Usually, the Dewar bottle is accompanied by a vacuum failure. A bottle containing a cryogenic liquid may cause a "sweating" of the bottle, frosting or a sharp increase in the pressure inside the bottle. However, for a new Dewar or a long-lasting Dewar, the pressure rises faster when the liquid is filled due to the higher temperature of the inner tank. This phenomenon is normal.

Excessive pressure rise in Dewar can be used as a basis for judging the failure of Dewar vacuum. The outer casing of the cylinder is equipped with a rupture disc that bursts when the dewar vacuum fails. Usually, the rupture disc is covered with a plastic cap. Do not open the cap or break it. If the Dewar vacuum is found to be invalid, please return it to the factory for repair.

In summary, vacuum failure is a rare phenomenon, usually the vacuum of the bottle can be maintained for several years, during which the vacuum of the Dewar is gradually decreasing (at a very slow speed). The so-called "soft" vacuum that appears on stationary Dewars can be judged by the rapid rise in pressure.

If the Dewar rupture disc is not abnormal, but it is suspected that the vacuum has failed, it must be judged by checking the pressure rise time. When testing the Dewar pressure rise time, first add the liquid to the Dewar, then stop the low temperature liquid in the bottle with 3/4 or 1/2 left. The Dewar is allowed to stand for at least 12 hours, and the system's pressure rise rate below about 0.3 MPa is normal. It should be noted that the first filling of the hot bottle or the overfilling of the bottle will also cause a sharp rise in pressure.

In a vacuum-deaded Dewar, the jacket pressure will rise rapidly and this pressure change is very noticeable. The Dewar shell, especially in the department where the pipeline is concentrated, and the temperature near the support are lower than the temperature in other parts. The frost or "sweating" of the shell depends on the temperature and humidity of the surrounding environment. The existence of this condensation phenomenon can not be used as a reliable indicator to judge the presence or absence of vacuum in a Dewar, and the test of the pressure rise rate of Dewar is the most reliable and effective method of judgment.

A dewar that has been vacuum-deactivated must be vacuumed again by special equipment. This can be done on-site or after the Dewar is removed. For details of the operation, please contact the customer service of AUYAN Technology. Contact number 400-0536-266