Section 14 in The Static And Mobile Pressure Vessels (Unfired) Rules, 1981
14. Design of vessels for gases at low temperature .-(1) Refrigerated vessels .-(i) Vessels used for storage of refrigerated gases shall be designed in accordance with low temperature requirements under the Design Code referred to in sub-rule (1) of rule 12.
(ii)The capacity of the refrigeration system shall be adequate to maintain the gas in the vessel at a temperature so that its vapour pressure does not exceed the design pressure of the vessel and shall also remain below the pressure-setting of the relief valve on the vessel.(2)Insulated vessels .-(i) The shell of the vessel and its manhole nozzle shall be insulated with a material approved by the Chief Controller. The entire insulation shall be covered with a metal jacket of a thickness not less than 3 mm. nominal and flashed around all openings so as to be weather-tight.(ii)The insulation shall be of sufficient thickness so that the thermal conductance at 150C (expressed in calories or sq. cm. per hour per degree centigrade temperature differential) does not exceed the limit prescribed by the Chief Controller.(3)[ Cryogenic pressure vessels .-(i) The design service temperature of the cryogenic pressure vessels shall not be warmer than the normal boiling point of the cryogenic liquid.(ii)The materials of construction of the inner vessel, its piping and fittings shall be suitable for the service temperature and compatible for the specific cryogenic liquid.(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.(iv)The inner supports between the inner vessel and the outer vessel shall be of non-inflammable materials and capable of supporting the inner vessel together with the maximum allowable cryogenic liquid. The supports shall be able to withstand expansion or contraction within the operating temperature range. Cryogenic pressure vessels meant for transport purpose, shall be able to withstand combined loading of vertical down of two, vertical upward of one and a half, longitudinal of one and a half and lateral of one and a half times the weight of the vessel with attachment and the full load of cryogenic liquid. The factor of safety of the supports shall be as per the design code.(v)The air in the annular space between the inner and outer vessel shall be evacuated and the space shall be filled with suitable insulating material compatible with the particular cryogenic liquid.]
