Flashback Explosion

[MUPH]

This happened to me yesterday. There was a flashback between my torch (GTT Phantom) and my foot pedal (electric smut boy). I went to kick on my outer flame and only the propane came on. I heard a pop, so I looked under my bench and saw the blue flame coming from the outer ring oxygen line. I ran to shut off the gases before any more damage was done. The flame settled down and the burning rubber stopped.

My order of operations, from the tanks to the torch: Tanks, regulators, flashback arrestors, hosing, Y valve, quick connects, hosing, foot pedal, hosing, torch. On the other side of my Y valve is a Smith mini hand torch. There were not flashback arrestors directly behind the hand torch, only on the main line running back to the tanks.

Wally mentioned that this was his only explanation he had: He thought that there could have been a vacuum created if the hand torch was left cracked open. He did say he heard of this happening once before. I didn't understand this, because the flashback occurred between the torch and the foot pedal.

I was using all grade T hosing. I have done leak tests on all of my connections and had the whole set-up looked over by two other lampworkers when I was first setting up the shop. The location of the hosing burst was under my bench, above the ground. I can't think of anyway it could have been hot glass that melted through the hose. I'll be redoing all of my hosing, flashback arrestors, quick connects, foot pedal, and torch. I think I've hit every detail as to my set up. If I left anything out, please let me know.

If anyone has any insight on to this situation, let me know. No one seems to have a definitive answer.

Everybody, use flashback arrestors.

65672

65670

65671

[MUPH]

Link to original thread (http://www.talkglass.com/forum/showthread.php?53417-Flashback-arrestor-arresting-a-flashback)

[chillrelaxglass]

Omg dude I have a pedal idental to that one. I never used it bc it was sketch as fuck. I had my dad double check it. He opened the propane solenoid and turned It on it was shooting sparks. Thank god I never pluged it up.

[BORO]

The vacuum thing..... not a vacuum per say as much as venturi ?

the 02 line on the hand torch is cracked. creating a venturi when the main bench burner is running .

The hand torch has the fuel line cracked as well... and the venturi draws propane from the mixing chamber , creating a combustible mix in the 02 line?

You light the outer fire , flame runs back down through the torch and lines , pressure blows the line out at the weakest link , as it hits the restriction in the pedal valves......

(I find that hard to believe. pure speculation. )

If it did go down like that , makes me worry that it may have happened before and burnt its self out.

I know I used to have issue with thinking my pre mix was extinguished after use , and it was still lit. (tiny , but still lit )
I fixed this problem when I started to put my torch out with 02. Just crank the o2 and it puts out the pre mix with no pop , and no worries it may be lit still

[chillrelaxglass]

I should take a video of the one I have thing is a death trap. Other reason I believe it was due to spark is bc its close to the solenoid.

[MUPH]

Omg dude I have a pedal idental to that one. I never used it bc it was sketch as fuck. I had my dad double check it. He opened the propane solenoid and turned It on it was shooting sparks. Thank god I never pluged it up.

I've been using this pedal for over 5 years, never had a problem with it. It might look sketch to you because there was just a flame blowing out of it?



The vacuum thing..... not a vacuum per say as much as venturi ?

the 02 line on the hand torch is cracked. creating a venturi when the main bench burner is running .

The hand torch has the fuel line cracked as well... and the venturi draws propane from the mixing chamber , creating a combustible mix in the 02 line?

You light the outer fire , flame runs back down through the torch and lines , pressure blows the line out at the weakest link , as it hits the restriction in the pedal valves......

(I find that hard to believe. pure speculation. )

If it did go down like that , makes me worry that it may have happened before and burnt its self out.

I know I used to have issue with thinking my pre mix was extinguished after use , and it was still lit. (tiny , but still lit )
I fixed this problem when I started to put my torch out with 02. Just crank the o2 and it puts out the pre mix with no pop , and no worries it may be lit still


This is what JJ at HotAssTools mentioned as well when I spoke with him. It make sense (although I've never heard the tern venturi before), but I hadn't used my hand torch in over a week.

[MUPH]

When u flip over the pedal are the electric contacts exposed to the ground? Mine is just one other thing that sketched me out.

No, it is entirely encased in the metal box.

[dustyg]

It make sense (although I've never heard the tern venturi before)

See "venturicycler (http://www.tokecity.com/forums/showthread.php?49420-The-Venturicycler)".

