Liquid Nitrogen Can Be Fun
Back in the final test area and in the environmental lab I have to run machinery that uses a ton of liquid nitrogen (LN2) as a coolant. There are a few of these big ass portable pressure tanks that have to be filled at least once a day. I ran out of LN2 on the swing shift a couple of times recently and as a result we lost some test time. The solution my supervisor came up with was to train me on the tank filling procedure so this wouldn't happen on the night shift again. Oh joy, yet another new thing to learn and be responsible for.
Marty is the top technician in the final test area and he dragged me out to the back entrance of the building where they have a heavy duty roll up garage door and they installed a high pressure LN2 line from the main storage tank. To fill up one of these beasts it's a little dicey. You have to wear a blast shield over your face that looks like a welding mask but it has a clear lens over it instead of a heavily darkened one. Then you grab some ear protection that looks like those giant headphones people wore back in the early 70s while listening to their Barry Manilow's Greatest Hits. And finally there's the super goofy light blue oven mitts that are rated for severe minus degree temperatures. One looks like a total fool wearing all this gear on top of your lab coat. If you get a few drops on your skin though you'll end up with cryogenic burns. So looking like a fool for a few minutes is the better alternative compared to a trip to the emergency room.
The best way for me to learn stuff is to just jump right in and try it while the trainer is talking me through it. Marty was right there with me telling me each step and what to watch out for. The first thing to do is to bleed out the high pressure line from the main LN2 tank. It can take up to five minutes before the line cools down enough to keep the nitrogen in a liquid state. When I first opened up the valve on the wall Marty warned me that the line would kick hard and it sure did. I was amazed at how hard the line lurched in my oven-mitted hands. The sound was awful too. It was like having your head inside a jet engine intake with added whistle. Really sucks. Once the LN2 finally makes it all the way to you the line kicks hard again and a steady stream of clear liquid arcs out onto the pavement and instantly boils from the ground into a pure white smoke. It looks like fluffly clouds rising up from the parking lot as it cooks off. The line is now ready to hook up to the portable tank.
There's three main valves on the top of the tank and it's tricky to set them up just right so you pressurize the tank enough to keep the nitrogen a liquid. If you don't do it right you'll just fill up the tank with gas. The method Marty showed me to use was to set one of the valves as a brake and only open it up just enough so that the gas inside the tank could bleed off, but just enough pressure would be there to keep the LN2 in it's liquid state. I screwed up the first couple of times so we had to stop and re-bleed off the tank and then start over from scratch. What a pain. Once I got it right though I realized filling up these tanks would be kinda cool. I'd get to have a twenty or thirty minute break while they are filling up. You have to stay there the whole time and watch the open door to make sure no one comes into the building as well as monitor the equipment while everything is pressurizing. I think I can dig it.
Along the wall there is another valve that is for a low-pressure LN2 line so you can fill up something small like a bucket. Later on I took a thermos sized container out to the low pressure line and filled it up about half way with the stuff. When the smoke clears it looks just like regular old water. The fun begins when you pour a few drops of it on the concrete. The droplets bounce around and smoke off the instant they come in contact with the ground. Wooden dowels and other objects smoke off inside the container. And I discovered you can dunk a bug in it, then drop 'em on the ground and watch it shatter. I don't know why but when I do that it makes me grin. Some of the other guys have been thinking about what other mischief we can get into with LN2 at night. I have no doubt we will be able to brainstorm up some dumb stuff to do in no time.
Marty is the top technician in the final test area and he dragged me out to the back entrance of the building where they have a heavy duty roll up garage door and they installed a high pressure LN2 line from the main storage tank. To fill up one of these beasts it's a little dicey. You have to wear a blast shield over your face that looks like a welding mask but it has a clear lens over it instead of a heavily darkened one. Then you grab some ear protection that looks like those giant headphones people wore back in the early 70s while listening to their Barry Manilow's Greatest Hits. And finally there's the super goofy light blue oven mitts that are rated for severe minus degree temperatures. One looks like a total fool wearing all this gear on top of your lab coat. If you get a few drops on your skin though you'll end up with cryogenic burns. So looking like a fool for a few minutes is the better alternative compared to a trip to the emergency room.
The best way for me to learn stuff is to just jump right in and try it while the trainer is talking me through it. Marty was right there with me telling me each step and what to watch out for. The first thing to do is to bleed out the high pressure line from the main LN2 tank. It can take up to five minutes before the line cools down enough to keep the nitrogen in a liquid state. When I first opened up the valve on the wall Marty warned me that the line would kick hard and it sure did. I was amazed at how hard the line lurched in my oven-mitted hands. The sound was awful too. It was like having your head inside a jet engine intake with added whistle. Really sucks. Once the LN2 finally makes it all the way to you the line kicks hard again and a steady stream of clear liquid arcs out onto the pavement and instantly boils from the ground into a pure white smoke. It looks like fluffly clouds rising up from the parking lot as it cooks off. The line is now ready to hook up to the portable tank.
There's three main valves on the top of the tank and it's tricky to set them up just right so you pressurize the tank enough to keep the nitrogen a liquid. If you don't do it right you'll just fill up the tank with gas. The method Marty showed me to use was to set one of the valves as a brake and only open it up just enough so that the gas inside the tank could bleed off, but just enough pressure would be there to keep the LN2 in it's liquid state. I screwed up the first couple of times so we had to stop and re-bleed off the tank and then start over from scratch. What a pain. Once I got it right though I realized filling up these tanks would be kinda cool. I'd get to have a twenty or thirty minute break while they are filling up. You have to stay there the whole time and watch the open door to make sure no one comes into the building as well as monitor the equipment while everything is pressurizing. I think I can dig it.
Along the wall there is another valve that is for a low-pressure LN2 line so you can fill up something small like a bucket. Later on I took a thermos sized container out to the low pressure line and filled it up about half way with the stuff. When the smoke clears it looks just like regular old water. The fun begins when you pour a few drops of it on the concrete. The droplets bounce around and smoke off the instant they come in contact with the ground. Wooden dowels and other objects smoke off inside the container. And I discovered you can dunk a bug in it, then drop 'em on the ground and watch it shatter. I don't know why but when I do that it makes me grin. Some of the other guys have been thinking about what other mischief we can get into with LN2 at night. I have no doubt we will be able to brainstorm up some dumb stuff to do in no time.
posted by factory_peasant at 10:52 AM
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