DNV-ST-N001: Marine Operations and Marine Warranty
What DNV’s standard for marine operations covers, the codes it replaced, how it treats lifting and weather, and where it fits next to the equipment standards.
- DNV-ST-N001 Marine operations and marine warranty is DNV’s standard for planning and carrying out marine operations, and the basis many marine warranty reviews work to. The current edition is December 2023.
- It replaced DNV-OS-H101, H102, H201, H202, H204 and H205 in June 2016, and DNV-OS-H206 in July 2018.
- For a lift it sets the requirements for the operation: design loads, rigging, weather limits and documentation. An in-air lift can use the standard’s own minimum dynamic amplification factors; the dynamic and hydrodynamic analysis of a subsea lift (splash zone, lowering, landing) follows DNV-RP-N103.
- It governs the operation. A crane or compensator certificate is an input to the review; it does not approve the lift.
DNV-ST-N001 covers marine operations during the development or decommissioning of offshore assets, and the movement of objects by water: load-out, construction afloat, voyages, and installation or removal. It is a standard for the operation. The equipment used in it, such as the crane and a heave compensator, is certified to its own standards.
Where DNV-ST-N001 applies
DNV’s published scope has four kinds of marine operation:
- Load-outMoving the object from the quay onto the vessel or barge
- Construction afloatWork on floating structures before they reach site
- VoyagesSea transport and towing to the installation site
- Installation and removalOffshore installation, including lifts, and decommissioning
Lifting sits inside installation and removal, but a lift can also be part of a load-out or of construction afloat. Where the contract names ST-N001, it applies to the whole operation, not only the moment the load is in the air.
What it replaced
ST-N001 brought DNV’s separate offshore standards for marine operations, the OS-H series, into one document; only OS-H203 went to DNV-ST-N002 instead. It was first issued as DNVGL-ST-N001 in June 2016 and has carried the DNV- prefix since 2021.
| Old code | Title | Replaced by (date withdrawn) |
|---|---|---|
| DNV-OS-H101 | Marine operations, general | ST-N001, June 2016 |
| DNV-OS-H102 | Marine operations, design and fabrication | ST-N001, June 2016 |
| DNV-OS-H201 | Load transfer operations | ST-N001, June 2016 |
| DNV-OS-H202 | Sea transport operations | ST-N001, June 2016 |
| DNV-OS-H203 | Transit and positioning of offshore units | ST-N002, November 2016 |
| DNV-OS-H204 | Offshore installation operations | ST-N001, June 2016 |
| DNV-OS-H205 | Lifting operations | ST-N001, June 2016 |
| DNV-OS-H206 | Loadout, transport and installation of subsea objects | ST-N001, July 2018 |
From DNV’s document register; the date is when the old code was withdrawn. ST-N001 editions: June 2016; September 2018 (amended January 2020 and September 2021); December 2023, the current one. DNV-ST-N002 is Site specific assessment of mobile offshore units for marine warranty.
Lifting operations
ST-N001’s lifting requirements come from DNV-OS-H205 Lifting operations. They cover the lift as a whole: the design loads on the lifted object and the rigging, the rigging and padeyes themselves, other lifting equipment in the load path such as an in-line heave compensator, and the crane’s capacity for the lift. Lowering through the splash zone to the seabed came from DNV-OS-H206, merged into ST-N001 in 2018.
The central load factor is the dynamic amplification factor (DAF): the total load in the lift, static plus dynamic, divided by the static load. The OS-H205 approach, which ST-N001 carries forward, sets it by dynamic analysis for major offshore lifts, with tabulated minimum values for lifts in air as a fallback. For subsea lifts the value comes from the hydrodynamic analysis described in DNV-RP-N103, and it is often higher than the in-air minimum. How the DAF is found, and how a compensator changes it, is covered in the dynamic amplification factor guide.
Weather: design limits and the alpha factor
A marine operation is designed for a sea state it can safely handle, its operational limit. Because a weather forecast is never exact, the operation only starts when the forecast is below a lower value, the forecast limit:
The alpha factor (\alpha, below 1) covers the uncertainty of the forecast. It gets smaller for longer operations and larger with better forecasting and on-site wave monitoring. The forecast has to stay below that limit for the whole reference period: the planned operation time plus a contingency for delays. Operations short enough to be planned against a forecast, up to about three days in DNV’s approach, are weather-restricted; longer ones are designed for the seasonal extremes instead. Weather windows for offshore lifting works through an example.
