flashback aresstors with surface mix torch

[MasterJoey05]

Are flashback aresstors necessary with a surface mix torch?

[Action Glass]

Yes. Although they don't typically flashback if there's too much carbon buildup or clogs they can flashback. Better to be safe.

[somewhere]

Simple answer:

No

Honestly I think you should understand how a torch works premix and surface mix, what a flashback is and know why the answer is no.
If that's to much work or over your head buy every bit of safety gear you can get your hands on.

[Action Glass]

I understand how a torch works man. I still use arrestors. I also have premix hand torches spliced in. Better reason tohave them. But yes I have heard of surface mix torches flashing back. Its rare but happens.

[Action Glass]

I swear this thread has come up before with mixed opinions just like this one. Grab the popcorn I see another repetitive debate coming.

[Greymatter Glass]

But yes I have heard of surface mix torches flashing back.

Really? In 13 years I've never heard of it...well, other than 3rd person anecdotal references people give but can't cite a source on .

That said, in answer to the OP... no you don't really need them.... BUT

That answer assumes your torch isn't damaged, and you know how to use it safely. There are still plenty of dangers when working with high pressure oxygen and propane...


There are only a couple scenarios I can see where a flashback could happen w/ a surface mix torch, and both are highly unlikely.

An internal leak in the manifold that allows oxygen and fuel to mix before it's discharged from thew port, while the entire face (or all the ports attached to the affected manifold) are blocked with something that would resist the pressure of the gas behind it.

Or, very quickly and specifically smashing glass onto the face of the torch in a manner that allows oxygen to force into the propane lines and carry the flame into the fuel lines....


Also, either of those scenarios would require defective regulators, as the modern design of regulators causes them to function as a check valve. A rapid rise in pressure pushing back one side would shut the diaphragm down.

No fuel, no fire.

...

Even with premix torches, flashback arrestors are worthless if they're just attached to a regulator that's connected directly to a tank. Any length of hose between the torch and the arrestors kind of defeats the purpose... they are often used on use points of a distribution system as well (hard lines) but that's a whole other thread (if you search you'll find it, high flow arrestors are not cheap) A flash back is where fire gets into the hoses, the arrestors go between the torch and the feed lines, the tanks are protected by science. In the case of hardlines, you sacrifice the hoses to save the larger "medium" pressure system...but like I said, another thread.

[Action Glass]

Your right Doug I cannot site a source. But everything I have ever read about surface mix is its not needed BUT reccomended. Thanks for the detail I left out

[Greymatter Glass]

Who's making these recommendations?

This has come up before, the only people I see recommending them are people who don't really know why, other than it's what they were told by someone who probably was in the same position....

I'm curious to find out if anyone has first hand experience with a flashback using a surface mix torch - not "I know a guy", if you know a guy tell them to get in here.

I think Sky summed it up pretty well early on:



If that's to much work or over your head buy every bit of safety gear you can get your hands on.

[Action Glass]

Last time I read it was in the Bethlehem bravo user manual.

[Action Glass]

I guess maybe its how I was brought up. Its habit. Even if not neccesary I still have a premix spliced in so I think it is. But you are right I've never first hand experienced it.

[aREa541]

While I really don't want to jump into a pissing match of torch knowledge (I am not an expert) I was curious about the whole flashback on a surface mix thing. After googling it a bit I found several sources that said while the odds of a flashback are at best rare on a surface mix they recommend using flashbacks as an extra layer of protection. Thing is, all these sources (except one who was just some machinist guy with a blog) were selling flashback arrestors and/or torches which is an obvious conflict of interest when searching for the truth.

Funny enough one of these sources was GTT, on their website where they sell Flashback Arrestors. http://www.glasstorchtech.com/flashbackarrestorset.html Now, I could see them saying this for two reasons even if they believe that a flashback would never happen: 1. To cover their ass in the extremely slight chance there was a flashback on one of their torches so they could say they recommended them and 2. To sell more sets of flashback arrestors on the page where this info came from.

