DNV vs NORSOK vs ISO
Standards: Complete Guide

Quick Comparison Table

The three standard families differ fundamentally in who creates them, what gives them legal force, and where they apply. The table below covers the top-line attributes engineers need to know before diving into the detail.

DNV — Det Norske Veritas

DNV Standard Families

DNV issues standards under four main document type prefixes:

When DNV Standards Are Mandatory

A DNV standard becomes mandatory in three main scenarios:

1. DNV classification: The owner has contracted DNV to class the vessel or structure. All applicable DNV-RU rules are then binding throughout the asset's life.
2. DNV certification of equipment: A lifting appliance, pressure vessel, or crane is contracted for DNV type approval or unit certification. The relevant DNV-ST or DNV-OS standard governs design and fabrication.
3. Contract reference: The project specification or purchase order explicitly requires compliance with named DNV documents, even where no classification is involved.

In all other cases, DNV-ST and DNV-RP documents are voluntary guidance — technically sound, but without mandatory force.

Key Practical Examples

• DNV-ST-0378:2023 — Lifting Appliances. Covers cranes, davits, winches, and associated lifting attachments (including pad eyes) installed on DNV-classed vessels and offshore units. Clause 4 covers design loads; Clause 6 covers structural design; Annex A covers pad eyes specifically.
• DNV-OS-D101 — Marine and Machinery Systems and Equipment. Applies to machinery, piping, and electrical systems on classified offshore units and ships.
• DNV-ST-0194 — Verification of Lifting Appliances for the Petroleum Activities. Used when PSA/Ptil requires a third-party verification body to verify lifting equipment on the NCS — the verifier typically follows DNV-ST-0194 as the verification framework.

NORSOK — Norsk Sokkels Konkurranseposisjon

PSA Regulations and NORSOK

The PSA (Petroleumstilsynet) operates a goal-based regulatory regime: regulations set objectives and operators must demonstrate compliance. The regulations identify standards that, if followed, constitute compliance ("deemed-to-satisfy"). NORSOK is the primary such standard set for most disciplines. Operators choosing an alternative approach must demonstrate equivalent safety to the PSA — a higher burden of proof.

Key NORSOK Standards by Discipline

NORSOK and the DNV Relationship

NORSOK R-002 and DNV-ST-0378 address overlapping scope — both cover lifting equipment, including pad eyes. On a DNV-classed vessel operating on the NCS, both can apply simultaneously. Where requirements differ, the project should identify the governing document. In practice, NORSOK R-002 tends to govern fabrication and testing requirements (load test factors, proof load requirements), while DNV-ST-0378 governs the classification-specific aspects (design approval, class notation).

ISO — International Organization for Standardization

Relevant ISO Series for Offshore Engineering

EN ISO — The European Adoption

Many ISO standards relevant to structural steel and welding are adopted without modification by the European Committee for Standardization (CEN), becoming EN ISO documents. When a standard is published as EN ISO, it supersedes any pre-existing national standard on the same topic in EU/EEA member states. Norway, as an EEA member, adopts EN ISO standards via Standards Norway. For the engineer, EN ISO and ISO are technically identical — the "EN" prefix confirms European adoption.

How DNV, NORSOK, and ISO Interact

The Regulatory Hierarchy

Understanding which standard takes precedence requires understanding the regulatory stack. From top to bottom:

Cross-Reference Chains

Standards rarely exist in isolation. A single design check may traverse all three families:

• DNV-ST-0378 references NORSOK R-002 for NCS lifting equipment requirements and references ISO 4309 for wire rope discard criteria.
• NORSOK N-004 references EN 10025 for steel material grades and EN ISO 5817 for weld quality levels.
• NORSOK M-101 references ISO 2553 for weld symbols and EN ISO 5817 for imperfection acceptance.
• NORSOK R-002 references DNV-ST-0378 for offshore crane design when a DNV-certified crane is used.

The practical consequence: a structural drawing for NCS lifting equipment may simultaneously need to comply with NORSOK R-002 (governing equipment), NORSOK N-004 (governing structure), DNV-ST-0378 (governing class), EN 10025 (governing material), ISO 2768 (governing tolerances), and EN ISO 5817 (governing weld quality). This is normal — not exceptional.

Conflicts Between Standards

When requirements conflict (for example, NORSOK and DNV specify different proof load factors), the resolution is:

1. Check whether the project specification or contract nominates a governing standard.
2. Apply the more conservative requirement, and document the decision.
3. For DNV-classed assets on the NCS, the classification surveyor and PSA verifier may both need to accept the approach — raise early.

Practical Decision Guide

The table below answers the question engineers most often ask: "Which standard governs this specific work on the NCS?" The answer frequently involves more than one standard. NORSOK governs the NCS regulatory requirement; DNV governs the class/certification requirement; ISO/EN governs the underlying material or geometry specification.