Marine warranty
For an insured marine operation, the insurance usually requires a marine warranty surveyor (MWS) to review it on the underwriters’ behalf. The MWS reviews the procedures, calculations and equipment certificates against the agreed standard, often ST-N001, attends the operation and issues a certificate of approval before it starts. The review covers the operation; the equipment’s own certification is one of the documents it checks.
How it fits with the other DNV standards
On a compensated lift, ST-N001 is one of four main DNV documents. The crane and the compensator’s load-carrying parts are certified to DNV-ST-0378, and a crane that lifts in subsea operations also meets DNV-RP-N201. The compensating system is validated to DNV-RP-N202. Dynamic and hydrodynamic analysis (splash zone, lowering, landing) follows DNV-RP-N103. ST-N001 covers the operation.
A type approval or product certificate shows the equipment is fit for its rating. It does not approve a particular lift; that is what the operation’s analysis and the MWS review are for. The overview of DNV standards for offshore lifting maps all of them.
DNV-ST-N001 is in DNV’s paid Explorer+ subscription: open DNV-ST-N001 in the Explorer, where its table of contents and first section are free to view with a Veracity login. The old OS-H documents are still free PDFs in DNV’s archive of legacy documents.
Frequently asked questions
What is DNV-ST-N001?
DNV-ST-N001 Marine operations and marine warranty is DNV’s standard for planning and carrying out marine operations such as load-out, sea transport, offshore installation and removal, including lifts. Marine warranty reviews often work to it. The current edition is December 2023.
What replaced DNV-OS-H205?
DNVGL-ST-N001, in June 2016, together with DNV-OS-H101, H102, H201, H202 and H204. DNV-OS-H206 followed in July 2018, and DNV-OS-H203 became DNVGL-ST-N002. The standard now carries the DNV- prefix: DNV-ST-N001. The old OS-H205 is still a free PDF in DNV’s archive of legacy documents.
What is the current edition of DNV-ST-N001?
December 2023. Earlier editions were June 2016 and September 2018, which was amended in January 2020 and September 2021.
What is an alpha factor?
The alpha factor (\alpha, below 1) reduces an operation’s operational limit to the forecast limit it may start under, to allow for forecast uncertainty: OP_{\mathrm{WF}} = \alpha \times OP_{\mathrm{LIM}}. The forecast must stay below that limit for the whole reference period, the planned operation time plus contingency. \alpha is smaller for longer operations and larger with better forecasting and wave monitoring.
Is DNV-ST-N001 free?
No. It is part of DNV’s paid Explorer+ subscription, but its table of contents and first section are free to view in DNV’s Rules and Standards Explorer with a free Veracity login, and DNV offers a one-time 14-day trial. The older OS-H documents it replaced are still free PDFs in DNV’s archive.
Does DNV-ST-N001 apply to heave compensators?
Not as a certification standard, but it does reach an in-line compensator. Under the lifting rules ST-N001 took over from DNV-OS-H205, a heave compensator in the rigging is lifting equipment: the marine warranty surveyor checks its certificate, safe working load and proof load against the lift’s design loads. The compensator’s load-carrying parts are certified to DNV-ST-0378, and its compensating function is validated to DNV-RP-N202.
Basis and sources
- DNV document register (rules.dnv.com service documents), read September 2026: ST-N001 editions and the OS-H codes it replaced, with titles and dates.
- DNV’s public catalogue description of DNV-ST-N001 Marine operations and marine warranty, edition December 2023, and DNV’s list of documents in the Explorer+ subscription.
- DNV-OS-H205 Lifting operations, April 2014 (legacy, public): the DAF definition [1.3.2], the analysis and minimum-value approach, and other lifting equipment including heave compensators [4.3.1].
- DNV-OS-H101 Marine operations, general (legacy, public): weather-restricted operations, the reference period and the alpha factor.
- DNV-ST-0378 [9.4.3] and DNV-RP-N202 [1.4] for DNV-RP-N201’s role on subsea cranes.
- The current ST-N001 is paraphrased from DNV’s public descriptions; check requirements in the edition your contract names.
Preparing a lift for marine warranty review?
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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.
