The following two types of tests are specified  for testing tanks

Structural Test:

A test to verify the structural adequacy of the tank construction of the tanks. This may be a hydrostatic test or, where the situation warrants, a hydropneumatic test.

Leak Test:

A test to verify the tightness of a the boundary. Unless a specific test is indicated, this may be a

a     Hydrostatic

b     hydropneumatic test or

c      air test.

Leak test with remark *3 in Table 1 includes A hose test as may be considered an acceptable medium form of leak test for certain boundaries, as indicated by Footnote 3 of Table 1. of the test.

Leak test require a access to inspection while structural test does not require to gain access

The definition of each test type is as follows

Hydrostatic Test: (Leak and Structural)	A test wherein a space is filled with a liquid to aspecified head.
Hydropneumatic Test: (Leak and Structural)	A test combining a hydrostatic test and an air test, wherein a space is partially filled with a liquid and  pressurized with air.
Hose Test: (Leak)	A test to verify the tightness of a joint by a jet of water with the joint visible from the opposite side
Air Tests: (Leak)	A test to verify the tightness by means of air pressure differential and leak indicating solution. It includes tank air tests and joint air tests, such as a compressed air fillet weld tests and vacuum box tests.	above atmospheric pressure not less than 0.15·105 Pa, with a leak indication indicating solution such as soapy water/detergent or a proprietary brand applied
Compressed Air Fillet Weld Test: (Leak	An air test of a fillet welded tee joints wherein a leak indicating solution is applied on fillet welds.
Vacuum Box Test: (Leak)	A box over a joint with leak indicating solution applied on the welds. A vacuum is created inside the box to detect any leaks
Ultrasonic Test: (Leak)	A test to verify the tightness of a the sealing of closing devices such as hatch covers by means of ultrasonic  detection techniques.
Penetration Test: (Leak)	A test to verify that no visual dye penetrant indications of potential continuous leakages exist in the boundaries of a compartment by the application means of low surface tension liquids (i.e. dye penetrant test)

Test Methods

 Hydrostatic Ttest

 Unless another liquid is approved, the hydrostatic tests are is to consist of filling the space by with fresh water or sea water, whichever is appropriate for testing of the space, to the level specified in Table 1 or Table 2. In cases where a tank for cargoes with higher density cargoes is to be tested with fresh water or sea water, the testing pressure height is to be specially considered. All external surfaces of the tested space are to be examined for structural distortion, bulging and buckling, other related damage and leaks.

 Hydropneumatic test

A Hydropneumatic tests, where approved, are to be such that test condition, in conjunction with the approved liquid level and supplemental air pressure, will simulate the actual loading as far as practicable. The requirements and recommendations for tank air tests in 4.4.4 will also apply to the hydropneumatic tests. S14 Page 6 of 12 IACS Req. 1996/Rev.5 2015 S14 (cont) All external surfaces of the tested space are to be examined for structural distortion, bulging and buckling, other related damage and leaks.

 Hose test

 A hose test is Hose tests are to be carried out with the pressure in the hose nozzle maintained at least at 2·105 Pa during the test. The nozzle is to have a minimum inside diameter of 12 mm and be at a perpendicular distance to from the joint not exceeding 1.5 m. The water jet is to impinge directly upon the weld. Where a hose test is not practical because of possible damage to machinery, electrical equipment insulation or outfitting items, it may be replaced by a careful visual examination of welded connections, supported where necessary by means such as a dye penetrant test or ultrasonic leak test or an the equivalent.

Tank air test

All boundary welds, erection joints and penetrations, including pipe connections, are to be examined in accordance with the approved procedure and under a stabilized pressure differential above atmospheric pressure not less than 0.15·105 Pa, with a leak indication indicating solution such as soapy water/detergent or a proprietary brand applied.

A double inspection is to be made of tested welds. The first is to be immediately upon applying the leak indication solution; the second is to be after approximately four or five minutes in order to detect those smaller leaks which may take time to appear.

4.4.5 Compressed air fillet weld test

 In this air test, compressed air is injected from one end of a fillet welded joint and the pressure verified at the other end of the joint by a pressure gauge on the opposite side. Pressure gauges are to be arranged so that an air pressure of at least 0.15·105 Pa can be verified at each end of all passages within the portion being tested. Note: Where a leak test of is required for fabrication involving partial penetration welding is required and the root face is sufficiently large (i.e.,6-8mm), the welds, a compressed air test is also to be applied in the same manner as for a to fillet weld where the root face is large, i.e., 6-8 mm.

 Vacuum box test

A box (vacuum testing box tester) with air connections, gauges and an inspection window is placed over the joint with a leak indicator indicating solution applied to the weld cap vicinity. The air within the box is removed by an ejector to create a vacuum of 0.20·105 – 0.26·105 Pa inside the box. S14 Page 7 of 12 IACS Req. 1996/Rev.5 2015 S14 (cont)

 Ultrasonic test

An arrangement of an ultrasonic echoes transmitter placed is to be arranged inside of a compartment and a receiver is to be arranged on the outside. The watertight/weathertight boundaries of the compartment are scanned with the receiver in order to detect an ultrasonic leak indication. A location where the sound is detectable by the receiver displays indicates a leakage in the sealing of the compartment.

 Penetration test

 A test of butt welds by applying a or other weld joints uses the application of a low surface tension liquid to at one side of a compartment boundary. When or structural arrangement. If no liquid is detected on the opposite sides of the boundary boundaries after the expiration of a definite defined period of time, the verification of this indicates tightness of the compartments boundary can boundaries. In certain cases, a developer solution may be assumed painted or sprayed on the other side of the weld to aid leak detection.

Tank or boundary to be tested

1 Double bottom

2 Double bottom voids*

3 Double side tanks

4 Double side voids  5 Deep tanks other than those listed elsewhere in this table

2 6 Cargo oil tanks  Ballast hold of bulk  8 Peak   tanks  1 Fore peak  spaces with equipment