I know I’m making a few assumptions here, but here is a picture of the box in question. I don’t know for sure that it is a liquid nitrogen tank except that I have only seen those particular style tanks used for it. The tank itself says that it is Nitrogen. I assume that it is a phone line rather than electrical because I have seen the phone truck there once in a while. If it is a liquid Nitrogen tank, then it can’t last long since it would take a long time in 100˚ F sun to get liquid Nitrogen to start coming out.
My guess is that it is attached to some thing hollow like pipes that contain wires/cabling…or maybe the cabling is somewhat hollow, or maybe just the boxes.
Yeah, that liquid nitrogen aint gonna last long.
Maybe they hook it up to whatever, let the N2 boil off awhile, the gaseous N2 feeds into whatever, and thats a good automatic, low pressure way to flush whatever with a bunch of nitrogen. Much better than a pressurized N2 bottle in some ways. My WAG.
Or in other words, just a convient way to flush things. I doubt they are actually using it for cooling purposes.
It would be compressed nitrogen - not liquid nitrogen. Many older phone lines used nitrogen to keep the moisture out. Periodically, that cable is depressurized so drive out moisture that has gotten inside. This is how lines in the 40 and 50s were done. And since they used proper wires back then, the same wires are still good today for advanced services such as DSL.
Today, cables wires contain water resistant grease. Nitrogen is no longer necessary to keep moisture out.
That makes sense. The only reason I suspected liquid Nitrogen was because of the style of tank. Naturally, if it were liquid Nitrogen, it wouldn’t be liquid in the tank. I suppose that tank style is used because it holds more N2 than a standard cylinder. Liquid Nitrogen is not something you’d want around if keeping things dry is a goal.
The tank in question does look rather like a dewar thermos, which would be necessary for cryogenically liquified gas but not for merely pressurized gas.
That certainly appears to be a liquid nitrogen tank to me. You can see the guage for determining the amount of remaining liquid sticking up in the middle. We use these for supplying low pressure nitrogen gas to some of the instruments in the lab here. Typically there is a “liquid” valve and a “gas” valve that you can tap into. We use a lot of compressed nitrogen as well and I have never seen it delivered in one of those types of tanks. I don’t think they are designed to withstand more than a few hundred psi.
A Verizon technician says nitrogen is used to pressurize underground cables to drive out moisture. The cables are not perfect, and will occasionally leak, causing shorts in copper strands. The nitrogen is used to dry them out if there is a leak.
That’s interesting. I never suspected that those tanks actually contained liquid Nitrogen. I always assumed it was similar to the little setup we had for making dry ice. I figured the depressurization caused it to cool off and liquify. Of course the CO2 tank for the dry ice had to have a dip stick to get to the bottom of the tank and get the liquid CO2, so that wasn’t really what was going on there either.
i agree that is a liquid nitrogen tank, a double walled dewar tank, not a thick walled compressed gas tank.
the insulation effect is fairly good. the tank can withstand enough pressure to keep it in a liquid state for a long time. it does have safety pressure relief system if needed.
ambient heat keeps some pressure of gaseous nitrogen which goes through regulators. that pressurized gas is fed into the cables.
this is preferred method because compressed gas is very hazardous and this an uncontrolled location. if a car hit a compressed gas tank and damaged it then that would be a real problem, if a car would hit the liquid tank and damaged it then it would just freeze some grass.