Either way, there are obviously industry leaders with knowledge putting this info out there (even if it is only for liability or profit reasons), so it might be a little harsh to make Action feel stupid for recommending them when other respectable people in our field are recommending them as well.

[Loki Glass]

I'm certainly not an expert either, but from what I've seen the reason you generally see the recommendation for flashbacks on a surface mix is in case of an internal damage issue where the gasses are getting premixed somehow. You might not even realize this is happening, so it's just an extra layer of protection.

With the enormous cost of gas, glass, torches and other tools, $50 seemed like it was well worth the peace of mind. For me at least.

[willy47]

(I'm new only months in) - but I do a lot of reading -- Why even second guess the need of flashback arrestors - its your life go put them on your tanks --- even the most experienced people on this forum are saying you don't need one "BUT" if you don't know how to safetly use your torch get it .... I believe you need one even if you know your torch .. Everybody has an off day and you don't want that to cause for you to blow up.

[FRGartifacts]

With the enormous cost of gas, glass, torches and other tools, $50 seemed like it was well worth the piece of mind. For me at least.

That's my general thought, though yes MGA recommended it, and I have a tingle in the back of my head that says Bandhu recommended it regardless as well as a general precaution in Cont. Lamping...

But I can't confirm that at the moment as I'm not in front of my copy.

[nodice]

It's better to be safe than sorry. Period.

[Greymatter Glass]

Even if not neccesary I still have a premix spliced in so I think it is.

IF you have a premix torch anywhere on your lines then you should have a flashback arrestors...


It's better to be safe than sorry. Period.

In other words, wrap yourself in protective foam and never leave your house. Just pray you're not allergic to foam, or a plane does crash into your house I guess....

I'm not saying flashbacks are a bad investment, but in terms of probability pretty much EVERY shop I've ever been in have far worse things wrong with them...even my own shop is guilty of a lot of things...

If you want things to be safe in a practical manner look elsewhere. Do you have 25 or 50 feet of rubber hose coiled up on the floor under your bench? Do you have a 5 gallon or larger propane tank inside? Do you have a LARGE sized ABC fire extinguisher placed near the exit of your shop? Do you have a well prepared first aid kit? Are your oxygen cylinders secured to a wall? Have you ever had a fire drill and know how and when to react in case of an emergency? Do you have proper placards on the outside of your shop so if the fire dept does have to come they know you have large amounts of oxygen/propane on the premises?

[BORO]

Every cc any one has ever screwed with has a surface mix that flashes back . Yes it is a torch with a pre mix center . The pre mix seal is much harder to screw up . , however, that is a case of surface mix , flashing back . Even if I had a black widow , I bet they could too .

I passed the doug test , ( But... I am guilty of things that need to change as well )

[LooseSeal Baller]

^^ can someone calm this dude down!!!

[Matt P]

^^ can someone calm this dude down!!!

nope....

[somewhere]

Every cc any one has ever screwed with has a surface mix that flashes back . Yes it is a torch with a pre mix center . The pre mix seal is much harder to screw up . , however, that is a case of surface mix , flashing back . Even if I had a black widow , I bet they could too .

I passed the doug test , ( But... I am guilty of things that need to change as well )

If you alter your surface mix burner so it becomes a premix then I would recommend them.

I would also recommend you do not "screw" with the inside of your burner. You can lay all you improbable scenarios you want but the bottom line is a surface mix burner will not cause a flash back. Besides the obvious as you stated the cc has a premix center fire. So what's your point?

[nodice]

In other words, wrap yourself in protective foam and never leave your house. Just pray you're not allergic to foam, or a plane does crash into your house I guess....

I'm not saying flashbacks are a bad investment, but in terms of probability pretty much EVERY shop I've ever been in have far worse things wrong with them...even my own shop is guilty of a lot of things...

