1. Upon the arrival of an LNG tanker truck at the station, guide and supervise it to park at the designated unloading bay; ensure the grounding cable is properly connected and wheel chocks are securely placed.
2. Inspect the temperatures of the liquid within both the tanker truck and the storage tank to determine the appropriate unloading strategy: if the storage tank's liquid temperature is higher than that of the tanker truck, top-loading (top liquid entry) is recommended; otherwise, bottom-loading (bottom liquid entry) should be utilized.
3. Verify the integrity and condition of the flexible hoses used for both the liquid and gas phases during the LNG unloading process.
4. Check the pressure and liquid levels within the storage tanks located in the tank farm area.
5. In accordance with the standard LNG filling procedure, verify that the open/closed positions of all valves-from the unloading platform to the storage tanks-are set correctly.
6. Once all the above points have been accurately verified, the station operator shall check the tanker truck's pressure, temperature, and liquid level, and record these readings.
7. Operations involving the pipeline section between the unloading area and the tank farm shall be performed by the station operator; operations involving the connection between the tanker truck and the unloading platform shall be performed by the tanker truck's escort/attendant. During the filling process, conduct periodic patrols to inspect the operating status of all process valves, pipelines, and instrumentation; maintain detailed records and remain vigilant regarding potential safety hazards.
8. Specific Unloading Procedures:
Pressurize the tanker truck: increase the tanker's internal pressure until it exceeds the storage tank's pressure by 0.2 MPa; the tanker's pressure must not exceed a maximum limit of 0.66 MPa.
Once it is confirmed that the tanker's pressure has reached the specified level, correctly open the liquid inlet valve.
Observe the liquid inlet pipeline: if frost formation is visible and the sound of flowing liquid can be heard, the unloading process is proceeding normally. If any leaks are detected (e.g., at joints or connections), immediately halt the unloading operation and take corrective measures to eliminate the hazard.
Monitor the pressure and liquid level fluctuations in both the tanker truck and the storage tank. By adjusting the pressure in the storage tank (venting) and the tanker truck (pressurizing), maintain a pressure differential of approximately 0.2 MPa; the tanker's pressure must not exceed a maximum limit of 0.66 MPa.
Once the LNG has been completely unloaded, close the inlet valve on the liquid-phase pipeline as well as the main inlet shut-off valve on the storage tank.
