Special requirements for Cryogenic LNG storage tanks

Natural gas is recognized as a clean, environmentally friendly, and safe high-quality energy source. The volume of liquefied natural gas is reduced by about 600 times, which brings great benefits to storage. Atmospheric cryogenic storage tanks are used to store liquefied natural gas.
1. Cryogenic resistance
The boiling point of LNG under normal pressure is -160℃. LNG chooses low-temperature and normal-pressure storage method to reduce the temperature of natural gas below the boiling point, so that the operating pressure of the storage tank is slightly higher than normal pressure. Compared with the high-pressure and normal temperature storage method, it can greatly reduce the thickness of the tank wall and improve safety performance. LNG requires that the liquid storage tank has good cryogenic resistance and excellent cold insulation performance.
2. High safety requirements
Because of the low temperature liquid stored in the tank, once an accident occurs in the storage tank, the refrigerated liquid will evaporate a lot, and the amount of gasification is 300 times that of the original refrigerated state, forming an air mass that will automatically detonate in the atmosphere.
Therefore, the storage tank is required to adopt a double-wall structure, using the blocking concept. When the first layer of tank leaks, the second layer of tank can completely block the leaked liquid and evaporated gas to ensure storage safety.
3. Special materials
The inner tank wall requires low temperature resistance, generally 9Ni steel or aluminum alloy materials are used, and the outer tank wall is prestressed reinforced concrete. 4. Strict insulation measures
Because the temperature difference between the inside and outside of the tank can be up to 200°C, to maintain the temperature inside the tank at -160°C, the tank body must have good cold insulation performance, and high-performance cold insulation materials are filled between the inner and outer tanks. The cold insulation material at the bottom of the storage tank should also have sufficient pressure bearing performance.
5. Good seismic performance
The seismic requirements of general buildings are to crack without falling under the prescribed seismic load. To ensure the safety of the storage tank under unexpected loads, the storage tank must have good seismic performance. For LNG storage tanks, it is required not to fall or crack under the prescribed seismic load.
For reasons, the selected construction site should generally avoid the seismic fault zone. Before the construction, the seismic test of the storage tank should be done to analyze the structural performance of the storage tank under dynamic conditions to ensure that the tank body is not damaged under a given seismic intensity.
6. Strict construction requirements
The welding seam of the LNG storage tank must be tested with 100% magnetic particle and 100% vacuum tightness. To strictly select cold-keeping materials, the prescribed procedures should be followed during construction. To prevent cracks in the concrete, post-tensioned prestressed construction is adopted, and the verticality of the tank wall is strictly controlled.