When a dynamic-positioning vessel changes — a generator swap, a thruster or drive replacement, a control-system upgrade, a re-class — the DP Failure Modes and Effects Analysis no longer describes the vessel as built. Class and the charterer’s assurance team both know this, and both ask the same question: has the change been analysed, and proven?
What an addendum has to do
- Identify every failure mode the change introduces or removes, down to the worst-case failure.
- Show the post-change redundancy still meets the vessel’s DP class — the worst-case-failure design intent.
- Define the proving-trials programme that demonstrates it in the water.
- Update the DP operations manual, the consequence analysis, and the ASOG/CAM/TAM where affected.
What Class actually wants
Not a re-issued document for its own sake — evidence that the worst-case failure has been thought through and tested. The addendum should trace cleanly from the change, to the failure mode, to the trial that closes it, to the witnessed result. Where a proving trial cannot run before a charter window, the gap is stated and managed, not hidden.
The cheapest time to get this right is before the change is installed, while the trials programme can still shape the dock scope.