If you want things to be safe in a practical manner look elsewhere. Do you have 25 or 50 feet of rubber hose coiled up on the floor under your bench? Do you have a 5 gallon or larger propane tank inside? Do you have a LARGE sized ABC fire extinguisher placed near the exit of your shop? Do you have a well prepared first aid kit? Are your oxygen cylinders secured to a wall? Have you ever had a fire drill and know how and when to react in case of an emergency? Do you have proper placards on the outside of your shop so if the fire dept does have to come they know you have large amounts of oxygen/propane on the premises?

This was my point. People who don't follow safety precautions are bound to be the ones who actually need the flashback arrestors, or fire extinguishers. They take unneeded chances with their lives, and the lives of others. They might randomly run 50psi on their Beth pm2d, even though beth says running more than 25 can turn it into a premix. They might take their torch apart and put it back together incorrectly, then sell it to other people who don't have backflash arrestors. The list goes on. I don't see why anyone would be against using them......

[nodice]

And just for the record, I've never had a fire where I needed to use an extinguisher.

[Greymatter Glass]

Every cc any one has ever screwed with has a surface mix that flashes back .

I can only assume you mean someone has taken it apart and not replaced the copper seals? Under perfectly normal operation the POP that you commonly get with CC's is from the center fire premix section...

I guess it bears mentioning: Glass blowing torches are NOT user serviceable tools. NEVER take one apart to see what's inside, there's pics online of just about every torch style tear downs if you're curious.

[Matt McKasty]

I'm about to set up a Bobcat. I'm going from working off a Hothead and have never used a real torch before. Should I get them just in case I do something wrong or will I be fine unless I'm a total idiot.

[RamblezMarblez]

I'm running a Mirage with no Flashbacks...I'm a crazy Mofo!

[Matt P]

jesus...

what's the fucking point of talking about this stuff!?

[Icarus]

I'm running a Mirage with no Flashbacks...I'm a crazy Mofo!

http://3.bp.blogspot.com/-ummSU5Dt_oo/UFFx5jU8rRI/AAAAAAAABUY/j_n2ezx11ME/s1600/Darwin-awards.jpg

[TlkQ]

^Man I wish that were a video...

[olddog]

I can only assume you mean someone has taken it apart and not replaced the copper seals? Under perfectly normal operation the POP that you commonly get with CC's is from the center fire premix section...

I guess it bears mentioning: Glass blowing torches are NOT user serviceable tools. NEVER take one apart to see what's inside, there's pics online of just about every torch style tear downs if you're curious.

Can you point me to the GTT tear down pix?

[menty666]

My Redmax has a surface mix major with a pre-mix rider. Where's your god now?!?!?!?!

I have flashback arrestors on the line, better safe than sorry. My bear repellent spray has been working for years as well.

[Matt P]

Can you point me to the GTT tear down pix?

They are here on talkglass.com, I don't remember who posted them, or what they called it, but hopefully it comes to me soon and if/when my memory does me a favor for once, i'll post the link.

[Matt P]

Can you point me to the GTT tear down pix?

hell yeah, that was easy:
http://www.talkglass.com/forum/showthread.php?37708-Disassembling-a-GTT-Delta-Elite-Manifold-and-Welding-a-Marver-Tab-On&highlight=disassembling

[Robert Mickelsen]

Another flashback arrestor thread. I have a question. How many people here have actually experienced a flashback? If so, what kind of torch were you using and what led to the flashback?

I will go first. I worked for around six years on a National 3A blowpipe before upgrading to a CC for the next fifteen years (yes, I am really old). I probably had more than a dozen actual flashbacks on my old National. Everyone of them happened when I accidentally rammed a hot gather of glass into the torch tip. There would be a loud bang, much like a gunshot, then a loud squealing noise as the internal fire began. Shutting of my propane valve would extinguish the flashback immediately and I would mutter a curse word, re-light my torch, and continue working. After upgrading to the CC I never had another one, even though I did run into the tip of that torch once or twice too (I do not claim to have always been the skilled worker I am today!).

