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Posted by JohnH on July 24, 2007, 11:28 pm
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I have been trying to set up oxyacetylene for cutting. I have a "#12 cutting
tip"... but I couldn't find any data accompanying it.
I wanted to cut pipe about 5mm thick. I read that
"For cutting, use 15 psi for the oxygen and 2 psi for the acetylene; but
these amounts can vary somewhat according to what is being cut".
The gauges on the oxygen regulator show 0 to 3500psi/0 to 240 kpa (x100)
And 0 to 200psi/0 to 14 (x100kpa)
The gauges for acetylene show 0 to 400psi /0 to 27kpa And 0 to 15 psi/0 to 1
kpa (x100)
15psi = 103.4kpa which is a setting which is barely visible.
I rang a shop and was told to use 40psi Oxygen and looking at charts for
torch tip types I set 5 (or was it 10?) on the acetylene. When I lit it
there was a large flame and a lot of soot it back fired and went out. The
second time I pushed the trigger and got a feathery looking flame..... (and
didn't know whether I was Arthur or Martha.... so I quit).
I'm too late to enrol in a course for this year.
John
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Posted by JohnH on July 25, 2007, 12:48 am
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The gas compnay told me a #12 cutting head should be set at 220kpa (oxygen)
and 100 kpa (Acetylene).... maybe bigger than I need.... (I don't want to
break into a bank vault)
John
>I have been trying to set up oxyacetylene for cutting. I have a "#12
>cutting tip"... but I couldn't find any data accompanying it.
> I wanted to cut pipe about 5mm thick. I read that
> "For cutting, use 15 psi for the oxygen and 2 psi for the acetylene; but
> these amounts can vary somewhat according to what is being cut".
> The gauges on the oxygen regulator show 0 to 3500psi/0 to 240 kpa (x100)
> And 0 to 200psi/0 to 14 (x100kpa)
> The gauges for acetylene show 0 to 400psi /0 to 27kpa And 0 to 15 psi/0 to
> 1 kpa (x100)
> 15psi = 103.4kpa which is a setting which is barely visible.
> I rang a shop and was told to use 40psi Oxygen and looking at charts for
> torch tip types I set 5 (or was it 10?) on the acetylene. When I lit it
> there was a large flame and a lot of soot it back fired and went out. The
> second time I pushed the trigger and got a feathery looking flame.....
> (and didn't know whether I was Arthur or Martha.... so I quit).
> I'm too late to enrol in a course for this year.
> John
>
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Posted by Grant Erwin on July 25, 2007, 1:17 am
Please log in for more thread options JohnH wrote:
> I have been trying to set up oxyacetylene for cutting. I have a "#12 cutting
> tip"... but I couldn't find any data accompanying it.
> I wanted to cut pipe about 5mm thick. I read that
> "For cutting, use 15 psi for the oxygen and 2 psi for the acetylene; but
> these amounts can vary somewhat according to what is being cut".
> The gauges on the oxygen regulator show 0 to 3500psi/0 to 240 kpa (x100)
> And 0 to 200psi/0 to 14 (x100kpa)
> The gauges for acetylene show 0 to 400psi /0 to 27kpa And 0 to 15 psi/0 to 1
> kpa (x100)
> 15psi = 103.4kpa which is a setting which is barely visible.
> I rang a shop and was told to use 40psi Oxygen and looking at charts for
> torch tip types I set 5 (or was it 10?) on the acetylene. When I lit it
> there was a large flame and a lot of soot it back fired and went out. The
> second time I pushed the trigger and got a feathery looking flame..... (and
> didn't know whether I was Arthur or Martha.... so I quit).
> I'm too late to enrol in a course for this year.
> John
>
>
You'd want probably a 00 or 0 tip, not number 12. A number 12 tip would be handy
though if you had to say scrap out a battleship's 16" armor plating.
GWE
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Posted by JohnH on July 25, 2007, 2:06 am
Please log in for more thread options I'm using my (late) fathers gear.
