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2004 O2 fire


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Just a good warning to all of you who deal with O2 regularly. I see a lot of people who are very cavalier about handling O2. 100% O2 is not to be taken lightly. It's more dangerous than Acet in many cases.  Everything burns in the presence of HP 100% O2.

Thought I'd post these picts and let you all see what happened to me back in July of 2004. For the record I am trained in O2 cleaning for Hp O2 service and special procedures for gas mixing so I knew what I was doing at the time.

Several years ago I worked part time for a dive shop. We frequently tranfilled O2 using the booster pump in the photos. I was mixing gas for our bank system. Hook up a new bottle of O2 to the inlet and slowly dump of into the bank to be filled until they equalize. Then turn on the booster, slowly sucking the O2 bottle down and pumping up the bank. Once the O2 bottle was depleted ( pressure in tank would vary depending on level being boosted to) unhook the O2 bottle and repeat until desired pressure in bank was reached, top with air to achieve final mix.

On this day I had already emptied 3 280cf bottles of O2 and had hooked up the 4th one. Bank equalized at around 1300 psi and I slowly started the booster. I generally monitor how the system was running by checking the temp on the output line. If the line became very warm to the touch, not as hot as hot water from a tap, I would slow the unit down or switch O2 bottles.

BTW I was the [Picky] one about mixing at the shop. If I had been any of the other guys, I'd have turned on the booster and walked away and ignored it for a while, returning later to turn it off and change bottles. I've seen guys get things so hot you can't touch the tank being filled, and it's sitting in water. But NO I had to be the responsible one and stand there and monitor it.

I had just checked the line and it was slightly warm when this happened. As you can see from the photos something went wrong. I wish I could find my before picts. If you look at the bottom of the booster you will see 2 loose lines. That’s what is left of the outlet lines. The 1/2"SS HP fitting that went into the booster, 5 of the SS 1/4" tube to 1/4" npt swageloc fittings that attached the 2 SS HP Tees, and the interconnecting 1/4" SS HP tubing is GONE, vaporized in an instant. If you look closely you can see the remaining half of the 6th adapter to the first tee in the bottom of the picts. The 2 tees survived but looked like someone burned all the threads out with a torch. My guess from the damage is that the fireball had to be about 24-30” in dia. in order to get all of my arm.
The yellow circles show where there were several 1/4" 316 HP tubing adapters and 1/4" 316 HP T's. That along with 20 some inches of HP SS tubing that flash burned. Note the fittings and tube just don't exist anymore. Poof gone in an instant. Not melted or blown off, vaporized. The event happened so fast I don't even remember it. The fire went out because there was insufficient O2 to maintain it, but the stainless steel WAS the fuel.

I wish I could have gotten the picts they took of my arm at the burn ward. They wouldn't give them to me, guess they thought I wanted to sue.

My hand was just about where you see that partial fitting. 3rd degree burns on my right hand from finger tips to elbow, about 85-90% of my lower arm. Lucky for me the heavy calluses on my hand from doing concrete ( my primary job) protected my hand and fingers. Basically turned the palm of my hand into shoe leather. Flash charred all the other skin but was over so fast there was little depth to the burns. One week in the burn ward and lite duty for the next couple of months, you can hardly see the scars. Small amounts pin point amounts of SS spatter on my upper arm, chest and face. Thank god for glasses! Burns stopped where my skin was protected by my cotton t shirt. I'd have been in real trouble if I'd been wearing polyester as it would have likely fused to my arm and chest.

Somehow I managed to shut off everything except the incoming O2. I don't remember anything for the next few minutes, but I had to have done it. The only reason the O2 wasn't turned off was that I would have done that with my right hand while my left hand was shutting off the other valves. Shut valves on left with left hand, shut valves on right with right hand. Talk about muscle memory!

Now what happened. Possible causes,
1) Foreign matter into system from valve (spider web perhaps)
2) Foreign matter from system ( piece of brass from valves due to poor maintenance)
3) Oil contamination from air system (due to poor maintenance)
4) Adiabatic compression ( heat simply caused by gas compressing itself in a system at a bend or restriction.)
5) Check valve failure on output of booster.
6) Operator error (unlikely due to the fact I was watching the pressure going in and it couldn’t do that if a valve was closed.)

We talked to the mfg of the booster and sent it to them for analysis. They were unable to determine the cause because most of the lower piston and valve assembly was vaporized in the flash. However they say this is not an uncommon occurrence in the airline industry where they use these boosters to fill O2 bottles for the flight crew. Their solution put the unit in a blast cabinet and LET IT BLOW UP! Go figure. Our sister companies compressor techs believe check valve failure due to similar failures on HP compressors. When the valve fails hot discharge gas flows back into the piston and is recompressed raising the temp. only a few cycles would have been needed to severely raise the output temps.

One other thing, the day after I got out of the hospital a woman with whom I was familiar died in an O2 explosion in a shop in Florida. Most likely cause was oil contaminated dirt that entered the valve when the customer dropped the tank in the parking lot. Tank exploded when she hooked up the partially filled tank. Tank valve open, fill valve closed. Valve disappeared, tank ruptured, she was killed, 4 other injured seriously, roof torn off and the shop trashed. Last pict shows the cylinder she was filling after the accident.
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Many of us who work with metal regularly deal with cylinders of 100% O2. Oil and O2 do not play well together at all. It takes almost nothing to get oil to ignite when in contact with 100% O2. You don't need an "ignition" source in the tradition sence. Simply the gas slamming int the oil can lite things up and things go from bad to worse from there. Reference the tank pictured above as a good example.



I see a lot of guys with O2 gear all covered in grease and oil. It wouldn't take much to get a small bit of that inside a vale when changing cylinders. Also never use paste to seal O2 connections. Even telfon tape is questionable at best ( they do make O2 "safe" teflon tape) Never check for O2 leaks with anything petroleum based. They make O2 safe leak solutions. If nothing else, a tiny drop of Dawn in a container of clean water will work with minimal safety issues. You just need enough to get it to suds and no more.



Never attempt to rebuild an O2 reg yourself. Even the oils from your fingers or a small piece of lint from a clean cloth can cause ignition if it's on the HP gas side of the reg. There are specialized procedures for cleaning O2 regs. Leave it to the pros. Most welding supply places can send regs and torch gear out for rebuild. If not there are a couple places online that offer these services. It's a whole lot cheaper than dead to get this done.



One other thing. Never use glycerine filled gauges on O2 systems. All gauges should be clearly marked "for O2 service". I know one guy who had an O2 based reg fire when the LP glycerine filled gauge he used leaked. He was extremely lucky it was on the LP side and not the HP side. He ended up with a small blowtorch, but was still able to shut down the cylinder. If it was on the Hp side, like the woman in Floria, he'd have never knew what hit him when the cylinder exploded.

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Having been in the industry since 1994 I've seen my fair share of oops's.  If you use O2 it should be noted that something as small as a spider crawling in your regulator while it's off can cause it to blow apart.  A few months back a customer had a manifold blow apart just from dust.  Dirt, oil, bugs and general bad upkeep of equipment can land you on an episode of !000 Ways to Die. 

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