Special requirements for LNG cryogenic storage tanks
LNG requires the liquid storage tank to have good low temperature resistance and excellent cold preservation performance.
(1) Low temperature resistance.
The boiling point of liquefied natural gas under normal pressure is -160℃. LNG chooses low temperature and normal pressure storage to reduce the temperature of natural gas to below the boiling point, so that the operating pressure of the liquid storage tank is slightly higher than the normal pressure. Compared with the high pressure and normal temperature storage method, the thickness of the tank wall can be greatly reduced and the safety performance can be improved. Therefore, LNG requires the liquid storage tank to have good low temperature resistance and excellent cold preservation performance.
(2) High safety requirements.
Since the tank stores low temperature liquid, once an accident occurs in the tank, the refrigerated liquid will evaporate in large quantities, and the gasification amount is about 300 times that of the original refrigerated state, forming a gas mass that will automatically explode in the atmosphere. Therefore, API, BS and other specifications require that the storage tank adopt a double-wall structure and use the blocking concept. When the first layer of the tank leaks, the second layer of the tank can completely block the leaking liquid and evaporating gas to ensure storage safety.
