Torch Safety

I manage construction of large projects. Most of the work I supervise does not involve welding and cutting operations, but occasionally it does and I am always expected to be knowledgeable about site safety.

My question is related to the requirements for flame arrestors/flashback arrestors on cutting equipment. In my mind, a safe system for a construction site (which takes more abuse than a shop) would have flashback arrestors on the torch to protect the hoses, and an additional flashback arrestor on the oxygen regulator to protect from flashbacks that occur as a result of hose punctures or impurities igniting in the hose.

My question is how much modern equipment made by reputable manufacturers wouldn't already have this internally? Are there standards requiring it on all new manufactured torch/regulator? Is it most likely that these components would need to be ordered separately? Do most manufacturers just include it even if it is not required?

Belt and suspenders is ok but keep in mind that flow becomes slightly restricted so slightly more pressure required. It is not a big deal. You should be more concerned with regulations. In most jurisdictions a small fire extinguisher is required on bottle cart. Also enforce a fire watch extending half an hour after operations cease and including lunch breaks. Make sure people operating are properly trained. ie: certified welders. They do not have to be top qualified but at least have some sort of welding course under their belt. Rarely do you hear or read of a news report involving a flashback or torch flare up. You all the time hear reports of fires caused by the generic term "welder's torch" even when there is no torch around and only electricity was used.
Some torch manufacturers do include a antiflashback/check valve in their torch bodies. In most jurisdictions it is mandatory now that the vavles be installed.

Genmake,

If you are actually MANAGING them, then, definitley have flash back arrestors on all your lines. If you are in a home shop, do as you wish. I have only worked in one major shop that did NOT have arrestors, and that is the ONLY shop where I have ever seen a flashback, burn, occur.

I won't go into heroics about how I saved the shop, but it was not a good place to work. All part timers. Dumb. And the Bosses were Bosses, which is, of course, dumb, else they would not BE Bosses, they would be producers.

Spend a few bucks and insist that they be installed on all hoses. You may actually save a life.

George

I agree, I have a set at the torch and tanks, they are cheap enough that you can afford the protection.

I see newly supplied CNC cutting machines shipped all the time with either no flash back suppressors on the torch supply lines, or they have installed simple check valves which are not rated for flashback suppression. One annoying case was for a good customer who bought a machine from a major player and then found they could no longer cut anything over 3" plate even with just a single torch. They used to routinely cut 6" plate with 4 torches. The manufactures technician in trying to solve the problem removed all the flash back suppression devices and the customer still couldn't cut anything over 3" thick. After a couple weeks of futzing around they had no solution. I simply chuckled because I've never seen the specific torch cut over 3". They simply lack the capacity to handle the required amount of fuel and air. My solution was to make up new torch mounts to handekl their old reliable Victor torches, replace the flash suppressors and voila, the machine could cut 6" plate with 4 torches again.

So yes, manufactures do ship equipment without flash supression. It's truly a case of buyer beware.

They also ship machines that violate the primary E-Stop rules.... Each switch in the E-stop chain should be wired in series, so if any switch is pressed the main contactor trips out. The same manufacturer wires each switch output as an input into the PLC, so that pressing an E-Stop brings the machine to a controlled stop. Of course when the PLC craps out the machine won't stop with an E-Stop pressed, and it continues happily on it's path to mowing down the operator...

The same manufacturer refuses to give out electrical schematics of their machine...wonder why?

Over here its commonly std to have bottle, regulator flash backs then the hoses, check valves at end of hoses then torch. Most new hoses come with integrated check valves. Check valves in the hose will be enough to stop flames going back from the torch into the hose. Flashback arrestors on the bottles will protect them from any possible down stream error. Its becoming ever increasingly common that acetylene is not used on site for cutting only propane or propylene. There both a lot safer in the event of a fire.

There is over here guide lines regarding re inspection - replacement of hoses and regs based on age - condition. Most regs have a date stamp regarding this.

By far the biggest risk though is the sparks - fire risk - process and the resulting fumes. That needs at least a basic risk assessment done at every location the equipment is used at.

Im willing to bet that actual equipment faliuer has probably caused only a few accidents compared to the fires and such that happens with most hot working processes.

George, I totally agree with you. Flash back arrestors are definitely the best. You will need to choose an appropriate size and ensure that it is in good working condition for proper functioning. Try following the manufacturer’s recommendations to keep the equipment well maintained.

