Section 20(2)(a) in The Merchant Shipping (Cargo Ship Construction And Survey) Rules, 1974
(a)Parts of every such compressed air system other than a pneumatic control system which are subjected to air pressure shall be so designed and constructed as to withstand, with adequate factor of safety, the maximum working stresses to which they may be subjected and every air pressure pipe or fitting in such system shall, before being put into service for the first time, be subjected to a hydraulic test to twice its maximum working pressure and be maintained in an efficient condition.