Under which circumstances is drydocking of a vessel required and what repair and maintenance works are carried out in dry dock?
Short answer
- Circumstances: IWS reveals damage/deterioration requiring early attention; underwater parts need out-of-water assessment; passenger ships at least twice in any 5-year period; temporary repairs must be made permanent; coating in double bottom/ballast tanks less than GOOD
- Typical works: hull cleaning and coating; underwater structural repairs; tailshaft survey/repairs; propeller inspection/repair; rudder inspection; sea chest and sea valve maintenance; sacrificial anode replacement; bottom survey and thickness measurements; sea connections and transducers maintenance; stern gland/seal inspection
- Instruments: IACS UR Z3 §Z3.3.6; MSC.1/Circ.1348 anx-1 §4.1; Rec 133 §8; Bahamas Bulletin No.73; SOLAS Chapter I
- Trap: Drydocking is not just for class—statutory surveys (SOLAS) also mandate it for passenger ships
Full answer
The full answer explains each point step by step, with the regulations and figures behind it and the discussion from other candidates. It is in the MEO Class IV section of the Marine One forum, open to members enrolled for the MEO Class IV exam.