Flame arrestors at both torch and regulator?

[Joel_BC]

I just recently heard about this idea: that it's wise to attach flame arrestors at both the torch and the regulators, with an O/A rig. My rig simply has arrestors at the torch end.

I didn't know much about this, so I went to one of my industrial-supply outlets (we don't have any purely "welding shops" here in this low-population part of Canada). The guys at the shop had not heard of this and they were not stocking the ones for the reg end. There are a couple other industrial or auto supply places in town that stock some welding gear - but I didn't have time, because town is an hour's drive from my home and I had to drive back. So far, though, I haven't talked with the other guys. I wanted to gather more info so I'd know a little something.

So I've done a bit of a Google search. The "European Industrial Gases Association" has put out info about flame arrestors, and they recommend having arrestors at both ends of each hose in an O/A rig. This may now be common knowledge and common recommendation with the big city shops (e.g., Vancouver, Calgary, etc) - or in the U.S., for all I know.

What do you think? Would it be a good idea for me to add the arrestors at tha regs end?

[PilotDan]

I would think it is more important to have arrestors at the regs than at the torch. The reason is, if you're hoses get severed and are ignited, you're cylinders are vulnerable. Hopefully people with more experience than me can share some info on this. I have arrestors at the regs, but not at the torch on my setup. It's probably better for me to have them at my torch as well though..

[Sandy]

It's not uncommon to have simple check valves at the reg ends.

[rlitman]

Originally Posted by PilotDan

I would think it is more important to have arrestors at the regs than at the torch. The reason is, if you're hoses get severed and are ignited, you're cylinders are vulnerable. Hopefully people with more experience than me can share some info on this. I have arrestors at the regs, but not at the torch on my setup. It's probably better for me to have them at my torch as well though..

Your cylinders are vulnerable, ONLY if you didn't have check-valve/flashbacks on the torch in the first place. With those on the torch end, it should not be possible for mixed gases to be in your hoses. Yes, you could ignite fuel coming out of a break in a hose, but without any air in that hose, the flame will be quite manageable (just shut the tank valve), and a flame cannot propagate back up the hose, without oxygen present.

[Joel_BC]

Originally Posted by rlitman

Your cylinders are vulnerable, ONLY if you didn't have check-valve/flashbacks on the torch in the first place. With those on the torch end, it should not be possible for mixed gases to be in your hoses. Yes, you could ignite fuel coming out of a break in a hose, but without any air in that hose, the flame will be quite manageable (just shut the tank valve), and a flame cannot propagate back up the hose, without oxygen present.

Do you think the info out of the European Industrial Gases Association, then, is just crass commercialism? Only published to promore sales of some gadget (regulator mounted check valve) that some European manufacturer is offering for sale?

[rlitman]

Hey, its up to you, and your level of comfort, and desire for safety, balanced against cost.

For me, check valve/arrestors on the torch is fine. Having a second set can't hurt much (although it can decrease flow). However, if you follow proper safety procedures already (such as purging your lines before lighting the torch, and checking your connections for leaks), they won't help any.

[PilotDan]

Originally Posted by rlitman

Your cylinders are vulnerable, ONLY if you didn't have check-valve/flashbacks on the torch in the first place. With those on the torch end, it should not be possible for mixed gases to be in your hoses. Yes, you could ignite fuel coming out of a break in a hose, but without any air in that hose, the flame will be quite manageable (just shut the tank valve), and a flame cannot propagate back up the hose, without oxygen present.

Really???

https://safety.army.mil/soh/INDUSTRI...1/Default.aspx

[PilotDan]

If you have trouble with the above link:

What Happened:
Oxygen/Acetylene Torch Set-up Catches Fire and Explodes
When:
Monday June 18, 2001

Incident Photos:







Incident Description:
An Ironworker crew was modifying a temporary structural steel bridge using an Oxygen/Acetylene torch setup on a cart, a portable welder, and a grinder. Apparently the Acetylene hose develop a leak and ignited during the grinding operation.
The torch setup was not equipped with a "flashback" arrestor check valve and the fire traveled through the hose into the compressed cylinder.

A worker attempted to extinguish the blaze with a nearby fire extinguisher however he quickly determined that the fire was beyond his capabilities. The area was evacuated and the fire department was immediately dispatched to put out the fire.


Injuries:
Thankfully there were NO injuries.



Property/Equipment Damage:
The Torch Setup and nearby portable welder were damaged beyond repair. A structural engineer s reviewing the garage for possible structural damage.



Lessons Learned:
Workers must inspect tools & equipment daily and immediately remove defective equipment from service.
All Oxygen/Acetylene setups must have a "Flashback" arrestor check valve at the regulators, NOT the torch head, to prevent this type of occurrence. This little device would have prevented this fire.



