Field notes

Offshore Skid Padeyes and Lifting Points: Design, Testing and the Certificate That Goes With Them

Published 26 September 2026

An offshore skid is lifted more times than it is used. It is lifted onto the truck, onto the quay, onto the supply vessel, off the vessel onto the platform and, in most cases, at least once more during installation. Every one of those lifts goes through four padeyes and a set of welds that a surveyor will want to see paperwork for.

This guide covers how padeyes and lifting points on offshore skids and module frames are designed, tested and documented. It is written for buyers who need the skid to clear a marine warranty surveyor without a return trip to the shop. The marine and offshore structures page lists the related structural work.

The lift is a design case

Offshore lifting rules treat the lift as a load case in its own right. DNV-ST-N001 (Marine Operations and Marine Warranty) and its predecessors are the usual reference, alongside client lifting specifications and, for the padeyes themselves, guidance such as the Lloyd’s Register or DNV lifting appliance codes. The essentials:

Dynamic amplification. The static weight is multiplied by a dynamic factor that depends on where the lift happens. A lift from a moving vessel offshore uses a higher factor than a quayside lift.
Skew load. Not all four slings carry an equal share. The rules assign a skew factor so that each padeye is designed for more than a quarter of the load.
Sling angle. The padeye sees a resultant force along the sling, not vertical. The angle changes the in-plane and out-of-plane loads.
Consequence factors. Padeyes and the structure around them get an additional factor because a failure drops the load.

The output of that calculation is a design load per padeye, and everything downstream follows from it.

Padeye geometry

A padeye is a plate with a hole and, usually, cheek plates that thicken the hole region. Its design checks:

Bearing of the pin on the hole.
Tear-out from the hole to the plate edge.
Tension across the net section beside the hole.
Weld between the padeye and the skid beam, in shear and bending.
The beam the padeye sits on, which sees a concentrated load it was not otherwise designed for.

The hole is sized to the shackle pin, with a clearance that the rules limit, and the plate thickness is matched to the shackle jaw width so that the shackle sits square. Cheek plates are welded with full penetration or with a fillet that the rules size, and the padeye is oriented so that the sling load acts in the plane of the plate. Out-of-plane loads on a padeye are what bend them, and the lift study should show the sling geometry that avoids it.

Material and welding

Padeye plate is usually a normalised or thermomechanically rolled grade with guaranteed through-thickness properties, because the padeye-to-beam weld loads the plate in its thickness direction. EN 10164 Z-grades (Z25 or Z35) or the equivalent are the common call-out. Material certificates are usually required at EN 10204 3.2 for the padeyes, meaning an independent inspector witnesses the tests, because the lifting point is a safety-critical element.

Welding follows the structural code the skid is built to, with the padeye welds identified as critical: full penetration where the design requires it, 100% MT on the toes and often UT where the weld is thick enough to test. The NDT guide covers the methods; the weld standards guide covers how the quality level is specified.

The lift study

A lift study is a short engineering document that shows:

The centre of gravity of the skid as built, with the weight.
The sling arrangement, lengths and angles, and the hook height needed.
The load in each sling and each padeye, with the dynamic, skew and consequence factors applied.
The padeye and structural checks against the rules.
The shackle and sling sizes.

The centre of gravity is the item most often wrong. It is calculated from the design at the start and it has to be confirmed by weighing the finished skid, because equipment gets added, pipe runs change and the actual CoG moves. A weighing certificate with the CoG measured on load cells is part of the delivery on most offshore packages.

The load test

Most client specifications and most marine warranty surveyors require a proof load test of the padeyes. The test loads each padeye, or the complete skid through all four padeyes together, to a multiple of the working load, typically in the range 1.25 to 2 times depending on the rule set, holds it and then inspects the padeyes and the welds. The inspection after the test is MT on the welds and a dimensional check of the hole for permanent deformation.

The test needs a certified test weight or a test rig, calibrated load cells and a witness. The witness is usually a third-party inspector or the class surveyor. The test certificate, with the load, the hold time, the witness and the post-test inspection results, goes into the documentation package.

Seafastening

The padeyes get the skid onto the vessel. Seafastening keeps it there. Seafastening is a separate structure: welded or bolted braces between the skid and the deck, designed for the vessel motions on the voyage. It is usually designed by the transport engineer rather than the skid fabricator, but the skid has to have the connection points for it, and those points are welded attachments with their own material and NDT requirements. If the fabricator is asked to supply seafastening steel, the drawing and the motion criteria have to come with the request.

The documentation package

A skid that clears the surveyor arrives with:

Weight and CoG certificate from the weighing.
Lift study, signed.
Padeye material certificates, usually 3.2.
WPS and welder qualifications for the padeye welds.
NDT reports for the padeye welds, before and after the load test.
Load test certificate with witness signature.
Shackle and sling certificates, if supplied with the skid.
Seafastening drawing and calculation, if in scope.

Missing any one of them can hold a skid on the quay. It is far cheaper to list them in the purchase order than to chase them afterwards. Our equipment skid design guide covers the rest of the skid; this article covers the part the surveyor looks at first.

Specifying it

Before an offshore skid goes out for quotes, the drawing or specification should state:

The rule set for lifting (DNV-ST-N001 or the client specification) and the lift location (quayside, inshore, offshore).
Padeye material grade with through-thickness requirement and certificate level.
Weld class for the padeye welds and NDT extent.
Load test requirement, factor, witness and post-test inspection.
Weighing and CoG certificate requirement.
Whether the lift study and seafastening are in the fabricator’s scope.

Lifting points are one decision among eight in the steel skid fabrication guide, and the terms are defined in the skid glossary.

Getting it quoted

Offshore skids need a shop that has done class-witnessed or third-party-witnessed work, has a load test arrangement and knows what a marine warranty surveyor asks for. We check for that before an offshore drawing moves. Send yours through the RFQ form with the destination and the lift location; within 24 business hours we tell you which shops fit, and up to three of them quote you directly. The marine and offshore structures page covers the related work.