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Another flaschback arrestor question

So I’m setting up my Hoke torch in the workshop…it is fueled by propane (1 lb cylinder) and a 5 l/min oxygen concentrator. I’m ordering a hose-barbed flashback arrestor to attach at the torch end of the propane line, but in my reading, I came across reference to the possibility that hot metal could fall on the torch hose and ignite it. Since the arrestor is at the torch end, it wouldn’t prevent a fire in the hose from going back to the regulator and tank…is this a realistic concern, or not? Should I install a check valve or another flashback arrestor at the regulator?? Or would this be overkill?

I have the same torch configuration and it replaced check valves, flashback arrestors, regulators, tanks and the whole ball of wax (so to speak). I currently don’t have flashback arrestors or check valves anywhere. I am not sure if there is enough pressure differential to seat a check valve. Flashback arrestors are another story. I am hoping that someone can answer this question as I could easily add flashback arrestors to my torch, but it would make them heavier, especially since I use a very light tinman hose. As for hot metal igniting the hose, that could happen regardless of how your torch is configured. I guess that flashbacks at the hose would make sense in this case. Looking forward to input from others…Rob

Maybe it’s my lack of skill, but this setup works with Meco except not with the smallest tips, and it doesn’t work with the Little Torch.


Thanks! I will give it a try and post what happens. FYI, Home Depot sells a refill system and cylinders that seems to work well…Rob

My experience with paired gas and oxygen hoses is largely from working in the commercial boat building industry. I can’t recall a single incident where a hot drop of metal burned through a gas line. I have seen hoses come apart when a sheet of steel fell edge wise on them but that was in a completely different environment from my little shop.

Has anyone ever done a simple experiment with old hoses and a direct pour of hot metal on it? I will probably give that a try today myself. I am not diminishing anyone’s concern for safety. And since I am moving from Prestolite to my brothers type of set up I think that it is information that is good to know.

Don Meixner

---- Robert Meixner wrote:

Ted here,
Over on this side of the pond, I can buy a box of neoprene O rings 250 off plus, in all sizes and therefore replace those that harden over time in my hand held prestolite and BOC torches.
Saddened to here your moving away from “P”. Ive replaced my O rings and its as good as new. being all brass .circa 1920’s.
any further help you might need, please ask.

Hi Ted,

In my case I am tired of running out of acetylene on a Friday nite and not being able to get it again until Monday am. Also I plan to travel with the torch to various kids houses around the country. A jar of propane can be bought at the hardware and all I will have to carry is my O2 generator which is lighter and easier to pack.

I’ll keep the presto around for large annealing jobs and starting the forge.


---- Edward Vladimir Frater wrote:

Hi Don,
Yes, I understand.
Here any torch that will run or is designed to use “A” will also run v/well on propane.
As im sure you know.
re using “A” in other folks houses/schools etc, yes “P” is much safer too.

When im away , tho its been some yrs since Iput my rig on ther road, I refill my portable ali “O” tank to 1000psi and use a 7 lb “P” tank for any soldering work.
Here at home! I have outside my 47kg "P"tank which is piped into my w/shops to my main forge station running a 2in dia burner, some 150,000btu’s heat and 2 ft flame! .
As of interest use s/steel gauze to provide an oxygen free flame area.
a quick second from that into the pickle keeps most metals oxide/ fire stain free.
Im sure you follow.
Ted. .

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I got my torches to work with flashback/check valves on both O2 and propane. I discovered a hose leak that I had previously missed and caused the experiment to fail. The torches do lack some capacity and I haven’t tried doing a melt with the Meco. More when I know it…Rob

Hi Rob,
your comment that the torches lack capacity, you may well know the reason but ill post it anyway.
these 2 fuel gases have the following differences.
“P” has a much higher calorific value than “A”,
however “P” has a much lower flame rate ie its ability to oxidise even with the use of “O”.
This accounts for the following, you cannot weld steel with “P” but you can weld steel with “A”.
Also “P” is inherently safer to use than “A” ie flash back arresters are not so important with “P”. However if your cutting up scrap ,then “P” plus “O” to heat to oxidising temp then turn on the “O” cutting jet and away you go.
Also ins co here in the UK dont like “A” around homes, consider it an unstable gas. they tolerate “P”
“P” beyond the mains is always “P”.
final thought all regulators and hoses and torches here in the UK are identical so interchangeable.
Irun my “P” lines at around 15 psi. “O” around 6/7 psi. for my hand soldering station torch.
Gas cutting steel “O”, around 30.psi. Thats for up to 1in thick plate.
up to 1/4in its quicker to cut with a cutting disc, also more accurate for me!!. Needed the thick stuff to repair trhe log splitter I made, broke it on a 2ft dia oak knotty butt. Im blessed with my own oak wood of some 4 acres, its growing faster than we use it and we run on wood 24/7. Around 5 tons a year. 1 straight piece in 50!!. impossible to use a log processor.
Have fun and make lots of nice things.

