This article is a structured walkthrough of DNV-ST-E271 (DNV 2.7-1) requirements, organised the way a designer or certification engineer actually works through them — from initial structural design through to the identification plate. Each section maps to a checklist you can use during design, procurement, and fabrication. It is not a substitute for reading the standard. But it tells you what to look for before you open it.
What DNV 2.7-1 actually is
DNV-ST-E271 (Offshore Containers, formerly DNV 2.7-1) is a certification standard — not a standalone design code. It specifies the requirements an offshore container must meet, the verification process for confirming compliance, and the documentation that must be produced and retained. It does not prescribe a single structural calculation method. Instead, it defines acceptance criteria and requires the designer to demonstrate compliance against those criteria using recognised engineering codes.
The practical consequence: DNV 2.7-1 gives you the freedom to use AISC, Eurocode, or API structural design methods — as long as the end result meets the acceptance criteria. Many designers new to DNV 2.7-1 find this uncomfortable. The standard does not hand you a formula. It hands you a performance requirement and says: prove it.
DNV 2.7-1 separates compliance verification into two stages.Design appraisal — where DNV reviews your calculations, drawings, and material specifications before fabrication begins. And prototype testing — where a physical unit is tested to verify the design actually performs. Both must pass. You cannot substitute one for the other.
Scope and applicability
DNV 2.7-1 applies to offshore containers with a Maximum Gross Weight (MGW) below 25,000 kg, designed for lifting and transport between vessels and offshore installations. It covers:
- Standard offshore cargo containers (10ft, 20ft, 30ft)
- Mud skips and bulk mud containers
- Chemical drums and bulk chemical containers
- Tool boxes and equipment containers
- Offshore baskets (though DNV 2.7-2 is often used for lighter baskets)
It does not cover: service modules with active equipment (DNV 2.7-3), pressurised tanks to DOT/ADR specification (separate standards), or containers with MGW above 25,000 kg (DNV 2.7-3 territory).
The25,000 kg MGW limit in DNV 2.7-1 is not a guideline. If your container, when loaded to its Safe Working Load, exceeds 25,000 kg MGW, DNV 2.7-1 does not apply — regardless of content type or configuration. You must certify under DNV 2.7-3. This catches out designers who add equipment or change payload assumptions mid-design.
Load cases the designer must account for
Before starting structural calculations, the load case matrix must be defined. DNV 2.7-1 requires the following load cases to be considered:
- Dead weight — tare weight of the empty container plus structural steel weight
- Payload (SWL) — the Safe Working Load, representing the maximum cargo weight the container is rated to carry
- Vertical lifting loads — twice the SWL plus tare weight, applied at the centre of gravity of the container in a vertical lift (this is the proof load test load)
- Eccentric lifting loads — the same vertical load applied at the extreme edge of the container's footprint, representing the worst-case lift with the load shifted to one corner
- Stacking loads — the container stacked under others on a vessel deck, accounting for dynamic vessel motion; typically a stack factor of 1.5–2.0 × payload applied simultaneously with compressive and bending loads
- Fork-lift loads — for containers designed to be fork-lifted, transverse point loads applied at the fork tunnels under the floor
- Impact loads — for bottom-impact scenarios during landing on uneven surfaces; DNV 2.7-1 specifies a defined impact load case for base impact
- Sea transport loads — dynamic accelerations in six degrees of freedom during vessel transport; typically derived from NOAA or DNV-specified sea state data for the intended operating area
The designer must demonstrate that the combined stress under all applicable load case combinations remains within the specified acceptance criteria — typically using a yield criterion (e.g., von Mises stress below yield strength with an appropriate safety factor) and a buckling check where compression dominates.
Structural frame requirements
Structural Design — Frame and Core
Material specifications
DNV 2.7-1 is prescriptive about material traceability and grade approval. The designer must specify materials that meet DNV-approved grades and ensure full traceability back to the mill certificate for every structural member.
Materials — Grade, Traceability, and Certification
Welding requirements
Welding is the most common source of non-conformance findings in DNV 2.7-1 certification. The standard requires pre-qualified welding procedures, qualified welders, and documented quality control — not post-fabrication inspection as a catch-all.
Welding — Procedures, Qualifications, and Quality Control
Corrosion protection
Offshore containers operate in a marine environment that is simultaneously corrosive and mechanically demanding. DNV 2.7-1 requires the corrosion protection system to be designed for the specific environment — not specified generically.
Corrosion Protection — Surface Preparation and Coating
Lifting set design
The lifting set is the most safety-critical system on the container. DNV 2.7-1 has specific requirements for the design, materials, and testing of the lifting set — including slings, shackles, and attachment points.
Lifting Set — Sling, Shackle, and Attachment Design
Prototype testing
Design appraisal must be completed before prototype testing begins. DNV will not witness a prototype test for a design that has not yet been approved. The sequence is: design approval → prototype fabrication → prototype test witnessed by DNV surveyor.