[chillrelaxglass]

No mine didn't even blow up bro. A buddie gave it to me for FREE said he never tried it. I took it home and was going to hook it up. But I didn't something told me not to so I went over to my dads had him give it a once over with me. He hooked it up and the FUEL solenoid starting shitting sparks. Everything seemed to be wired just like the one in the photo. And yes the one in dudes photo looks sketch bc it caught fire. I never gave mine the chance to catch fire. I didn't trust it from the beginning.



This is what JJ at HotAssTools mentioned as well when I spoke with him. It make sense (although I've never heard the tern venturi before), but I hadn't used my hand torch in over a week.[/QUOTE]

[chillrelaxglass]

No, it is entirely encased in the metal box.

The pedal is inside a metal box?

[glassdocnc]

Wow. That's some scary shit. I'm glad you are ok. Thank you for posting.

It goes to show that the importance of routine safety checks should never be overlooked because even when we are trying to do everything as safely as possible shit will happen.

[chillrelaxglass]

Maybe 5 or so years is all the solenoids are good for. Bc mine looks as old as yours.

[Firekist]

that venturi explaination makes some sense to me as well.

i had a wack setup with a handtorch T'd off my centerfire a while back. if i messed with the inline reg pressures, with both the centerfire on, and the premix handtorch, the fuel mixture coming out of the centerfire would change. i could see that oxygen was somehow being added into the centerfire's fuel line, by the flame's characteristics.

your foot pedal should have nothing at all to do with this.

[brads]

This seems to bear mentioning. Flashback arrestors and check valves are not the same thing, although they are often/usually combined into one unit. A check valve prevents backflow of gas in the lines. It won't necessarily prevent a flashback.

On the other hand, a flashback arrestor prevents a flame front from propagating backwards through the lines, but doesn't necessarily prevent the backflow of gas.

So when looking for a flashback arrestor, look for one that specifically includes both. Some better ones also include thermally triggered shutdown of gas flow.

If you have just a flashback arrestor or a check valve alone, you only have half of the safety equation. Most units these days incorporate both, but not all do. So be careful to read the fine print before you buy.

Here are some $18 combination flashback arrestor/check valves on Amazon (http://www.amazon.com/exec/obidos/ASIN/B005UUQJOG/bradshuteswicked). There are others there as cheap as $7 each or as expensive as $200 each. I can't comment intelligently on which of them may or may not be worth the price.

[misled youth]

I would have to agree with the Venturi effect as well.
Sure am glad you are ok, that is some freaky shit!

I make a lot of Venturi burners myself for different forges that I have built. Over the years i have seen some crazy shit happen that has given me a much better understanding of the things that can happen.

And yes PLEASE everyone always use flashbacks.
I currently have them at the tanks right after the regs and a set inline. I am actually planning to install a 3rd set right before the torch.

[brads]

I was going to include this in my other post but forgot. The sudden shut-off of gas flowing rapidly through a pressurized line can create a temporary vacuum downstream of the shut-off point. This will be more pronounced at higher pressures and the faster the shut-off happens, so someone running a high pressure oxygen torch, such as a larger GTT, and an electric solenoid foot valve, which shuts off very quickly, would be most likely to experience it.

In the earlier thread on this subject Misha mentioned experiencing a flashback when using a foot pedal and a GTT torch. Whether or not her pedal was electric, she didn't say. Muph was using a GTT Phantom and an electric solenoid when his flashback occurred. While the torches themselves are very unlikely to have anything to do with this, GTTs do run on higher oxygen pressures than most torches, and that pressure may have something to do with it. Combined with the rapid closure of an electric solenoid, this could create a low pressure area between the torch and the foot valve with the potential to possibly suck in some gas.

Whether this was the cause of the problem in either of these cases, I don't know. Although I think it's improbable, the similar setups seem to make it something worth considering, especially since Wally mentioned a vacuum in the line as a possible cause. But a venturi effect sucking in gas is probably more likely.

Edit: After I posted this Misha mentioned below that her foot pedal isn't electric, which seems to make my improbable theory above even less probable. So forget you just read the previous two paragraphs, okay?

And Muph, as far as starting a thread on this subject back in January and then having it happen to you 9 months later - if you decide to start a psychic friends network, I want to join.

