Flashback Arrestors

[artwhim]

This is probably a really dumb question, but I've never used one before. Now that I'm setting the Lynx up again, I would prefer to have the extra safety feature.

I understand flashback arrestors can be placed either between the torch and the hose, or between the hose and the regulator. Are the flashback arrestors the same for either placement? If not, who sells the ones designed to go between the torch and the hose. I only need to buy gas.

[Dale M.]

The configuration (placement) of the FB arrestor is determined by the way the connectors (male & female) are configured according to the direction of flow in arrestor...

IF you want them at regulator, directional arrow needs to point away from female end that connects to regulator, if you want them at torch arrow has to point towards female end that connects to torch....

Both style arrestors should be available where hoses and regulators are sold....

Dale

[artwhim]

Thanks Dale, that makes sense.

[NMLinda]

Dale is correct in his description. I find it hard to see the direction on the arrows if I'm ordering on-line, however. The picture resolution is usually too poor. The most commonly available FB's I've found are from Western Enterprises. Most welding supply companies and glass suppliers seem to carry that brand. If you go to Western's website

http://www.westernenterprises.com/en...arrestors.php#

you'll see several choices. The FA-200P is probably the one you want. The picture isn't clear enough for me to see the arrow, though. If you find the same true for you, you might want to get it at a welding supply store so that you can see which direction the arrow points and therefore which end attaches to the torch vs the hose so that you can get the right mating fittings to install it.

Good luck!
Linda

[ArtcoInc]

Originally Posted by NMLinda

Dale is correct in his description. I find it hard to see the direction on the arrows if I'm ordering on-line, however. The picture resolution is usually too poor. The most commonly available FB's I've found are from Western Enterprises. Most welding supply companies and glass suppliers seem to carry that brand. If you go to Western's website

http://www.westernenterprises.com/en...arrestors.php#

you'll see several choices. The FA-200P is probably the one you want. The picture isn't clear enough for me to see the arrow, though. If you find the same true for you, you might want to get it at a welding supply store so that you can see which direction the arrow points and therefore which end attaches to the torch vs the hose so that you can get the right mating fittings to install it.

According to the page in your link, the FA-200P is a "Torch Flashback Arrestor", and the FA-230P is the "Regulator Flashback Arrestor".

Malcolm

[NMLinda]

Sounds like Kathy is interested in the torch flasback arrestors from her first post. Thanks for adding the clarification, Malcom, I hope it helps her.

Linda

[kbinkster]

If you're going to get one for the gas, you might as well get one for the oxygen side, too. The ones that I have seen at the welding shop are sold in pairs, anyway. The flashbacks that I have heard accounts of went up the oxygen side. If you are connected to a concentrator, it might just burn the outside of it, but you would still want to save your hose if you can.

[artwhim]

Originally Posted by kbinkster

If you're going to get one for the gas, you might as well get one for the oxygen side, too. The ones that I have seen at the welding shop are sold in pairs, anyway. The flashbacks that I have heard accounts of went up the oxygen side. If you are connected to a concentrator, it might just burn the outside of it, but you would still want to save your hose if you can.

I was under the impression that flashback arrestors can't be used with an oxycon, am I mistaken? If they can be used on a M-15, then I would prefer to do so.


After reading enough old threads on flashback arrestors and the debate between putting it at the torch or at the regulator, I went ahead and ordered one that goes at the regulator. It will fit between the regulator and the Y with shut off valves. One hose will go to the Lynx and the other to the Smith Little Torch. Admittedly, I've dropped and rolled a hot marble before, so thought it might be better for me to have the arrestor at the regulator. I'm seriously considering the additional safety feature (overkill really) of having arrestors at the torches also. Yes, I know how ridiculous that sounds when I've already admitted to dropping a marble. Hopefully though, having overkill on safety equipment will lesson the chance of catastrophe if user error (dropping a marble) happens again.

Does anyone know if the Smith Little Torch is premix or surface mix? It hasn't arrived yet and I haven't been able to find the answer in the catalogs.

Thanks everyone!

[ArtcoInc]

Originally Posted by artwhim

I was under the impression that flashback arrestors can't be used with an oxycon, am I mistaken?

Flashback arrestors require a minimum gas (or oxygen) pressure to work. Thus, they typically won't work when used with low pressure natural gas.

A flashback arrestor is rarely needed with an oxycon. But, if you want to, and if your oxycon can deliver the minimum necessary pressure, then one can be used.

Malcolm

[ArtcoInc]

Originally Posted by artwhim

Does anyone know if the Smith Little Torch is premix or surface mix? It hasn't arrived yet and I haven't been able to find the answer in the catalogs.

The Smith Little Torch is a premix.

Malcolm

[artwhim]

Originally Posted by ArtcoInc

The Smith Little Torch is a premix.

Malcolm

Thanks! If it arrives before the arrestor, I'll resist the urge to try it out.


