P.O.O.P-Why?

[Quicksilverart]

Propane-Oxygen-Oxygen-Propane when turning on and off a torch. I'm just curious why it is so important to follow this procedure. I see a lot about how we HAVE to do this, but I've searched for why and haven't found an answer. Can anyone give me a clear explanation?

[ChaoticGlass]

This is what I was told: P-O-O-P-O.
P-You first need to turn on the gas to ignite a flame,
O-the oxygen is the catalyst so you slowly add the oxy to achieve the concentration you need for working.
(Not 100% sure on this last part as it was explained to me by a big time burn-out)
O-Turning the oxygen off before the propane ensures there isn't a re-ignition of the flame due to any heat accumulated in the torch head.
P-Turn off propane to extinguish the flame.
O-If you use internal mix torches you can blow out any gas trapped inside the torch by a quick burst of oxygen, it will prevent the pop.
Like I said, I'm not sure about the reason for turning the oxy off before the propane...logically it would make sense that this action would be less work for the torch, possibly helping to reduce carbon build-up inside the torch (that's just my theory).

[Dale M.]

It also prevents the loud POP you some times get that scares everybody when you turn off propane first ....

Dale

[MikeAurelius]

I prefer POPO, myself. But either way works just fine.

It's a memonic so it is easier to remember.

It could also be FOFO for FUEL OXYGEN FUEL OXYGEN, doesn't really matter as long as you remember to turn them both off.

[shawnette]

I use POPO. I'm on concentrators, so I actually just use POP until I'm sure that I'm done for the day and then I just turn off the concentrators.

[i09172]

Propane-Oxygen-Oxygen-Propane when turning on and off a torch. I'm just curious why it is so important to follow this procedure. I see a lot about how we HAVE to do this, but I've searched for why and haven't found an answer. Can anyone give me a clear explanation?

Hi Carolyn,

I'm not sure how clear it will be but here's the explanation I received when I was a welder's apprentice 30 some odd years ago in a previous life (Gawd! Has it really been that long?).

Anyway, as others have mentioned, there is sometimes a "pop" when you extinguish your torch by closing off the oxygen before shutting down the fuel. The sound is particularly pronounced in an oxy-acetylene torch and is closer to a "bang" than a "pop". The sound is produced when the fuel is being reduced in proportion to the amount of oxygen available. At a certain point there is an optimum level of fuel and oxygen that is actually explosive but the pressure of the fuel escaping at the torch head is pretty small. This tiny explosion produces the sound you hear and, at those dwindling pressures, actually extinguishes the flame (blows it out).

The danger in this (and it's pretty damn minor, in my opinion and experience, is that given the right conditions (I'll tell you what they are in a minute) the explosion can actually travel up the hose to the regulator with somewhat disastrous results. In order for this to occur you would need to have a certain amount of oxygen in your fuel line or fuel in your oxygen line. This could occur if, for example, your fuel hose fitting at the regulator was slightly loose allowing air to be sucked into the hose via venturi effects as the fuel is flowing to your torch in normal use. This mixture of fuel and air in the hose could be explosive under just the right conditions and could be set off by the bang of the torch shutting down. At that pressure the fuel/air flowing from your torch would be slower than the propagation of the flame front started by the bang resulting in a series of "bangs" all the way back up the hose to the regulator. Theoretically, the regulator could be blown apart internally allowing a ruture with a fire. Probably not a nice thing to have happen.

Fortunately, in all of my tears of experience I never saw it happen. Nor did I ever talk first hand to anyone who saw it happen although we all heard the horror stories. My feeling is that it may have been a bigger problem in the past before the advent of modern regulator and hose materials and construction. I think the Moon would have to be in Virgo with Saturn rising and your mouth held at a 25 degree angle in relation to the tilt of the planet while one eye is winking before you'll ever see it happen to you. But, the possibilty does exist, no matter how minor (no pun intended) it may be hence the admonishment to shut off the oxygen first. With the oxygen shut down there is still enough fuel flowing from the torch that the mixture never becomes explosive. When you shut the propane down, next, the supply of fuel dwindles until there's no longer enough flowing to cause a problem and the flame quietly extinguishes.

Hope this helps,
Kevin W. Miller
Blue Moon GemWorks
http://www.bluemoongemworks.com

[MikeAurelius]

But, and this is a BIG BUT, this only happens on pre-mix torches...surface mix torches have all the gas outside the torch body where they mix (surface mix, get it?).

[i09172]

But, and this is a BIG BUT, this only happens on pre-mix torches...surface mix torches have all the gas outside the torch body where they mix (surface mix, get it?).

