LNG low-temperature and normal-pressure storage tank
Thread Content
Which senior colleague has information on equipment for LNG storage tanks at low temperature and normal pressure, with an internal tank pressure of 20 kPa and an external tank pressure of 5 kPa? How is this type of equipment unloaded from the vehicle? The equipment manufacturer said that the liquid can be unloaded directly using a tank truck, without the need for a booster? What is this unloading process?
The tank truck is equipped with its own pressure boosting device. You also need to check whether the pressure inside the tank truck is higher than that inside the tank; this requires flexible judgment.
LNG tank truck unloading process: 1. Connect the flexible metal hose to the tank truck, and determine the setting pressure of the tank truck’s safety valve； 2. Open the valves for discharging residual gases and liquids from the vapor and liquid phases, and purge the pipelines. Open the inlet valves at the top of the storage tanks as well as those at the bottom of the tank trucks to equalize the pressures. When the pressure in the tank truck rises to 0.05 Mpa (this value depends on the setting of the tank truck’s safety valve), close the valve at the bottom of the tank truck for 3–5 minutes. Once the pressure in the tank truck drops, proceed with another round of pressure equalization, and repeat this process until the pressures in both storage tanks are equal. In special cases, if it is not possible to further reduce the pressure, release the pressure from the storage tanks to a level below the setting of the tank truck’s safety valve ； 3. Open the liquid-phase and gas-phase valves of the tank truck, and use a vaporizer to increase the pressure inside the tank truck. When the pressure in the tank truck rises to 0.005 Mpa above the pressure in the storage tank, or when it reaches the setting pressure of the safety valve, which is also 0.005 Mpa (this value depends on the setting pressure of the tank truck’s safety valve), slowly open the liquid outlet valve at the bottom of the tank truck to begin unloading. It is important to monitor the pressure changes in the tank truck; if the pressure drops too rapidly, close the liquid outlet valve and wait until the pressure stabilizes before opening it again to continue unloading. When the liquid level indicated by the gauge in the tank truck is one-quarter full, close the liquid outlet valve and continue to increase the pressure inside the tank truck. Once the pressure reaches 0.005 Mpa again, slowly open the liquid outlet valve to continue unloading until the process is complete ；
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