5 Maintenance considerations
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Statutory Documents - IMO Publications and Documents - Circulars - Maritime Safety Committee - MSC.1/Circular.1348 – Guidelines for the Assessment of Technical Provisions for the Performance of an In-Water Survey in Lieu of Bottom Inspection in Dry-Dock – (2 June 2010) - Annex – Guidelines for the Assessment of Technical Provisions for the Performance of an In-Water Survey in Lieu of Bottom Inspection in Dry-Dock to Permit one Dry-Dock Examination in any Five-Year Period for Passenger Ships Other than Ro-Ro Passenger Ships - 5 Maintenance considerations

5 Maintenance considerations

  5.1 A basic requirement for consideration to allow one inspection in dry-dock in five years is that a comprehensive maintenance regime based upon a five-year cycle should be effectively implemented by the company for the relevant items. The items to be considered may include the following:

  • .1 Shafting and stern tube — Stern tube bearings should be oil lubricated or, in the case of water lubricated systems, the shafting should be of corrosion resistant material. Where weardown measurements are unable to be taken, special consideration may be given to ascertaining sternbush clearances based on a review of the operating history, onboard testing and stern bearing oil analysis.

  • .2 Shell coating —The hull coating system should be able to perform its functions of corrosion protection and anti-fouling over the anticipated five-year period in water. The use of a high resistance coating or advanced coating, such as silicone-based paint, would be examples of typical coating systems that could be accepted.

  • .3 Shaft seals – Shaft seals should be capable of five-year service. The use of advanced systems such as air seals with failure mode redundancy could be considered as offering added confidence of service life.

  • .4 Bow thrusters and stern thrusters — Inspection and replacement of propeller blade foot seals of the bow thrusters and stern thrusters should be based upon a five-year interval, taking into account the lubricating oil record. Bow and stern thrusters dismantling for general overhauling may be considered at intervals greater than five years, in accordance with manufacturer's recommendations.

  • .5 Rope cutters – The fitting of rope cutters may be an added safeguard to give confidence to continued trouble-free operation of propulsion shaft, propeller and seals.

  • .6 Main propellers and shafting for controllable pitch propellers (CPP) ships – Main propeller blade foot seals and the shaft seals replacement interval should be in accordance with the five-year regime, taking into account the lubricating oil record. Main propeller hub dismantling for general overhauling may be considered at intervals greater than five years. Screwshaft surveys should normally be carried out at five-year intervals, unless a screwshaft condition monitoring scheme is in effect.

  • .7 Rudders − Rudders and rudder bearings (e.g., pintles and stocks) should be inspected and bearing clearances taken at those in-water surveys carried out in lieu of dry-dock surveys. Additionally, rudders should be inspected and rudder bearing clearances taken every five years in dry-dock. When oil lubricated bearing clearances are unable to be taken at those in-water surveys carried out in lieu of dry-dock surveys, special consideration may be given to ascertaining those bearing clearances based on a review of the operating history and onboard testing. Replacement of the sliding block and flap bushes of Becker rudders may be considered at intervals greater than five years.

  • .8 Sea chests – Means, such as hinged gratings, should be provided on all sea chests to allow divers access to each sea chest to inspect the external sides of through hull connections and sea valves.

  • .9 Anodes and cathodic protection and sea valves – The operator's maintenance regime should include provisions for inspection and replacement of cathodic protection anodes, taking into account that replacement of sacrificial anodes is variable, according to the conditions experienced. Sea valves that are found to be in need of replacement at the in-water survey should be replaced without delay.

  • .10 Hull thickness measurements — Requirements for thickness measurements of hull structure should not be prohibited by any in-water survey.

  • .11 Podded Propulsion Units (PODs) – Scheduled replacement of the drive end and non-drive end bearings on the PODs and inspection and replacement of seals should be based upon a five-year maintenance regime.

  5.2 The items listed above are not exhaustive and other items of fittings and equipment may be considered to be included in such a maintenance regime.

  5.3 In all cases, the design life of components, manufacturers recommended maintenance, company's implemented ship's maintenance system and classification society survey requirements should not conflict with the bottom inspection of passenger ships when the inspection is intended to be carried out in dry-dock only once in any five-year period.

Parent topic: Annex – Guidelines for the Assessment of Technical Provisions for the Performance of an In-Water Survey in Lieu of Bottom Inspection in Dry-Dock to Permit one Dry-Dock Examination in any Five-Year Period for Passenger Ships Other than Ro-Ro Passenger Ships
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