I’ve noticed big metal canisters (4797 cubic feet) of liquid nitrogen gas on the sidewalk at several corners in Manhattan. On the corner where I work, there are always two or three of them. One has a rubber tube leading into a manhole cover that says E C S Co Ltd. I think some of them have leaks; there is ice and frost on the side. One of them had a label that said “Warning: contains human souls” :eek:
What are they for? Isn’t a leaking gas canister dangerous, especially sitting out in the hot sun?
I’m not sure what they would be for specifically, but cooling something or pressurizing cables–I know it’s sometimes used with heliax, although dehumidified air is more common. Fortunately, leaky nitrogen containers aren’t particularly dangerous, since the stuff is about as explosive as a stack of snails. The only problem is if the gas pools in a low place–it could asphyxiate someone who lacked an air source.
(I see in preview that the function’s been covered–at least I can offer something on the safety issue.)
I can think of two possible uses for a large container of liquid nitrogen on a sidewalk with hoses leading to a manhole. First, they could be using it to create a freeze seal (for example see http://www.freezesealinc.com) on a pipe in the manhole. The liquid N[sub]2[/sub] is used to freeze an ice plug in the pipe to allow it to be cut an welded on downstream of the freeze. This is done if the placement of isolation valve in the pipe does not allow the area to be worked on to be easily isolated and drained.
A second reason I can think of would be to use an inert gas like nitrogen to flush and fill a pipe prior to working on it. Perhaps it’s being used on a pipe that carries natural gas of some other flamable substance and they want to weld on it with blowing themselves to bits.
(On preview, it looks like Jargent has the best answer)
Fortunately, nitrogen doesn’t so much “pool” the way heavier gasses do. Given that air is mostly nitrogen, and that most of what’s left is heavier than nitrogen, nitrogen gas itself certainly isn’t going to be heavier than air. Now, that’s not to say that you couldn’t flush too much air out of an enclosed space and suffocate, but it would take some doing.
The real problem with exposed LN is that it will condense liquid Oxygen (LOX) out of the atmosphere, and LOX is very reactive. But this setup doesn’t sound like it carries much of a risk of this.
Also, I’m surprised they’re leaving these dewars out in the open, so conspicuously. I wonder how long until teenagers find out how much fun the stuff is and start making off with the tanks?
At STP, nitrogen won’t pool–but extremely cold gaseous nitrogen (say, just-evaporated from N[sub]L[/sub]) may under some circumstances, because it’s denser than the air around it. This may be something of a concern if it’s being piped down into a hole in the ground.
They’d have to really want it. Most of these aren’t the skinny 5-foot tall ones with the nipple on top. They’re 6+ feet tall and four feet around and look like they weigh a billion pounds.
Also those tanks are used to freeze oil in pipes that have cable (either telephone or electric). The oil prevents the cable from rusting and prevents the pipes from collection water. If repair to the cables are needed the oil must be frozen on both sides to prevent the oil from draining.
You don’t have to try, you’re inhaling 78% nitrogen right now. Breathing 100% nitrogen for a while would give you a slight buzz from lack of oxygen, then you’d pass out and eventually die of asphyxiation if your normal air supply wasn’t restored.
Ah, I see Anthracite is with us, welcome back… Do you happen to have a CRC Table book handy? Or perhaps you’d know this off the top of your head. Due to bughunter’s question, I’m curious about the liquification points of nitrogen and oxygen.
Not confusing the two, just making a different point. Sure nothing is going to happen when you inhale Nitrogen. As someone pointed out, we’re breathing 78% Nitrogen now.
But it’s not at -300 degrees, as I was postulating. I imagine at that temperature it would have some interesting side effects, like collapsing the lungs or some other such fun. At least clearing the sinuses.
I couldn’t get to your link at work, because my browser is not current enough and I can’t upgrade it. But I can get into it at home. That’s exactly what I was talking about.
Thanks for the information, guys. It looks like I don’t have to worry about the thing exploding. ::whew::
Thanks, bughunter, I wasn’t aware of that site, it looks like a good replacement for britannica.com since they went pay. I’m always looking for new better cheaper reference sources. Oh how I wish the CRC Handbook was online.
I used to work doing computers in a hospital’s anaesthesiology lab, we did research in sensors for bottled gas respirator machines. The holy grail was a compact liquid air system but the gas it emits is too cold to work with, it takes too much energy getting it to room temperature in a controllable fashion, it’s not practical. A standard pressurized gas cylinder anaesthesiology cart uses small bottles of O2 and other anaesthetic gases (like nitrous oxide) that release gas cold enough to freeze lung tissue. Drying and burning of tissue is also a problem since the bottled gas is 0% humidity. You have to put a gas warmer and a humidifier into the system to make it breathable. And this gas is not really that cold compared to liquid gas vapor.
In other words, one direct puff of liquid nitrogen vapor and your lungs would be freeze-dried.