Padeye Design Calculator —
DNV-ST-0378 & NORSOK R-002

What is a padeye in offshore engineering?

A padeye (also called a lifting lug or pad eye) is a structural attachment point welded to offshore equipment, vessels, or structures to enable lifting by crane or rigging. It consists of a circular or tapered steel plate with a machined pin hole, sized to accept a shackle or hook from the lifting tackle.

• Primary plate: The main steel plate carrying tensile and bearing loads through the pin hole, typically fabricated from S355 or higher grade steel.
• Cheek plates: Reinforcing plates welded on each face of the primary plate, increasing the bearing area and reducing stress concentration around the pin hole.
• Weld connection: Fillet or full-penetration welds transfer the load from the padeye into the parent structure — weld sizing is a critical design output.
• SWL marking: Per NORSOK R-002 §5.3.3, the Safe Working Load must be legibly and permanently marked on every lifting attachment.
• Pin hole diameter: Sized to provide minimum clearance over the shackle pin whilst preventing excessive lateral movement that causes out-of-plane bending.

Which standard governs padeye design?

Two Norwegian/DNV standards form the primary regulatory framework for offshore padeye design:

• DNV-ST-0378:2023 — Standard for Offshore and Platform Lifting Appliances. Governs design of lifting attachments fitted to structures and equipment lifted offshore. Section 6 covers structural requirements for lifting lugs and padeyes including net section, hole tolerance, and geometry. Section 7 covers weld design.
• NORSOK R-002:2019 — Lifting Equipment. Applies to all lifting equipment used on the Norwegian Continental Shelf. Requires marking, inspection, and design verification of lifting attachments. References DNV-ST-0378 for structural design but adds requirements for marking and certification.
• ISO 2768 — General tolerances for machined parts. Applied to pin hole diameter tolerances per DNV-ST-0378 §6.3.4 requirements on clearance.
• EN 10025 / DNV-OS-B101 — Material standards governing yield strength of structural steel grades (S235 through S420) used in padeye plates.

Padeye design requirements per DNV-ST-0378

• Pin hole clearance DNV-ST-0378 §6.3.4 — The pin hole diameter shall be not less than the nominal shackle pin diameter plus 6 mm minimum clearance. Excessive clearance (more than 6% of pin diameter) is also flagged, as it can induce bending.
• Net section width DNV-ST-0378 §6.3.2 — The net section on each side of the hole (b − d)/2 shall be not less than 0.75 × d (hole diameter). This ensures adequate net area against shear and tension tearout.
• Plate bearing stress DNV-ST-0378 §6.4.1 — Contact bearing stress σ = F/(d × t) shall not exceed the material yield strength f_y. For offshore lifting, the SWL is the design load; DAF and rigging factors should be applied separately per DNV-ST-0378 §4.
• Weld throat minimum DNV-ST-0378 §7.3.4 — For fillet welds connecting padeye plates, the effective throat a shall not be less than 0.7 × t_min (where t_min is the thinner of the two plates joined). Full-penetration welds may be required for primary lifting attachments above 50t SWL.
• Geometry — hole eccentricity DNV-ST-0378 §6.3.1 — The distance from the centre of the pin hole to the free edge shall be not less than the hole radius plus 75% of the hole diameter on each side, ensuring the plate does not fail in shear plug or edge tearout.
• SWL marking NORSOK R-002 §5.3.3 — All lifting attachments shall be permanently marked with the SWL in tonnes. Marking shall be stamped, welded, or otherwise indelible — paint alone is not acceptable.
• Material certification DNV-ST-0378 §5.2 — Steel plates for padeyes shall be certified to EN 10204 3.1 or 3.2 minimum. For padeyes above 25t SWL, DNV-OS-B101 material certification is typically required by the certifying authority.