[PyroChixRock]

Sorry for the confusion on my experience. I run a mirage and rock-it, which is not electric. I've always been scared to run the electric ones so spent more for the rock-it which is a beast. I love it, would buy it again anyday.

[brads]

Sorry for the confusion on my experience. I run a mirage and rock-it, which is not electric. I've always been scared to run the electric ones so spent more for the rock-it which is a beast. I love it, would buy it again anyday.

Well, that does tend to lessen the plausibility of that theory. Oh well... ;)

I'm with you on electric foot valves. I've never felt comfy with them either. Give me an old fashioned mechanical valve any day.

[misled youth]

I miss my foot pedal. It even had a meatwad sticker on it

[Northwinds Glass]

http://img.tapatalk.com/d/14/09/14/5yzuzynu.jpgI had a bad flasback and explosion several years ago. It sounded like a bomb going off, ruined my flasback arrestor on my o2 line , completely blew out the hose and flames and sparks were shooting out at the regulator at the lox tank. It was a bad scene. After that i put inline check valves about a foot back from the torch just for a little added safety.

[Northwinds Glass]

Sorry. It was my check valve that got blown out. Not the flashback arrestor. I will try to post a pic in a minute

[Northwinds Glass]

http://img.tapatalk.com/d/14/09/14/3e6e4ugy.jpgcompletely blown out

[PyroChixRock]

Can you add your set up info? Torch, foot pedal if you run one, hand torch, etc.

[Northwinds Glass]

Gosh. It was almost 10 years ago and we had some y's involed but i believe it was basicaly lox tank > reg > arrestor > check valve > hose > Redmax.

[PyroChixRock]

Thanks :)

[Northwinds Glass]

Heres the hosehttp://img.tapatalk.com/d/14/09/14/5udy5aze.jpg

[PyroChixRock]

No foot pedal or hand torch in the equation?

[ALIEN!]

sorry to hear that happened to you Muph, glad you weren't hurt. I know I would have probly stained my drawers a bit.

I want to see a video of this solenoid that shoots sparks.

Even if a solenoid sparks, the gasses should still be safe as the valve innards are separate from the electric solenoid so long as the valve itself isnt completely fucked.

The venturi theory sounds pretty plausable, glad I read this thread, Ill be sure to be double checking my hand torch for safety in the future.

[hashcat]

pretty wild stuff here guys, glad everyone is ok

any tips for preventing a venturi?? just make sure the mini is turned off completely each time?

definitely going to be adding arrestors/check valves closer to my torch

[Northwinds Glass]

No pedals or hand torch. The consensus was that propane had backed up the o2 line......we had run out of o2 and were waiting on the delivery guy. I had NOT shut down my propane so it sat with no pressure in the o2 line for a while. Delivery showed, switched tanks , introduced o2 , lit the torch and instant kaboom.

[Northwinds Glass]

Heh. The last thing you ever want to have to do in a glass shop is discharge a fire estinguisher. Trust me.

[brads]

pretty wild stuff here guys, glad everyone is ok

any tips for preventing a venturi?? just make sure the mini is turned off completely each time?

definitely going to be adding arrestors/check valves closer to my torch

A check valve between the torch and any Y in the lines should prevent it from happening. If it can't backflow it can't suck in gas via a venturi effect.

[brads]

Heh. The last thing you ever want to have to do in a glass shop is discharge a fire estinguisher. Trust me.

Especially while standing next to a LOX tank spewing flames out of the regulator, I would think... :fire

[Northwinds Glass]

No wait...... maybe it was....after switching out the tank i lit the propane and when i introduced the o2 kaboom

[Northwinds Glass]

You know what....as i sit here and think back i am pretty sure i did have a national hooked in there also.

[PyroChixRock]

Hmm. Def goes back to the Venturi effect then. Good to know.

[D. dino i ninjah]

pre mix torchs can flash back.. I don't think it is a problem with surface mix torches if they are run on their own syestem... this is based on info in beths own litature I guess you should have them .. just to be safe ... but the proability or a flashback happening is not really likely on a surface mix burner. Somewhere and graymater explain it here http://www.talkglass.com/forum/archive/index.php/t-49867.html

from the bethleham users manual

"Flashback
A flashback is when pre-mixed fuels burn inside the burner
body, resulting in a flame blow out, or even an internal
flame that will destroy a burner.
The surface-mixed burner, as in the Alpha, is safer because
they will not allow the fuel mixture to burn inside the
burner body. Therefore, as in pre-mix burners, fire checks
and flame arrestors are not required with the Bravo."

