Oxy/Acetylene Flashback Arrestor Issue

admin

I bought [ame="http://www.amazon.com/Flashback-Arrestor-Sets-Style-Torch/dp/B002BXR8AO/ref=sr_1_6?ie=UTF8&qid=1370667550&sr=8-6&keywords=flashback+arrestor"]these Western Enterprises flashback arrestors[/ame] from my LWS. The first pair seemed fine, but the oxygen FA would "burble" or tick when run at low pressure, as if the check valve was not opening fully, just tapping open and closed. At first I thought it was my torch, but it happens even without the torch connected. I returned them for another set, and BOTH of the new ones have the issue. Before it was mostly an annoyance, but didn't make the flame pulse too badly. Now with both valves clicking, it is very noticeable, and I'm having issue with my flame size pulsing when using small tips. (I'm using a Harris 85 torch with 0-2 tips). At this point I assume I need to switch brands, as these ones appear to be designed for higher pressure applications, and my 3-5 psi stuff is just asking too much. Does anyone make a flashback arrestor specifically for low psi, or do I just need to buy a better quality part? I wasn't impressed by the fit and finish of these parts, and they are 1/2 the price of Victor ones. I can open the normal check valves with gentle blowing through them, but the valves in the FAs are very stiff.
Reply:Sounds more like a regulator issue.  Does it reproduce the problem without the flashback arrestor too?
Reply:I'm not sure if I've ever explicitly tested it with just the torch and no check valve or flashback arrestor, but the oxy reg is brand new, and the acetylene side never buzzed until I got the new set of arrestors. I'll test the regs and torches individually next time I'm in the shop.
Reply:Probably not the regulators (they are upstream of the check-valves and flashback arrestors).And it's not the flashback part, as that is typically just a fine mesh screen or finely porous sintered metal piece inside the fitting (so that a flame or flashback can't go past the screen).It sure sounds (no pun intended) like the check valve portion is sticking or pulsing.And 'recent' Harris #85 torch handles (are you using a Lincoln/Harris Port-a-Torch, by chance?) include Flashguard check valves already.  Which appear, despite the name, to just be check valves.Standard welding pressure for those 'small' tips are 3-5 psi, which is nothing really too low or anything.  And actually, the Harris 0 and 1 welding tips (acetylene) call out for 1 psi oxy and acetylene, the #2 calls for 2 psi, the #3 calls  for 3 psi, etc.Normally, the check valves should open with a very low pressure (you found that out by just gently blowing on/through them ( WARNING Spit or dust inside the oxygen lines can be dangerous!!!!  Not quite as badly dangerous as on the high-pressure side upstream of the regulator, but still dangerous.)The Victor catalog indicates that their flashback arrestors (Flashbuster) can produce a 5 psi pressure drop (pressure difference from inlet to outlet of the flashback arrestor), depending on flow rates (and the little acetylene welding tips don't really have a huge flow rate at all). Maybe you have to slightly increase the regulator pressure settings to account for the pressure drop through the flashback arrestor?If that doesn't work, I'd just say to ditch the 'off' brand arrestors and just put some Harris or Victor ones on and be done with it.  The best laid schemes ... Gang oft agley ...
Reply:I agree, it's pretty clear to me that the check valve is rocking or flapping on one side instead of fully opening at low pressures/flows. One of my 85s is old (Harrison Calorific, made in Ireland), another is the newer one that comes with a porta torch kit (Harris, Made in Poland). I am not using a porta torch setup, I have 40CF tanks feeding the torch through a harris 25C (acetelyene) and a uniweld RUH8310 (oxygen) regulator.The Flashguard check valves are what I replaced with the western flashback arrestors, wanting a safer setup. I've tried increasing pressure, but then I just end up with a hotter flame or over sensitive flame control at the torch valves (which is already touchy on these small tips). I've been trying to figure out what brand/model I can buy that will work in this application, I assume I don't need a high flow one, as I'm really using very low flow. What I do need is nice sensitive, easily opened check valves.