OS-C501

Offshore Standard DNV-OS-C501, November 2013
Sec.11 Fabrication – Page 172
recommended but not required by this standard. If a FAT test is not planned to be performed all parties of the
project shall be informed about this decision and the system integrity test shall identify the same aspects as a
FAT test.
Guidance note:
The factory acceptance test has the advantage that gross manufacturing errors are detected before the component
leaves the factory. In some cases it is inconvenient or to perform a FAT test. The system integrity test will detect the
same manufacturing mistakes as a FAT test, and the defect will be detected before operation starts. However,
replacement or repair may be more complicated if a defect is detected as late as in a system integrity test.
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5.2.4 The system integrity test is performed after final installation of all components and before the system
goes into service.
5.2.5 The system integrity test shall be performed on all structures according to the requirements for pressure
testing or other testing.
5.3 Pressure testing of vessels and pipes
5.3.1 All pressure vessels and pipes of safety class normal or high shall be pressure tested before going into
service.
5.3.2 A test pressure of 1.3 x maximum service pressure shall be used unless such a pressure would introduce
damage to the component that may reduce its lifetime. The maximum service pressure shall be the minimum
test pressure.
5.3.3 A detailed test programme shall be defined. The following shall be stated as a minimum:
— rates of pressure increase
— holding times
— time over which the pressure in the system shall not drop without actively applying pressure, i.e. a leakage
test.
5.3.4 The test schedule shall be developed for each application. The testing should allow detecting as many
possible defects in the structure as possible. As a general guidance the following schedules are recommended:
— the minimum time over which the maximum test pressure in the system (from [5.3.2]) shall not drop
without actively applying pressure should be at least 10 minutes for systems that do not creep
— for systems that show creep the maximum test pressure should be kept for 1 hour applying active pressure.
The pressure should be monitored for another hour without actively applying pressure. The pressure drop
shall be predicted before the test and the test result should be within 10% of the prediction.
5.3.5 Pressure vessels of low safety class shall be tested up to their service pressure. Pressures shall be applied
for at least 10 minutes.
5.3.6 Most authorities give general test requirements for pressure vessels. The requirements of the authorities
that govern the location of the application shall be followed.
5.4 Other testing
5.4.1 It is recommended to test structures of safety class normal or high up to their main maximum service
loads before going into service.
5.4.2 A test programme should be established based on the requirements of the application and the possibilities
to test the structure before it goes into service.
5.4.3 An equivalent approach as the one described for pressure testing should be used.
5.5 Dimensions
5.5.1 The dimensions of the component shall be checked to be within the specified tolerances.
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