The flash back suppressor is supposed to be on the torch. Over the years in PDX alone, I've repaired 4 systems that had flashbacks. One happened on a machine a couple hundred feet away from the one I was servicing. (they wiped out 5 of the 8 Oxyfuel starions by removing them from the gantry with a hunk of 4" plate...)The machine had and older festoon style carrier for the hoses and was running Natural Gas for the fuel gas. Piercing heavy plate, the operator got to cose to the puddle, or the puddle climbed to the tip. A flashback occurred, followed by a high pitched whistle which was the obvious clue that something was amiss. It got my attention and I looked at the operator who was standing right beside the control as if nothing was wrong. Before I could wander over, a loud bang occurred, followed by a hose rupture and a hose whipping around like a frantic snake.

While repairing the damage later, it was noted that no flash backs were in place on the system. They were either never installed, or removed by soem bozos attmept to get better performance from the torch. They also made the mistake I see that is very common. They were using Acytelene grad hose for the fuel gas, which is inappropriatte for Natural gas or Propane in the first place.

From my perspective in the Fire Service: All newer torches come with check valves to prevent gas mixing. The regulators also contain check valves ,at least the better ones. While this is a good thing it in itself is not sufficient. All mechanical parts wear and thus leak. A good operator will know when it is time to service his tools ,but most belong to the Company so they just stay in service until failure. The flash arrestors are there to prevent the flame from traveling down the line to the regulator and blowing it out possibly causing a large problem (read fire /explosion or both). I prefer to see the arrestor on the regulator side of the lines as it is less likely to get knocked about and removed by the operator. In my arguments about this with contractors when issuing hot work permits, I point out that it is a requirement for this site and is listed on the permit that they must sign. I do not issue one without seeing these either on the regulators or on the torch. Checks may work to keep a flash from the line at the torch ,but my argument is that the line can be cut or burned through and that the arrestor on the regulator will both prevent a problem and save the regulator. A Flash arrestor is less expensive than a regulator and most definitely cheaper than a fire. The best is a pair on each line at both ends

This got me curious, after a bit of goggling seams the ideal is both at the torch and at the regulator. Less ideal at just regulator end. Just at torch end leaves the hoses unprotected and in some ways there very very exposed to accidental damage compared to damage than the rest of the system. Check valves should be in there too, but a good few flash backs have them integrated + there common on the hoses over here too.

Any flow restriction should be delt with geting sutable sized hoses + flash backs, not removing them.

Another Key thing that praphs should be on a cart is a can of leak detection spray, changing bottles - torches and such theres a very very real leak risk present. Its not uncommon here in the uk to encounter bottles with leaky valves, damaged regulator stem seats etc, Dead simple to identify and fix too so long as you have something that bubbles :-)

We are also required to have a firewall between the tanks. This used to be only in the bottle rack but now it is required on the torch carts as well.

There is plenty of material on the subject online, and it's worth a read.

A good procedure is one we used at the welding school where I ran the toolroom, which was to have someone check/shut off all cylinder valves at end of day.

The MSHA folks have the greatest incentive to be safe, since explosions underground with no immediate rescue are a Bad Thing. No place to run and all that...

American Welding Society overview:

www.aws.org/technical/facts/FACT-28.pdf

Here is What OSHA has to say. Note that the only clear thing in their response is that they will continue to enforce.

Worker Type: Private Employee or Employer
Topic: General Industry
Quest ID: 35282702
Question: Question about flashback/flame arrestors for oxy-gas heating and
cutting torch operations:

1 - Are flashback arrestors required?

2 - If so, are they required on both the torch and the regulators?

3 - Finally, are any of these requirements a manufacturing requirement,
meaning products without the required integral safety devices would seldom
be available from reputable manufacturers?


Sent: Friday, March 29, 2013 10:00 AM
Subject: RE: General Industry question

"We reviewed the latest ANSI Z49.1-1988 standard and noted that protective equipment devices for service piping systems were eliminated; however, paragraph 1.3 of the above standard (attached) stated that those requirements were only deleted from ANSI Z49.1-1988 to avoid their being included in two separate standards under separate auspices. The paragraph also stated that the protective devices are still considered necessary and important for safety, and therefore the requirements must be followed. The requirement for protective devices are contained in the list of ANSI/NFPA standards found in paragraph F1.3 of ANSI Z49.1-1988.

The removal from ANSI Z49.1-1988 of the requirements for protective devices does not warrant a change in the OSHA requirements. The Agency will continue to enforce the requirements of 29 CFR 1910.253(e)."

29 CFR 1910.253 can be found at - http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=9854.