Natural gas is widely recognized as a clean, environmentally friendly, and safe high-quality energy source. Once liquefied, natural gas is reduced in volume by approximately 600 times, offering significant benefits for storage. Liquefied Natural Gas (LNG) storage is achieved using atmospheric pressure and low-temperature tanks. Let's discuss the unique features of these LNG storage tanks.

What are the special requirements for LNG low-temperature storage tanks?

1.Low-temperature resistant

The boiling point of liquefied natural gas (LNG) at atmospheric pressure is -160°C. LNG is stored at low temperatures and atmospheric pressure, lowering the gas temperature below its boiling point. This results in storage tanks operating at slightly higher pressure than atmospheric, which, compared to high-pressure, ambient-temperature storage, significantly reduces the tank wall thickness and enhances safety performance.

Therefore, LNG requires storage tanks with excellent low-temperature resistance and superior insulation properties.

2.High safety requirements

Due to the storage of low-temperature liquids inside the tank, in the event of an accident, the refrigerated liquid will evaporate in large quantities, with the vaporization rate being approximately 300 times the original refrigerated state, forming explosive gas clouds in the atmosphere.

Therefore, standards such as API and BS require double-walled tank structures and the use of containment principles. In the event of a leak in the first layer, the second layer can completely seal off the leaked liquid and evaporated gases, ensuring storage safety.

3.Special material

The inner tank wall must withstand low temperatures, typically made of 9Ni steel or aluminum alloys, while the outer tank wall is made of prestressed reinforced concrete.

4.Strict thermal insulation measures

The tank must have excellent thermal insulation properties to maintain an internal temperature of -160°C, given the maximum temperature difference between inside and outside the tank can reach up to 200°C. High-performance thermal insulation materials must be filled between the inner and outer tanks. The insulation material at the bottom of the tank must also possess sufficient pressure-bearing capabilities.

5.Excellent seismic performance

The seismic requirements for general buildings are to crack but not collapse under specified earthquake loads. To ensure the safety of storage tanks under accidental loads, they must possess excellent seismic performance. For LNG tanks, it is required that they neither collapse nor crack under the specified earthquake loads.

Therefore, the selected construction site typically avoids seismic fault zones, and anti-seismic tests must be conducted on the storage tanks before construction. This ensures the structural performance of the tanks under dynamic conditions, guaranteeing that the tank body will not be damaged under the given seismic intensity.

6.Stringent construction requirements

Tanks must undergo 100% magnetic particle testing (MT) and 100% vacuum tightness testing (VBT). Select insulating materials strictly, and follow the specified procedures during construction. To prevent cracks in concrete, post-tensioned prestressed construction is used universally, with strict control over the verticality of the tank walls.