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Thread: Oxy /Acetylene torch Shut down
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22nd Mar 2019, 01:35 AM #1China
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Oxy /Acetylene torch Shut down
Hi,
When I did my welding course many years ago I was taught when shutting down the torch, Acetylene first followed by Oxygen, a acquaintance of mine said this is incorrect
and I should shut down the Oxygen first, apparently this is how it is taught on YouTube so which is correct.
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22nd Mar 2019, 03:40 PM #2Most Valued Member
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I was alway told/taught/shown that the FUEL is ALWAYS turned off First. The reason being that the flow of oxygen purges out any remaining fuel in the handpiece.
Just checked it out and there are 2 ways of doing it, the top one I feel is correct, while the bottom one is from Harris, a company that make Oxy Acetylene equipment, their recomendation if for the oxygen to be turned off first.
Cutting Torch - How to setup and shutdown an Oxygen and Acetylene Torch
https://www.harrisproductsgroup.com/...h-torches.aspx
So China, we're no better off than we were before
KrynTo grow old is mandatory, growing up is optional.
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22nd Mar 2019, 06:08 PM #3
The way I've done it is as follows. Have not blown myself up yet.
- Screw regulators on to cylinders, then attach hose to reg, gently purge hose with respective gas to get any crap out of the line.
- Open respective valve on the blowpipe/ handpiece, then set your desired gas pressures on the reg.
- Do you leak checks etc.
- Set up:
- Crack acetylene valve then ignite acetylene, and open handpiece valve until it becomes a clean (acetylene only) combustion.
- Introduce Oxygen to a neutral flame.
- Shut down:
- Turn off acetylene at the handpiece valve.
- Turn off oxygen at the handpiece valve.
- Turn off cylinders, then purge lines when done, using both the handpiece valves (for hose pressure), and regulator handwheel for the regulator pressure.
- Disassemble fully if transporting.
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22nd Mar 2019, 07:11 PM #4Diamond Member
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I was taught nothing more complex than acetylene on first and off first, with the idea that the oxygen would blow out the flame and avid any risk of flashback.
Given the opposite seems to be recommended in some cases, I'm wondering what the logic is behind it?
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23rd Mar 2019, 12:43 PM #5Senior Member
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I much prefer fuel off first. Turning oxy off first results in a big bright acetylene flame.
Russ
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23rd Mar 2019, 06:26 PM #6Senior Member
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I was taught to turn off the oxygen first too, then purge both afterwards, but a mate was taught the opposite and he never purges...strangely we're both still alive.
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24th Mar 2019, 03:42 PM #7China
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Well this is interesting seems as though it is almost 50/50
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24th Mar 2019, 05:43 PM #8Diamond Member
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Purging and winding the regulators back out never happens in a workplace though. Pretty much turn the bottles off and walk away.
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24th Mar 2019, 06:07 PM #9Member: Blue and white apron brigade
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I was taught to turn acetylene on first and off last.
But if I was to turn the fuel off after the air supply (vacuum cleaner blowing not sucking) on my mains gas powered forge I would fill the shed with a HUGE gas fire ball. To prevent this the forge has an air pressure sensor on the air supply hose - if the air supply is accidentally turned of or fails the gas supply is automatically cut by a solenoid.
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24th Mar 2019, 06:31 PM #10Golden Member
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24th Mar 2019, 10:41 PM #11Most Valued Member
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I had one Peanut work for me, he turned the bottles fully open instead of closing them, found this out one morning when I came in early one day.
Thankfully, it wasn't acetylene that was left on.
KrynTo grow old is mandatory, growing up is optional.
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25th Mar 2019, 09:13 PM #12
There is probably a reason to do with flashbacks, which can lead to cylinder fire or rupture. But we are all using flashback arrestors... right guys?!
I'm thinking that the 'oxy off first' shutdown method would lead to a lower oxy line pressure and the fuel combustion would try to travel back down the handpiece chasing the oxy (AKA flashback).
By turning the fuel gas off first, the complete combustion of the fuel is allowed, hence less flashback risk overall...
Just my thinking on the matter.
What's our mates in the gas companys say? I'm sure I read something on the speedygas website about it once.
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26th Mar 2019, 12:45 PM #13
Acetylene turned off first. Cigweld did it this way.
! have only just chucked the booklet which came with my set.
Commander keens shut down sequence is spot on.
I question how many in our workplaces can perform the sequence properly?
Grahame
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26th Mar 2019, 03:21 PM #14Member: Blue and white apron brigade
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BOC operations has Fuel on and off first.
p17 of https://www.boc.com.au/wcsstore/AU_B...nd-Cutting.pdf
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26th Mar 2019, 04:53 PM #15
I've been known to do the odd spot check.
It's probably one of the larger 'silent' risks in the workshop- most people will look out for a forklift coming their way, or will be vigilant around rotating machinery etc... but the oxy set can (and has) cause some serious strife if things come a gutsa.
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