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What is the general pressure of the Dewar liquid nitrogen container?

2024-07-08 10:07:22

There has been a lot of discussion about the pressure of the Dewar liquid nitrogen container;

The reason for the discussion is that this container, regardless of its type, can store liquid nitrogen.

Liquid nitrogen has a temperature of -196℃ and a boiling point of -196.56℃. One of its characteristics is that it is volatile. After volatilization, it becomes gas and expands in volume. Expansion and gas will bring pressure, so some users think that the Dewar liquid nitrogen container has pressure, and want to know what its pressure is generally?

How much is it?

Depending on the type of liquid nitrogen container, not all liquid nitrogen Dewar containers are pressurized!

Like the aluminum liquid nitrogen dewar, there is no pressure.

This type of low-temperature container is made for storing liquid nitrogen and samples. The inner liner contains both liquid nitrogen and samples. Because of the sample in and out, the caliber must be set, and the caliber is 50-216mm. It is difficult to have pressure with a caliber. Once the lid is opened, the nitrogen will leak out, and there is no chance for pressure to form in the container.

Of course, the aluminum Dewar liquid nitrogen container you see has an opening but a plug, so you may worry that the nitrogen cannot be exhausted. But in fact, for the sake of sample storage safety, manufacturers have left vent holes at the mouth of the tank, and the neck plug is designed to be loose with grooves, so nitrogen cannot accumulate in the Dewar container, and it has no pressure.

But if it is a stainless steel liquid nitrogen supply tank, then there is working pressure, which is within 0.1MPa.

Liquid nitrogen supply tanks are pressurized Dewar liquid nitrogen containers, which are manufactured for refilling other cryogenic tanks. They rely on internal self-pressurization to achieve liquid nitrogen delivery. There is no doubt that they have pressure. However, it should be noted that this type of liquid nitrogen tank has no pressure when storing liquid nitrogen at rest. It is only when pressurizing and refilling that it is necessary to open the pressure to ≥0.05MPa to discharge the liquid nitrogen.

Therefore, the general pressure of the Dewar liquid nitrogen container depends on the type. Sample storage containers are pressure-free, while liquid nitrogen supply and transportation containers are under pressure, which is a low pressure of 0.1MPa.

What is the general pressure of the Dewar liquid nitrogen container