Seeking advice: What precautions should be taken when loading LNG?

1. Use quick connectors and metal pipes during loading; it is recommended to use a dedicated loading arm. I won’t go into details about the minor issues; the disadvantages are high costs, complex maintenance, and less flexibility in operation compared to hoses. 2. The tank truck used for loading must be equipped with on-site level gauges, high-level alarms, and proper anti-static measures. 3. The tank truck has two connections, one for the liquid phase and one for the gas phase, along with an emergency shut-off valve. 4. After LNG is pumped from the tank into the tank truck, the gas phase from the tank truck returns to the tank or is sent directly to the flare. 5. The initial loading speed must be strictly controlled at 1 M/S. 6. Check the pressure and temperature inside the tank before loading to prevent abnormal pressure and temperature levels in the tank. 7. Before the loading process, conduct inspections using the checklist; during loading, operators must monitor the site and pay attention to changes in pressure and temperature. 8. When loading the vehicle, appropriate PPE must be worn, including frost-resistant gloves, masks, and other necessary protective equipment. 9. The on-site fire-fighting equipment, gas detectors, and emergency alarms are well installed, and there are two sets of full-face respirator systems. Develop feasible and reliable emergency plans. 10. The advantage of automated loading is that once the loading volume is set based on the order quantity, the computer controls the loading process, while the personnel on site and those at the DCS simply monitor it. This way, the operator does not need to adjust parameters such as flow rate and pressure every time.

2# cwmine Thank you, it’s very detailed and very helpful to me.

So, are CNC valves or ball valves used for LNG loading? That one is better/

4# poly0924: We use automatically controlled shut-off valves (ball valves). Before loading, the driver swipes a card; once the swipe is made, loading begins automatically. Once the predetermined amount of LNG has been loaded as recorded on the card, the control system automatically shuts off the ESD valves and FV valves in the liquid phase pipeline, as well as the ESD valve in the gas phase pipeline. After that, nitrogen is used for purging, and the loading arm is removed, thus completing the LNG loading process.

The equipment upstairs is so advanced~ We use everything manually...

5# htrs001 Thank you for your detailed explanation. I still have two questions I’m not clear about, so I’d like to ask you for help 1. What pressure is generally required to maintain the temperature and pressure inside the truck when it enters the loading area? 2. During loading, is this pressure constant, or is it maintained at a constant level using control valves? 3. Once the return air arms are connected, does the pressure inside the tank decrease to atmospheric pressure?

Hello! 1. The tank of the tank truck is not equipped with a thermometer, so it is not possible to determine the exact temperature value; however, as long as LNG is present inside, the tank should be at a low temperature. The pressure should generally not exceed 5 Bar before loading. 2. When starting the loading process, liquid is introduced from the top of the tank; if a decrease in pressure is observed, liquid is introduced from the bottom as well, with liquid being supplied simultaneously from both the top and bottom. After that, the pressure inside the tank will still drop a bit, but not significantly. 3. It can remain unused after the return air arm is connected; pressure reduction is carried out through this arm only when the pressure in the tank is particularly high. After the air return arm is put into use, the pressure inside the tank will decrease, but it will not reach atmospheric pressure. 7# shzx603

Also, the unloading of LNG tankers is generally not as advanced as what was mentioned above. Unloading is generally done using an unloading booster, and the process is quite simple. LNG tank trucks usually have three connections: two for the liquid phase and one for the gas phase. Once the liquid phase connection is opened, the LNG liquid flows into the booster vaporizer; the vaporized liquid then enters the tank truck, raising its pressure by about 2 bar compared to that of the storage tank. By opening the other liquid phase connection, the liquid can directly flow into the storage tank! Many stations these days use this method for unloading and loading. Of course, in liquefaction plants, low-temperature pumps are often used for loading, and liquid flow meters are generally installed for measurement, with the process being controlled by a control system. As for loading, manual valves are used in ordinary small LNG plants, while cryopumps are operated in a sequential manner. So, if you have money, you can use a control valve; if not, a manual one will do just fine! The above are personal opinions for reference only.

I’ve learned something new; thank you to the person who replied above. Which type of measurement method offers greater accuracy for measuring LNG during loading? Online weighing or a gas flow meter installed in the gas line?

Please share more, so that we can learn more about the current situation