DNV Standards – Offshore Container Certification Guide

DNV 2.7-3 (DNVGL-ST-E273) is the standard for portable offshore units weighing more than 25,000 kg, covering design, certification, and operation using a design-by-analysis approach. Unlike the prescriptive code-based method of 2.7-1, DNV 2.7-3 requires the design engineer to provide the full design basis, conduct limits-of-operation analyses, and define acceptance criteria for each load case scenario. Maximum gross weight for units under this standard can reach approximately 100 tonnes. The standard covers five POU types (A through E), each classified by operational profile and structural configuration, including laboratories, workshops, stores, power plants, control stations, tank containers, skids, and non-standard geometries that do not conform to a container profile.

The longer review cycle and higher certification cost compared to 2.7-1 reflect the depth of engineering analysis required. For procurement teams, the key distinction is structural: if the unit lacks a box-like crash-frame structure, or weighs above 25 tonnes, 2.7-3 applies. SCS manufactures portable offshore units to this standard, including engineered skids and frames for equipment that exceeds standard container profiles.

DNV 2.7-2 (DNVGL-ST-E272) covers installation requirements for container-shaped service modules on offshore installations, including electrical systems, safety systems, and hook-up procedures. Published in February 2016, this standard consolidates requirements from IMO, SOLAS, FTP, MODU, and explosion safety frameworks into a single reference document. Where 2.7-1 certifies the container for safe crane lifting and sea transport, 2.7-2 certifies the module for operation once installed on the platform. A service container deployed offshore typically requires both certifications: 2.7-1 for transport and 2.7-2 for installation.

This dual certification requirement applies to offshore workshop containers, control rooms, laboratories, data logging units, MCC rooms, and equipment enclosures. For procurement teams, specifying 2.7-2 alongside 2.7-1 is standard practice for any service module that will operate as a permanent or semi-permanent installation on an offshore facility.

DNV 2.7-1 (DNVGL-ST-E271) is the certification standard for offshore containers weighing up to 25,000 kg, governing design, manufacture, testing, and periodic inspection using a design-by-code approach. The current edition (2023-03, amended 2024-12) is based on the European standard EN 12079. The design-by-code philosophy means that if a container falls within specified categories, designated design criteria apply directly, producing a streamlined review process and a faster, less expensive certification cycle compared to 2.7-3. SCS manufactures across all three categories, including certified cargo containers, offshore baskets, and mud skip containers.

The main difference between DNV 2.7-1 vs 2.7-3 is weight and design philosophy: 2.7-1 certifies box-like containers under 25 tonnes using design-by-code, while 2.7-3 certifies heavier portable offshore units using design-by-analysis. If the unit weighs under 25 tonnes and fits a standard container profile, specify 2.7-1. If it exceeds 25 tonnes, has a non-standard shape, requires subsea rating, or will only be transported once, specify 2.7-3. Some units near the 25-tonne boundary may qualify under either standard, and the classification society confirms this during the design review stage.

The Container Safety Convention (CSC) is a 1972 IMO treaty that sets international design-approval and safety-inspection standards for all containers used in international transport by sea, land, and road. Every container in international transport must carry a CSC safety approval plate and undergo periodic examination. This framework operates independently of DNV offshore-specific standards but applies to all shipping containers, including those that also hold 2.7-1 certification. The first examination must occur no more than 5 years after manufacture, with subsequent examinations at intervals of no more than 30 months.

The European standard BS EN 12079 was the original basis for 2.7-1 and has been withdrawn and replaced by EN ISO 10855. ISO 10855 adds snagging requirements absent from EN 12079 and references ISO and ASNT standards instead of exclusively European ones. All containers certified to EN 12079 or DNV 2.7-1 are considered equivalent to ISO 10855, so existing certifications remain valid without re-certification.

What is DNV certification?

DNV certification is a classification society's formal verification that an offshore container's design, materials, welding, and testing meet the DNV standard it is built to, most commonly DNV 2.7-1 for cargo carrying units. The certificate, plate, and documentation pack are what an operator's marine warranty surveyor accepts at mobilisation.

How do you get DNV certification?

Certification is arranged by the manufacturer with a classification society: design review against the standard, qualified welding procedures, witnessed load and NDT testing, documentation, then the certificate, plate, and marking issued before dispatch.

DNV type approval for offshore containers follows a seven-step process: design review, manufacturing oversight, testing, documentation, certification, marking, and periodic in-service inspection. The process applies whether the certifying body is DNV itself, Lloyd's Register, Bureau Veritas, or ABS, as all major classification societies work to the same standard. SCS completes this process at our manufacturing facility for every offshore container produced, with third-party inspection by the project's nominated certifying body. For the full scope of SCS certification and compliance services, each unit ships with complete engineering documentation, mill certificates, and inspection reports.

The four major classification societies for offshore container certification are DNV, Lloyd's Register (LR), Bureau Veritas (BV), and the American Bureau of Shipping (ABS), each with different specialisations by product type and geography. Which society to nominate on a purchase order depends on the operator's existing fleet, flag state requirements, and contract conditions. SCS Global certifies through all four major societies plus SGS and Intertek for additional third-party inspection and verification. Most operators accept certification from any member of the International Association of Classification Societies (IACS).

An A60 fire rating means a structure can withstand a cellulosic fire for 60 minutes while maintaining structural integrity and preventing flame or smoke penetration, tested per SOLAS and IMO FTP Code (MSC.307(88)) standards. The classification centres on three simultaneous criteria maintained for the full 60-minute test: integrity (no flame penetration), insulation (average temperature rise on the unexposed face below 140°C, with no single point exceeding 180°C), and structural stability. The hydrocarbon fire curve is substantially more aggressive, exceeding 1,000°C within minutes, so modules on production platforms where hydrocarbon pool fires are the primary risk may require H-class ratings. The governing standards are SOLAS (1974), the IMO FTP Code, and ISO 834. SCS builds A60 fire rated modules for offshore deployment as hazardous area modules and offshore living quarters.

To specify offshore containers correctly, procurement teams need to confirm the applicable standard, maximum gross weight, fire rating requirement, classification society preference, and lifting arrangement before issuing the RFQ. Getting the specification right at the enquiry stage prevents re-engineering and re-certification costs that arise when requirements change after production begins. The specification should reference specific standard document numbers (DNVGL-ST-E271 for 2.7-1, DNVGL-ST-E273 for 2.7-3) rather than general terms. SCS engineers review each enquiry specification for offshore container compliance and flag gaps before production quotation.