[Engineering][Knowledge]Leaking test requirement for shop assembled tank

As per Annex J of API 650(12th ed),

J.4.2.2    Testing
Unless otherwise specified by the Purchaser, as an alternative to the requirements of 7.3.2 through 7.3.7, a tank may be shop tested for leaks by the following method:

a)  The  tank  bottom  shall  be  braced  by  securely  attaching  an  external  stiffening  member  as  required  to  prevent permanent deformation during the test.
b)  All openings shall be closed with plugs or covers as needed. Bolts and gaskets of the size and type required for final installation shall be used during the test.
c)  An internal air pressure of 14 kPa to 21 kPa (2 lbf/in.2 to 3 lbf/in.2) gauge shall be applied to the tank. For tanks with a diameter of 3.7 m (12 ft) or less, a maximum pressure of 35 kPa (5 lbf/in.2) gauge shall be used.
d)  Soap film, linseed oil, or another material suitable for the detection of leaks shall be applied to all shell, bottom, roof, and attachment welds, and the tank shall be carefully examined for leaks.
e)  After the air pressure is released, the external stiffening member shall be removed, and any weld scars shall be repaired.