How to choose a liquid nitrogen tank
- Determine the purpose
According to the purpose, liquid nitrogen tanks can generally be divided into liquid nitrogen storage tanks and liquid nitrogen transport tanks.
The liquid nitrogen storage tank is mainly used to store liquid nitrogen for later low-temperature experiments or to store samples that require low-temperature preservation such as cells, tissues, etc.
Liquid nitrogen transport tanks are used for cryogenic sample transport.
In order to meet the transportation conditions, a special shock-proof design has been made. In addition to being stored at rest, it can also be used for transportation in the state of being filled with liquid nitrogen, but severe collisions and vibrations should also be avoided.
- Determine the required frozen sample volume, diameter and volume
The amount of frozen specimens will determine the volume of the liquid nitrogen tank. If there are few specimens, a small liquid nitrogen tank should be selected.
If you need to store liquid nitrogen for a longer period of time, you can choose a liquid nitrogen tank with a volume of 30 liters or 35 liters of 50mm diameter for storage. The static storage days of liquid nitrogen are more than half a year.
If the volume of the specimen is large, it is necessary to choose a liquid nitrogen tank with a larger volume. If a small-volume liquid nitrogen tank is purchased for freezing, the specimen will occupy the space inside the liquid nitrogen tank, and only a small amount of liquid nitrogen can be placed in the liquid nitrogen tank, thereby reducing the Due to the storage days of liquid nitrogen, it is possible that the frozen specimens are necrotic due to the lack of liquid nitrogen.
The size of the specimen diameter is also critical for the selection of liquid nitrogen tanks. Generally, the diameter of the liquid nitrogen tank should be larger than the diameter of the frozen specimen. For example, the diameter of your specimen is 90mm, and if you buy a liquid nitrogen tank with a diameter of 80mm, your specimen cannot be put in it and cannot meet your needs. .
There are about two kinds of buckets inside the liquid nitrogen tank. One is a round bucket, which can be used to place larger tissue samples or large-capacity cryopreservation tubes. The other is the extraction bucket, which can be placed in a standard 2ml cryovial to store cells and other products.
Precautions for the use of liquid nitrogen tanks
- Inspection before use
Before filling the liquid nitrogen tank with liquid nitrogen, first check whether the shell is dented and whether the vacuum exhaust port is in good condition. If it is damaged, the vacuum degree will be reduced. In severe cases, the intake air cannot be kept warm, so that the upper part of the tank will be frosted, the liquid nitrogen loss will be large, and the value of continued use will be lost. Secondly, check the inside of the tank. If there is foreign matter, it must be taken out to prevent the liner from being corroded.
- Filling of liquid nitrogen
Use caution when filling liquid nitrogen. For new cans or cans in a dry state, be sure to fill them slowly and pre-cool them to prevent too fast cooling damage to the liner and reducing the service life.
When filling liquid nitrogen, do not pour the liquid nitrogen on the vacuum exhaust port, so as not to cause the vacuum degree to drop.
The cover plug is made of thermal insulation material, which can not only prevent the evaporation of liquid nitrogen, but also play the role of fixing the lifting cylinder, so try to reduce the wear and tear when switching to prolong the service life.
- Inspection during use
Check frequently during use. You can observe with your eyes or touch the shell with your hands. If you find frost on the surface, you should stop using it;
In particular, it is not advisable to scrape with a knife when the inner wall of the neck tube is frosted and frozen, to prevent the inner wall of the neck tube from being damaged and cause poor vacuum. Instead, the liquid nitrogen should be taken out and let it melt naturally.
Storage of liquid nitrogen tanks
- Placement of liquid nitrogen tank
The liquid nitrogen tank should be stored in a well-ventilated and cool place, and should not be exposed to direct sunlight.
Due to its precision in manufacturing and its inherent characteristics, liquid nitrogen tanks are not allowed to be tilted, placed horizontally, upside down, stacked, bumped against each other or collided with other objects, whether in use or storage. upright.
- Cleaning of liquid nitrogen tank
When the liquid nitrogen tank is not in use, rinse it with clean water, drain the water, dry it with a blower, and place it at room temperature for use.
After the liquid nitrogen in the liquid nitrogen tank is volatilized, the remaining missing material quickly melts and becomes liquid material and attaches to the inner tank, which will cause corrosion to the inner tank of the aluminum alloy. If a cavity is formed, the liquid nitrogen tank will be scrapped. Therefore, it is very necessary to brush the tank after the liquid nitrogen in the liquid nitrogen tank is exhausted.
The specific brushing method is as follows: first, take out the lifting cylinder in the liquid nitrogen tank, remove the liquid nitrogen, and leave it for 2-3 days. When the temperature in the tank rises to about 0 °C, pour warm water at about 30 °C and scrub with a cloth. If you find that individual melted substances stick to the bottom of the inner tank, be sure to wash it carefully. Then rinse it with clean water several times, then invert the liquid nitrogen tank, put it in a safe place indoors that should not be overturned, and air dry it naturally, or air dry it with a blower as described above. Note that in the whole brushing process, the action should be light and slow, the temperature of the water should not exceed 40 ℃, and the total weight should not exceed 2kg.
- Safe transportation of liquid nitrogen tanks
The liquid nitrogen tank must be placed in a wooden frame with soft pads and fixed during transportation.
Fillers should be used to separate the cans from each other to prevent bumps and impacts and prevent dumping.
When loading and unloading the truck, it is necessary to prevent the liquid nitrogen tank from hitting, let alone drag it on the ground, so as not to reduce the service life of the liquid nitrogen tank.