With the rapid development of biomedicine, food industry and other fields, the application of liquid nitrogen tanks is more and more extensive and has become an indispensable and important tool for scientific research and production. Liquid nitrogen tank, also known as liquid nitrogen bio-container, is a kind of biological storage container, usually used to preserve active biological materials, and its use is very extensive. Then what is its working principle? What are the precautions in the use of liquid nitrogen tank? Let us unveil the mysterious veil of liquid nitrogen tank and explore its correct use.

Liquid Nitrogen Tank Structure

Liquid Nitrogen Tank Structure

Liquid nitrogen tanks are generally composed of a stainless steel inner liner, an outer liner and an insulating material. The inner liner is used to hold liquid nitrogen, and the outer liner is filled with multi-layer insulation material to reduce the evaporation loss of liquid nitrogen. Liquid nitrogen tanks are usually equipped with accessories such as carrying handles, liquid level meters, pressure gauges, pressurization valves, drain valves, filling valves and so on, which are convenient for daily use.

  1. Shell: The outside layer of liquid nitrogen tank is the shell, and its upper part is the tank mouth.
  2. Inner tank: The space in the inner layer of the liquid nitrogen tank is called the inner tank, which is generally corrosion-resistant aluminum alloy. There is a base at the bottom of the inner tank for fixing the carrying tube, and liquid nitrogen and samples can be stored in the inner tank.
  3. Mezzanine: Mezzanine refers to the space between the inner and outer layers of the tank, which is in a vacuum state. The purpose of vacuum is to enhance the adiabatic properties of the tank, while the sandwich is equipped with adiabatic materials and adsorbents.
  4. Neck: The neck is usually fiberglass fiber-reinforced plastic material, and the inner and outer layers are connected. Around the neck tube, the bottom of the sandwich is equipped with adsorbent. The neck opening at the top is specially designed, and its structure should have pores that can discharge the nitrogen evaporated from the liquid nitrogen to ensure safety, and it should have adiabatic properties to minimize the amount of liquid nitrogen vaporization.
  5. Cover plug: The cover plug is made of plastic with good adiabatic properties to prevent the evaporation of liquid nitrogen while fixing the handle of the lifting cylinder.
  6. Carrying bucket: Carry tube placed in the tank, which can be stored in the fine tube. The handle of the barrel is hung on the neck and fixed with a cover plug.

How do liquid nitrogen tanks work

Open the liquid piping discharge valve at the bottom of the tank and the liquid nitrogen is discharged through the piping and vaporized by the evaporator at the bottom of the tank. The vaporized gas enters the top of the tank, and the pressure inside the tank to provide liquid nitrogen will be self-pressurized. When the liquid nitrogen tank needs to supply gas to the outside world, the liquid is pressed out by the pressure inside the tank and then sent out through the pipeline, and the liquid nitrogen is released after vaporization.

Liquid nitrogen tank preparation before use

  1. The appearance of the liquid nitrogen tank should be checked before use to confirm that there are no dents, cracks, leaks and other problems;
  2. Check whether the connecting parts of the liquid nitrogen tank are tightened to make sure they are well sealed;
  3. Check whether the supporting equipment of the liquid nitrogen tank is intact and undamaged, including the carrying handle, liquid level meter, pressure gauge, pressurizing valve, liquid drain valve, filling valve and other accessories;
  4. Confirm that the workplace is well-ventilated to avoid the danger of asphyxiation caused by liquid nitrogen leakage;
  5. Operators should wear protective equipment, such as protective glasses, anti-freezing gloves, anti-freezing clothes, non-slip shoes, etc. avoid personal injury;
  6. When used for the first time or not used for a long time, nitrogen should be purged to remove the moisture and impurities in the tank.

Precautions in the use of liquid nitrogen tank

  1. When filling liquid nitrogen, the valve should be opened slowly to avoid excessive impact resulting in damage to the liquid nitrogen tank;
  2. Strictly prohibit the liquid nitrogen tank inverted, to prevent the liquid nitrogen outflow from directly causing danger;
  3. The liquid nitrogen tank should not be stored in a high-temperature environment or direct sunlight, so as not to cause an explosion due to the rise in pressure inside the tank;
  4. Check the liquid level of the liquid nitrogen tank regularly and replenish the liquid nitrogen in time, to avoid damage to the samples due to elevated temperature;
  5. When taking liquid nitrogen, the action should be gentle to avoid violent shaking resulting in liquid nitrogen splash;
  6. It is strictly prohibited to privately disassemble the safety devices of liquid nitrogen tank, such as safety valves, rupture discs, etc., to prevent accidents;

Liquid nitrogen tank treatment measures after use

  1. After use, all the valves of the liquid nitrogen tank should be closed in time to prevent liquid nitrogen from leaking;
  2. Place the liquid nitrogen tank in a cool and ventilated place, avoid direct sunlight or close to the fire source;
  3. Clean up the debris around the liquid nitrogen tank and keep the working area clean and tidy;
  4. Check whether there is residual liquid nitrogen in the liquid nitrogen tank, if so, it should be discharged in time;

Can liquid nitrogen tanks explode

Liquid nitrogen tanks are divided into pressurized and unpressurized, those used for storing samples are usually unpressurized, and those used for outputting liquid nitrogen are pressurized. Can liquid nitrogen tanks without pressure are mostly used to store frozen semen and cells, which are used for livestock improvement and experimental research and other experiments that require high activity of biological samples. Therefore, users not only emphasize the insulation effect, but also pay attention to container safety issues, such as explosion!

Will the liquid nitrogen tank without pressure explode?

Of course not!

Containers filled with non-flammable and explosive liquids, the material itself does not belong to the explosive category, the explosion can occur mostly because of pressure.

Therefore, liquid nitrogen tanks without pressure will not explode.

Then with the pressure of the liquid nitrogen tank will be easy to explode under what circumstances?

I. External environmental impact

a. High temperature and pressure

Liquid nitrogen is made of air compressed and cooled, and can be restored to nitrogen by gasification. When the external temperature and pressure exceed the cooling temperature and pressure that the tank can withstand, it will explode.

b. Collision and vibration

Liquid nitrogen container tank design has a special anti-vibration design, in addition to static storage, transportation of liquid nitrogen tanks can also be used in the filling state of transportation. However, the liquid nitrogen tank tank in a very strong collision and vibration, will cause damage to the tank insulation or other components, so that the external environment will have a direct impact on the gasification, resulting in an explosion.

II. Quality factors

1. Improper selection of materials

Liquid nitrogen container tanks are generally made of pure aluminum foil and stainless steel cold and hot rolled steel plate. If the specifications and quality of these materials do not meet the requirements of norms and standards, and can not meet the conditions of frozen liquid nitrogen, there may be an explosion.

2. Poor temperature preservation

Liquid nitrogen tanks have internal and external double gallons, once the outer reflective material and heat insulation material of the inner gallon fall off, it will cause the adjacent reflective material and the outer gallon to come into direct contact with the liquid nitrogen in the inner gallon to expand and gasify, or even explode.

3. Valve, instrumentation and other accessories old and aging

In the process of long-term use, if the liquid nitrogen tank valves, meters and other accessories are aging, it will cause the liquid nitrogen temperature to rise or leakage and lead to an explosion.

Conclusion

The importance of liquid nitrogen tanks as an indispensable tool in scientific research and production cannot be overstated. However, at the same time, liquid nitrogen tanks also have a certain degree of danger, once improperly operated, may cause serious injury to the user. When using liquid nitrogen tanks, relevant regulations and precautions must be strictly observed to ensure safety.