[PyroChixRock]

This is horrible misinformation. All these flashbacks have occurred with surface mix torches. You need flashback arresters and check valves on surface mix torches too.

[somewhere]

This is horrible misinformation. All these flashbacks have occurred with surface mix torches. You need flashback arresters and check valves on surface mix torches too.

Wasn't a hand torch involved in each scenario?

On another note I'm not really sure the rapid shut off will cause any type of vacuum or lessen the pressure as commented. If the hand torch leaked or was left cracked open I can see a Venturi effect happening but that goes back to a premix hand torch.

[PyroChixRock]

No, no hand torch in mine.

[somewhere]

No, no hand torch in mine.

That's interesting I would like to understand what's going on.

my mind says something else happened. I have a hard time thinking gases are being sucked off the face of the surface mix and drawn back into the torch. If this is happening it's isolated incidents and they happen for a reason. Not common but something has caused it. Flashback arrestors certainly won't stop exploding hoses or random fires in the shop unless they are mounted directly to the torch before any hoses.

[PyroChixRock]

I always thought it had something to do with the pedal but totally don't get it either.

Set up was tanks - y - regulator - flashbacks - hoses - pedal - hoses - torch.

Mirage and rock-it. Flashback occurred between tanks and pedal. If I didn't have arresters installed it would have been worse than a flaming hose flapping around.

That was in like 2006. I'm still running the same mirage and pedal and haven't had anything happen since, but I'd never run without arresters just in case. Surface mix or not why risk it?

[Northwinds Glass]

I also find this all interesting and enjoy hearing the chatter. In my case the redmax had the premix top fire with #3 on it. And as i mentioned it sat with 8 lbs or so in the propane line and 0 lbs in the o2 line for a while.

[PyroChixRock]

This conversation is a little confusing as it started in another thread. Matt always thought it could have been hot glass that fell on my line and caused it to ignite. I never agreed with that theory because of my glass blowing style; I am very clean and glass doesn't fly anywhere I don't want it to. Plus I was making a marble at the time and rounding it off so there was no clinking of punties or tearing off glass or anything that could have caused falling hot glass aside from me dropping the marble.

But the theory brings up a very valid point. If hot glass fell on your hoses you'd better have flashback arresters at the tanks! Regardless of what torch, hand torch, pedal, or anything is involved.

[D. dino i ninjah]

If you read the papers that come with a new beth ... they clearly say flashback arrestors or check valves are not nessary with surface mix torches.. that is where I got the information from ..

[Riley]

I recall somebody I respect saying that flashbacks can stop explosion in the lines but that the flame can't travel back through into the tank? You can open and ignite a propane tank with no regulator can't you? Just trying to gauge the likeliness of total catastrophic failure. It sounds like the worst of it is the line pops/explodes and the risk of injury or fire is from that alone. Is that a fair assessment or are their actually instances of tanks exploding from flashback?

[brads]

" saying that flashbacks can stop explosion in the lines" <--- Can we assume you mean "flashback arrestors" can stop explosion in the lines? Since "flashbacks" can START an explosion in the lines.

How far a flame can travel depends on the pressure and velocity of the flame and gas. If the flame front is travelling faster than the velocity of the gas travelling forward, you get a flashback. While it is unlikely it would travel into a pressurized tank, it certainly isn't impossible, especially if the tank pressure is low. Why take the chance?

The chance of getting hit by lighting is pretty slim too. Yet every year it happens to a bunch of people. It actually happened to me 3 years ago. Luckily mine wasn't a direct hit, but it hurt like hell anyway. So these days I figure a "slim chance" is another way of saying it CAN happen, not that it probably won't.

[Riley]

I use protection, I'm not advocating otherwise just wondering. This kind of thing sucks and nobody wants to explode. It's like a bad acid trip coming to fruition.

[PyroChixRock]

If you read the papers that come with a new beth ... they clearly say flashback arrestors or check valves are not nessary with surface mix torches.. that is where I got the information from ..

I'd like to see proof of that. We can advocate that they change their information if this is actually true. It's not sound advice, one of the main points in this thread.

[Skipjack]

I am reasonably sure that this is a common statement for other manufacturers of surface mix burners and that I will be able to compile instruction excerpts to back this up. (Edit: Apparently I am incorrect as of the current instructions available.)

