1. Liquid nitrogen pre-cooling:

1. Vent the pressure of the storage tank to slightly positive pressure, and close the lower inlet valve. Close the balance valve of the level gauge and use the level gauge.

2. Slowly open the liquid phase valve of the tanker to a smaller opening, and slowly close the gas phase valve of the small tanker to allow liquid nitrogen to enter the liquid from the upper part of the storage tank. Control the opening of the unloading platform valve to keep the pressure at 0.3MPa. When the pressure of the storage tank rises to 0.2MPa～0.3MPa, the unloading platform valve should be closed in time, and the gas phase of the storage tank should be manually vented and relieved, and this operation should be repeated.　　

3. Listen carefully to the sound in the storage tank and observe the pressure of the storage tank at the same time. When the sound decreases and the pressure no longer rises, you can slowly open the front and rear valves of the emergency shut-off valve at the lower part of the storage tank to feed liquid up and down simultaneously. Closely observe and record the pressure of the storage tank during the liquid feeding process to prevent the pressure from rising. When the pressure rises, the outlet valve of the tank truck should be closed in time, and the gas phase of the storage tank should be opened to manually vent and relieve the pressure.

4. When the liquid level gauge of the storage tank reaches a certain value (usually 20% of the storage tank), the liquid inlet ends.

5. After the liquid inlet task is completed, close the liquid phase valve of the tanker, open the gas phase valve of the tanker, and purge the unloading pipeline to the storage tank.　　

6. Close the tank truck valve and the unloading valve of the unloading platform, and unload the hose. After closing the unloading platform valve, the liquid between the valve and the check valve should be vented.

7. Close the manual vent valve of the gas phase of the storage tank and the front stop valve of the emergency shut-off valve for the lower part of the tank. The inlet valve on the upper part of the storage tank will be closed after the unloading truck LNG pipeline returns to normal temperature.

8. Use the liquid nitrogen in the storage tank to pre-cool the supercharger, air-bath vaporizer and other low-temperature pipelines.