oxygen regulator blowout

[evfreek]

Hi. A friend asked me if I had a spare oxygen regulator, since his was broken. I brought him one of my spares (in poor condition, but still worked) and took a close look at his, since I am interested in this kind of thing . Yeah, I know, but that's why I am interested in blacksmithing too. Failure intrigues and inspires me.

First, a safety note. When the safety instructions tell you to stand clear of the front of a regulator when you turn on the gas, pay attention! Many of the scary failure modes involve projectiles shooting out along the axis of the control knob. When you turn on the gas, stand behind the cylinder valve on the opposite side of the outlet. These projectiles move fast enough to penetrate safety goggles and leather aprons.

Anyway, the diaphragm in his regulator got ruptured. The safety vents on the regulator did their job and gas was diverted radially away from the front of the regulator body. Interestingly, the overpressure relief did not fail. These safety valves can fail closed, and should not be relied upon. Another indication of overpressure relief failure is that the needle on the low pressure gauge was permanently bent over at 60 psi. The gauge, therefore, was blown too. I then turned my attention to the inlet pipe. I unscrewed the 1/4" mpt fitting and sighted through the gas passage. No sintered filter! This is a big problem. There should be a sintered bronze inlet filter. Even cheap regulators should have this feature. A sintered filter has two important functions. First, it prevents particles from entering the diaphragm valve and sticking it open. If that valve gets stuck open, the regulator could blow. Typically, the overpressure valve will actuate, and the regulator can either be cleared or repaired readily. If not, the regulator will be ruined. Second, and more subtly, the bronze filter shortens the maximum free path of high velocity particles. This is very important, since this quantity is highly correlated with regulator body ignition potential. If your regulator body catches on fire, you are in big trouble. High intensity burning metal flames (much hotter than oxy-acetylene flames) can shoot out 4 feet from the regulator body in random directions. These flames can be deadly if you are anywhere near the failing regulator. It is recommended that an inlet filter be employed. My friend is an ex-firefighter and EMT, so he knows this very well. He not only cracks the valve before pressuring up the regulator, he also connects the regulator loosely, then intentionally allows it to leak around the inlet fitting for a few seconds to encourage the initial stream of particles to curve around back to the the threads of the fitting. Then, he tightens it up. This is a valuable tip.

The regulator is a Cutwelder brand. I looked around on the Internet for this, and it seems that it is marked by Century and Lincoln in some of the low end kits, selling for between $175 and $250. This is a step up from the cheap import kits, and one would usually expect better. The warranty looks like 1 year, compared with 3 year warranties on the Harris and 5 year on the Victor brands. I replaced this failing regulator with a Victor 200 series (medium duty) which seemed to perform well.

Be safe out there. Those of you who are using propane instead of acetylene (raises hand :cool:) in an attempt to be safer should remember that oxygen requires much attention to safety as well.

[moya034]

Also, make sure the regulator screw is backed out completely, and open the cylinder valve SLOWLY.

[Bryce Masuk]

I tryed fixing one of mine after many failures it went bang with a burning smell of rubber,

I figured the spring had weakened as nothing inside was damaged or leaking

could have been one of those mistakes worth a life

[WM Mark]

How do you clear or repair the overpressure valve after the gauge has had the blow by around the face of the regulator?

[Frosty]

Welcome aboard WM Mark, glad to have you. If you put your general location in the header you'll have a better chance of meeting up with members living within visiting distance.

To address your question Re repairing a gas regulator. Take it to the welding shop so they can dispose of it properly and buy a new one. If you take it back to the place you bought it they'll likely exchange it for a new one. The big brands, Victor, Harris, etc. exchange their old regulators no matter how old. 

IIRC nobody has repaired gas regulators since the depression if not before it's just too great a liability for the price of a new one. The last I talked to Rocket at my old Lincoln dealer about regulators he said they destroy them so nobody will be tempted. 

Frosty The Lucy.

 

[Irondragon Forge ClayWorks]

I would replace the regulator as Frosty recommended.

I can't control the wind, all I can do is adjust my sail’s.
Semper Paratus

 

[LeeJustice]

Make sure that flashback arrestors are installed on both oxygen and fuel lines.

[JHCC]

Flashback arrestors can be either regulator-mounted or torch-mounted. Some torches come with the arrestors built in, but I don't know whether or not any regulators come with built-in arrestors these days. The add-on versions I've seen for sale are all designed for the outlet side of the regulator, not the inlet side as described (as "sintered filters") in the OP. I will admit, however, that my experience in this area is limited.

[Frosty]

That's a good question for the welding supply. My All States oxy prop torch has the arrestors in the handle. The propane flows at a very low psi making a flash back a very real possibility without arrestors.

If arrestors weren't between torch and regulator imagine an oxy acetylene explosion taking place IN a regulator. Shrapnel city.

Frosty The Lucky.

[JHCC]

I added arrestors between the torch body and the hose on my Victor oxypropane rig, as I didn't like the idea of a flashback happening inside the hose. One unexpected benefit was that they shifted the center of gravity of the torch slightly backward, making the torch just a little bit easier to handle.

[Frosty]

I don't recall, is your torch a purpose built multi fuel or a conversion? I have trouble imagining Victor not putting arrestors on their oxy fuel torches. 

Frosty The Lucky.

[JHCC]

Purpose-built; it's a Victor WH411-C, which comes with built-in check valves, but not flashback arrestors. It came in the Medalist 250AF outfit that I got a couple of years ago back; this outfit has been replaced with the Medalist 250LP, which has a WH270FC torch handle with both check valves and built-in flashback arrestors. I don't know if Victor is still making the WH411-C; a bunch of places list it for sale, but I don't see it on the ESAB/Victor webpage.

[Frosty]

The check valves were the old type flash back preventers, the current arrestors don't have moving parts so they last indefinitely. Well . . . that's what I heard for what second hand  hearsay is worth.

Frosty The Lucky.

 

[bubba682]

 Any time i got a regulator failure i get new ones i ain't qualified to fix'em and i wouldn't attempt it thats why we have repair techs who are certified.Those  flashback /arresters arn't cheap but they'll stop a catastrophe i like brand name not the i got them cheap off the interweb brand when it comes to torche gear..