What are the preparations for the initial filling of the cryogenic storage tank?


What are the preparations for the initial filling of the cryogenic storage tank?

1 The initial filling is usually a low-temperature liquid filling of the inner container of a low-temperature storage tank at room temperature (including a low-temperature storage tank that has been stored for a period of time and reactivated). 
2 Before filling for the first time, check and correct the liquid level gauge and pressure gauge, check whether the various valves are in the correct opening and closing state, and whether the pipeline is unblocked; open the pressure gauge valve, and keep the liquid level gauge in working status. 
3 When the cryogenic storage tank is used for high-purity cryogenic liquid, it must be purged and replaced. The method is: use dry oil-free air or nitrogen at 70 ℃ ~ 80 ℃, heat and blow off the inner container, the blowing time should not be less than 8 hours, and then replace it with product gas; for nitrogen lighter than air, it should be removed from the vent valve. Introduce at V-12 and discharge from bottom liquid inlet and outlet valve V-1. For oxygen or argon heavier than air, it should be introduced from bottom liquid inlet and outlet valve V-1 and discharged from vent valve V-12. When the tank pressure reaches 0.1-0.2MPa, discharge the replaced gas, repeat this several times, and test the purity of the discharged gas, and stop the replacement after it is satisfied; the product gas should also be blown off for each valve pipeline, and the purity should be satisfied. Requirements; positive pressure seal after replacement to prevent outside air inhalation. 
4 It is not necessary to carry out the above blowing and replacement treatment when filling and storing general low-temperature liquids. 
5. For the initial filling, it is recommended to use normal pressure filling, that is, open the inner container vent valve V-12 before filling, and close it after the full treatment filling is completed. The inner container is at normal pressure or low pressure during the filling process, which is easy to operate; For filling rare or precious cryogenic liquids, the inner cylinder of the cryogenic storage tank can be cooled with liquid nitrogen first, and then replaced with low-temperature product gas to the specified purity, and then filled with cryogenic liquids, which can be filled with pressure.