John
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Posted by Shaun Van Poecke on July 25, 2007, 7:37 am
Please log in for more thread options Hi John,
The question you have asked here is at once pretty broad and pretty
specific; pretty much akin to asking someone 'should i turn the gas up all
the way when i want to cook some food?' Setting an oxy torch is a pretty
basic skill that many people can do, but then a whole bunch of variables
come in to play..... someone with some experience can sum up in 10 seconds
what it might take a whole book to explain. so, with tongue only slightly
in cheek, here is your worded guide to setting up an oxy;
lets start with the tip.... every company has their own numbering system
and designation for tip types. In australia for example where i live, one
of our biggest suppliers is CIG. A #12 tip in their range is suitable for a
wide range of purposes, I would probably cut just about anything from 5mm to
20mm with this tip, though its a bit fat for 5mm and a bit thin for 20mm. a
#8 or #6 would be more appropriate for 5mm steel in their range. but each
company has their own system. Once you have a bit of experience you dont
really need to know the number; a quick look at the size of the holes will
tell you what that tip will cut. But be aware that your #12 may be designed
to cut hugely thick plate depending on who manufactured it.
Is it second hand? do you have and know how to use a set of tip cleaners?
If it's new, you dont need to worry... it will be easy to set. A large
part of setting a tip by feel (rather than by the book) relates to the sound
of it. A worn tip will never cut cleanly, and will never sound right. Buy
a new one if you have to, they only cost a couple of dollars.
So lets start.... hopefully your bottles are full? empty bottles wont
have enough 'drive' to keep a good flame going. Are they big bottles or
small ones? can you pick them up with one hand? Then they are very small
and you wont be doing much cutting with them! Are they about 3 feet high?
Then you will get some good usable service from them. Are they 5 feet high?
Then you needn't worry too much... you have plenty of time to set your
flame correctly. Do you have a 6 or 12 pack of 5 feet high bottles on a
common manifold? Then what the hell are you doing? Come to australia and
I'll give you a job doing destructive cutting!
Let's start with a look at the torch... does it have a separate cutting
head? Who made it? How many nobs does it have, 2, or 3? I will assume
that you have 3 knobs; 2 down the bottom (oxy and acetylene) and one at the
cutting head for mixing. Lets start by setting the acetylene since it's the
easiest to set. Set your pressure to about 5psi on acetylene, open the
valve on the torch and light the flame. how big is the flame? If its only
a couple of inches, start turning the acetylene knob on the torch to be more
open.... open it up all the way if you can. Thats the goal here. If it is
very small then its probably very quiet, and very sooty, leaving black
things floating around the air and landing on everything! Now that you
turned it up all the way, what is the condition of the flame? Is it roaring
loadly, or still quiet and relatively small? You will notice when you light
the flame, that the flame itself is directly 'connected' to the tip ie.
touching. as you turn it up, it will become less sooty, louder, and at some
point the flame will separate from the tip, leaving a gap. The goal for
setting an acetylene torch, is to have the flame as big as possible *without
the flame separating from the tip*. Once the flame separates from the tip,
that is too much acetylene. So open that acetylene valve on the torch as
much as you can, now adjust the *regulator* so that the flame is only just
separated from the tip. That is plenty of pressure (no matter what the
gauge, or the book says). Leave it at that pressure, and then turn down the
acetylene knob on the torch *just a little bit* until the flame joins back
onto the tip.
Now for something a bit trickier, setting the oxygen pressure. Most people
set it *way* too high. this doesnt make a bad cut, but it wastes a lot of
oxygen! For oxygen, you want as little as possible, but as much as
necessary. Generally, you want to err on the high side. Start at somewhere
around 10-15psi. If you have 3 knobs (two on the bottom and one mixing knob
at the cutting head) then close the mixing valve completely, and open the
bottom valve all the way. The flame should still be acetylene only at this
stage. If there is some oxy in there, then you have a leaking mixing valve.
now turn the mixing valve on a bit.... do you know how to set a ballanced
flame? turn the oxy on more, until you see a blue cone appear.... turn it
on a bit more, and the cone will get smaller until you see 5 or 6 (depending
on the number of holes in the tip) small blue cones off the tip. At some
point, it wont matter how much more you turn the mixing valve, those little
cones wont really get any smaller. It will get noiser though, and it will
eventually blow itself out. What you are aiming for is to make the cones
small, and then stop at the point where they become as small as they can
get, or maybe just slightly bigger than that. You dont want to keep on
adding more and more oxy.
Ok, so now here comes the tricky bit.... Youve got a ballanced flame, now
press the cutting lever. What happened? Did the shape of the flame change?
