What it is: an online calculation application for DP Capability Level 1 in accordance with DNV-ST-0111, Assessment of station keeping capability of DP vessels Issued by: DNV Made generally available: 2020
The problem it solves
Before DNV-ST-0111, station-keeping capability numbers were produced by different parties using different assumptions, and two capability plots for similar vessels could not honestly be compared. ST-0111 fixed the method; Level 1 is its most prescriptive rung — a fixed set of formulas balancing environmental forces against thrust output on the Beaufort scale, for ship-shaped, single-hull vessels.
Because Level 1 is fully prescriptive, it is the level suited to verification and benchmarking: the same vessel data entered by any competent party gives the same answer.
What the application does
- Takes the vessel's principal particulars, thruster arrangement and thrust data.
- Applies the Level 1 method of DNV-ST-0111 — no analyst-specific modelling assumptions to argue about.
- Returns the capability result in the standard form, for the intact condition and for defined failure cases, so results can be compared vessel to vessel and tender to tender.
Higher levels remain engineering work rather than a form: Level 2 is a quasi-static method with project-specific adjustments for any hull shape, Level 3 uses time-domain simulation, and the Site variants of both substitute site-specific environmental data and external forces. Each step up the scale is a significant improvement — the environmental forces a vessel is shown to withstand typically increase by more than 50 per cent from one step to the next.
How to use it in practice
| Purpose | Level to use |
|---|---|
| Benchmarking, screening, verification of a claim | Level 1 — prescriptive and comparable |
| Project-specific assessment, any hull form | Level 2 (or Level 2 — Site) |
| Understanding dynamic behaviour and post-failure limits | Level 3 (or Level 3 — Site) |
A Level 1 result is a comparison tool, not an operating limit. Operational limits come from the vessel's capability analysis, FMEA, proving trials and the ASOG — and, where an alternate centre of rotation is used for the industrial mission, from capability plots developed for that condition intact and post worst-case failure, as DNV-RP-E306 requires.
One method, one set of formulas, one comparable number. That is the whole point of Level 1.
See also: the Dynamic Positioning entry for the full DNV-ST-0111 capability-level table, and IMO MSC.1/Circ.1580 for the equipment classes the capability work supports.