(i) Each tube shall be tested by the manufacturer and shall withstand a hydraulic pressure to one and a half time the design pressure subject to a minimum of 1.00 kgf/mm², but not greater than pressure calculated by the following formula:-

           P = 2 St/D

where  P = test Pressure

           D = specified out side diameter of the tube

           t = specified wall thickness of the tube

           S = stress which shall be taken as 40% of the minimum tensile strength at room temperature for carbon and ferritic steel and 80% of the minimum yield strength at room temperature for austenitic stainless steel

(ii)  Notwithstanding anything contained in the above clause, the hydraulic test at the maker's works may be dispensed with, provided that the tubes are subject to non destructive testing by an appropriate method like Ultrasonic or Eddy current or Stray Flux testing.