Welding tank Check valves

[37chief]

I have two welding, or cutting tank setups. One has check valves, the other doesn't. Just what can happen without these check valves. I have heard in the past the flame can travel up the hose into the acetylene tank. Is this even possible? Or what else can happen? Stan

 

[JD Seller]

They are flash back protectors. I have them on one of the newer torches I have. I dislike them on the torch head itself as it makes the torch longer. I think they will work fine installed at the out let of the regulator too.

Now I have three other torch sets and they have nothing on them. I do not worry as I always turn the fuel off first and then the oxygen. This keeps the flame out of the internal part torch tip. Flash backs can happen if you smoother the tip and put out the flame or if you shut off the oxygen first then the fuel. The flames can follow the fuel back inside the hose/tank.

 

[jon f mn]

They are required by law for any torch used in a commercial environment. Mine has them. But I never even knew what they were til I opened my shop and got told I needed them. They seem like fairly cheap security to me. Mine are on the gages rather than the torch head as well.

 

[Steve@Advance]

I used to work at a place that made condenser and evaporator coils, brazed the fittings and return bends to the coil slab. The brazing line had a liquid oxygen tank outside and the fuel was plumbed in natural gas.

When I first went to work there the torches didn't have the check valves. Not sure how it would happen, getting the pressures set wrong, low oxygen pressure, but some how every now and then one of the hoses would explode! Always happened right at the torch end.

It was enough to blow the hose out, don't remember which one, but it was really loud. Never any continuing fire, no one ever got hurt, but the potential was certainly there.

I put check valves on all the torches, never had it happen after that.

 

[4play]

There are check valves and there are flashback arrestors or both. Check valves don't stop flames, they stop gasses from travelling back up the hoses. If you ever hear a pop or popping, that is a flashback, usually something annoying but can be very dangerous. If you hear a hissing or squeal, that usually means a flame is burning inside the torch/hoses, better shut the valves off immediately.

 

[MarkB_MI]

You really shouldn't use a torch without check valves; they're cheap insurance. My torch set came with a pair.

As someone else said, <a href="http://store.cyberweld.com/wechvasretoh.html">check valves</a> are not <a href="http://store.cyberweld.com/smflarsre.html">flashback arrestors</a>. Flashback arrestors are much more expensive. I suppose I'd want them if I used my torch on a daily basis.

Check valves simply prevent gas from traveling backwards through the hose, resulting in a flammable mixture in the hose and cylinder. It's more likely that oxygen will travel into the acetylene hose, but the opposite could happen with an empty O2 tank.
AWS on check valves and flashback arrestors

 

[504]

Victor has a set out that has them built in to the regulators. As do you really need them,my large torch cart survived the fire but the regulators and hoses did not. I got the cart because our tanks were on it, and the insurance said it all had to go to scrap. All because there were no flash back valves.