Their point is that in a properly operating surface mix burner connected to the fuel and oxygen systems by itself and with no branches to other burners or torches, there is no direct path between the fuel and oxygen lines and so a flashback cannot occur. That is not to say that this cannot happen in a defective burner if there is an internal leak and/or blockage which will allow the fuel or oxygen to mix and be forced back into whichever line is at lower pressure.

1) GTT: GTT does not mention the use of flashback arrestors in any instructions or torch descriptions. GTT includes instructions on how to hook up their torches to the gas and oxygen source.

2) Nortel: Nortel does not mention the use of flashback arrestors. Nortel does not include specific instructions on how to hook up their torches to the gas and oxygen source.

3) Bethlehem:

Flashback
A flashback is when pre-mixed fuels burn inside the burner body, resulting in a flame blow out, or even an internal flame that will destroy a burner.
The surface-mixed burner, as in the Alpha, is safer because they will not allow the fuel mixture to burn inside the burner body. Therefore, as in pre-mix burners, fire checks and flame arrestors are not required with the Bravo. To test your burner for proper performance, just simply turn off the oxygen flow. If there is a loud bang, then pre-mixing is occurring and the burner should be returned to Bethlehem Apparatus for repairs.
CAUTION
DO NOT USE BURNERS THAT MAKE A LOUD BANG WHEN THE OXYGEN SUPPLY IS ABRUPTLY CUT OFF.

Safety Regulations
All Bethlehem burners are surface-mixed and do not require a flashback arrestor, which is required for pre-mix torches. However, the need for a flashback arrestor may be subject to regulation. Therefore, we advise all of our burner customers to check with their local, state and federal regulations regarding burner/ torch requirements.

Bethlehem does acknowledge the possibility of flashback in a defective burner -
"If you start to experience FLASHBACK (covered below) return the burner for O-ring replacement."

4) Carlisle: Carlisle does not mention the use of flashback arrestors, but do manufacture fire check and combination fire check/flashback arrestors. The only mention of flashback precautions I could find was with the use of their foot pedal -

Foot Controllers
By utilizing a foot controller, users free their hands from the need to constantly meter the flame. Carlisle has two separate types of foot controllers available for the CC burner series. The EL-2 (Bulletin 28A) is designed with two solenoid valves operated by a foot pedal. When the foot pedal is pressed, the solenoid valves for both the gas and oxygen will fully open. With the next press, the same valves
will completely shut down. It is important to note that this type of foot controller can only be used with the outer fire (surface mixed) of the CC series burners. Using this type of control with the center fire (pre- mixed) would be sure to invite the chance for flashback.

5) Arnold: The Arnold Group does not mention the use of flashback arrestors and does not offer them as listed accessories.

6) Knight: Knight does not mention the use of flashback arrestors in their descriptions of bead making or bench burners. They do mention this in regard to other surface mix burners they manufacture:

The K-1000 Series Burners can be safely used with hydrogen – oxygen, natural gas – oxygen, or propane – oxygen, and do not require the use of special mixing equipment. The dangers of flashback are eliminated when properly used.

Knight does manufacture fire check units and, in one place, specifies their use with pre-mix burners -
Firechecks are a necessary line component in all premix burner installations where oxygen is being used, or where a possibility of flashback (backfire) is considered a hazard.

Knight is less specific in its general description of its fire check -
DEFINITION
Firechecks are a necessary component in all burner installations, where oxygen is being used, or where the possibility of flashback (backfire) is considered a hazard. Firechecks do not prevent flashback, nor do they stop the resulting concussion.

Note that the Knight fire check is not a check valve, but is more like what other companies describe as a flashback arrestor without the check valve; that is, a device to dissipate heat. Knight specifically does not recommend the use of tandem fire checks (as well as oversized or undersized fire checks).

7) Premier (National): Premier does not mention the use of flashback arrestors.

8) OSHA: OSHA regulations for welding and cutting require the use of flashback arrestors to prevent the leakage of oxygen or flashback into fuel-gas lines.

