What is the purpose of a secondary containment system in a double containment LNG tank?

The primary purpose of a secondary containment system in a double containment LNG tank is to provide a backup barrier to prevent the uncontrolled release of LNG to the environment in the event of a leak or failure in the primary (inner) tank. The secondary containment typically consists of an outer tank surrounding the inner tank, with a designed space between them. Should the inner tank develop a leak, the leaked LNG would be contained within this space, preventing it from spreading to the surrounding area. This containment prevents the formation of a large vapor cloud, reducing the risk of fire or explosion. The secondary containment system also provides time for emergency response teams to assess the situation and take appropriate action, such as transferring the remaining LNG to another tank or implementing mitigation measures. The design of the secondary containment system includes considerations for the volume of LNG that it must contain, the rate at which LNG might leak from the primary tank, and the thermal properties of the materials used in the secondary containment structure. The system is also designed to withstand the cryogenic temperatures of LNG and the hydrostatic pressure exerted by the contained liquid. The secondary containment may also include features such as leak detection systems, vapor suppression systems, and remote-operated valves to further enhance its effectiveness.