Generally speaking, vacuum-failed Dewar’s cylinders are subject to isobaric phenomena such as frosting of the bottle or a sharp increase in the pressure inside the bottle. However, for new bottles or long-term placement of unused cylinders, due to its internal gallbladder temperature is high, when inflated, the pressure rise will also rise rapidly, this scenario should be a normal phenomenon.

Excessive pressure can be used as one of the bases for determining the vacuum failure of a gas cylinder. Dewar’s bottles are fitted with a vacuum stopper, which will come loose when the cylinder’s vacuum fails (under normal circumstances, the stopper will be pressurized by atmospheric pressure). A plastic cap is usually placed over the vacuum plug. Do not open the cap or the vacuum plug. If you find that the cylinder vacuum is not working properly, return it to a repair shop for repair.

In the final analysis, vacuum failure is a very rare phenomenon, with ordinary gas cylinders lasting for years or even longer than the service life of the gas cylinder, when the vacuum of the cylinder is (slowly) gradually decreasing. The so-called “soft” vacuum on stationary cylinders can be recognized by the increasing pressure.

If there are no abnormalities in the gas vacuum plugs and a vacuum failure is suspected, a test must be carried out to determine whether there is a moment of pressurization.

When measuring the moment of pressure rise in the Dewar’s bottle, attention should be paid to the beginning of the inspection and guarding time:

1. To know the liquid temperature of the filling station, the liquid temperature of the filling station shall not be lower than -135℃.
2. It should be used 2/3 or 1/2 time to measure the cylinder level.
3. Place . Cylinder pressure is reduced to 0.6MPa, close all valves, check every half hour, check the boosting situation, investigate for 4 hours, assuming that the pressure of 0.1mpa per hour, you can begin to determine that the vacuum is falling, please inform our after-sales personnel to judge on the spot.
4. The volume of the liquid in the cylinder is half of the volume, it can’t be full of liquid, otherwise it will affect the accuracy of judgment.
5. After the judgment starts, you can notify the service personnel of the gas cylinder factory to judge on the spot.

Vacuum failure in the cylinder, its sleeve pressure will rise at a rate close to 0.007MPa/min, this pressure change is very obvious; especially in the pipeline in the more concentrated part of the nearby temperature is lower, so the shell of the frost or condensation or not depends on the humidity of the surrounding environment. The existence of such condensation phenomenon can not be used to determine the existence of gas cylinder vacuum reliable indicators, and the cylinder pressure increase rate test is a reliable and useful method of discrimination.

Dewar’s cylinders that can no longer be used with a vacuum must be re-vacuumed with specialized equipment so that they can be carried out in the vehicle or after the cylinders have been removed.