LPG storage tank pressure

Taking nitrogen as an example, the brief description is as follows: Nitrogen is injected into the storage tank from the liquid inlet to raise the tank pressure to 0.6MPa. After maintaining the pressure for 10 minutes, the gas is discharged from the drain outlet and the tank pressure drops to 0.2MPa (storage tank Always maintain a positive pressure nitrogen sealing state to prevent air from entering) and close the drain outlet (when deflating, you can momentarily open the end valves of the gas phase port, return port, and liquid outlet pipeline to remove the air in the pipeline).