This European Standard specifies the requirements for materials, design and installation of the insulation of refrigerated liquefied gas (RLG) storage tanks. RLG storage tanks store liquefied gas with a low boiling point, i.e. below normal ambient temperature. The concept of storing such products in liquid form and in non-pressurized tanks therefore depends on the combination of latent heat of vaporization and thermal insulation. Consequently thermal insulation for RLG storage tanks is not an ancillary part of the containment system (as for most ambient atmospheric hydrocarbon tanks) but it is an essential component and the storage tank cannot operate without a properly designed, installed and maintained insulation system. The main functions of the insulation in RLG storage tanks are: ? to maintain the boil off below the specific limits; ? to protect the non low temperature parts/materials of the tank (mainly the outer tank) by maintaining these parts at their required ambient temperature; ? to limit the cool-down of the foundations/soil underneath the tank to prevent damage by frost heave; ? to prevent/minimize condensation and icing on the outer surfaces of the tank. A wide range of insulation materials is available. However the material properties differ greatly amongst the various generically different materials and also within the same generic group of materials. Therefore within the scope of this European Standard, only general guidance on selection of materials is given. NOTE For general guidance on selection of materials see Annex A. This European Standard deals with the design and manufacture of site built, vertical, cylindrical, flat-bottomed steel tanks for the storage of refrigerated, liquefied gases with operating temperatures between 0 °C and –165 °C.