Preventative Measures:
Literature on Victor "Flashback" Arrestors & Safety Check Valves are attached. Please take a look at all your torch setups on the project and make sure they have the required safety check valves to prevent this from reoccurring.
For improved safety use reverse flow "flashback" arrestor check valves The use of check valves on regulators is strongly recommended to reduce the possibility of reverse flow of gas, which can create a dangerous mixture of fuel and oxygen.
Mixed gases will burn rapidly once the torch is lighted and can explode in the hoses, regulators, or cylinders, resulting in serious damage to the equipment and/or injury to the operator. Reverse flow from one line to another can be caused by:

■A damaged or plugged tip
■Loss of pressure in one line
■A cylinder emptying in use
■Flashback
Caution: valves should be tested for proper function at least every six months. Careless usage, dirt or abuse can shorten check valve service life and require more frequent testing.

[MontyPitts]

Any of you who don't have a flame arrestor (also a "blowback" or Flame-check" valve) at the regulators should stop using your O/A rig right now. This is super dangerous. They aren't expensive, but can save your life. Having arrestors at the torch can save you a hose, too, but having them on the regulators is a MUST!

[rlitman]

Originally Posted by PilotDan

Really???

https://safety.army.mil/soh/INDUSTRI...1/Default.aspx

Yes, REALLY!

Whoever wrote the "Lessons Learned" section is completely misinformed.
The pictures are quite moving, but do not show the torch, or ANY proof that flame progressed up the hose, and into the tank. In fact, the clean and intact nature of the hose just inches behind the break, confirm the opposite. Had oxygen actually managed to get into the acetylene hose, the rapid (almost explosive) flame propagation would have ripped the hose apart (that CAN happen with no check valves and a blocked cutting torch tip, and there are images of that sort of horrible scenario floating out there).

I will admit (having seen this sort of thing first hand), that the flame coming out of the end of a cut hose will be quite intimidating. An acetylene flame without any oxygen mixed in is incredibly bright, and would be a huge flame considering that there was no torch valve or tip to restrict the flow of fuel through the regulator. The large amount of dark black soot, confirms presence of a large, oxygen starved, acetylene flame. That same flow of gas could also cause the hose to whip around like a cut air hose (especially, with oxygen at higher pressure in the other cut hose), spreading the soot in all directions, and making the cart dangerous to approach,
BUT,
a check valve, and/or flashback arrestor on the regulators WOULD NOT have prevented any of this. They will still allow fuel to be fed through an open hose (I've seen propane regulators recently that stop fuel flow when the hose has been cut, and something like that would actually help in this scenario), and will not stop a hose cut from causing a huge flame.

THE IMPORTANT THING TO UNDERSTAND, is that proper safety procedures and training prevent these sorts of accidents, NOT expensive and mostly useless gear.

In those pictures, I see an acetylene tank (which was abandoned with a presumably open valve), WITH NO WRENCH ON THE VALVE. All the operator had to do in this situation, was CLOSE THE VALVE. That's it. This is something that should have been trained on day one.
On that note, I also need to comment, that the pictures show a cloth strap securing the cylinders to the cart, which could melt/burn in a real fire, allowing a tank to fall. Chain really should be used here, and could be supplemented with a strap, if one wants a tighter fit. Also, had there been a sizable fire (and not just flames whipping out of an open fuel hose), there would probably have been enough heat to melt the fusable plugs on the acetylene tank causing it to vent, and there are no signs of that.

Yes, check valves and flashback arrestors are absolutely important, but it makes no difference which end you have them on.

[OAdoctor]

Flash arrestor restrict gas flow. They are basically a very dense stainless steel mess. Have a set at both the regulator and the torch will make a flash back more likely.

As to the european agency recommending F.A. on torches and regulators, I do not but much stock in that. The Mine Safety in the U.S. requires rock quarries with Victor torches that have Built in flash arrestors to have an external set of F.A. also.

One safety tip I do recommend is changing F.A. annually. They get clogged and dirt and can lead to damage to the torch.

[bebo]

I have read that arrestors at both ends restricts flow too much (as stated above). Since the major manufacturers include them as part of the torch body, I guess they know what they are doing. A few years ago, I was on a rush job, cutting some angle. I even looked at my hoses and thought " I'd better get those out of the way when this piece of angle drops to the floor", well, they weren't out of the way enough. When that red hot steel chopped the hoses, as another poster said, it was intimidating! My coworker tried stomping the flames out as I immediately jumped down from the platform I was on and shut down the valves QUICK! Good lesson in why you leave the acetylene wrench on the tank and only opened a half turn or so.

[PilotDan]

Interesting, well I guess I'm still learning something everyday! Thanks for the info everyone.