I have always thought it was impossible to cause a surface mix torch to flash back. The definition of flashback is a fire inside the torch body and, since the fuel and oxygen are kept separate until they exit the tip, there cannot be combustion inside the torch. At least that is how I understand it. If anyone has had an actual flashback using a purely surface mix torch I would like to know about it.

- RAM

[Greymatter Glass]

A flashback is actually more than that, and they're scary as hell from what I've heard. They seem to be most common with cutting torches that have the oxygen booster valve on them.

A flashback is where the oxygen manages to get into the fuel line and there's a fire in the lines. The result is the hose explodes and then the fuel blows out and starts whipping around like a garden hose on full blast let loose. If the oxygen gets to the tank it can be a real problem, but modern regulators act as a check valve so that's all but impossible. Still, if you have 50 feet of hose that explodes (or burns up very rapidly) it can cause serious damage and fires.

With a blowpipe style torch if you have it set at pressures it's not designed for or you block the tip up briefly you can force the flame to burn back into the body of the torch, which CAN damage the torch, and will often make a crazy noise... it happened a lot to me when I was in school on an air/acetylene jewelry torch...and yeah, turning the gas off kills the fire.

Thing is, with a true flashback, putting the flashback arrestors on the regulator before the hoses doesn't really do much.

[Robert Mickelsen]

Thanks, Greymatter. My definition of "flashback" is any combustion in the wrong direction from the torch body on back. For me, I always managed to extinguish the flashback before it burned back to the lines. Anyone else here actually experience flashback or are you all just repeating what you have heard about it?

- RAM

[hnk]

my first and probably only experience with a flashback was at Salem community college on the beat up cc's they have for the students. not being used to the set(always worked on gtts) i did something wierd one day and it made that loud CC pop we all know an love, aftera minute the whole torch became so hot you couldn't even touch it(even the knobs). after shutting the propane line off and letting cool for 10-15mins it was ok again.

[Greymatter Glass]

My definition of "flashback" is any combustion in the wrong direction from the torch body on back.

Really we're talking about 3 things here.

There's 3 terms I've heard in welding and jewelery classes, from least concern to most: Backfire, backburn, flashback.

Backfire is that loud pop you get, usually when turning off or adjusting a premix torch. It's not much of a concern, especially when associated with turning a torch off. Anyone who's used a CC or National 3a bowpipe or similar has experienced a backfire.

Burnback / backburn is what you're describing, where the flame fails to properly seat on the tip of a torch and instead gets into the mixing chamber. That can make a strange noise and will damage the torch if not extinguished quickly. These are much more serious than a backfire and if it happens you should really double and triple check everything about your torch. Line pressures, leaks, bad torch valves. Usually an alert operator will have several seconds to turn off the oxygen and get things sorted out safely. Do NOT turn off the gas first, always turn off oxygen, POOP applies here for safety more than a funny mnemonic. Turning off the gas first greatly increases the chance of a flashback

Either of those situations CAN result in a flashback, as can clogging the tip or bad pressures, or broken torches...a few other things as well.

A flashback is any time the flame gets back behind the mixing chamber. Technically it STARTS inside the torch body in any internal manifold or gas feed channels, and this is where flashback arrestors can make the difference between a burnback and a flashback. If you don't have the arrestors attached directly to or in very close proximity to the torch then the flashback can freely propagate to the hoses and they will very rapidly burn up or explode resulting in major fire risk, property damage, and personal injury. Putting your arrestors on a foot or two of hose pigtails works fine and can make the torch easier to work with than having them directly on the torch. Having them at the far end of 25-50 feet of welding hose doesn't help at all.

A human being cannot react fast enough to shut off a valve to stop a flashback once it's started. Flashback arrestors can actuate in microseconds.

Putting flashback arrestors on the back end of the hoses closer to the tank/regulator does little good. A quality regulator in proper use and good maintenance will prevent backflow of gases. Better regulators and Western Enterprise style quick connects also have build in check valves, which function as a sort of low rent flashback preventive device.