Section 21 in The Static And Mobile Pressure Vessels (Unfired) Rules, 1981
21. General .-(1) All vessels meant for storage of compressed gas shall be installed entirely above-ground, that is to say, no part of the vessel shall be buried below the ground level.
(2)Vessels and first stage regulating equipment shall be located in the open.(3)Vessels shall not be installed one above the other.(4)Vessels within a group shall be so located that their longitudinal axes are parallel to each other.(5)No vessel shall be located within the bonded area of petroleum or other flammable liquid storages.(6)Sufficient space shall be provided between two vessels to permit fire-fighting operations.(7)Two or more vessels installed in batteries shall be so installed that the top surface of the vessels are on the same plane.(8)Vessels installed with their dished ends facing each other shall have screen walls in between them.(9)[ Notwithstanding anything contained in sub-rules (1) to (8) above, vessels for storage of liquefied petroleum gas can be placed underground or covered by earth in such manner and subject to such conditions as may be specified by notifications by the Central Government.](10)[ Aboveground vessel for storage of corrosive, flammable or toxic gas in liquefied state shall be provided with enclosure wall all around the ground. The minimum distance between vessel and enclosure wall shall be the diameter of the vessel or five metres, whichever is less. The ground shall be graded to form a slope away from pumps, compressors or other equipments. The height of the enclosure wall shall be thirty centimetres on the upper side and gradually increasing to maximum sixty centimetres on the lower side, at the end of which a shallow sump for collection of the spilled liquid, if any, shall be provided. The minimum separation distance between the vessel and the sump shall be,-(a)diameter of the vessel, in case of vessels with water capacity not exceeding forty thousand litres,(b)fifteen metres, if the water capacity of the vessels exceeds forty thousand litres.]