Hum.... the M-15 puts out 8psi, I wonder if that is enough pressure to work with an arrestor?

[Dale M.]

Originally Posted by artwhim

Thanks! If it arrives before the arrestor, I'll resist the urge to try it out.


Hum.... the M-15 puts out 8psi, I wonder if that is enough pressure to work with an arrestor?

Probably.... FB's have problems at 0 to 2 psi range but above that they should be fine....

Dale

[artwhim]

Ah, I also had a brain fart, 8 is the LPM, the PSI is 15 on a M-15, so it looks like I should have ordered a set. Thanks!

[NMLinda]

Kathy - You'll want to be extra safety conscious when combining a surface mix with a premix torch. Kbinkster's right about the risk of an oxy flashback. There was a thread last year started by an LE member (forget if it was in Safety, Torches or Studio) who I believe had a National pre-mix torch and a surface mix torch going, and had a pretty scary flashback 'event'. I don't believe he had FB's at either torch. I recall the post talking about a heck of a bang and shredded hoses. I think he even ran out of the studio. If you can find the post, it's worth reading. Since your arrangement sounds similar, you might want to seriously consider FB's at your torch.

Linda

[kbinkster]

Any time you run a premix torch with a surface mix torch, you increase your chances of not only a FB (from the premix) but from that FB going up the lines to the other torch and causing problems.

As for installing FB arrestors at both ends of the lines, that will choke down the flow quite a bit. Standard T grade lines are very thick and it would take a lot to burn through one. However, if you are worried about that, you can cover your lines.

The way that I understand FB arrestors work is when there is an explosion from a premix flashback, the valve in the FB arrestor closes. It's the pressure change (the burst from the explosion) that triggers it to shut. If you burn through a line, the pressure actually drops and the gas still flows. A FB arrestor will do you no good in that senario.

[NMLinda]

Kimberly - thanks for adding your greater knowledge. If I understand your post correctly, an FB arrestor at each torch would at least contain the FB right there and keep it from travelling down the hose and compromising either the hoses or the other torch. For a studio using both surface and pre-mix torches, I would assume, from your post, that it would be important to have FB's at both the propane and oxygen sources, also. If there is a hose failure (made more remote by FBs at each torch as well as thick T-grade hoses), at least there isn't a greater safety risk from unprotected fule/oxy sources. Is that correct?

Linda

[kbinkster]

[

If I understand your post correctly, an FB arrestor at each torch would at least contain the FB right there and keep it from travelling down the hose and compromising either the hoses or the other torch.

Yes, exactly.

For a studio using both surface and pre-mix torches, I would assume, from your post, that it would be important to have FB's at both the propane and oxygen sources, also.

If you have the FB arrestors at the torches (on both the fuel and oxygen intakes), you do not need them at the propane regulator or oxygen regulator or concentrator.

If there is a hose failure (made more remote by FBs at each torch as well as thick T-grade hoses), at least there isn't a greater safety risk from unprotected fule/oxy sources. Is that correct?

In the event of a hose failure, FB arrestors at the fuel and oxygen sources aren't going to do anything - at least that's my impression.

[NMLinda]

Thanks, Kimberly, I appreciate your responses, and hope Kathy finds them helpful, too. You're right, once the hose is compromised, all the gases would escape through any slit or gash and the FB wouldn't do anything. Best to prevent conditions which might cause a hose rupture to happen in the first place. FB's at the torch, especially with a pre-mix, is perhaps the safest.

Linda

[artwhim]

Hum..... lots more to think about. The Smith Little Torch will only be used for soldering and therefore won't be in use at the same time as the Lynx. The Y I installed has shut off valves which I intend to use depending on which torch is in use at the time, so the risk of each torch should be independent from the other. If there ever was a reason to run a glass torch and the soldering torch at the same time, my Betta is still hooked up to NG, so it could be used instead of the Lynx, leaving only one torch on the propane line.

The Little Torch arrived today. It comes with 8' hoses attached and I don't believe there is any way to attach a flashback arrestor closer to the torch than the end of the hoses. At that point it isn't much further to the regulator. The instructions say to purge both the gas and oxy lines each time before lighting the torch. Is that because it's a premix?

Linda, I did run across that thread about the flashback. I believe he said he was glad the arrestor wasn't at the torch because he wouldn't want the explosion happening in his lap which sounds like a valid point. Can't imagine how scary that would have been. Hopefully none of us will ever find out!

[Dale M.]

Originally Posted by artwhim

Linda, I did run across that thread about the flashback. I believe he said he was glad the arrestor wasn't at the torch because he wouldn't want the explosion happening in his lap which sounds like a valid point. Can't imagine how scary that would have been. Hopefully none of us will ever find out!

