Dry Dock Scheduling for Sister Ships (Sister Ship Scheduling)
Experience from the first ship helps prepare sister ships’ dockings when it leads to targeted verification on each vessel. Differences, inspection outcomes and individual due dates guide work, quantities and docking sequence.
Operational Explanation
Ships in one series may share drawings, equipment and failure modes, but modifications, operation, corrosion, incidents and survey history create differences. The previous ship’s dossier is an input to risk review, not a scope to copy.
Staggering can support learning, but actual sequence depends on individual due dates, yard availability, commercial requirements and risk. HSSC does not impose one identical “five-year cycle” on every sister ship.
The benefit is anticipating the right questions: which component might have the same problem, what differences could change its behaviour and what evidence is needed before ordering work. A transferred finding remains a hypothesis until verified; a different outcome on the second ship is useful fleet information.
Regulatory Reference
Each ship retains its own certificates, windows and survey status under applicable statutory instruments and Rules. Fleet management and reuse of lessons learned are Company processes, not a separate IMO regime.
Risk assessment within the safety management system considers the ship’s actual conditions. To apply this principle across a fleet, use a matrix recording the first ship’s finding, equivalent component, differences, required verification, responsible person and outcome on the second ship. This is a Company working tool, not a mandatory IMO form. IMO: ISM Code.
If a finding may compromise safety, assess verification on other affected ships promptly rather than automatically waiting for their next docking. Record the technical decision and any temporary measures in the Company system; update the repair specification with the evidence obtained.
ISM 1.2.2.2 requires assessment of identified risks and safeguards; 9.1 and 10.2 connect findings, analysis, action and records. Reusing evidence belongs within this system and does not replace verification on the individual ship. IMO: ISM Code; MSC.273(85), amendment to 1.2.2.2.
Scope of Application
Fleets with ships of a common or similar design. Reuse depends on design identity, modifications, equipment, operating profile, age, condition and documented history.
Procedure / How to Complete It
- Compare design baseline, modifications, equipment and survey status.
- Transfer findings as hypotheses to verify on the next ship.
- Adapt scope, quantities, spares and criteria to individual condition.
- Plan sequence around due dates and actual constraints.
- Record confirmed, unconfirmed and ship-specific lessons.
For each transferred hypothesis, record whether it is confirmed, unconfirmed or still to be checked, retaining the ship, location/component, method and inspection result. Assign a responsible person and next action for an open finding; update the specification after the decision. Then build the fleet sequence using each vessel’s survey windows, resource availability and spare-part lead times.
Practical Example
Corrosion found on the first ship triggers a targeted inspection on the second. Renewal enters the scope only after evidence or as a priced option, considering the second ship’s own coating history and thickness.
If checks on the second ship do not confirm the corrosion, record the outcome and relevant differences; steel quantity from the first vessel is not transferred as work to execute. A priced option prepares for the possibility, but execution depends on verification and the work decision for that ship.
What Typically Goes Wrong
Common Mistakes Mistake Library
| Mistake | Consequence | How to avoid it |
|---|---|---|
| Treating a finding on the first ship as already verified on the second | Unnecessary work may be ordered or the actual defect left unchecked. | Compare configuration and condition; record verification and outcome on each ship before confirming its work. |
| Specification copied | Scope over or understated | Revalidate every item |
| Fixed sequence | Due dates or capacity ignored | Optimize within individual constraints |
What the PSCO Checks
Operational Tips
- Use a difference matrix across ships.
- Separate common and ship-specific findings.
- Retain evidence of verification on each unit.
Preparation checklist
- Design and modifications compared
- Individual survey status checked
- Findings revalidated
- Scope adapted to condition
- Lessons tracked
FAQ
Related Topics
Certified substantive revision: 13 October 2026 · page fingerprint cb88b4c509f5