1910.253(e)(3)(ii)
Approved protective equipment (designated P(F) in Figs. Q-1, Q-2, and Q-3) shall be installed in fuel-gas piping to prevent:
1910.253(e)(3)(ii)(A)
Backflow of oxygen into the fuel-gas supply system;
1910.253(e)(3)(ii)(B)
Passage of a flash back into the fuel-gas supply system; and
1910.253(e)(3)(ii)(C)
Excessive back pressure of oxygen in the fuel-gas supply system. The three functions of the protective equipment may be combined in one device or may be provided by separate devices.
1910.253(e)(3)(ii)(C)(1)
The protective equipment shall be located in the main supply line, as in Figure Q-1 or at the head of each branch line, as in Figure Q-2 or at each location where fuel-gas is withdrawn, as in Figure Q-3. Where branch lines are of 2-inch pipe size or larger or of substantial length, protective equipment (designated as P(F)) shall be located as shown in either Q-2 and Q-3.
1910.253(e)(3)(ii)(C)(2)
Backflow protection shall be provided by an approved device that will prevent oxygen from flowing into the fuel-gas system or fuel from flowing into the oxygen system (see S(F), Figs. Q-1 and Q-2)
1910.253(e)(3)(ii)(C)(3)
Flash-back protection shall be provided by an approved device that will prevent flame from passing into the fuel-gas system.
1910.253(e)(3)(ii)(C)(4)
Back-pressure protection shall be provided by an approved pressure-relief device set at a pressure not greater than the pressure rating of the backflow or the flashback protection device, whichever is lower. The pressure-relief device shall be located on the downstream side of the backflow and flashback protection devices. The vent from the pressure-relief device shall be at least as large as the relief device inlet and shall be installed without low points that may collect moisture. If low points are unavoidable, drip pots with drains closed with screw plugs or caps shall be installed at the low points. The vent terminus shall not endanger personnel or property through gas discharge; shall be located away from ignition sources; and shall terminate in a hood or bend.

Literature survey (probably needs to be separate since it may take longer than the allowed editing period):
Contemporary Lampwork (Dunham) advises the use of flashback arrestors with no further explanation.
More than you ever wanted to know about glass beadmaking (Kervin, p. 31) "Another set of fittings that needs to be included in your gas system is either check valves or flashback arrestors. The purpose of these fittings is to prevent back flow of gas possibly resulting in a fire in your hoses, regulators, or tanks. One or the other should be included in both the oxygen and the fuel gas line. Most glass bead makers use check valves because they are cheaper and because they use surfaced mixed torches that are much less likely to flashback than premixed torches. … Again, flashback is mainly a problem for concern with premixed torches for reasons that will be explained later."

[BORO]

I think brads theory may be closer to what actually is going on.


I can see where a torch on hydrogen , or a lighter than air gas , could never flash back . But propane is heavy , and can easily sink into ports . ( I run my torch almost vertical, perhaps I am at more risk )

What if you had the Venturi effect happening back words .... You hand torch running , and you get the suction right on the head of your surface mix. ( if the propane valve leaks/is cracked as well ) you get propane sucked into the 02 line.



Even if the hand torch and the bench torch were surface mix only . Still at risk

Even if you were using a lighter than air fuel . Still at risk

Even if its just two bench torches on one set of regulators . Still at risk.

I know I check and re check the valves on our line splitters . No reason to pump pressure to a torch not in use.

Edit. You could get the Venturi on one torch. Especially if your running a foot pedal? ( more valves to trust , and your torch valves are open for sure. ) It's essentially two torches. No reason a reducing inner fire can't Venturi the outer fire , makes even more sense. ( how many times do you get a back draft into a hollow form , even tho you thought you were running neutral )

[PyroChixRock]

Is there some benefit to not having arrestors installed that I'm not aware of? I don't understand why anyone would ever consider skipping this.

[D. dino i ninjah]

this conversation though has me a little worried .. I have been running a kNight and then a cc with out them for 14 years .. I think Im going to buy some tomorrow..

Im not saying don't get them .. but if your trying to trace the source of your flash back .. as people were in this discussion.. IT is nice to know .. that the surface mix burner when run on its own syestem is highly unlikely to flash back .. and thus not likely the source of the problem ..

that was the point I was trying to make .. is that the flash back would more likely come from the premix hand torch. or a foot pedal .. than the surface mix gtt.. as it is highly unlikely that the surface mix burner .. would do this on its own. It helps to know what part of the system is not the problem .. so you can find the part that is ..

