen off first is if you've
had a blow back and the flame is burning in the torch - or horror of
horrors in the pipe.

So was I - I disagreed with it then and I do now (so do many others
too as this argument has been around for years!)

The only side effect of turning off the oxy first is you temporarily
get a large sooty flame. Where the explosion comes from I'll be
buggered, when you light the torch, fuel on first then oxy - no bang.
All you are doing when switching off is removing the oxidiser and
going back to raw fuel again. If you light a torch, get the fuel on,
then before the oxy is on you change your mind then turning off the
fuel makes the flame go out - end of story.

Turn the fuel off first and you might just end up leaving the oxy on -
a far more dangerous situation.


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