DSW
04-06-2008, 11:56 AM
This will be a long post so bear with me.
Thought I'd post these picts and let you all see what happened to me. I am trained in O2 cleaning for Hp O2 service and special procedures for gas mixing.
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 anal 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.
18470
18471
18472
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.
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
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. Several others were injured in the explosion. I'm still looking for my copies of the picts of that tank and will post them if I find them.
Just a good warning to all of you who deal with O2 regularly.
Thought I'd post these picts and let you all see what happened to me. I am trained in O2 cleaning for Hp O2 service and special procedures for gas mixing.
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 anal 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.
18470
18471
18472
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.
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
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. Several others were injured in the explosion. I'm still looking for my copies of the picts of that tank and will post them if I find them.
Just a good warning to all of you who deal with O2 regularly.