Section 15(3) in The Static And Mobile Pressure Vessels (Unfired) Rules, 1981
(3)[ The water capacity of the cryogenic pressure vessel shall be rated in terms of gross water capacity and the usable water capacity in litres at 150C. The usable water capacity shall not exceed 95% of the gross water capacity. An overflow pipe shall be provided at the maximum usable capacity level as a safeguard against filling the vessel beyond the maximum usable capacity.]