That's true and I get it. But I understood that she was asking for an explanation for the POOP rule and that's what my explanation was intended to answer. Not that it necessarily applies in each and every oxy/fuel situation known to man (and woman). But, if always you apply that rule, you won't ever experience that particular issue and you won't have to think about which type of torch you may be using. Of course, if you apply that rule with an oxy/acetylene torch, you'll have a house or shop full of fine carbon snowflakes.

FTR, I use POPO with my minor.

Kevin W. Miller
Blue Moon GemWorks
http://www.bluemoongemworks.com

[Quicksilverart]

Thanks for all your answers folks! I would always prefer more information, rather than less. I'm using a Minor with OxyCon right now, but that may not (and probably won't) always be.

[i09172]

A fellow was kind enough to point out to me that I have it exactly backwards when I wrote the following (in part):


Anyway, as others have mentioned, there is sometimes a "pop" when you extinguish your torch by closing off the oxygen before shutting down the fuel.

Please note that I was thinking fuel and writing oxygen. I'm pretty sure I messed up 'cause it's my birthday today and I've been feeling pretty dang old. Anyway, I, of course should have written what I was thinking which is:

"Anyway, as others have mentioned, there is sometimes a "pop" when you extinguish your torch by closing off the FUEL before shutting down the OXYGEN."

Sorry for any confusion on your part caused by confusion on my part and many thanks to that fellow for pointing out my error to me.

Kevin W. Miller
Blue Moon GemWorks
http://www.bluemoongemworks.com

[meister1981]

I prefer POPO, myself. But either way works just fine.

It's a memonic so it is easier to remember.

It could also be FOFO for FUEL OXYGEN FUEL OXYGEN, doesn't really matter as long as you remember to turn them both off.


I agree with Mike for the POPO! An advantage also to the POPO is that the oxygen that is still ON while you turn off the gas helps prevent any carbon deposits that might stick to the torch face. It isn't common that carbon will stick like crazy while you turn off the torch but hey it's free to do POPO!

[hotflashwanda]

I like to POPO too.
Anita
www.fireflybeads.com

[bolimasa]

I'm a bad, bad girl... I OPOP
I use natural gas and 2 concentrators. My oxygen valve is always open, as it is my impression that it is not good for your concentrators to run with the torch valve closed. So I turn the concencentrators on, after they quit beeping I turn on the natural gas at a very low flow rate, just enough to light the torch. I just continously click my striker as I slowly turn up the gas,when there is enough natural gas flow it lights. After the flame is lit I turn up the gas. My torch barely pops at all, unless I'm careless and turn up the gas a little too fast. On the rare occasion this happens I figure I'm giving my ports a nice little blow out. I can't think of any reason why this method would be problematic....but if there is one, please let me know!

[LouiseI]

Interesting thread! A welder told me just the other other day that he'd been taught to always turn off the fuel first and then the oxy, his explanation made a lot of sense to me, so I tried it, but was wondering if it held for our setup too. From now on I think I'll be doing popo too!
The saying he learned was 'A (or P) before O, or up you go' saying in theory that there's a chance the flame could get sucked backwards into the torch when the oxygen was turned off.

Being on an oxycon it's also simpler to just turn off the propane with the option of leaving the oxycon running, instead of what I was doing, turning off oxygen, turning off propane, turning back on oxygen.

Thanks for all the info :wave:

[Sue in Maine]

I'm going to throw my two cents in here. Since either way will work, my thought is that as long as you ALWAYS do it the same way, you should be okay. For me, I turn the oxy off from my 2 oxy-cons first, then turn off the flame. Then I go outside and turn my fuel off at the tank. Then I come inside and burn the residual fuel off in my line. Then I go back outside and loosen my PA (pressure adjustment) Screw. Then I go back inside and open the oxy line cuz someone told me it's bad to leave the oxy pressure from the oxy-cons in the line. Now comes MY magic moment-- I hang my striker on the oxy knob so the next time I go to light my torch, it reminds me to shut off the oxy before I light my torch.

Turning on is less steps cuz I just turn the fuel on and adjust the PA Screw but I ALWAYS ALWAYS do my ritual ons and offs the same way.

Btw, I learned it as "POOP" too.

Sue

[Mr. Smiley]

I'm OPPOsite... OPPO works for me because I'm on concentrators. I turn them on, let them cycle for a few and then bring in some propane while I hold a flame under the torch face. When I'm done, I turn the propane off and shut the concentrators down. Works great...

[Alison D]

OPOP here for same reasons as bolimasa.


Alison

[PittsGlass]

I understood POOP was to prevent flashback of flame into your hoses. It has recently happened to an LE member with a surface mix torch.

http://www.lampworketc.com/forums/showthread.php?t=96149&highlight=FLASHBACK

Its the second I have heard of it occurring with a surface mix, both from known sources. Keep those flashback arrestors on your lines even if someone tells you your torch won't do it. Once would be to much, especially if it makes it to a tank of oxy or prop.