I believe his comments were from a uninformed point of view.... IF flashback arrestors were at torch the shredding of hose would never have happened. That simple. And the theory if you burn through hose, its a explosive event (flash back), it is not, it is a "leak"... And it will burn only if its the fuel hose, and it will burn like a candle or just like a flame off the torch head before you introduce the oxygen......

Several misconceptions in the the "flashback" thread because of what people want to believe, not from intellectual research... Kbinkster has it correct and I agree with her one hundred percent. Also NMLinda has correct interpretation on the FB arrestor concept..... I also backed out of "flashback" thread because people did not want to believe some simple truths about the application of flashback arrestors and how best to apply them, and I hope those people with the misconceptions never have to discover the truths the hard way.......

Dale

[NMLinda]

Kathy - I'm glad you found that thread. It came to mind because your set up sounded somewhat similar and you had been asking about FB's. I agree with Dale (and with Kimberly), had the other poster had FB's at his torch, the flashback would have been arrested right there, at a point in his set up where there would have been very little fuel to combust (just in the torch, which was open, anyway), and he wouldn't have had a dramatic experience. I don't use pre-mix torches myself, so I don't know about the tendencies of the Smith Little Torch that you will be using, but I've read that pre-mix's in general can be prone to developing flashbacks.

As you described, if you plan on only running your Little Torch when soldering and don't plan on having two torches on your system at the same time, I suspect you would be far less at risk of an event than the other poster. Even though your soldering torch came with hoses attached, you can still patch in a flashback arrestor close to the torch. You need only cut the hose relatively close to the torch (say, 4"-6" away - you need room for the length of the barb you're going to install plus that of any barb that might be installed on the torch), push in barbs with the right gender nut for the FB (which usually come male on one end and female on the other), use small hose clamps on the barbs to seal the hose and off you go. If need be, you can do the same with your Lynx. I did this with my lampworking torches, all of which happened to come with barbs for the hose connections, so I have a very short (less that 6") section of hose between my torch the the FB arrestor.

If your tank-mounted FB's haven't been shipped, you can consider changing your order to torch-mounted, or you can return and exchange. PTIA, I know, but Kimberly is very knowledgeable about torches and has had some interesting posts in the past about how surface and premix torches can influence each other. Kimberly or Dale can also best answer your question about purging the lines, first.

In reading your posts again, especially about dropping marbles (haven't we all done that...) and why you chose FB's for your tank, it made me wonder about how you're running your hoses. Are they resting on the floor? If so, I assume you were worried about a hot piece of glass damaging them.

Linda

[Dale M.]

Just a note about hoses, they should be up off floor and preferable tucked up under bench where they are not exposed to any hot glass, other than where hoses come out from under bench and up to torch.... Hoses also should not be on floor anywhere near where your feet/legs can become entangled in them...

Imagine with torch burning on your bench and you jump up because you dropped a hot marble and want to get away from it and your feet are entangled with hoses, you go down and lit torch comes off bench "looking for you"..... NOT pretty picture....

Dale

[artwhim]

I was pretty sure I wanted arrestors at the torch till I read that thread and then I too had a knee jerk reaction at the idea of an explosion in my lap, so I decided on the regulator arrestor. What you are saying makes perfect sense, you've all convinced me to go back to my original plan of arrestors at the torches.

I haven't finished adjusting everything for the new setup yet, but the hoses won't be on the floor when finished. I didn't want to risk having them too short till I knew everything would work. Thanks for reminding me though.

Dale, Linda, Kimberly and Malcolm, thank you so much for helping me not only figure out the best way to set this system up, but information about "why" to set it up this way. I appreciate your expertise!

[tenor_ringer]

Originally Posted by Dale M.

Just a note about hoses, they should be up off floor and preferable tucked up under bench where they are not exposed to any hot glass, other than where hoses come out from under bench and up to torch....
Dale

I have some disturbing memories of visiting a rental studio and watching someone crawling around on the wooden floor under the bench chasing a still-glowing marble as it rolled along a flaming, smoking path amongst the oxygen and gas hoses. Nobody there seemed very concerned. Haven't been back...

[Dale M.]

Sad to say there are some "professional" studios that are absolutely clueless when it come to safety aspects of hot glass.... The either have never been taught about safety or addressed safety or just don't care...

Dale

[JoeDeM]

They should be installed at the torch, it's more important with premix, and larger torches.

from Safety and Health Fact Sheet No. 28 April 2005
© 2005 American Welding Society

A flashback is a momentary or sustained retrogression of the flame upstream of the mixer usually in the torch or hoses. This is a potentially hazardous situation, particularly if the flame reaches the hoses where an explosion will result causing a rupture or separation of the hose. A flashback is generally caused by the reverse flow of gases upstream into the hoses or other equipment. This reverse flow is usually the result of 1) improper shutdown and/or startup procedures or 2) by allowing cylinder pressures to become too low or 3) by a check valve that is not working properly.