Did a big blue cone appear when you did it? Did it blow itself out? Then,
while pressing the lever, adjust the mix until you get the same ballanced
flame back again. Now you have the ballanced flame, when you release the
cutting lever, does your flame become very noisy or blow out? then most
likely your torch needs attention. The mixing valve at some stage when it
is worn will not keep a ballanced flame during all times. You can have them
rebuilt, or you can buy a new one. Most torches will give so-so results for
a while before they fail.... They wont be quite ballanced at rest, or quite
ballanced at cut, but you can set them somewhere slightly in the middle and
still cut with them.
Now if your torch still ballanced, were you able to get a ballanced flame in
both states? If you couldnt make your 'cone' small enough, then you need to
turn up your oxy pressure. If you had no trouble, then its time to turn it
down. If you press the cutting lever and the torch takes off like a rocket,
almost pushing your hand back, then you need to turn it down a lot. If you
have a good new, or freshly cleaned tip then you can tune the oxy pressure
by the sound. When you press the cutting lever is it very loud? Too much
pressure, turn it down! The perfect sound is a little bit quieter, and it
sounds exactly like paper tearing... a kind of 'ffffffffffft' sound. If
you only get a quiet 'sssssssss' sound, then you may need to turn your
pressure up a bit, but most people set way high, so you can assume you need
to turn down. Just hold that lever, and while you are holding it, start
turning the pressure down and listen. At some point you will start to hear
the sound of paper tearing. This is the right pressure. You will only get
this sound with a good new or very well cleaned tip (which will also give
you excellent cutting!). Now reballance your flame, because it will have
changed with the new oxy pressure... when you get the flame reballanced,
press the cutting lever again... it should come in with a gentle pressure,
not like a rocket, and should give you that 'tearing paper' sound. You've
got it right. Now start cutting. bear in mind though, that tip doesnt
need to be as close to the metal as you think. Keeping it 10mm off the
surface will prevent spatter entering the tip and destroying it, it will
also give a cleaner cut.
While this action is hard to describe in writing, its easy to do once you
have seen and heard it. A practiced person can pick up any torch/bottle/tip
combination with no knowledge of that particular item, even if the bottles
have no gauges on the regulators (very common in mining!) and have the
pressures and flame perfectly set in 20-30 seconds. And then you can get a
ballanced perfect flame in about 3 or 4 seconds every time after that. It
does take a bit of understanding, so watch someone else do it if you can
(who knows what they are doing!)
Shaun
>I have been trying to set up oxyacetylene for cutting. I have a "#12
>cutting tip"... but I couldn't find any data accompanying it.
> I wanted to cut pipe about 5mm thick. I read that
> "For cutting, use 15 psi for the oxygen and 2 psi for the acetylene; but
> these amounts can vary somewhat according to what is being cut".
> The gauges on the oxygen regulator show 0 to 3500psi/0 to 240 kpa (x100)
> And 0 to 200psi/0 to 14 (x100kpa)
> The gauges for acetylene show 0 to 400psi /0 to 27kpa And 0 to 15 psi/0 to
> 1 kpa (x100)
> 15psi = 103.4kpa which is a setting which is barely visible.
> I rang a shop and was told to use 40psi Oxygen and looking at charts for
> torch tip types I set 5 (or was it 10?) on the acetylene. When I lit it
> there was a large flame and a lot of soot it back fired and went out. The
> second time I pushed the trigger and got a feathery looking flame.....
> (and didn't know whether I was Arthur or Martha.... so I quit).
> I'm too late to enrol in a course for this year.
> John
>
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>cutting tip"... but I couldn't find any data accompanying it.
> I wanted to cut pipe about 5mm thick. I read that
> "For cutting, use 15 psi for the oxygen and 2 psi for the acetylene; but
> these amounts can vary somewhat according to what is being cut".
> The gauges on the oxygen regulator show 0 to 3500psi/0 to 240 kpa (x100)
> And 0 to 200psi/0 to 14 (x100kpa)
> The gauges for acetylene show 0 to 400psi /0 to 27kpa And 0 to 15 psi/0 to
> 1 kpa (x100)
> 15psi = 103.4kpa which is a setting which is barely visible.
> I rang a shop and was told to use 40psi Oxygen and looking at charts for
> torch tip types I set 5 (or was it 10?) on the acetylene. When I lit it
> there was a large flame and a lot of soot it back fired and went out. The
> second time I pushed the trigger and got a feathery looking flame.....
> (and didn't know whether I was Arthur or Martha.... so I quit).
> I'm too late to enrol in a course for this year.
> John
>