The liquid nitrogen Dewar for storing animal semen and cells is indeed a vacuum container, but its vacuum part is between the inner and outer bladders, and there is a neck tube connection “seal”. The inner tank that actually contains liquid nitrogen is designed to be open to facilitate the entry of liquid nitrogen and samples, but it is equipped with an accessory neck plug and a lock cover to cover this opening.
As we all know, the neck plug is made of polyurethane, which can insulate heat and prevent liquid nitrogen from evaporating from the opening;
What about the lock cap over the neck plug? Is it added outside the neck plug, is it equivalent to another line of defense against volatilization?
Of course not!
In the design of the liquid nitrogen Dewar, the inner and outer tank vacuum + neck tube + neck plug form a vacuum closed loop. The inner and outer tanks are filled with thermal insulation and adsorption materials, which not only isolates external heat, but also prevents the leakage of liquid nitrogen cold air. The neck tube and the neck plug fit together. The neck tube prevents vacuum leakage between the inner tank and the outer tank. The neck plug prevents external heat and debris from entering The key to the liquid nitrogen tank.
Except for the above parts, other accessories of the liquid nitrogen Dewar do not involve heat preservation. Although the lock cap is installed outside the neck plug, it has no heat preservation content regardless of its material or structural design. It is only a lock cap used to lock the liquid nitrogen container to prevent the loss of precious samples or unknown personnel from touching the samples.
Therefore, if the liquid nitrogen Dewar does not lock the cover, it will not accelerate the volatilization of liquid nitrogen!