[Skipjack]

Probably the most likely reason is just the expense for quality flashback arrestors versus the unlikely possibility, with a surface mix burner, that it will happen. People use worm screw-type automotive hose clamps even though they are not recommended because they are cheap and readily available (see Western Enterprises hose clamps, Oetiker clamps, and hose ferrules/crimps).

Having said that, another reason is that there is always some pressure and flow loss through such a device. Western Enterprises gives values in their data sheet:

"• Rated capacity of 40 SCFH with a 5 PSIG pressure drop"

Additionally, they have a pressure rating. Again, from Western Enterprises:

"• Maximum operating pressures are 15 PSIG for acetylene, 22 PSIG for other fuel gases, and 125 PSIG for oxygen"

Carlisle does not give a nominal pressure drop value or a maximum operating pressure for its flashback arrestors, but instead gives flow rates versus pressure and working pressure for various gases for its series 8491 unit:

FLOW PERFORMANCE
Inlet Pressure PSIG Air Flow SCFH
7.3 231.0
14.5 465.0
21.8 725.0
36.3 1041.0
72.5 1933.0

WORKING PRESSURE (U/L)
Gas Pressure PSIG
Acetylene 15.0
Hydrogen/oxygen 50.0
Hydrogen/air 150.0
Methane/LPG 50.0
Oxygen 143.0

Here is information for the Victor/Harris (Thermodyne) flashback arrestor:

Gas Maximum pressure (psig)
Acetylene 15
Hydrogen 30
MAPP 22
Methane 50
Oxygen 143
Propane 50

FB (FlameBuster) series flow
65749

FBHC (FlameBuster high flow) series
65750

[art vandelay]

I'd like to see proof of that. We can advocate that they change their information if this is actually true. It's not sound advice, one of the main points in this thread.

http://www.bethlehemburners.com/pdf/Alpha_Operating_Instructions.pdf

^^^they say "All Bethlehem burners are surface-mixed and do not require a flashback arrestor, which is required for pre-mix torches. However, the need for a flashback arrestor may be subject to regulation. Therefore, we advise all of our burner customers to check with their local, state and federal regulations regarding burner/ torch requirements."

good advice???

[chillrelaxglass]

Well only reason I believe its the pedal is bc that's where the damage seems to be.

[MUPH]

Just had the foot pedal looked over. There were no leaks in the valves and the solenoids were working properly. There was no damage done to the pedal. I should be hearing back about my torch today.

[raul24]

Arnold do advice the use of safety devices against flashback and backflow, DIN 8521. Some people don't use flashback/check valves because they feel it reduces the pressure. You should have flashback/check valves at your tank regulator, on your in-line regulator and at your torch.

[Skipjack]

Yes, I agree that Arnold mandates the use of flashback arrestors. My previous statement was based on a search of the burner catalog and also use of the search function of their website, which found only one mention of flashback, as an integrated feature of a flame polishing machine. On further investigation, the caution was located in the individual burner instructions.

"To prevent a back flow of gas into the air/oxygen hose or of air/oxygen into the gas hose suitable constructive measures must be arranged for the burner concept. If this is not possible, the main hoses must be secured by gas back-flow valves or flame arresters acc. DIN 8521."

[MUPH]

Many thanks to everyone that helped me figure this whole mess out and their generosity with my repairs. I now have my cleaned torch and foot pedal back up and running. GTT was crazy quick on their repair/cleaning turnaround and JJ was very helpful with his foot pedal.

If you want to prevent a freak accident like this one, you'll need to have flashback/check valves at the end of every torch in your set up. Not just one at the regulator and not just one at your Y valve. I spoke with Wally about this, and he said he's only heard of this happening once before. He said it could have been prevented if I had arrestor/check valves at the end of every torch (premix or surface mix) in my set up.

Western Enterprises flashback arrestors have both a flashback arrestor and a check valve. They can be found online on Amazon or Ebay for around $30-$40 per set.

[hammer]

I prefer the flashbacks at the Y and then using the quick connects with built in check valves at the torch.


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[hawkglass]

Check with the manufacturer of ur torches some come with arestors built in now

[chillrelaxglass]

This happened to me yesterday. There was a flashback between my torch (GTT Phantom) and my foot pedal (electric smut boy). I went to kick on my outer flame and only the propane came on. I heard a pop, so I looked under my bench and saw the blue flame coming from the outer ring oxygen line. I ran to shut off the gases before any more damage was done. The flame settled down and the burning rubber stopped.

