(a) Each tube shall be hydraulically tested at the makers’ works and shall withstand a hydraulic pressure to one and half times, the design pressure, subject to a minimum of 1.00 kg/mm sq. and for tube OD larger than 101 mm outside diameter minimum of 0.8 kg/mm sq.  However, the test pressure shall not be greater than the pressure calculated by the following formula. 

                             2 S t

                P  =  -------------

                          D

Where P = test pressure  (in kg/mm sq.)

           D = specified outside diameter of the tube

            t   = specified wall thickness

            S = stress (in kgf/mm sq.) which shall be taken as 40% of the specified minimum tensile strength at room temperature.

(b) Notwithstanding anything contained in the above regulation, the hydraulic test at the maker’s works may be dispensed with, provided that the tubes are subjected to non destructive testing by an appropriate method like Ultrasonic or Eddy current testing.