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Reasons why the cover of the dewar tank for liquid nitrogen is frozen

2024-06-26 10:12:51

Containers filled with liquid nitrogen have a vacuum structure and are filled with -196℃ liquid, so more precautions should be taken when using them than ordinary insulation containers.

The most prominent problem is that it is afraid of bumps, because the collision may cause dents or even damage the outer liner of the dewar tank for liquid nitrogen, which will reduce the vacuum degree and affect the insulation effect. Another problem is its environment. If the environment is not chosen well, either the liquid nitrogen evaporates too fast or the lid is frozen!

Therefore, the frozen cover of the dewar tank for liquid nitrogen is actually caused by environmental problems!

Most of the time, it is due to indoor humidity. When the lid is opened to take samples, the humid air enters the tank and condenses into water droplets after contacting the nitrogen at the tank mouth. When the liquid nitrogen container is covered with a cap, the temperature in the entire tank drops, and the condensed water droplets become ice. If the ambient humidity has not improved, as time goes by, water vapor enters and freezes again, and the cycle continues. One day, you will find that the lid is frozen!

This situation may also occur when you replace the original dewar tank for liquid nitrogen neck plug and happen to choose a neck plug with poor insulation effect and some liquid nitrogen adsorption. In this case, water molecules in the air contact the top of the plug and condense into ice on the upper part due to the transfer of cold air. Over time, the lid will also be frozen.

For the former, if you want to avoid such problems from happening again, you need to use hot air to de-ice the lid, then ventilate and dehumidify the room to ensure that the dewar tank for liquid nitrogen is in a dry and well-ventilated environment. For the latter, you can avoid such problems by replacing the original neck plug, but of course, a dry and well-ventilated environment must also be ensured.

Finally, I would like to remind everyone that when you find that the lid of the dewar tank for liquid nitrogen is frozen, do not blindly try to pry it open with your hands. This will easily cause the lid plug to break and affect subsequent use. The correct way to deal with it is to blow it off with hot air or transfer the nitrogen container to another environment with a slightly higher temperature to wait for the ice to melt naturally!

Now, do you know?

Reasons why the cover of the dewar tank for liquid nitrogen is frozen