Liquid nitrogen at -196°C can freeze all living things!
However, the Ln2 tank is a liquid nitrogen container with a vacuum insulated construction to reduce the loss of liquid nitrogen.
So, normally, the ln2 tank is immune to the low temperature of liquid nitrogen, only when the vacuum is not sufficient, the walls of the tank will “sweat”!
But if there’s ice build-up, consider whether you’re doing the ln2 tank right!
Ln2 tank ice buildup mostly occurs at the location of the booster or discharge pipe, due to ice blockage in the pipe.
The reason for the ice blockage is that moisture in the air enters the tank and condenses into ice at the low temperature of th0e liquid nitrogen, blocking the pipes.
The entry of water molecules in the air is caused by the fact that the venting valve is not opened when the liquid nitrogen is exported and the entire ln2 tank is stored in a static state, resulting in the entry of wet air.
The treatment is in two steps.
1.Solve the ice jam first
The ln2 tank pressure may be increased to ≥ 0.05 MPa by first filling the vessel with nitrogen gas from a nitrogen cylinder against it.
After which the liquid medium inside the vessel is emptied.
Finally, the ice-clogged pipe is blown out with a hair dryer or hot nitrogen gas to melt and drain the ice.
2. Avoid re-freezing of the ln2 tank
Close the other valves after blowdown, leaving only the venting valve.
To avoid the ln2 tank being blocked in ice, remember to open the drain valve when the tank is in static storage after the liquid nitrogen has been exported!
The venting valve prevents the entry of moist air from outside!