Back to installing flashback/check valves on 1 lb. propane and O2 generator Meco torch systems. I was able to install a flashback/check valve on both the propane and O2 side of my torches and run them with very little diminished capacity. Did a 1 oz. silver melt with no problem. My sense is that there is a minor loss due to the pressure differential across both valves. I would be interested in knowing if there is a flashback only with no check valve available as it is the check valve that probably creates most of the pressure drop. My original problem was a leak in my O2 hose. I am flying by the seat of my pants here, but the question was asked by another poster. If anyone has more accurate data or advice about this setup, please let us know as we are dealing with shop safety. Thanks…Rob

Hello Rob,
Thanks for your replies…It seems I read here on another of these threads that a flashback arrestor or check valve was not needed on the oxygen side when using an oxygen generator because there is no tank, therefore no quantity of oxygen to blow up…but IDK whether it would be possible to start a fire somewhere in the generator mechanism or not…so maybe someone else can speak to this issue.

Oops! I said oxygen generator when I meant oxygen concentrator…meanwhile I was looking at other threads and noticed that in one someone said that the concentrator has a built in check valve…can anyone confirm this?

I have always assumed that to be the case, but I visited my local O2 generator re-builder and he showed where there were small reservoirs of O2. This is well inside the device, so a fire there would be a real problem. In the end, I don’t think that the pressures in this type of system would lead to a problem. I don’t think that I need the flashback/check valve on the propane regulator at all. My experiment was to see if the torch would work with them installed and it will. I look forward to seeing if someone can answer our collected questions. I do see that the systems that Rio sells appear to have check valves installed. Maybe a Rio Technician could set us straight.

Hi Rob,
Ive thought about this FBA question since you have asked several times.
To me the installation of FBG’s is really aimed at industrial users, who run their gas supplies at different pressures, for example gas cutting.
However their use is a safety factor, thats worth having wether its a S little torch or a big gas cutting one in a scrap yourd.
also most ,latest hoses also have in the brass end connectors nowa days one way valves with the dir of gas flow signed by an arrow.
I used such a hose recently and wondered why it didnt work. Reversed it and it did.
They the FBA’s also come here in the UK in different flow rates of gas.
As your over there we say, only an industrial gas equipment supplier will have the nessesary tech info on what type you might need.
Buying online is not really valid where safety is an issue.
Finlly I mention to all other folk who might not know, fuel gas fittings have the fiting fittings with threads the other way, so you cannot interchange them withv O2 fittings.

I did some further research on oxygen fires with concentrators and it seems there is a risk of these…regulations require a “firebreak” at the concentrator and at the cannula nearest the patient. One brand of these is the Firesafe Cannula Valve and the Firesafe Nozzle, the latter installed at the concentrator. I can’t seem to find these for sale except in bulk at ebay, so I may check my local medical concentrator sales outlet. They should be only a few dollars each. Otherwise, I guess I will go with a flashback arrestor at the torch. HTH, royjohn

Well, I should search more thoroughly before posting…I did find the cannula valves for sale individually and also found that they can be used at both ends of the oxygen line for max safety. This because I couldn’t find the Firesafe nozzle for sale individually for use at the concentrator…So just install the Firesafe Cannula valve at the torch and then another one at the concentrator nozzle. You will just need to have a nozzle on the concentrator and then splice the Friesafe cannula valve into the line just past it. Takes a couple of small clamps, but that is all…I found these at and bought two for about $23 with the shipping, so that’s the way that I’ll be going. A flashback arrestor on the propane line at the torch and one of the cannula valves, with a second cannula valve at the concentrator end. Slight pressure drop with both safety devices, but a small price to pay, I suppose. The Firesafe valves are plastic, so slightly less weight on the line than a flashback arrestor would be. Best I can do for now. HTH, royjohn

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Bit of unintended humor with “Friesafe”. I hope not…LOL

I always have flashback arrestors at both ends. Overkill? Maybe, but I’d rather not be that one in a million.

Ruthanne Robertson