We know that there is one thing to note when using liquid nitrogen containers: Do not fill the liquid nitrogen too full!
Conventional models of liquid nitrogen tanks require this, and liquid nitrogen supply tanks also emphasize the same, and directly recommend that users leave 10% of the gas phase space. In order to ensure safe use and the life of the tank, it must be pre-cooled and then filled. Does this also apply to liquid nitrogen freezers?
As a cryogenic container for vapor phase storage, does it also need to follow this principle?
The reason lies in the internal structure of the liquid nitrogen freezer!
The biggest difference between it and the conventional model, that is, the liquid nitrogen tank, is the inside. There is nothing else in the liner of the liquid tank except the accessories for fixing the shelf or the round bucket. Liquid nitrogen and samples coexist. The liquid nitrogen freezer is different. Its inner tank is divided into two parts. The upper part stores samples and the lower part stores liquid nitrogen. There is a tray in the middle of the two parts, which does not meet each other.
This tip is not to fill up directly. The reason why it is mostly suitable for conventional models, that is, 1-175 liter liquid nitrogen containers, is because the liquid nitrogen and the sample are in the same space, and liquid nitrogen is used directly. If the filling is too full, cover the neck plug. It will overflow later, and unprotected skin may be frozen if you accidentally touch it, so it is not recommended to top up.
As for pre-cooling, first inject a little liquid nitrogen to cool down the can. The purpose is to prevent a large amount of frost on the can body, which may cause users to mistakenly think that the can is of poor quality. The sudden stimulation of alternating hot and cold may reduce the service life of the container.
The neck plug of the liquid nitrogen freezer is integrated with the tank lid and is located above the sample storage area. It does not come into contact with liquid nitrogen, so there is no problem of overflow. It is made of 304 stainless steel and has a large capacity. Compared with the tank container, the amount of liquid nitrogen injected is almost the same as the pre-cooling capacity of an ordinary liquid nitrogen container, so there is no need and you can top it up directly.
Now everyone can rest assured! When storing samples, the liquid nitrogen in the liquid nitrogen freezer can be topped up!