Section 14(3)(iii) in The Static And Mobile Pressure Vessels (Unfired) Rules, 1981
(iii)The outer vessel shall be made of steel not less than 3 mm nominal thickness or of aluminium not less than 4 mm nominal thickness and shall have required structural strength and capable for supporting the inner vessel together with cryogenic liquid, insulation and other fittings. The outer vessel of vacuum insulated cryogenic tanks shall be designed for a minimum collapsible pressure of one atmosphere (gauge). The suitable protecting coating shall be provided on the outer vessel to avoid corrosion. The outer vessel shall also be provided with suitable lifting arrangement and supports for installation or mounting.