Abstract: Heat barrier components and improved thermal insulation techniques are provided for an external tank insulation system of ships carrying liquefied natural gas, propane, ammonia, etc. Reduction of liquid boil-off rate or initial cost of insulation through the reduction of radiant heat leak is accomplished by a composite insulation system including a high reflectance component material on the external surface of insulation and/or interior surface of the ship facing the tank. Further, refrigeration in tank boil-off is used to cool a radiation shield located between the tank insulation and surrounding enclosure, and to cool the skirt support.

Abstract: Multiple insulation barrier layers are held against the interior of a tank by plastic fasteners. Preferably three insulation component layers are used with a layer of fiberglass between the first and second layers to provide independent movement. Two composite membranes, one in contact with the tank and one in contact with the liquid cryogen, provide a barrier to liquid/vapor passage through the system.