LNG Gas Loss Control Point Resolution

LNG Gas Loss Control Point Resolution

Equipment Aspect

    Due to current manufacturing technology limitations of vacuum equipment, the equipment cannot           reach absolute vacuum state. Therefore, measures need to be taken to control this issue as much as       possible. The main approaches include: Firstly, using equipment with good insulation effects, such as using vacuum-wrapped storage tanks instead of pearl sand-filled LNG storage tanks. It is necessary      to regularly inspect the vacuum degree of equipment and vacuum pipelines, and if they do not meet        standards, re-evacuate the vacuum to ensure the equipment is in optimal working condition.

Personnel Operation Aspect

1. Standardize the operational procedures corresponding to various processes at the refueling station, enhance the training of refueling station staff, and improve the operational level and technical capabilities of personnel. When unloading the vehicle, it must be uniformly pressurized. During the pressurization operation, the gas phase of the storage tank must be connected to the liquid phase of the tank truck to balance the pressure. After completing the pressurization when gas enters the tank truck, the pressure of the storage tank will stabilize at a lower value. Strictly adopt the method of replacing the unloading pipeline with tank gas three times using the gas phase of the storage tank.

2. Post-unloading Stage

   When unloading LNG in the tank truck is complete, switch the liquid inlet from top to bottom by opening the discharge valve, and transfer the remaining LNG in the tank truck to the storage tank. This method can reduce the pressure of the tank truck to around 0.3 MPa, reducing unloading losses by approximately 80 kg.

3. Reasonably arrange liquid inlet plans to prevent situations where three or more refueling stations jointly unload a single vehicle.

4. After unloading, adjust the frequency of the suction liquid pump based on the liquid inlet situation in the pump pit to balance the inflow and outflow of the pump pit. The maximum frequency of the suction liquid pump should not exceed 95Hz.

5. When the liquid temperature is low (below -140°C) and the tank pressure is high, perform a "liquid-pump-top liquid" circulation operation to cool and liquefy part of the gas in the gas space to reduce the tank pressure and frequency of emissions.

6. Regularly check if the liquid inlet control valve is leaking internally. Check by using a gun to add liquid; if the screen displays a liquid volume, it can be determined that the valve is leaking internally and needs to be replaced. If there is a squeaking sound in the gas hose when adding liquid before the control valve jumps, it can be determined that it is leaking internally.

7. During venting, slowly open the vent valve, and a person must be present on-site to monitor. When the pressure drops to a normal value, promptly close the vent valve.