The real liquid nitrogen tanks we see are generally white tank bodies, which contain 3 or more buckets and freezer racks, and there is a cover on the top of the container.
There are two types of lids, one needs to be taken vertically, and the other can be opened. They may appear on the same liquid nitrogen tank, or there may be only the one with a stopper.
Why do liquid nitrogen tanks have lids? Isn’t it already a vacuum insulated structure?
Does this cover have to be covered again?
If your cover refers to the one with a stopper, it must be covered; if it can be opened, it is called a lock cover, and it is not necessary to cover it!
It is true that the liquid nitrogen tank has a vacuum insulation structure, but its vacuum is between the inner tank and the outer tank, and the heat insulating adsorption material is also wrapped there. There is an opening at the upper part of the connection between the inner tank and the outer tank, between 50mm and 216mm, the opening is the entrance of liquid nitrogen and biological samples, which must exist.
But the opening also means that the external heat inlet is left, and the hot air will enter from the opening of the liquid nitrogen tank, so various manufacturers have designed “neck plugs” for their own liquid nitrogen containers, that is, the lids with plugs mentioned above . It is made of polyurethane foam, heat-insulating, resistant to low temperature of liquid nitrogen, and can block external heat, so it must be covered.
Some liquid nitrogen tanks are mostly used in laboratories, and there is a need to lock the samples, so the manufacturer installs a lock cover on the neck plug. The locking cover does not have the function of heat preservation, but only prevents the sample from being lost, so it is not necessary to cover it!