My order of operations, from the tanks to the torch: Tanks, regulators, flashback arrestors, hosing, Y valve, quick connects, hosing, foot pedal, hosing, torch. On the other side of my Y valve is a Smith mini hand torch. There were not flashback arrestors directly behind the hand torch, only on the main line running back to the tanks.

Wally mentioned that this was his only explanation he had: He thought that there could have been a vacuum created if the hand torch was left cracked open. He did say he heard of this happening once before. I didn't understand this, because the flashback occurred between the torch and the foot pedal.

I was using all grade T hosing. I have done leak tests on all of my connections and had the whole set-up looked over by two other lampworkers when I was first setting up the shop. The location of the hosing burst was under my bench, above the ground. I can't think of anyway it could have been hot glass that melted through the hose. I'll be redoing all of my hosing, flashback arrestors, quick connects, foot pedal, and torch. I think I've hit every detail as to my set up. If I left anything out, please let me know.

If anyone has any insight on to this situation, let me know. No one seems to have a definitive answer.

Everybody, use flashback arrestors.

65672

65670

65671

Muph- I pulled out my smutt boy pedal lastnight and compaired it to yours. Seems that the check valves I have on mine you don't have on your pedal. Did you remove the ones that came on it? Mine are on both propane and oxy and they came on there when I got it. Just wondering why yours doesn't have it.

[piedpiper608]

I see in the last photo that one of the screens on the barbs for your torch? Is cloged to shit, maybe a pressure buildup could be a problem aswell?

[BORO]

Was just ordering color yesterday, and noticed the warning in the description....

"*not recommended for pre mix torches , due to a high number of flash backs" , flash arestors mounted behind the torch can alleviate this concern"
68137

[chillrelaxglass]

Those are all mech pedals tho right?

[BORO]

Says pedal is " non electric "

[chillrelaxglass]

Yea muphs issue was with a surfacemix torch

[MUPH]

Muph- I pulled out my smutt boy pedal lastnight and compaired it to yours. Seems that the check valves I have on mine you don't have on your pedal. Did you remove the ones that came on it? Mine are on both propane and oxy and they came on there when I got it. Just wondering why yours doesn't have it.

I installed and used my foot pedal exactly how it came. I made no adjustments to it.


I see in the last photo that one of the screens on the barbs for your torch? Is cloged to shit, maybe a pressure buildup could be a problem aswell?

The carbon you see came from the flashback. It was burnt rubber from the hose melting. The same thing happened to the barbs at the foot pedal. There was no clogging issue.

[chillrelaxglass]

I need to take a picture of mine. Maybe they started adding check vavles later I just noticed mine had checks in a spot yours didn't? Are you still using the pedal? Maybe just add checks. Like I said I was sketch about mine but I hooked it up and its working good. That is literally the only difference I see in our pedals it the check valves.

[istandalone24/7]

this just happened to someone a week or so ago, or so i read on FB. it involved a GTT handtorch....not sure what bench burner. scary shit....my FBA's are on the tanks....i think i'm going to spring for torch mount FBA's!

[CrassGlass]

After reading this thread, I ordered a set of flashback arrestors. Sorry you had some bad luck, but it was a good wake up call for me.

[hammer]

this just happened to someone a week or so ago, or so i read on FB. it involved a GTT handtorch....not sure what bench burner. scary shit....my FBA's are on the tanks....i think i'm going to spring for torch mount FBA's!

Hey do you have a link for the FB incident? I'd keep your FBA's at the tank and maybe get some quick connects with check valves. Propane won't make it through 2 FBA's.

[chillrelaxglass]

Maybe ill blow up today who knows. Bout to start switching it on and off.

[MUPH]

I need to take a picture of mine. Maybe they started adding check vavles later I just noticed mine had checks in a spot yours didn't? Are you still using the pedal? Maybe just add checks. Like I said I was sketch about mine but I hooked it up and its working good. That is literally the only difference I see in our pedals it the check valves.

I'm still using my pedal. Check valves or flashback arrestors off of the foot pedal would have no effect on the incident. The hose burst in between the foot pedal and the torch.

The only way to prevent this is to have flashback/check valves behind each torch.

[PyroChixRock]

I still use mine, too. It happened to me in like 2006 or 2007, and hasn't happened since that one incident. Set up is basically the same.