Simplified formulations for marine-operation design loads — selected and qualified for the actual case.
DNV-RP-N103: Modelling and Analysis of Marine Operations
What DNV-RP-N103 contributes to modelling and analysis of marine operations. The public edition is 2017-07, amended 2021-09; the contract-nominated edition and project basis govern the methods, inputs and acceptance criteria used.
By Tord Martinsen & Peter Wang · · Reviewed · 7 min read
DNV-RP-N103 is DNV’s recommended practice for modelling and analysis of marine operations. DNV’s public catalogue lists edition 2017-07, amended 2021-09, and states its objective as providing simplified formulations for establishing design loads used in the planning and execution of marine operations.
The contract-nominated edition, operation and analysis basis determine which formulations, coefficients and validity limits apply. This page is an orientation and does not reproduce design coefficients or acceptance criteria.
Practical application: see engineering studies and analysis and product / system design for a project-specific model and calculation summary.
What RP-N103 covers
RP-N103 provides simplified formulations for establishing marine-operation design loads. The actual model must be defined for the operation, including its phases, geometry, environment, motions, boundaries, rigging and equipment dynamics as applicable.
Do not assume that the splash zone always governs or that one analysis type is prescribed for every case. State the nominated edition, selected method, inputs, force components, assumptions, validity limits and required outputs in the project analysis basis.
Define the model phase by phase
| Phase | Define | Report |
|---|---|---|
| In air | Support motion, rigging, load path and equipment state | Loads, relative motion and assumptions |
| Water entry / exit | Free-surface crossing, submergence history and applicable transient-load model | Time history, extrema and validity limits |
| Submerged | Relative flow, inertia treatment, geometry, boundaries and equipment dynamics | Loads, motion, tension and stroke demand |
| Landing / recovery | Boundary effects, contact or landing criteria and control state | Landing response, sensitivities and limitations |
The governing phase and analysis method are case-specific. This table is an analysis checklist, not a reproduced RP-N103 clause.
Drag forces on offshore lifts
Hydrodynamic drag depends on the relative flow and a coefficient and reference area selected for the geometry and flow regime. The applicable formulation, coefficient source and validity limits must be taken from the contract-nominated RP-N103 edition or another approved project source.
The previous version of this page reproduced generic coefficient values and described a bounding box as inherently conservative. Those values and that claim have been removed because orientation, geometry, flow regime and interaction effects can change the result.
Added mass — accelerating water
Added-mass or inertia treatment is part of the operation model where acceleration of surrounding water is relevant. Select the formulation and coefficient for the actual geometry, direction, submergence and boundary conditions from the approved analysis basis.
Proximity to the seabed or another boundary can modify the hydrodynamic response, but this page does not prescribe a universal increase or coefficient. State the method and its validity for the landing case.
Coefficient selection is part of the analysis basis
Use coefficients and formulations from the contract-nominated edition or another approved project source, with the geometry, direction, flow regime, boundary conditions and validity limits stated. This article intentionally does not reproduce generic coefficient constants.
Slamming and splash zone
Water entry, exit and partial submergence can introduce rapidly changing buoyancy and hydrodynamic loads. Whether slamming or another contribution governs is case-specific.
Define the free-surface model, geometry, relative motion, submergence history, load formulation and combination method in the project analysis. Do not infer a universal governing phase from this article.
Snap loads
Snap loading can occur when a line loses or approaches loss of tension and subsequently re-tensions. Its likelihood and peak response depend on the coupled operation model, including motions, mass and hydrodynamic effects, line and rigging stiffness, damping, equipment dynamics and available compensator stroke.
A heave compensator or shock absorber may reduce relative motion or peak response within its validated envelope, but it does not automatically eliminate slack or snap risk. Verify minimum tension, stroke demand, end stops, failure modes and re-tension response in the project analysis.
Combined hydrodynamic analysis
Choose the analysis method from the operation physics, required outputs, non-linearity, transient events, available data and the contract-nominated standard. A one-line rule such as “time-domain for every critical lift” or “frequency-domain for narrow-band seas” is not a substitute for a documented method-selection rationale.
The calculation summary should identify the method, software and version, model scope, assumptions, input provenance, verification checks and limitations.
How RP-N103 feeds compensator sizing
Do not describe an RP-N103 analysis as producing only three outputs. Define the required inputs and outputs for each operation phase in the project analysis basis.
A compensator-sizing package should identify, as applicable, the governing load and motion time histories and extrema, minimum line tension and slack/snap indicators, relative motion and stroke demand, equipment force/pressure/energy demands, boundary or landing effects, operational limits, sensitivities and model limitations.
These are project-analysis deliverables, not a reproduced RP-N103 clause list. The system-level heave-compensator framework may also reference DNV-RP-N202, edition 2024-06, where nominated.
The sizing loop, in one strip
The project analysis produces the documented inputs; RP-N103 may form part of the nominated method basis. This loop turns those inputs into a compensator — the system-level framework for that design step is DNV-RP-N202, DNV’s 2024 recommended practice on heave compensating systems. A CONSTELLATION study can document the operation model together with the compensator dynamics.
Where to get the RP
DNV-RP-N103 source page. DNV public catalogue: edition 2017-07, amended 2021-09; verify the contract-nominated edition before use.
DNV-RP-N103 — frequently asked
What is DNV-RP-N103?
Where should I get hydrodynamic coefficients?
Does the splash zone always govern?
Does a passive heave compensator eliminate snap loads?
Which analysis type does my lift need?
Related on Norwegian Dynamics
- DNV Standards for Offshore Lifting — how RP-N103 can fit alongside other project-nominated documents.
- Subsea Lifts — worked hydrodynamic examples; select coefficients and validity limits from the approved project source.
- Passive Heave Compensation Basics — compensator response concepts and project-specific verification.
- Dynamic Amplification Factor (DAF) — response-ratio concepts rather than a universal acceptance value.
Running the RP-N103 numbers on a real case?
We define the hydrodynamic and coupled-response model for the actual operation, then select the analysis method, coefficients and outputs against the approved project basis. Send the lift case for a proposed calculation scope and compensator-sizing summary.
Free download · 8 pages
Offshore Lift Load Cases — ND benchmark figures
What a lift actually measures, with and without passive compensation, from Norwegian Dynamics' own time-domain simulations. It reproduces no standard — the value is the figures, which no standard publishes.