Prototype Testing — DNV Witness Requirements
Fabrication surveillance
DNV surveyors visit the fabrication facility during production to verify that the as-built container matches the approved design. This is not a quality audit — it is a compliance verification. The surveyor checks specific items and has the authority to halt production if non-conformances are found.
Fabrication Surveillance — DNV Surveyor Visits
Identification plate and marking
The identification plate is the physical evidence of certification. Without it, the container is not DNV-certified — regardless of what the certificate document says. The plate must be permanently attached, clearly legible, and contain specific data.
Identification Plate and Marking
Periodic inspection
DNV 2.7-1 certification is not a one-time event. The standard requires periodic in-service inspection throughout the container's operational life. This is frequently the most overlooked requirement in the chain — both by manufacturers who do not communicate it clearly to buyers, and by operators who do not have a system to track it.
Periodic Inspection — In-Service Requirements
"DNV 2.7-1 certification is a chain of documents: design calcs, material certs, WPS, PQR, WPQ, weldmap, NDT records, prototype test report, surveyor visit reports, and the certificate itself. Each link must be intact. Missing one is not a minor issue — it is a break in the compliance chain."
The complete checklist: summary table
For quick reference during design review or procurement, the table below maps each DNV 2.7-1 requirement to its phase in the project lifecycle.
| Requirement | Phase | Status |
|---|---|---|
| Load case matrix defined and documented | Design — upfront | Required |
| Structural calculations (yield + buckling) | Design — upfront | Required |
| DNV design appraisal approval obtained | Design — gate | Required |
| Material certificates (EN 10204 3.1) for all structural members | Procurement | Required |
| WPS and PQR for all primary structural welds | Procurement / Pre-fab | Required |
| Welder WPQ records current | Pre-fab | Required |
| Weldmap prepared and traceable | Pre-fab | Required |
| NDT plan defined for primary structural welds | Pre-fab | Required |
| Corrosion protection system specified (internal + external) | Design | Required |
| Lifting set components certified (shackles, slings, castings) | Procurement | Required |
| DNV surveyor notified at start of fabrication | Fabrication | Required |
| Fabrication surveillance visits completed and NCRs closed | Fabrication | Required |
| Prototype testing witnessed by DNV surveyor | Testing | Required |
| Identification plate fitted under DNV witness | Final inspection | Required |
| Certificate issued by DNV | Final inspection | Required |
| Periodic inspection scheduled and tracked | In-service | Required |
| Modification control process in place | In-service | Required |
Most common non-conformances in DNV 2.7-1 certification
Based on the patterns seen across certification projects, these are the issues that most frequently cause delays, re-work, or failed prototype tests:
- Incomplete load case coverage — designers who account for vertical lifting loads but forget sea transport accelerations or eccentric lift; DNV will catch it at design appraisal, but the fix takes time
- Unqualified welders on primary structural welds — WPQ records not current or not covering the specific WPS being used; easy to prevent, hard to fix after the fact
- Coating specification mismatch — specifying a generic marine coating without confirming media compatibility for the specific cargo (OBM, chemical, brine); requires a full re-coat
- Material substitution without change order — swapping S355 for S420 mid-fabrication without DNV approval; voids the design appraisal
- Missing lifting set component certificates — slings or shackles purchased with certificates that do not cover the specific batch being used; DNV will not accept supplier declarations without batch traceability
- Failing to notify DNV before fabrication starts — fabrication beginning before the design appraisal is approved; DNV may require hold points to be placed retroactively
The worst-case outcome: a container is fabricated, arrives on site, and the prototype test fails because the floor design did not account for the dynamic fluid load case. The container must be repaired or rebuilt, re-presented to DNV, and re-tested. The project delay cost typically far exceeds the original certification cost. This is entirely preventable with a complete load case matrix reviewed by DNV before fabrication.
How to use this checklist
This checklist is designed to be used at three stages:
- Design phase — use it to verify your design package is complete before submitting to DNV for design appraisal; missing items here will surface as information requests that delay approval
- Procurement phase — use it to verify supplier documentation against the requirements; material certs, WPS, WPQ, and component certificates must be in hand before fabrication starts
- Fabrication phase — use it to track surveillance visit readiness; knowing which items the DNV surveyor will check at each visit allows the manufacturer to prepare and close non-conformances before the visit, not during it
Print it, put it in your project quality plan, and treat every Required item as a gate. The cost of catching a non-conformance at the checklist stage is a fraction of the cost of catching it at prototype test — or worse, after the container is on a vessel bound for an offshore installation.
Need a DNV design appraisal review before fabrication?
We support structural designers and manufacturers through the DNV 2.7-1 design appraisal process — from load case definition through to prototype test witness. Contact us to discuss your project scope.
Share your project requirements below. We’ll review your specifications and respond with a detailed engineering proposal.