Code of Federal Regulations Title 46. Shipping § 46.137.300 Intervals for drydock and internal structural examinations

(1) A vessel that is exposed to salt water more than 6 months in any 12–month period since the last examination or initial certification must undergo a drydock and internal structural examination at least twice every 5 years, with not more than 36 months between examinations.

(2) A vessel that is exposed to salt water not more than 6 months in any 12–month period since the last examination or initial certification must undergo a drydock and internal structural examination at least once every 5 years.

(1) An internal structural examination of any affected space of a vessel, including its fuel tanks;

(2) A removal of the vessel from service to assess the extent of the damage and to affect permanent repairs;  or

(3) An adjustment of the drydock examination intervals to monitor the vessel's structural condition.