Leak detection and storage of cryogenic dewars

The detection of Dewars generally has two modes, vacuum mode and positive pressure mode. Dewars (welded insulated gas cylinders) mostly use the negative pressure mode of the helium mass spectrometer leak detector, which is vacuum mode leak detection. Connect the helium mass spectrometer leak detector to the vacuum system. Since the HLT550 does not have a foreline pump, you can use the site The vacuum system is used as the front pump of the helium mass spectrometer leak detector. It is best to connect it near the air inlet (that is, the air inlet of the vacuum pump group). The vacuum system will have the pump group pumping vacuum, so the pump inlet The leak detector is connected to the air port in the direction of the air flow, and it is easy to have a partial pressure divided into the leak detector, so as to achieve the effect of leak detection.

The storage of cryogenic dewars needs attention in the following aspects:
1. Dewar dissolved gas cylinders are not allowed to be used horizontally;
2. The gas in the bottle should not be exhausted. The residual pressure of compressed gas and dissolved acetylene gas cylinders should not be less than 0.05MPa; liquefied gas, low-temperature liquefied gas and low-temperature liquid gas cylinders should have at least 0.5% ~ 1.0% Amount of remaining gas; 3. Dewar acetylene bottle should be installed with tempering prevention device when working;
4. The storage capacity of the gas cylinders at the work site shall not exceed 20 bottles at the same location; if more than 20 cylinders, a secondary gas cylinder storehouse shall be built;
5. It is forbidden to put the gas cylinder containing the gas in a place where people are dense or close to the heat source (except for car bottles), and it is forbidden to use any heat source to heat the gas cylinder;
6. The distance between the combustible gas, combustion-supporting gas cylinder and the open flame should be greater than 5m.