Section 19(2) in The Static and Mobile Pressure Vessels (Unfired) Rules, 2016
(2)In case of vessels which are so designed, constructed or supported that they cannot be safely filled with water or liquids for hydraulic testing or which are used in services where traces of water cannot be tolerated, the Chief Controller may permit pneumatic testing along with non-destructive tests instead of hydraulic testing, as per procedure laid down in vessel fabrication code; after satisfying himself about the adequacy of the safety precautions undertaken.
